# Yes, your stove is over drafting... Blame the ...



## sadpanda (Dec 7, 2020)

As @BKVP and others can confirm, this year marks the 20th anniversary of this EPA/manufacturer/consumer merry-go-round BS...    

As explained in the ancient The Florida Bungalow Syndrome article, if you have experienced a cracked stove, creosote buildup, short burn times, run away/over fire, chimney fire, combusters only lasting 1-2 seasons etc. then you have been victim of this bureaucratic idiocy.

The end user is always left holding the bag... Anything we do to remedy the situation is strictly vorboten:

Key damper - EPA says no
Smaller flue diameter - NFPA says no
Flue restrictor - UL and NFPA says no
Barometric draft control - Sweeps scream creosote, UL says only on tested devices, manufacturers say...?
Modify the stove - EVERYONE says NO
My issue is this:  Why in the hell is a wood burning stove NOT treated like every other system in a home regulated by the IBC?

Plumbing contractors are required to perform DFU calculations for drain/vent sizing  
Electrical contractors are required to perform load/voltage drop/box fill calculations
Framers are given prescriptive tables for common header/beam/fastening etc.  Anything beyond 'cook book' can be done with engineering evaluation
- - and the really ironic one - -​
Natural gas appliances require draft testing and calibration during commissioning.  Flue pipe diameter *IS* allowed to be sized down as needed with caution

From a risk perspective:

plumbing is rather trivial, for most residential situations, worst case is property damage, not death
Even the most egregious electrical errors are typically saved by breakers
Framing code is super conservative and even the most bone headed mistakes (cutting joists nearly in half, cutting trusses etc) almost never result in catastrophic failure
Natural gas appliances have multiple safeties in place with the default condition being full shut down unless conditions are met
By contrast, LIGHTING A RAGING FIRE IN STEEL BOX IN THE MIDDLE OF YOUR HOUSE?  meh, send it bro.

I'm 100% against more regulatory involvement but the current regulations are irrational and have us over a barrel.

Just give us the formulas / reference tables like everything else.   The formula for calculating theoretical draft is simple enough.  Adjust for local average winter ambient temperature, type of flue pipe and installation method and BOOM we are in the ball park.   Two k-type thermocouples, a data logger and a manometer can all  can be had for peanuts on Amazon.  Heck even wide band O2 sensors are standard fare for the average automotive enthusiast if we want to go full EU emissions geek.  Do the calcs, add in a couple of monitored test burns for fine tuning/user training/validation and voila!   We have a fully commissioned, safe, functional installation that keeps the EPA dweebs happy.


Why is this so hard?

/rantff


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## begreen (Dec 7, 2020)

Point taken, though there are exceptions. All the calculations and tables can fail due to negative pressure in the stove room or geographical effects on the draft. Thus field measurement is critical.


sadpanda said:


> Even the most egregious electrical errors are typically saved by breakers


Have to disagree with this statement. It is not untypical to find someone cheating and putting a lower gauge wire on an oversized breaker. This was in my last two houses. The first had the whole kitchen on a 40 amp circuit, outlets and all. Our current house comingled 14ga lighting wiring with 12ga on a 20 amp circuit. Happens all the time and once buried behind walls no one knows until there is trouble or fire.  There have also been a lot of deaths due to poor or no ground circuits. Egregious errors in electricity can be fatal.


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## Highbeam (Dec 7, 2020)

What do the epa’s ever tightening regulations have to do with my catalyst only lasting 2 seasons?They’ve only been rated to last 12,000 hours for decades.


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## sadpanda (Dec 7, 2020)

Highbeam said:


> What do the epa’s ever tightening regulations have to do with my catalyst only lasting 2 seasons?They’ve only been rated to last 12,000 hours for decades.


I'm not saying anything about the tightening of emissions, I'm positing given low draft vs over draft, a cat in lower draft conditions will last longer.  Obviously we are doing something wrong, catalytic technology has been around since the 70s and now last the life of the vehicle...


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## Bad LP (Dec 7, 2020)

After installation put it the way it should be.


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## ejsechler (Dec 7, 2020)

Sums it up pretty well... my 2020 Drolet ht3000 overdrafting hard.


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## begreen (Dec 7, 2020)

ejsechler said:


> Sums it up pretty well... my 2020 Drolet ht3000 overdrafting hard.


Was this a professional install or DIY?

Have you started a thread on this topic? If not, please do. In it let us know the specifics of the install including the height of the entire flue system.


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## Nigel459 (Dec 7, 2020)

I agree with the OP. 

I think most topics on this thread like "my new EPA stove sucks/doesn't work/doesn't heat/heats too well" are draft issues, once fuel quality is ruled out.


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## brenndatomu (Dec 7, 2020)

I've been saying for years that half the problems people come here with are due to wet wood...the other half are draft issues....and I am just shocked that you almost never see anybody suggest checking the draft (in the stove forums) or somebody says, "they checked it when they put it in...back in September"...say what?! They checked the draft with no fire, and when it was 60* out?!


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## tabner (Dec 7, 2020)

brenndatomu said:


> I've been saying for years that half the problems people come here with are due to wet wood...the other half are draft issues....and I am just shocked that you almost never see anybody suggest checking the draft (in the stove forums) or somebody says, "they checked it when they put it in...back in September"...say what?! They checked the draft with no fire, and when it was 60* out?!


So is there no way to check your draft prior to your stove install?  I have the installer coming tomorrow for a quote, and it'd be nice to measure a draft prior to a full install.  I guess you just have to go off the installer's experience and assumptions based on your chimney size, location, geography, etc? - and then hold off on a formal draft measurement until it's installed and running (at which point you already paid for everything)


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## bholler (Dec 7, 2020)

sadpanda said:


> As @BKVP and others can confirm, this year marks the 20th anniversary of this EPA/manufacturer/consumer merry-go-round BS...
> 
> As explained in the ancient The Florida Bungalow Syndrome article, if you have experienced a cracked stove, creosote buildup, short burn times, run away/over fire, chimney fire, combusters only lasting 1-2 seasons etc. then you have been victim of this bureaucratic idiocy.
> 
> ...


You are a little confused about what is allowed and what isn't and who determines that.

The epa only sets emissions standards.  They have absolutely no input at all in the design installation operation etc of stoves.  

Key dampers are allowed unless the manufacturer says you can't use one.  No agency says you can't.  

Flue size.  Nfpa allows downsizing or upsizing by 1" unless the manufacturer says otherwise.

Flue restrictor.  Same as the others a manufacturer can allow it.  

Barometric dampers.  Again same as above but I honestly still believe they are a horrible solution to draft control on a wood stove.

Modify the stove yes everyone has to say it isn't allowed because making untested modifications to a stove could be extremely dangerous.  But many people have successfully restricted the intake of their stove if they have excessive draft.  

Now all that being said I do agree there is a problem that there is no set way to compensate for excessive draft.  I really wish there was a way as an installer that I could preset the intake for the draft in that particular installation.  Especially for inserts.  Freestanding stoves are pretty easy to address with a key damper.

Now we also have to look back before regulations.  All of those problems you listed absolutely existed before regulations came into the equation.  And honestly for the vast majority people if they install correctly and use good fuel modern stoves work very well.


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## bholler (Dec 7, 2020)

brenndatomu said:


> I've been saying for years that half the problems people come here with are due to wet wood...the other half are draft issues....and I am just shocked that you almost never see anybody suggest checking the draft (in the stove forums) or somebody says, "they checked it when they put it in...back in September"...say what?! They checked the draft with no fire, and when it was 60* out?!


Well I have to disagree.  Most problems are fuel.  Next is operator error.  Then draft.  But honestly those really are the only real problems you can have with a natural draft appliance.  You just have fuel air and user input.  Those are the only variables.


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## bholler (Dec 7, 2020)

tabner said:


> So is there no way to check your draft prior to your stove install?  I have the installer coming tomorrow for a quote, and it'd be nice to measure a draft prior to a full install.  I guess you just have to go off the installer's experience and assumptions based on your chimney size, location, geography, etc? - and then hold off on a formal draft measurement until it's installed and running (at which point you already paid for everything)


No there is no way to check draft ahead of time.  How tall is your chimney and where will the stove be located


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## SpaceBus (Dec 7, 2020)

Will the same flue have the same draft readings with different stoves?


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## bholler (Dec 7, 2020)

SpaceBus said:


> Will the same flue have the same draft readings with different stoves?


Not the same but very similar


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## SpaceBus (Dec 7, 2020)

bholler said:


> Not the same but very similar


At least current stove owners can get a reference before selecting a new stove.


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## bholler (Dec 7, 2020)

SpaceBus said:


> At least current stove owners can get a reference before selecting a new stove.


Yes but it can also really only be tested during the burning season


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## tabner (Dec 7, 2020)

bholler said:


> No there is no way to check draft ahead of time.  How tall is your chimney and where will the stove be located


It's an internal chimney from the basement floor up through the center peak in the middle of the house. So three floors plus about 4 feet of attic and 4 feet above the roof. The stove connects about 6 or 7 feet above the basement floor. So maybe 25 ~ 30 feet total. It's 8" square clay tile inside square cinder blocks.  But stove has to be offset a little bit and connected sideways rather than directly from behind. So I've got to go horizontal about 30 inches. But I'm gonna use two 45s, so it'll really only be about 12" of actual horizontal through the thimble and into the chimney.  6" double wall.


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## bholler (Dec 7, 2020)

tabner said:


> It's an internal chimney from the basement floor up through the center peak in the middle of the house. So three floors plus about 4 feet of attic and 4 feet above the roof. The stove connects about 6 or 7 feet above the basement floor. So maybe 25 ~ 30 feet total. It's 8" square clay tile inside square cinder blocks.  But stove has to be offset a little bit and connected sideways rather than directly from behind. So I've got to go horizontal about 30 inches. But I'm gonna use two 45s, so it'll really only be about 12" of actual horizontal through the thimble and into the chimney.  6" double wall.


You will have excessive draft.  Unless your basement is a negative pressure area.


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## tabner (Dec 7, 2020)

bholler said:


> You will have excessive draft.  Unless your basement is a negative pressure area.


Thanks, I guess that is preferable to the alternative problem - not enough. You think it's worth asking for a damper with the install? Can I put it in the 45 section? Otherwise the only spot would be right on top of the stove, like 8 inches up.


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## bholler (Dec 7, 2020)

tabner said:


> Thanks, I guess that is preferable to the alternative problem - not enough. You think it's worth asking for a damper with the install? Can I put it in the 45 section? Otherwise the only spot would be right on top of the stove, like 8 inches up.


Yes you will need atleast one damper if not 2.  It can go anywhere in the connector pipe


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## tabner (Dec 7, 2020)

bholler said:


> Yes you will need atleast one damper if not 2.  It can go anywhere in the connector pipe


Thank you very much


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## Highbeam (Dec 7, 2020)

tabner said:


> Thanks, I guess that is preferable to the alternative problem - not enough. You think it's worth asking for a damper with the install? Can I put it in the 45 section? Otherwise the only spot would be right on top of the stove, like 8 inches up.



You can buy appliance adapters, that first 6" section of pipe on the stove, that come with a key damper preinstalled. It's okay to be right on top of the stove. The only bummer is measuring daft between the key damper and the stove gets harder when you have no pipe length there.


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## tabner (Dec 7, 2020)

Highbeam said:


> You can buy appliance adapters, that first 6" section of pipe on the stove, that come with a key damper preinstalled. It's okay to be right on top of the stove. The only bummer is measuring daft between the key damper and the stove gets harder when you have no pipe length there.


Is it preferable to have your flue probe above or below the damper? Or doesn't matter?


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## bholler (Dec 7, 2020)

tabner said:


> Is it preferable to have your flue probe above or below the damper? Or doesn't matter?


Draft needs to be measured on the stove side of the damper.  Temp on the chimney side


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## sadpanda (Dec 7, 2020)

tabner said:


> So is there no way to check your draft prior to your stove install?  I have the installer coming tomorrow for a quote, and it'd be nice to measure a draft prior to a full install.  I guess you just have to go off the installer's experience and assumptions based on your chimney size, location, geography, etc? - and then hold off on a formal draft measurement until it's installed and running (at which point you already paid for everything)


  Yes draft can be estimated given all of the fixed variables that are out of your control:

Flue size is fixed by a)what fits down your masonry if doing a re-line  which can impact the main determinant: b) the collar size of the appliance you are seeking to install.

Flue height has a minimum set by building/fire code.

Flue average temp is something I think could be calculated if the industry decided to help on this but annecdotally my 24 ft flex liner with wrap going through exterior masonry chimney was loosing around 200F from collar to cap.   This would be drastically different for an exterior exposed Class A installation.

Outside ambient temp, again per my recommendation the building code uses this for your heating/cooling calcs so it readily available.






						Chimney Sizing
					

Calculate chimney draft and required chimney area - online calculator.




					www.engineeringtoolbox.com


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## Bad LP (Dec 7, 2020)

At the end of the day the manufacturers call the shots on what is and is not allowed.


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## bholler (Dec 7, 2020)

sadpanda said:


> Yes draft can be estimated given all of the fixed variables that are out of your control:
> 
> Flue size is fixed by a)what fits down your masonry if doing a re-line  which can impact the main determinant: b) the collar size of the appliance you are seeking to install.
> 
> ...


There are way to many variables to get anywhere near an accurate number.     But it is a safe bet that if you get much over 20' straight up off the stove your draft will be to strong.   More height if going through a wall.  

Flue height does not have a minimum according to fire  code.   It has to be a certain distance above the surrounding structure.  And stove manufacturers specify a minimum height.


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## sadpanda (Dec 7, 2020)

bholler said:


> You are a little confused about what is allowed and what isn't and who determines that.
> 
> The epa only sets emissions standards.  They have absolutely no input at all in the design installation operation etc of stoves.
> 
> ...



EPA sets emissions standards.... The stoves are #1 designed to pass this test.  Otherwise they are not allowed to be sold.  Any other considerations are secondary.

From what I've seen, no current EPA stove mfg is publically encouraging the use of Key dampers for fear of EPA reprecussions (that would basically be the folksy version of VW Diesel-Gate).


What section of NFPA 211 allows for up size or down size?

9.2.2.2.1: reduced clearance connectors permitted if they are in accordance with mfg
9.4.2: effective area of connector shall not be less than the area of the appliance flue collar

I did not look for size reduction allowed on B-vent but I remember seeing it in Selkirk installation manual... perhaps that falls under 'engineered ventilation' because, oh, I dunno, someone actually had a table/procedure to reference and could do maths to verify it would work


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## sadpanda (Dec 7, 2020)

bholler said:


> There are way to many variables to get anywhere near an accurate number.     But it is a safe bet that if you get much over 20' straight up off the stove your draft will be to strong.   More height if going through a wall.
> 
> Flue height does not have a minimum according to fire  code.   It has to be a certain distance above the surrounding structure.  And stove manufacturers specify a minimum height.



Erm... "It has to be a certain distance above the surrounding structure."  aka there is a minimum set by fire/building code.

If I have a 20ft tall house and too much draft, shortening my flue is not an option


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## sadpanda (Dec 7, 2020)

bholler said:


> Draft needs to be measured on the stove side of the damper.  Temp on the chimney side



And you are back to the issue at hand.   Draft during shoulder season for me(ambient temp 50F) vs dead winter on the coldest night (12F) is dramatically different.   Draft with the air controls open on a fresh load are dramatically different than they are at high cruise (aka riding the hole for BK owners) vs coaling end of the load.  ALL of this is WAY different than the FL warm day worst case scenario the EPA tests with and the stoves are designed for.

So when is this magical 0.05" WC suppose to happen and how are you suppose to maintain it without some sort of barometric control?


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## sadpanda (Dec 7, 2020)

bholler said:


> There are way to many variables to get anywhere near an accurate number.     But it is a safe bet that if you get much over 20' straight up off the stove your draft will be to strong.   More height if going through a wall.


I logged every fire for two years using a 4ch thermocouple data logger because no one believed the readings I was getting on the draft gauge, myself included.  After running the numbers, the formulas work.  If someone took the time to generate data for the resulting R value for various chimney configurations it would be a piece of cake.  This still would only put you in the average though, without barometric or some other CFM controls, we are just playing with hand grenades .


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## bholler (Dec 7, 2020)

sadpanda said:


> From what I've seen, no current EPA stove mfg is publically encouraging the use of Key dampers for fear of EPA reprecussions (that would basically be the folksy version of VW Diesel-Gate).


Nothing to do with epa standards at all.  The epa has nothing to do with it after it passes emission testing.



sadpanda said:


> What section of NFPA 211 allows for up size or down size?


I don't remember off hand and after a 10 he day working on chimneys for paying customers I am not looking it up now.  I will another time.



sadpanda said:


> Erm... "It has to be a certain distance above the surrounding structure." aka there is a minimum set by fire/building code.


That height is set by your house.  But yes I guess there is a minimum chimney height required.  That would be the thickness of your roof plus 3'   not enough to cause draft problems.



sadpanda said:


> And you are back to the issue at hand.   Draft during shoulder season for me(ambient temp 50F) vs dead winter on the coldest night (12F) is dramatically different.   Draft with the air controls open on a fresh load are dramatically different than they are at high cruise (aka riding the hole for BK owners) vs coaling end of the load.  ALL of this is WAY different than the FL warm day worst case scenario the EPA tests with and the stoves are designed for.
> 
> So when is this magical 0.05" WC suppose to happen and how are you suppose to maintain it without some sort of barometric control?


Like I said check with the manufacturer.  What I gave were very general rules.  


sadpanda said:


> I logged every fire for two years using a 4ch thermocouple data logger because no one believed the readings I was getting on the draft gauge, myself included.  After running the numbers, the formulas work.  If someone took the time to generate data for the resulting R value for various chimney configurations it would be a piece of cake.  This still would only put you in the average though, without barometric or some other CFM controls, we are just playing with hand grenades .


You are forgetting all of the variables of house pressures,  effects from topography trees etc.


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## ejsechler (Dec 7, 2020)

begreen said:


> Was this a professional install or DIY?
> 
> Have you started a thread on this topic? If not, please do. In it let us know the specifics of the install including the height of the entire flue system.


 I have a 25ft chimney. DIY install, wood is 15 to 20 percent 6" to 8"  splits have been sitting for 2 years. I start backing down the stove once the probe temp reads 375 when it hits 450 I am closing the primary air completely. Yet the stove still goes up to 1300 degrees. Probe is 20" from stove top. I have a excessive draft i did some experimenting. I covered the unregulated air hole drilled through the primary air and ramped my stove up on purpose and then completely shut her down and my stove stayed at 900 and that is with the hole covered completely. So I need a damper or just run it with a modified primary air damper. But even with  plugging it complelty I still feel like I could run a damper on top of it.


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## bholler (Dec 7, 2020)

ejsechler said:


> I have a 25ft chimney. DIY install, wood is 15 to 20 percent 6" to 8"  splits have been sitting for 2 years. I start backing down the stove once the probe temp reads 375 when it hits 450 I am closing the primary air completely. Yet the stove still goes up to 1300 degrees. Probe is 20" from stove top. I have a excessive draft i did some experimenting. I covered the unregulated air hole drilled through the primary air and ramped my stove up on purpose and then completely shut her down and my stove stayed at 900 and that is with the hole covered completely. So I need a damper or just run it with a modified primary air damper. But even with  plugging it complelty I still feel like I could run a damper on top of it.


I really prefer to limit the draft when possible over limiting the intake.   There are times both are nessecary though.


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## ejsechler (Dec 7, 2020)

bholler said:


> I really prefer to limit the draft when possible over limiting the intake.   There are times both are nessecary though.


I get it but as of now I am not able to make it to my local shop to pick one up. This is just temporary until I get up there this weekend. I honestly don't get why they put a hole in the primary air anyways. The only thing I can come up with is it is for epa bullshit so you can't smudge the fire out and it burns cleaner to keep the particulates down. Well I say screw the EPA.


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## bholler (Dec 7, 2020)

ejsechler said:


> I get it but as of now I am not able to make it to my local shop to pick one up. This is just temporary until I get up there this weekend. I honestly don't get why they put a hole in the primary air anyways. The only thing I can come up with is it is for epa bullshit so you can't smudge the fire out and it burns cleaner to keep the particulates down. Well I say screw the EPA.


Epa regulations on woodstove have given us far better stoves to use than we would have otherwise.  Yes I will readily admit there are some problems.  But generally if installed properly those problems can be overcome without much issue.   You may find partly obstructing that hole in combination with a damper may work best.


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## kennyp2339 (Dec 8, 2020)

After scanning this thread (which has some valid points by quite a number of posters) I have to say we are all forgetting a few important details, we're all on this forum, so we are all kinda like stove nerds to an extent, maybe not nerds but helicopter stove users lol, many of us strive to take advice from senior members and get ahead on wood supply so we can have dry premium fuel, a number of us have taken the time to learn about stove & chimney mechanic's and a few have become actual data collectors. 
Remember the current tests were set and based off of Oregon testing method back in the mid 80's to provide standardization for all, as technology improves so does delivery and advantage, which can open up to new unforeseen issues that were not around during initial testing. 
Back in the day if a stove was drafting harder then the minimum of .05wc not many were complaining because the stove was burning cleaner, people didnt have moisture meter available to them at a cheap price so to old bang 2 splits together to hear the ping noise was sufficient. 
Times have improved so much especially after 2010 that we all, this includes our current testing have gotten ahead of ourselves, now you have a stoves that are designed to run into the mid 70's and above efficiency at the lowest possible draft of .05wc, this is a problem for the stove designer and not the regulator, we here on this forum are seeing the higher end of this problem because many of us are actually following the rules and burning dry wood, so many are hyper sensitive. 
Now running around and blasting people for this issue isnt the right way of going about business, the baro dampers may work for some, but for a guy like me with a high efficiency cat stove with low flue temps to begin with, I know better then to try that, I need as much heat in my flue gasses as possible or I will have an issue (prob icicles clogging the cap) but maybe for someone with a reburn tube stove that can maintain 650 deg flue gases during the main fire stage of the burn, it could work for them, basically what I'm saying is that the general paint brush method of painting everything one color isnt the answer, testing individual chimney's is a good start, figuring the actual flue temps during a low, medium and high burn helps, knowing your stove and fuel source is the biggest.


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## Woody5506 (Dec 8, 2020)

After reading through this thread I think I might be a bit more grateful now for my 12' stack on my T5 which I have wondered if it was under drafting.


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## SpaceBus (Dec 8, 2020)

To prevent excessive draft you need to close the intake with rising flue temps. I start closing my Morso down when the flue reads 175 surface temp, maybe even lower if the fire has taken off. You have to ride that line between killing the fire and keeping it going.


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## Nigel459 (Dec 8, 2020)

SpaceBus said:


> To prevent excessive draft you need to close the intake with rising flue temps. I start closing my Morso down when the flue reads 175 surface temp, maybe even lower if the fire has taken off. You have to ride that line between killing the fire and keeping it going.


This is the ideal, when one _can _"ride the line" as you describe. Many modern stoves, usually with long >20' flues in cold climates, simply can't ride that line no matter how early and how much you turn them down. They just go. Nowhere close to stated burn times or efficiencies (which does seem to me to be on the mfg who is advertising said attributes) even with proper fuel and operation. Thus the decades-old discussion about what to do about it. 

It does seem curious to me that there hasn't been any standardization or requirement to measure draft, especially when some excessive draft conditions can be downright dangerous, as reported on these forums many times...


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## SpaceBus (Dec 8, 2020)

Nigel459 said:


> This is the ideal, when one _can _"ride the line" as you describe. Many modern stoves, usually with long >20' flues in cold climates, simply can't ride that line no matter how early and how much you turn them down. They just go. Nowhere close to stated burn times or efficiencies (which does seem to me to be on the mfg who is advertising said attributes) even with proper fuel and operation. Thus the decades-old discussion about what to do about it.
> 
> It does seem curious to me that there hasn't been any standardization or requirement to measure draft, especially when some excessive draft conditions can be downright dangerous, as reported on these forums many times...



I also have an oversized chimney, lots of 90's in the flue, and single wall which probably helps me tame the draft. When I update the square liner with insulated 6" I might change my opinion and get a key damper. My cookstove has few bends and sometimes I have to control the output with fuel load rather than control the draft. Since the cooker doesn't need to have long burn times this doesn't really affect anything, but on the primary heater it could.


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## sadpanda (Dec 8, 2020)

From the barometric damper thread



bholler said:


> As far as measuring draft you would have to check with the manufacturer but it can be pretty much anywhere in the stove or connector pipe. And it is typically measured at high operating temp with full air.



My draft during these conditions easily exceeds 2.0" and turns my stove into a runaway forge, sucking flames well into the stove pipe.

The BK manual states minimum flue height of 15ft.  Lets assume flue pipe matches appliance collar as per normal recommendations.  Using calculations at hand ( I made an excel doc for everyone to scrutinize/play with : FlueCalc  ) , the only way to achieve this magic number is with 70F ambient temp and an average flue temp of 230F resulting in a calculated 140 CFM.  With that low of an average temp, this seems to match the EPA's  very 'lossy' worst case scenario installation, aka class A pipe outside the structure.  If you drop ambient temp down to freezing you get 0.06" @ 162 CFM and if you go to 0F you get 0.08" @ 181 CFM.  Furthermore if you reset ambient back to 70 but bump the average temp to what I was observing last year (400F,  average of flue temp vs cap temp over duration of entire burn cycle)  you get  *0.083" and 202 CFM*.

 Draft varies significantly with ambient temperature and wildly depending on stove operating mode ( when my BK reaches set point via thermostat and is 'riding the hole' my draft goes up 0.04"+).  Back to 'ideal' scenario (70F/230F), adding 10ft of chimney also gets us up to 0.083" but *only 181 CFM*.

Assuming my maths are correct (anyone please verify), CFM rather than draft is what we should be concerned with.  A key damper does reduce CFM via restriction however, it seems the most direct way to control CFM is via average flue temp.

Enter the heat reclaimer...  If you had heat reclaimer, draft controlled and thermostatically controlled via thermocouple at the chimney cap (not allowing cap temp to fall below 250F), that would satisfy your 'no diluted exhaust' argument against barometric controls yes?

Back to barometric dampers, so what if a damper is admitting cold air into the exhaust?  If the cap temp never falls below 250F it should not matter.

There is of course another option; snorkeling the stove inlet:  Air tight OAK with a vertical extension on the pipe, effectively shortening the stack.  The BK manual says 'do not route this any where' however in reality this is no different than having a stove in a basement IMHO.


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## bholler (Dec 8, 2020)

sadpanda said:


> From the barometric damper thread
> 
> 
> 
> ...


You can calculate all you want but those calculations don't mean a thing quite honestly.  Like I said before there are way to many variables involved.

If you are maintaining the same flue gas temps with the heatreclaimer how would it reduce draft other than from the physical obstruction?

*If you can't understand the potential dangers of an air intake elevated above the stove and the difference between that and a stove in the basement you have allot to learn.  *


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## BKVP (Dec 8, 2020)

Highbeam said:


> What do the epa’s ever tightening regulations have to do with my catalyst only lasting 2 seasons?They’ve only been rated to last 12,000 hours for decades.


It should always be kept in mind the certain online retailers of catalytic combustors suggest replacing them at 12,000 hours.  My local tire shop told me I should replace my Toyo $800 each tires every 20,000 miles.  I have no idea why they would suggest that!


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## BKVP (Dec 8, 2020)

bholler said:


> You are a little confused about what is allowed and what isn't and who determines that.
> 
> The epa only sets emissions standards.  They have absolutely no input at all in the design installation operation etc of stoves.
> 
> ...


Not exactly accurate.  EPA's NSPS specifically makes certain acts illegal.  Installations that can alter low burn rates are illegal.  Installing a solid fuel heater inconsistent with the Owners & Operator manual is also a Federal violation.  They do in fact regulate particulates, but there is much, much more they regulate.  If you need more let me know...the rule sits on my desk.


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## BKVP (Dec 8, 2020)

And, it really should be noted the EPA can delegate the authority to other agencies.  That did not exist prior to 2015.  Lest your neighbor complains about excessive smoke and you have a local authority schedule a visit to review your installation.


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## bholler (Dec 8, 2020)

BKVP said:


> Not exactly accurate.  EPA's NSPS specifically makes certain acts illegal.  Installations that can alter low burn rates are illegal.  Installing a solid fuel heater inconsistent with the Owners & Operator manual is also a Federal violation.  They do in fact regulate particulates, but there is much, much more they regulate.  If you need more let me know...the rule sits on my desk.


Fair enough I didn't know that.  But wouldn't installing a stove that is not withing draft specifications therefore be illegal as well?  By installing a damper I am making it conform to those specifications.    I completely agree modifying the stove should be against regulations.  But modifying the vent with products approved for that venting system in order to meet draft specifications should not be a violation.  But I could be completely wrong there.


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## begreen (Dec 8, 2020)

Woody5506 said:


> After reading through this thread I think I might be a bit more grateful now for my 12' stack on my T5 which I have wondered if it was under drafting.


The T5 breathes pretty easily. So do several SBI and some Regency models. This is a function of the stove design, not an externally applied regulation.

It should also be noted that Drolet and some others specifically allow downsizing in their documentation when the flue height exceeds 25 ft. The whole thought that a key damper or downsizing the flue to reduce draft in a high draft installation is a bit silly. It would knock the use of some draft-fussy cat and downdraft stoves right off the market.  A stove with a max .06" draft requirement probably couldn't be installed on a 25-30' flue without some sort of draft reduction. Yet we see them here regularly. It is this wink wink nod nod relationship that I think sadpanda is calling out. He has some facts wrong, but this grey area is real and stove mfgs. dance around it by telling owners to call in a sweep or their tech support if draft is excessive.


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## Highbeam (Dec 8, 2020)

BKVP said:


> It should always be kept in mind the certain online retailers of catalytic combustors suggest replacing them at 12,000 hours.  My local tire shop told me I should replace my Toyo $800 each tires every 20,000 miles.  I have no idea why they would suggest that!



If the Toyo tires are bald and worthless at 20,000 miles every dang time then you might get an idea why they would suggest that. If nobody made a longer lasting tire (cat) you can budget and plan for new tires(cats) at 20,000 mile intervals. Wouldn't it be exceedingly wrong of TOYO to rate/warranty their tire in terms of "years"? Some users drive 100,000 miles per year!

Not certain online retailers, the actual manufacturers rate these cats for 12,000 hours. That and repeated forum members sharing real life experience. I'm willing to go along with your usual argument that we use our stoves more than the general public though, 12000 hours might take 20 years for an average wood stove user.

Please please invent a longer lasting catalyst. These things really work well until they wear out.

On Edit: Yikes, Applied Ceramics writes that we can only expect to squeeze 10,000 hours out of a catalyst and should replace at 6 year intervals. http://firecatcombustors.blogspot.com/


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## SpaceBus (Dec 8, 2020)

BKVP said:


> It should always be kept in mind the certain online retailers of catalytic combustors suggest replacing them at 12,000 hours.  My local tire shop told me I should replace my Toyo $800 each tires every 20,000 miles.  I have no idea why they would suggest that!


To be fair most expensive tires generally don't last past 20,000 miles, but that is due to being made from high performance compounds that just don't last long.


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## BKVP (Dec 8, 2020)

kennyp2339 said:


> After scanning this thread (which has some valid points by quite a number of posters) I have to say we are all forgetting a few important details, we're all on this forum, so we are all kinda like stove nerds to an extent, maybe not nerds but helicopter stove users lol, many of us strive to take advice from senior members and get ahead on wood supply so we can have dry premium fuel, a number of us have taken the time to learn about stove & chimney mechanic's and a few have become actual data collectors.
> Remember the current tests were set and based off of Oregon testing method back in the mid 80's to provide standardization for all, as technology improves so does delivery and advantage, which can open up to new unforeseen issues that were not around during initial testing.
> Back in the day if a stove was drafting harder then the minimum of .05wc not many were complaining because the stove was burning cleaner, people didnt have moisture meter available to them at a cheap price so to old bang 2 splits together to hear the ping noise was sufficient.
> Times have improved so much especially after 2010 that we all, this includes our current testing have gotten ahead of ourselves, now you have a stoves that are designed to run into the mid 70's and above efficiency at the lowest possible draft of .05wc, this is a problem for the stove designer and not the regulator, we here on this forum are seeing the higher end of this problem because many of us are actually following the rules and burning dry wood, so many are hyper sensitive.
> Now running around and blasting people for this issue isnt the right way of going about business, the baro dampers may work for some, but for a guy like me with a high efficiency cat stove with low flue temps to begin with, I know better then to try that, I need as much heat in my flue gasses as possible or I will have an issue (prob icicles clogging the cap) but maybe for someone with a reburn tube stove that can maintain 650 deg flue gases during the main fire stage of the burn, it could work for them, basically what I'm saying is that the general paint brush method of painting everything one color isnt the answer, testing individual chimney's is a good start, figuring the actual flue temps during a low, medium and high burn helps, knowing your stove and fuel source is the biggest.



Remember, in the method and in a lab we can control stack velocity.  Our gases/emissions are dumped into a hood and do not exit in the manner a home installation occurs.


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## BKVP (Dec 8, 2020)

bholler said:


> Fair enough I didn't know that.  But wouldn't installing a stove that is not withing draft specifications therefore be illegal as well?  By installing a damper I am making it conform to those specifications.    I completely agree modifying the stove should be against regulations.  But modifying the vent with products approved for that venting system in order to meet draft specifications should not be a violation.  But I could be completely wrong there.



You know, a couple of years ago a certain agency began calling hearth retailers to ask them how often they used dampers in their installations.  You are very familiar with single burn rate stoves that have become more common since 2015.  Well, they are not allowed to have any control mechanism to alter that single burn rate.  The use of a damper in the flue can alter the burn rate.

The keys words are "as tested".  No manufacturer to my knowledge tests with a flue damper....because it's not permitted in the dilution tunnel configuration.  And if isn't used that way to test.....default to the first sentence.

You are VERY correct about the calculations/numbers not meaning much.  The reason, variability.  That will be my new buzz word for 2021!


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## BKVP (Dec 8, 2020)

begreen said:


> The T5 breathes pretty easily. So do several SBI and some Regency models. This is a function of the stove design, not an externally applied regulation.
> 
> It should also be noted that Drolet and some others specifically allow downsizing in their documentation when the flue height exceeds 25 ft. The whole thought that a key damper or downsizing the flue to reduce draft in a high draft installation is a bit silly. It would knock the use of some draft-fussy cat and downdraft stoves right off the market.  A stove with a max .06" draft requirement probably couldn't be installed on a 25-30' flue without some sort of draft reduction. Yet we see them here regularly. It is this wink wink nod nod relationship that I think sadpanda is calling out. He has some facts wrong, but this grey area is real and stove mfgs. dance around it by telling owners to call in a sweep or their tech support if draft is excessive.


Not all manufacturers.  We often here of stacks greater than 30' that we suggest they look at other options.  When you have folks unwilling to run a liner "My clay liner has worked for over 40 years with my XXXX model"...  Keep in mind that as of 2015, Owners & Operator Manuals have become Federally regulated documents.  They are part of the certification process and must cover operational and installation specifications.  So while some may wink wink nod nod, not here!


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## BKVP (Dec 8, 2020)

SpaceBus said:


> To be fair most expensive tires generally don't last past 20,000 miles, but that is due to being made from high performance compounds that just don't last long.


It has nothing to do with the 3,000 lbs of wood in the back being driven over course gravel roads.  Or driving to Missoula or Helena at 90 mph and having a state trooper pass you!


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## bholler (Dec 8, 2020)

BKVP said:


> You know, a couple of years ago a certain agency began calling hearth retailers to ask them how often they used dampers in their installations.  You are very familiar with single burn rate stoves that have become more common since 2015.  Well, they are not allowed to have any control mechanism to alter that single burn rate.  The use of a damper in the flue can alter the burn rate.
> 
> The keys words are "as tested".  No manufacturer to my knowledge tests with a flue damper....because it's not permitted in the dilution tunnel configuration.  And if isn't used that way to test.....default to the first sentence.
> 
> You are VERY correct about the calculations/numbers not meaning much.  The reason, variability.  That will be my new buzz word for 2021!


Yes but no stoves are installed on a venting system like the one used in testing.


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## BKVP (Dec 8, 2020)

bholler said:


> Yes but no stoves are installed on a venting system like the one used in testing.


You are absolutely correct! From the post a few above.."Remember, in the method and in a lab we can control stack velocity. Our gases/emissions are dumped into a hood and do not exit in the manner a home installation occurs."


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## bholler (Dec 8, 2020)

BKVP said:


> You are absolutely correct! From the post a few above.."Remember, in the method and in a lab we can control stack velocity. Our gases/emissions are dumped into a hood and do not exit in the manner a home installation occurs."


I know that.  So if we are not installing on the vent system as tested why can't we manipulate the vent system within the guidelines of code and the vents listing to meet the draft requirements?


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## begreen (Dec 8, 2020)

BKVP said:


> Not all manufacturers.  We often here of stacks greater than 30' that we suggest they look at other options.  When you have folks unwilling to run a liner "My clay liner has worked for over 40 years with my XXXX model"...  Keep in mind that as of 2015, Owners & Operator Manuals have become Federally regulated documents.  They are part of the certification process and must cover operational and installation specifications.  So while some may wink wink nod nod, not here!


It's what's not being said in manuals that counts. Should stoves never be installed on a venting system where the draft exceeds the manual's specified upper limit, in spite of practical means to reduce draft?


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## BKVP (Dec 8, 2020)

I can't obviously speak for others.  However, we state desired draft measurements.  We state minimum chimney lengths. In real world applications we know certain designs can address excessive draft better than others. The same holds true for inadequate draft as well.  I'll review our manuals with this in mind.


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## Crocks (Dec 8, 2020)

My 1997 Opel 2000 was a joke before I removed the "epa screw" in the draft control that kept the plate held open atleast 3/16" I now run a 28 guage shim  ......


I call it a epa screw because it seems like a poor way to pass a emissions standard. Sure it will burn clean if you have no way to control the burn


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## Crocks (Dec 8, 2020)

I should probably add I have about a 15' stove pipe. Straight shot to the cap.  8" diameter


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## bholler (Dec 8, 2020)

Crocks said:


> I should probably add I have about a 15' stove pipe. Straight shot to the cap.  8" diameter


I have never heard of an opel 2000.  What temps was it running at before you modified it?


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## Crocks (Dec 8, 2020)

It is basically the same stove as a opel 2 from my understanding.
I never ran a guage on the top of stove before I modified my intake. I can say before the modification,  when I  closed the stove down(typically very early, trying to extend the burn)  it would climb temp for about 1 hr then start declining. I would usually only get about 3-4 hrs of usable heat.  I also almost never fully loaded the box because I was scared it was over firing . The stove would almost never have coals left in the morning and I felt like all my heat was blasting out the stack.


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## sadpanda (Dec 9, 2020)

TL;DR

Getting additional draft is easy: add more pipe.  Reducing draft is wrought with compromise and with current restrictions is _*technically *_impossible. The overdraft problem is virtually universal; even with a flat roof, any two story house will have a stack taller then mfg recommendations. This is illogical, poses eminent danger and should be rectified with extreme prudence




bholler said:


> You can calculate all you want but those calculations don't mean a thing quite honestly. Like I said before there are way to many variables involved.
> 
> If you are maintaining the same flue gas temps with the heatreclaimer how would it reduce draft other than from the physical obstruction?
> 
> *If you can't understand the potential dangers of an air intake elevated above the stove and the difference between that and a stove in the basement you have allot to learn. *


As we are typing at each other with no verbal/facial cues, I will assume you are not being snarky and just scanning / reading quickly...  So I will elaborate.

The calculations DO mean something, maybe not in your world but in theory and in practice for other professions.   A heat reclaimer by definition reduces flue temp.  I'm proposing a heat reclaimer with enhanced controls that does not allow excessive cooling.

A device like this is not currently made in the US as far as I know but could easily be diy...  I'm thinking it would include a bypass damper and variable control fan.  Once the fire was established, reclaimer bypass would be closed and flu gases would be redirected through tubes similar to boilers/current reclaimers.  A continuously variable digitally controlled fan would use a thermocouple probe inserted near the chimney cap to ensure the flue exit temps do not drop below critical level.  Depending on the thermal efficiency, it may be necessary to also track inlet temp or draft itself to ensure the total system draft is maintained through the entire burn cycle.

Regarding the potential pitfalls of an elevated air intake, please elaborate.  I'm pretty sure I've got a firm grasp of all potential pitfalls, however I actually enjoy learning and encourage critiques so please, I'm all ears.




SpaceBus said:


> To be fair most expensive tires generally don't last past 20,000 miles, but that is due to being made from high performance compounds that just don't last long.


HA!   Thats nothing!    I'm happy if I get 20k miles on my brakes!   Brake late, brake hard.   I'm roughly 1:1 brake/tire changes right now.



BKVP said:


> Remember, in the method and in a lab we can control stack velocity. Our gases/emissions are dumped into a hood and do not exit in the manner a home installation occurs.


So EPA emissions and fuel economy testing is at least designed to mimic real life end user conditions.... It's GREAT to hear that the big brain regulators throw that logic out of the window when trying to regulate on of MANS OLDEST TECHNOLOGIES.

How many burning hours/cords per year are used in zones <4 vs zones 4 and above?   At least 3/4 of the country is in climate zone 4 or higher, which I wager is where most wood burning occurs and where wood burning most dramatically effects air quality.   EPA does not test emissions of vehicles at full throttle/max RPM, they test where the car spends 99% of its life: startup, idle, part throttle acceleration and freeway cruise.  If 99% of the burning is done at 32F ambient and flues have virtually no maximum height but do have a hard minimum height, what cat brained bureaucrat decided testing in the current manner was a good idea?  If I put on my tin foil hat, the only explanation that makes sense is the EPA is purposefully trying to put us in an impossible situation so we stop burning wood all together.



BKVP said:


> Well, they are not allowed to have any control mechanism to alter that single burn rate. The use of a damper in the flue can alter the burn rate.
> 
> The keys words are "as tested". No manufacturer to my knowledge tests with a flue damper....because it's not permitted in the dilution tunnel configuration. And if isn't used that way to test.....default to the first sentence.
> 
> You are VERY correct about the calculations/numbers not meaning much. The reason, variability. That will be my new buzz word for 2021!


OK....   I have a few thoughts on this. 

Commercial boiler/power generation/gas residential appliances ALL have to cope with the same variables and have controls in place to regulate them; designed and integrated based on CALCULATIONS
if all responsibilities fall on the mfg for allowing installation configurations, there should be more guidance
if that responsibility is shoved down to sweeps/installers, where is their training/guidelines/certifications?  Why are they not held to the same standards that all other contractors are held to ie calculations, not guess and check
if calculations are useless, how did you @BKVP  arrive at thechimney height recommendations for various elevations?  SWAG?  Seems you are at least doing some basic air density adjustments
draft, stack velocity, thermo dynamics are not PFM...   The fundamentals are very basic, and we have this new thing called Computational Fluid Dynamics.  If we can correctly model/predict/design the thermal transfer of a heat sink, the airflow around a body in motion, the way atomized fuel droplets bounce off of a piston or the thermal losses through a complex building envelop comprised of many varying materials and assemblies... we can CERTAINLY generate some common flue models and establish some standards.



BKVP said:


> I can't obviously speak for others. However, we state desired draft measurements. We state minimum chimney lengths. In real world applications we know certain designs can address excessive draft better than others. The same holds true for inadequate draft as well. I'll review our manuals with this in mind.
> 
> By the way, stick a coupon good for a $100 bill in 50 random manuals. Insert those manuals along with 950 others into stoves coming off the line. Put an expiration date of 12/31/2020 on them. You won't wind up paying more than $1500. Sad.....but as pointed out earlier in another post and many times before.....this family is unique amongst wood burners.



If mfgs put $100 bills in manuals, I would be a very wealthy man!   Speaking of manuals

My old PI1010A manual does in fact state 0.05" WC operating on high and 0.06"  as unsafe...  That's a very, very tight band. 
- - - - HOWEVER - - - -

NONE of the current manuals that I checked have any draft specification (I looked at 5, I'll keep my eye on the mailbox for that $500 check ), though .'...maintain draft to manufactured specifications' is sited in combustor troubleshooting and sections 'DRAFTS' and 'CHIMNEY DRAFTS' sections are referenced but are MIA.  The only exception I found was PI29 manual where the 'Combustor Troubleshooting' does at least mention 'do not exceed 0.06"WC'


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## SpaceBus (Dec 9, 2020)

sadpanda said:


> HA!   Thats nothing!    I'm happy if I get 20k miles on my brakes!   Brake late, brake hard.   I'm roughly 1:1 brake/tire changes right now.



Are you daily driving on your race brakes? Even with super aggressive autocross compounds I get pretty long life out of my brakes, usually outlasting two sets of 200tw tires. I'm driving a giant truck now, so no more race car stuff for a while.


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## sadpanda (Dec 9, 2020)

SpaceBus said:


> Are you daily driving on your race brakes? Even with super aggressive autocross compounds I get pretty long life out of my brakes, usually outlasting two sets of 200tw tires. I'm driving a giant truck now, so no more race car stuff for a while.



I did for a summer because I liked them so much and the dust trashed my wheels   I'm back on OE brembos for the winter.   Despite being in ohio, I live in the sticks and happen to have a few good roads and a very early commute so I take full advantage every day.  My current daily should be getting 31mpg+   My total average is 17.


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## BKVP (Dec 9, 2020)

The point I was trying to make is not all buyers of wood stoves read the manuals and of those that do most discard the technical suggestions.

Sit at my desk for a day and you'll see it!


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## john26 (Dec 9, 2020)

I like sadpandas thought of controlling draft  but I don't think a heat reclaimer would be practical even though it may help some.  I think a more logically solution would be some sort of permeant installed manometer  built into the chimney system then a manual adjustment draft limiting damper built in the stove top.  Yes it would rely on the user to be be educated on its use and use it properly, but every stove user should do that anyway.  Most people who are not using their stoves in properly are running out of date smoke dragons are just bought a house with an existing install many wind up here any way to be educated.   A thermocouple mounted in the chimney to open and close an automated damper similar to a barometric may work but would also need to  take a chimney draft measurement into account.  At that point it would only regulate when the chimney is  above 250F.  A built in draft regulator on the stove top would be the most practical and aesthetically pleasing but in all reality its would be nothing more than a key damper.


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## begreen (Dec 9, 2020)

Installers should be required to read the manuals. The installation documentation should include maximum flue height as well as the minimums when the max is known to be an issue for the stove or insert. We get several cases of too strong draft a week where the documentation is zero help or passes the buck by saying something like consult your dealer or a chimney sweep.


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## begreen (Dec 9, 2020)

A basic heat reclaimer can reduce draft, at the expense of dramatically increasing creosote accumulation. They are also butt ugly and noisy. The reclaimer that sadpanda describes is not too far from what MF Fire was testing, but with the upper thermocouple in the room IIRC. It's a costly setup.


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## Nate R (Dec 9, 2020)

sadpanda said:


> Using calculations at hand ( I made an excel doc for everyone to scrutinize/play with : FlueCalc ) , the only way to achieve this magic number is with 70F ambient temp and an average flue temp of 230F resulting in a calculated 140 CFM. With that low of an average temp, this seems to match the EPA's very 'lossy' worst case scenario installation, aka class A pipe outside the structure. If you drop ambient temp down to freezing you get 0.06" @ 162 CFM and if you go to 0F you get 0.08" @ 181 CFM. Furthermore if you reset ambient back to 70 but bump the average temp to what I was observing last year (400F, average of flue temp vs cap temp over duration of entire burn cycle) you get *0.083" and 202 CFM*.



The CFM #s here don't make sense in relation to wood stoves.  From my glance at your fluecalc sheet, I suspect the stack effect CFM calcs would apply in an open room, but don't account for intake air restriction. So, maybe these CFM numbers are accurate for an open fireplace, but I don't think they apply to a modern wood stove. 

Example: I entered these numbers: 6 inch flue, 70 deg ambient temp, 15 ft chimney, and 500F flue temp. Your calculator says that should result in 230 CFM of flow.

OK, let's check this another way. To get 230 CFM of air to go from 70 degrees to 500, you'd need nearly 107,000 BTU an hour JUST to heat the air going up the flue...not even looking at the btus going into the room! Modern wood stoves aren't delivering more heat up the flue than they are to the room. I don't think we're burning 12+ lbs of wood an hour JUST to heat the flue air.     
  (see https://www.heatco.com/btu-calculator/#   )

EPA test reports for wood stoves sometimes contain flue CFM measurements. They sometimes also contain a drawing/sketch/description of the flue setup used.  Jotul has theirs online here: https://www.jotul.com/epa-certifications
The 2001 F100 test report showed only 5-11 CFM average stack flows during their test burns, into a 14 foot chimney. (Looks like they measured it as well as calculated it from a mass-balance standpoint). 

My point is, the calcuations don't seem to make sense in this case, and we can sometimes see what tested drafts and flue flows are if you look at the EPA Cert Reports.


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## Nate R (Dec 9, 2020)

I should add that I get the OP's points, and I think there's definitely some valid ones there in how things are looked at in this realm. Not knocking that, but I'm maybe at a different....order of magnitude than the OP in how I think about this.


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## bholler (Dec 9, 2020)

sadpanda said:


> The calculations DO mean something, maybe not in your world but in theory and in practice for other professions.



I am not bring snarky at all.  I am simply telling you  that your calculations don't take into account many many variables we deal with every day in the field that can drastically effect the actual measured draft.   I would love it if there was a simple formula that could tell us accurately what the draft in a given chimney will be.  But there simply is not.


sadpanda said:


> A heat reclaimer by definition reduces flue temp. I'm proposing a heat reclaimer with enhanced controls that does not allow excessive cooling.


I know what you are saying.  And if an appliances output temp was high enough  it may work.  But most modern stoves do not have high enough output temps to be able to pull extra heat off of the stack and stay above the condensation point.  You are also talking about adding a massive amount of electronics to woodstoves when a simple manually controlled key damper almost always works perfectly fine.


sadpanda said:


> Regarding the potential pitfalls of an elevated air intake, please elaborate. I'm pretty sure I've got a firm grasp of all potential pitfalls, however I actually enjoy learning and encourage critiques so please, I'm all ears.


An elevated air intake can and has acted as a second chimney sucking flue gasses out of the stove through  the intake pipe causing a fire.

This is no longer allowed because of problems that arose which is how many codes come about.


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## Highbeam (Dec 9, 2020)

Heat reclaimers above a modern wood burner work very well in the wood furnace world. They call them heat exchangers but the exhaust from the firebox is routed through a back and forth series of small pipes within a blower box prior to leaving the appliance. Often, these things run output flue temperatures below 200 as measured with a flue probe! Minimal electronics prevent overcooling the exhaust, rather, they measure plenum temperatures and vary the blower speed. 

Above a woodstove designed to strip as much heat as possible from the flue gasses to be efficient, I would not add a heat reclaimer.


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## sadpanda (Dec 9, 2020)

begreen said:


> A basic heat reclaimer can reduce draft, at the expense of dramatically increasing creosote accumulation. They are also butt ugly and noisy. The reclaimer that sadpanda describes is not too far from what MF Fire was testing, but with the upper thermocouple in the room IIRC. It's a costly setup.




I'm for any and ALL possible solutions...

The best most fool proof solution is the one with zero user intervention.  Honestly given the 'variability' monster, every tool available should be fair game if the system is calibrated and validated.

Step 1 should be a simple draft evaluation, pipe diameter should be specified based on this calc.   If that means 4in pipe on a 6in collar, so be it.

Step 2 stoves should have a barometric control to adjust for seasonal / burn cycle variance.  A simple mechanical bimetallic spring can disable it if flue temps are too low and air can be pulled from the back side/top of the stove so its pre-heated.

Key damper and the rest should be available but avoided...  How many times have you/wifey/spawn/newb forgotten to open the key damper(s?) before opening the door?

re: creosote forming on reclaimers... So what?  If we are using dry wood, there should be no creosote and if we turn the stove down too far, the magic EPA honeycomb thingy is there to burn all the bad stuff away right? so again no problem.  Even still, if creosote is likely to form anywhere it will be in the reclaimer tubes... Which normally have scrapers etc.  If the reclaimer is emptied every load, whats the issue?  What about building the reclaimer function into the stove?  Aside from trying to simultaneously burn all of the hydrocarbons AND shoot them out the cap before they can condense, we don't need 600F air in the flue to generate sufficient draft (according to meaningless maths), so why not send it through some more steel/surface area and cool it off?

re: snorkeling the intake...  I'm still waiting for the list perils and certain death


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## sadpanda (Dec 9, 2020)

Highbeam said:


> Heat reclaimers above a modern wood burner work very well in the wood furnace world. They call them heat exchangers but the exhaust from the firebox is routed through a back and forth series of small pipes within a blower box prior to leaving the appliance. Often, these things run output flue temperatures below 200 as measured with a flue probe! Minimal electronics prevent overcooling the exhaust, rather, they measure plenum temperatures and vary the blower speed.
> 
> Above a woodstove designed to strip as much heat as possible from the flue gasses to be efficient, I would not add a heat reclaimer.


You posted while I was tapping on a phone.

But they are illegal yes?


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## bholler (Dec 9, 2020)

sadpanda said:


> I'm for any and ALL possible solutions...
> 
> The best most fool proof solution is the one with zero user intervention.  Honestly given the 'variability' monster, every tool available should be fair game if the system is calibrated and validated.
> 
> ...


Do you really think dry wood means no creosote can accumulate???

And I told you exactly why you can't "snorkel " the air intake


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## bholler (Dec 9, 2020)

sadpanda said:


> You posted while I was tapping on a phone.
> 
> But they are illegal yes?


They are not allowed to be used on a ul listed appliance as it should be they are horrible creosote making devices.


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## john26 (Dec 9, 2020)

sadpanda said:


> Key damper and the rest should be available but avoided... How many times have you/wifey/spawn/newb forgotten to open the key damper(s?) before opening the door?


Not much different than a cat bypass or bypass that Lopi uses


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## bholler (Dec 9, 2020)

sadpanda said:


> I'm for any and ALL possible solutions...
> 
> The best most fool proof solution is the one with zero user intervention.  Honestly given the 'variability' monster, every tool available should be fair game if the system is calibrated and validated.
> 
> ...


A 4" pipe on a 6" stove will not have enough volume on startup and will smoke back into the house.  Draft measurement is only one part of the equation.  You also have to have the correct volume.  

Why should key dampers be avoided???   If you are using it to bring draft into spec you would not have smoke spillage at all when you open the door.

Also the "magic EPA honeycomb thing"  only works. 
1 if there is one which many stoves don't have one.  
2 if there is enough temp to keep that cat active.


----------



## sadpanda (Dec 9, 2020)

bholler said:


> I am not bring snarky at all.  I am simply telling you  that your calculations don't take into account many many variables we deal with every day in the field that can drastically effect the actual measured draft.   I would love it if there was a simple formula that could tell us accurately what the draft in a given chimney will be.  But there simply is not.
> 
> I know what you are saying.  And if an appliances output temp was high enough  it may work.  But most modern stoves do not have high enough output temps to be able to pull extra heat off of the stack and stay above the condensation point.  You are also talking about adding a massive amount of electronics to woodstoves when a simple manually controlled key damper almost always works perfectly fine.
> 
> ...


Ah there it is. Again I'm behind the posts.  Secondary chimney yes.

If only there was a way to figure out the likelyhood of this happening...  Perhaps something with numbers.

Without significant intervention, my flue will happily pull 1.5" with the stove turned down and peg my gauge at 2.5"+ and spike 2000F flue temps if I followed @BKVP reload instructions and opened the taps on a fresh reload.

Using my basic math, assuming the intake is in fact routed outside, even something silly like a 15ft pipe would only pull .02" @25 cfm.   That's obviously not factoring 'variables' like wind shear but it illustrates my point... Just like adding an evil key damper or heat exchanger, its not instant death.  Its all against the law anyway


----------



## bholler (Dec 9, 2020)

sadpanda said:


> Ah there it is. Again I'm behind the posts.  Secondary chimney yes.
> 
> If only there was a way to figure out the likelyhood of this happening...  Perhaps something with numbers.
> 
> ...


Ok you can run what ever numbers you want but the fact is that it is not allowed because doing so has caused to many house fires and they determined it was unsafe.

Again your numbers don't take into account the thousands of variables that go into this.  And actual real world experience tells us elevating the air intake carries to much risk.

So only things that cause instant death every time should be against code?  What about possible death say 50% of the time?  10%?  5%? 1%? 

I know as a professional if one of my installs cause a death I couldn't live with myself.  Even without death the loss of a house is not something I am willing to risk for my customers.


----------



## BKVP (Dec 9, 2020)

sadpanda said:


> You posted while I was tapping on a phone.
> 
> But they are illegal yes?



Good question.  Around 8 years ago a state regulator was complaining to me and an EPA staff person about the amount of smoke that was coming from the outdoor wood heater (OWH) next to their home.  The state regulator said he had spoke with his neighbor about the problem.  The owner of the OWH said "Pound sand, this is exempt!"  Fast forward to 2015's new rule.  First, EPA can now delegate the authority of enforcement to state and local authorities.  Check that box!  Second, the 2015 does not have any exempt products.  Before any of you say what about cook stoves or masonry heaters or blah, blah, blah, each of those products is now defined within the rule.  Prior rules did not define what constituted a wood burning fireplace etc.

Now the rule also states it is illegal to install or operate a covered product (not products with set max emissions levels) but covered (meaning mentioned in the rule) other than as tested or described in the Owners & Operators Manual.  So you can take that for what you want.

Heat reclaimers and there are many types on the market still to this day, played a role in the past or with inefficient wood burning products. However, most wood heaters being manufactured today are vastly cleaner and vastly more efficient.  Speaking strictly for our company, we do not endorse their use on our products.


----------



## BKVP (Dec 9, 2020)

bholler said:


> A 4" pipe on a 6" stove will not have enough volume on startup and will smoke back into the house.  Draft measurement is only one part of the equation.  You also have to have the correct volume.
> 
> Why should key dampers be avoided???   If you are using it to bring draft into spec you would not have smoke spillage at all when you open the door.
> 
> ...


Not temp...gases.


----------



## bholler (Dec 9, 2020)

BKVP said:


> Not temp...gases.


But it needs heat as well doesn't it?  I know if I turn mine down to low there are still plenty of gasses but the cat stalls.


----------



## SpaceBus (Dec 9, 2020)

begreen said:


> A basic heat reclaimer can reduce draft, at the expense of dramatically increasing creosote accumulation. They are also butt ugly and noisy. The reclaimer that sadpanda describes is not too far from what MF Fire was testing, but with the upper thermocouple in the room IIRC. It's a costly setup.



Did MF Fire bring a product to market? I thought they were the ones building the boxy SBR stoves.


----------



## SpaceBus (Dec 9, 2020)

BKVP said:


> Good question.  Around 8 years ago a state regulator was complaining to me and an EPA staff person about the amount of smoke that was coming from the outdoor wood heater (OWH) next to their home.  The state regulator said he had spoke with his neighbor about the problem.  The owner of the OWH said "Pound sand, this is exempt!"  Fast forward to 2015's new rule.  First, EPA can now delegate the authority of enforcement to state and local authorities.  Check that box!  Second, the 2015 does not have any exempt products.  Before any of you say what about cook stoves or masonry heaters or blah, blah, blah, each of those products is now defined within the rule.  Prior rules did not define what constituted a wood burning fireplace etc.
> 
> Now the rule also states it is illegal to install or operate a covered product (not products with set max emissions levels) but covered (meaning mentioned in the rule) other than as tested or described in the Owners & Operators Manual.  So you can take that for what you want.
> 
> Heat reclaimers and there are many types on the market still to this day, played a role in the past or with inefficient wood burning products. However, most wood heaters being manufactured today are vastly cleaner and vastly more efficient.  Speaking strictly for our company, we do not endorse their use on our products.




Will site built masonry "stoves" be regulated moving forward? Seems like a relatively miniscule market to watch. It also sound like you are saying there will be regulation on wood cookstoves as well. I haven't read any of the legislation so I've been under the impression that cookers and masonry heaters/stoves were indeed unregulated.


----------



## begreen (Dec 9, 2020)

SpaceBus said:


> Did MF Fire bring a product to market? I thought they were the ones building the boxy SBR stoves.


Yes, but it is different from the test model they demonstrated at the Green Heat decathlon several years ago in DC. They have a couple of stoves out, the Catalyst and the Nova. The Catalyst is what evolved from the contest. It has 3 thermocouples feeding a processor. They measure stove temp, cat temp and room temp. It has a combustion fan governed by a smart controller, that apparently regulates the air supply too. Cat engagement appears to be manual. The Nova is a single burn-rate stove. We've only seen a couple reports from owners so far, but they have been favorable.


----------



## SpaceBus (Dec 9, 2020)

begreen said:


> Yes, but it is different from the test model they demonstrated at the Green Heat decathlon several years ago in DC. They have a couple of stoves out, the Catalyst and the Nova. The Catalyst is what evolved from the contest. It has 3 thermocouples feeding a processor. They measure stove temp, cat temp and room temp. It has a combustion fan governed by a smart controller, that apparently regulates the air supply too. Cat engagement appears to be manual. The Nova is a single burn-rate stove. We've only seen a couple reports from owners so far, but they have been favorable.


It really sounds like a pretty good system. It's a shame they had to put the tech in such a homely package.


----------



## begreen (Dec 9, 2020)

SpaceBus said:


> It really sounds like a pretty good system. It's a shame they had to put the tech in such a homely package.


Yes, they did a lot better with the Nova on the looks end.


----------



## SpaceBus (Dec 9, 2020)

begreen said:


> Yes, they did a lot better with the Nova on the looks end.


There's also something about the website that makes it all look like a scam or "as seen on TV" type product as well. It does seem like the kind of stove I would put in my MIL's house and trust it not to burn the house down, assuming it all works properly.


----------



## begreen (Dec 9, 2020)

SpaceBus said:


> There's also something about the website that makes it all look like a scam or "as seen on TV" type product as well. It does seem like the kind of stove I would put in my MIL's house and trust it not to burn the house down, assuming it all works properly.


They started the business straight out of college. It's a small enterprise, but the stoves are not cheaply made. I'd love to try both out just to expand my burning knowledge. They are interesting engineering designs.


----------



## john26 (Dec 9, 2020)

MFfire say burn time up to 12 hours I would imagine if the draft fan ran much it would greatly decrease burn times.  The draft inducing fan on the chimney instead of the air intake looks a lot like how high efficiency gas furnaces are designed.  I wonder if the control kicks the draft blower on if the cat falls below a set temp even if the room thermostat is satisfied? 
My idea is a thermocouple on the cat feeding back to a small PLC with a 4-20 milliamp out put controlling an electrically actuated damper that would control air to the intake with out a draft blower that would be more efficient.  If a PLC was used a digital manometer could be installed to control an automated flu damper.  And Or programming could be used to open the flue damper if the flu temp drops below a set point.  A variable speed blower motor could be added as well to maintain temps in the air jacket as well or possibly even thermostat controlled for room comfort.  Now that being said that is a lot of stuff for a wood stove and would be very pricey it would be better suited for a wood furnace.


----------



## begreen (Dec 9, 2020)

I think the combustion blower is just for startup. The objective being to get smoke free asap. The convection blower is variable speed and can also be controlled by the remote app.


----------



## john26 (Dec 9, 2020)

begreen said:


> I think the combustion blower is just for startup. The objective being to get smoke free asap.


you are probably right  I could not find it in the manual or on there web site  but i did find this on page 33 of the manual 
“Boost Mode Activated” – If your fire is dying Catalyst will go into
boost mode, speeding up your combustion fan to deliver essential air
to the fire. Boost mode is commonly occurs after start-up at the
beginning of a cold burn or as the wood runs out and your fire dies.


----------



## begreen (Dec 9, 2020)

john26 said:


> you are probably right  I could not find it in the manual or on there web site  but i did find this on page 33 of the manual
> “Boost Mode Activated” – If your fire is dying Catalyst will go into
> boost mode, speeding up your combustion fan to deliver essential air
> to the fire. Boost mode is commonly occurs after start-up at the
> beginning of a cold burn or as the wood runs out and your fire dies.


 The combustion blower is variable speed. During the 5 minute start up mode it is at high speed.


----------



## BKVP (Dec 9, 2020)

bholler said:


> But it needs heat as well doesn't it?  I know if I turn mine down to low there are still plenty of gasses but the cat stalls.


There are fewer than 2 stoves that can run as low as ours in kg/h and produce as low emissions.   Can we work on your stove...perhaps swap out the cat?  It should not stall in low burn rates.  Is  your stack 15' +.....let's not consume this thread, just give me a call.  509-522-2730.


----------



## BKVP (Dec 9, 2020)

SpaceBus said:


> Will site built masonry "stoves" be regulated moving forward? Seems like a relatively miniscule market to watch. It also sound like you are saying there will be regulation on wood cookstoves as well. I haven't read any of the legislation so I've been under the impression that cookers and masonry heaters/stoves were indeed unregulated.


So interestingly,  the masonry heater council voted to litigate against the EPA.  They want to be a regulated product so that they can be included in many incentive programs.  Subsequently,  they have dropped their case...as I recall.  It's really tough to set up, site (lab) your heater and then test and remove.  Great group of manufacturers that want to be recognized for stove change outs, tax credits etc.


----------



## BKVP (Dec 9, 2020)

john26 said:


> MFfire say burn time up to 12 hours I would imagine if the draft fan ran much it would greatly decrease burn times.  The draft inducing fan on the chimney instead of the air intake looks a lot like how high efficiency gas furnaces are designed.  I wonder if the control kicks the draft blower on if the cat falls below a set temp even if the room thermostat is satisfied?
> My idea is a thermocouple on the cat feeding back to a small PLC with a 4-20 milliamp out put controlling an electrically actuated damper that would control air to the intake with out a draft blower that would be more efficient.  If a PLC was used a digital manometer could be installed to control an automated flu damper.  And Or programming could be used to open the flue damper if the flu temp drops below a set point.  A variable speed blower motor could be added as well to maintain temps in the air jacket as well or possibly even thermostat controlled for room comfort.  Now that being said that is a lot of stuff for a wood stove and would be very pricey it would be better suited for a wood furnace.


I know a certain stove manufacturer/nerd that designed a stove that had 3 tiered cats, multi O2 sensors, 3 different fan systems for air introduction etc.  Emissions were nearly zero.  One day an EPA random compliance audit took place at the factory.  The guy shared the prototype with the inspector.

When asked. "what's keeping you from bring it to market?" my friend said 2 things.  First the cost.  It would retail at $20-$30k.  Second, his research showed 97% or more wood burners preferred low tech for minimal technical issues.  He is still a dear friend and has not shelved the project!!  I've seen the stove...it has a future.


----------



## bholler (Dec 9, 2020)

BKVP said:


> There fewer than 2 stoves that can run as low as ours in kg/h and produce as low emissions.   Can we work on your stove...perhaps swap out the cat?  It should not stall in low burn rates.  Is  your stack 15' +.....let's not consume this thread, just give me a call.  509-522-2730.


I will do that.  But give some basics here.  I have 21' but it goes through the wall so it works out so the draft is within spec.    .05 to .06.  it was a bit low but I reworked the pipe and got it right. 

I actually think the cat is currently on its last legs.  This is the 3rd season and it doesn't get active as fast or stay active as long.  But I could always stall it like that even when the cat was new.  I will call you tomorrow


----------



## ABMax24 (Dec 9, 2020)

BKVP said:


> I know a certain stove manufacturer/nerd that designed a stove that had 3 tiered cats, multi O2 sensors, 3 different fan systems for air introduction etc.  Emissions were nearly zero.  One day an EPA random compliance audit took place at the factory.  The guy shared the prototype with the inspector.
> 
> When asked. "what's keeping you from bring it to market?" my friend said 2 things.  First the cost.  It would retail at $20-$30k.  Second, his research showed 97% or more wood burners preferred low tech for minimal technical issues.  He is still a dear friend and has not shelved the project!!  I've seen the stove...it has a future.



I think that would be interesting to see, in many ways I believe its only a matter of time before more manufacturers head to electronics to control the stove.

In many way I'd liken wood stove technology to a 2-stroke vs 4 stroke engine. A 2 stroke is simpler to build, cheaper, and has less moving parts. The problem comes in with tuning, tuning with port timing/sizing, changing tuned pipes and finnicky air fuel ratios make them dirtier and more temperamental. Where a 4 stroke has more moving parts and is costlier to build, but everything can be precisely controlled with hard parts such as cam profile, or in the electronic tuning. 

Once electronically controlled stoves hit the market things like draft issues will be a thing of the past, as the computer will either automatically adopt to changes via sensor inputs, or these parameters could be programmed into the stove at the time of install.


----------



## Highbeam (Dec 9, 2020)

bholler said:


> I will do that.  But give some basics here.  I have 21' but it goes through the wall so it works out so the draft is within spec.    .05 to .06.  it was a bit low but I reworked the pipe and got it right.
> 
> I actually think the cat is currently on its last legs.  This is the 3rd season and it doesn't get active as fast or stay active as long.  But I could always stall it like that even when the cat was new.  I will call you tomorrow



I thought all operators should find that low setting at which their cat would barely not stall. I know I can always stall my cat if I just swing the stat dial to full low.


----------



## Crocks (Dec 10, 2020)

ABMax24 said:


> I think that would be interesting to see, in many ways I believe its only a matter of time before more manufacturers head to electronics to control the stove.
> 
> In many way I'd liken wood stove technology to a 2-stroke vs 4 stroke engine. A 2 stroke is simpler to build, cheaper, and has less moving parts. The problem comes in with tuning, tuning with port timing/sizing, changing tuned pipes and finnicky air fuel ratios make them dirtier and more temperamental. Where a 4 stroke has more moving parts and is costlier to build, but everything can be precisely controlled with hard parts such as cam profile, or in the electronic tuning.
> 
> Once electronically controlled stoves hit the market things like draft issues will be a thing of the past, as the computer will either automatically adopt to changes via sensor inputs, or these parameters could be programmed into the stove at the time of install.



I love two strokes. The smell, the sound, simplicity and so on. 

Wood stoves on the other hand all I ask for is a long atleast 12 hour burn time, enough coals to toss full size splints / load ontop of and it light up, close down and repeat.  Then comes all the variables to achieve such. Crazy wood stove world we live in


----------



## bholler (Dec 10, 2020)

Highbeam said:


> I thought all operators should find that low setting at which their cat would barely not stall. I know I can always stall my cat if I just swing the stat dial to full low.


That's what I thought


----------



## bholler (Dec 10, 2020)

ABMax24 said:


> I think that would be interesting to see, in many ways I believe its only a matter of time before more manufacturers head to electronics to control the stove.
> 
> In many way I'd liken wood stove technology to a 2-stroke vs 4 stroke engine. A 2 stroke is simpler to build, cheaper, and has less moving parts. The problem comes in with tuning, tuning with port timing/sizing, changing tuned pipes and finnicky air fuel ratios make them dirtier and more temperamental. Where a 4 stroke has more moving parts and is costlier to build, but everything can be precisely controlled with hard parts such as cam profile, or in the electronic tuning.
> 
> Once electronically controlled stoves hit the market things like draft issues will be a thing of the past, as the computer will either automatically adopt to changes via sensor inputs, or these parameters could be programmed into the stove at the time of install.


Unless they are lazy and say screw efficiency I will just slap a barometric damper in the pipe.  Lol


----------



## BKVP (Dec 10, 2020)

ABMax24 said:


> I think that would be interesting to see, in many ways I believe its only a matter of time before more manufacturers head to electronics to control the stove.
> 
> In many way I'd liken wood stove technology to a 2-stroke vs 4 stroke engine. A 2 stroke is simpler to build, cheaper, and has less moving parts. The problem comes in with tuning, tuning with port timing/sizing, changing tuned pipes and finnicky air fuel ratios make them dirtier and more temperamental. Where a 4 stroke has more moving parts and is costlier to build, but everything can be precisely controlled with hard parts such as cam profile, or in the electronic tuning.
> 
> Once electronically controlled stoves hit the market things like draft issues will be a thing of the past, as the computer will either automatically adopt to changes via sensor inputs, or these parameters could be programmed into the stove at the time of install.


Well other research is focusing on the chimney system being smarter.  Imagine a smart cap that would control the amount of draft, after all fuel and draft are outside the control of stove designers.  It would still increase cost of installation, but if you had an older stove, would a smart cap for say $1500 be a good option versus $10,000 or more for a stove? We'll see.....


----------



## kennyp2339 (Dec 10, 2020)

BKVP said:


> Well other research is focusing on the chimney system being smarter.  Imagine a smart cap that would control the amount of draft, after all fuel and draft are outside the control of stove designers.  It would still increase cost of installation, but if you had an older stove, would a smart cap for say $1500 be a good option versus $10,000 or more for a stove? We'll see.....


That is something I would be very interested in, I have so much variables in my chimney draft, the one size fits all approach does not fit my needs. I literally go from a .06 to a .18 just from a change in wind direction, the higher draft just happens to come from my winter prevailing winds, so it is manageable, but its annoying to at the same time.
Now with new designs, how much can a homeowner do to service or fix a problem that may occur? I know in the farming community there is a big push with right to work on equipment (the big green machines installed software locks on electronic hardware forcing expensive service calls for simple fixes) Just food for thought while the industry is in the planning stages of new tech.


----------



## moresnow (Dec 10, 2020)

kennyp2339 said:


> That is something I would be very interested in, I have so much variables in my chimney draft, the one size fits all approach does not fit my needs. I literally go from a .06 to a .18 just from a change in wind direction, the higher draft just happens to come from my winter prevailing winds, so it is manageable, but its annoying to at the same time.
> Now with new designs, how much can a homeowner do to service or fix a problem that may occur? I know in the farming community there is a big push with right to work on equipment (the big green machines installed software locks on electronic hardware forcing expensive service calls for simple fixes) Just food for thought while the industry is in the planning stages of new tech.



Old big green machines are brining huge bucks at auction right now because of this very reason. Stupid expensive service calls for what is quite simply... Goofed up eeeeelectronic gadgets/gizmo's that are causing crazy down time in a mother nature limited time frame. Noooo good.


----------



## SpaceBus (Dec 10, 2020)

This is mostly a problem faced by smaller farmers who are buying the big green computer controlled tractors second hand. The original owners get all the dealer support. I could see the same thing happening to the second or third owner of a computer controlled stoves. Especially with the way folks change out their home every five years.


----------



## moresnow (Dec 10, 2020)

SpaceBus said:


> This is mostly a problem faced by smaller farmers who are buying the big green computer controlled tractors second hand. The original owners get all the dealer support. I could see the same thing happening to the second or third owner of a computer controlled stoves. Especially with the way folks change out their home every five years.



Um. No. The original owner's are just as unhappy (if not more so) with down time as the smaller farmer's. Now back to the topic


----------



## MTASH (Dec 10, 2020)

BKVP said:


> The point I was trying to make is not all buyers of wood stoves read the manuals and of those that do most discard the technical suggestions.
> 
> Sit at my desk for a day and you'll see it!



To be fair though, do you think the dealers should attempt to better inform buyers?  I am a technical person, engineer by profession, and knew I had a sub-optimal chimney based on the recommendations in the Ashford install manual. It was a 9'-4" 6x10 clay flue, "But it always worked fine with my Schrader". The new EPA stoves were a different animal to me, and I was looking for dealer's advice, thinking they'd have real world experience and could help explain. I talked to two different dealers (ironically located in the two towns you mentioned in a previous post!), and this is what happened:

1) Dealer #1 was reluctant to sell me a BK at all.  They simply don't work well at my elevation (5400').  No discussion about how I could modify/improve my chimney, and I left there feeling like they really just wanted to push another brand.

2) Dealer #2 was more than willing to sell me the stove, and didn't attempt at all to steer me to another brand, but again no discussion about install until I prompted them. After learning about my chimney, he suggested I go ahead and do the install, but did say that I might need to install a liner if it doesn't work out.

I chose Option 2. I ran the stove on the existing chimney for the last half of the season, and it worked reasonably well, but certainly not optimal.  At that point I'd spent quite a lot of time on this forum and knew I needed a insulated liner (for more than one reason) and to add height.  So I ended up installing a liner prior to the next season. I still only have 12', but it is correctly sized and insulated which made a huge difference. Although knowing what I know now, I don't recommend anyone run an Ashford on less than 15'.

I realize this thread started out as an overdraft discussion, but the point is that I don't think your average buyer is going to digest all the information in the manual, and certainly doesn't spend time on forums like this other than to research reviews on stove brands (as I did). It would be helpful to have dealers that take the extra step to review the install rather than simply sell a stove (or not, as in my example).


----------



## BKVP (Dec 10, 2020)

MTASH said:


> To be fair though, do you think the dealers should attempt to better inform buyers?
> 
> _*YES!!  Some dealers are superb, others not so much.*_
> 
> ...


----------



## ABMax24 (Dec 10, 2020)

BKVP said:


> Well other research is focusing on the chimney system being smarter.  Imagine a smart cap that would control the amount of draft, after all fuel and draft are outside the control of stove designers.  It would still increase cost of installation, but if you had an older stove, would a smart cap for say $1500
> be a good option versus $10,000 or more for a stove. We'll see.....



The way I see it a couple temp probes, a small microprocessor, and an actuator is all that's needed at the current time to control a stove and pass emissions. It shouldn't be a costly endeavor.

It could even be a manual stove with a built in automated flue damper to control draft. A very simple pressure sensor, basic microcontroller, damper and actuator would be all that's needed, and would solve 95% of high-draft related issues. It could even have a temp sensor built in to prevent an operator induced overfire.


----------



## ABMax24 (Dec 10, 2020)

Crocks said:


> I love two strokes. The smell, the sound, simplicity and so on.
> 
> Wood stoves on the other hand all I ask for is a long atleast 12 hour burn time, enough coals to toss full size splints / load ontop of and it light up, close down and repeat.  Then comes all the variables to achieve such. Crazy wood stove world we live in



So do I, I love the fact that I can make 220+hp from my turbocharged 800cc snowmobile engine at 9lbs boost. But do I want that maintenance and temperamental nature in my daily driver, no.

I think most people feel the same about wood stoves, if I had one that required lighting and walking away, then reload again in 12 or 24 hrs and walk away again with the stove controlling output would be awesome. The closest stove to this on the market now seems to be the BK stoves, which is why I believe they've developed a cult-like following.


----------



## sadpanda (Dec 10, 2020)

bholler said:


> A 4" pipe on a 6" stove will not have enough volume on startup and will smoke back into the house.  Draft measurement is only one part of the equation.  You also have to have the correct volume.



I did not think sweeps/installers did calculations?  You keep saying calculations are useless because there are too many variables to consider yet you site equations.  The Slkirk Chimney and Venting Sizing handbook is full of calculations and tables... Nobody uses them?



bholler said:


> Why should key dampers be avoided???   If you are using it to bring draft into spec you would not have smoke spillage at all when you open the door.
> 
> Also the "magic EPA honeycomb thing"  only works.
> 1 if there is one which many stoves don't have one.
> 2 if there is enough temp to keep that cat active.



Re: seasoned wood/magic combustor I was purposefully being obtuse...  The default answer for creosote formation is always 'do not burn green wood'

How do you know a pipe smaller than 6in can not support stove startup?  Given the weight given to real world experience over science,  have you ever done a 5" install?  Did it also include a key damper?

I'm not saying key dampers should be avoided.  I'm saying they are:

subject to user error
not effective in controlling variable draft situations
apparently can only solve slight overdraft situations
compared to properly sizing the flue system from the onset, seems like a band-aid
Are you are saying a key damper is a set it and forget it device in your installations?  Even fully closed, my key damper does not bring me in spec.  That said, if I do not open it prior to door opening, I get smoke spillage. ¯\_(ツ)_/¯





bholler said:


> Ok you can run what ever numbers you want but the fact is that it is not allowed because doing so has caused to many house fires and they determined it was unsafe.
> 
> Again your numbers don't take into account the thousands of variables that go into this.  And actual real world experience tells us elevating the air intake carries to much risk.


My numbers are admittedly crude...  I keep asking for smarter people than me to jump in and enhance them but the most logical player (@BKVP) seems content sitting back.   Your solution is to not use math at all and simply intuit everything from your years of experience?

I found this excel sheet which addresses at least some of those thousands of missing variables...



bholler said:


> So only things that cause instant death every time should be against code?  What about possible death say 50% of the time?  10%?  5%? 1%?
> 
> I know as a professional if one of my installs cause a death I couldn't live with myself.  Even without death the loss of a house is not something I am willing to risk for my customers.



Honestly this is exactly what I'm driving at and why this is so damn frustrating.  MFG's have put all of the risk and liability squarely on your (installers/sweeps) shoulders...  Anything YOU do to try and make the installation safe and functional is ILLEGAL!   How does anyone square this?   I'm looking at NFI, WETT, CSIA, National Sweep Guild etc.   Hell, even the EPA.  Aside from making money, why force certification under conditions that do not exist in the real world?

Are you comfortable with this liability?  Is your local guild/CSIA/liability insurer/local fire marshal/local building inspector/federal judge?  Why hasn't this alphabet soup of specials banded together and put this back on the powers that be (aka MFGs)?

So to summarize the current dialog:

<owner>: I have too much draft
<mfg>: follow the guidelines NOT in the  manual.  call a sweep.  if you overfire the stove, the stove will break and you will die.
<sweep>:  here is a key damper.  Its illegal for you to use but its $8 and easy to install.  Here is your invoice.
<owner>: But I still have too much draft
<mfg>: yep.  Our engineers knew that would happen, we could help buuuuh we can't  'cause EPAss-ho...  call your sweep.
<sweep>: you need more key damper
<owner>:  But I have an insert and there isnt' any room for another key damper.  What about a barome...
<sweep>: CREOSOTE
<owner>: but what if the pipe was sma...
<sweep>:   Yer dumb.  Here is your invoice.  see you next year.


----------



## MTASH (Dec 10, 2020)

BKVP said:


> To be fair though, do you think the dealers should attempt to better inform buyers?
> 
> _*YES!! Some dealers are superb, others not so much.*_
> 
> ...



Yeah, I agree that staff turnover and inexperience is probably a big issue that's not easily controlled. And I certainly don't want to throw dealers under the bus, as it's possible or even likely those individuals I spoke with may not work there anymore, but it was a bit disappointing nevertheless.  Fortunately I was prepared, but Joe Schmow who doesn't know the right questions to ask may be in for a big surprise when they contact an installer after already dropping $$$ on a new stove. (apologies in advance to anyone actually named Joe Schmow).


----------



## sadpanda (Dec 10, 2020)

ABMax24 said:


> The way I see it a couple temp probes, a small microprocessor, and an actuator is all that's needed at the current time to control a stove and pass emissions. It shouldn't be a costly endeavor.
> 
> It could even be a manual stove with a built in automated flue damper to control draft. A very simple pressure sensor, basic microcontroller, damper and actuator would be all that's needed, and would solve 95% of high-draft related issues. It could even have a temp sensor built in to prevent an operator induced overfire.



Kutzner  & Weber is a German company that has a 100% automated control system that can be retrofitted to any stove.  It uses temp probes, a draft inducer (if needed) a motorized intake damper and a motorized barometric damper.  Can include additional fun things like integration with central HVAC, kitchen vent hood lockout (to prevent depressurization), a smoke ionizer, app control etc.    Its expensive.  I wanted to buy one on our last Euro trip but between trying to get it back in checked bags and wife approval, it was nixed.

So the Germans have decided barometric dampers are safe to use on wood burners...   Math must work differently over there.


----------



## sadpanda (Dec 10, 2020)

MTASH said:


> Yeah, I agree that staff turnover and inexperience is probably a big issue that's not easily controlled. And I certainly don't want to throw dealers under the bus, as it's possible or even likely those individuals I spoke with may not work there anymore, but it was a bit disappointing nevertheless.  Fortunately I was prepared, but Joe Schmow who doesn't know the right questions to ask may be in for a big surprise when they contact an installer after already dropping $$$ on a new stove. (apologies in advance to anyone actually named Joe Schmow).



I too had a bad experience with my local dealer/sweep and ended up DIY... Hence this conversation.

I think the biggest issue is like all trades, the certification really doesn't mean anything...  Certification does not guarantee quality of work, it only proves that one person at the company managed to pass a test.


----------



## sadpanda (Dec 10, 2020)

ABMax24 said:


> The way I see it a couple temp probes, a small microprocessor, and an actuator is all that's needed at the current time to control a stove and pass emissions. It shouldn't be a costly endeavor.
> 
> It could even be a manual stove with a built in automated flue damper to control draft. A very simple pressure sensor, basic microcontroller, damper and actuator would be all that's needed, and would solve 95% of high-draft related issues. It could even have a temp sensor built in to prevent an operator induced overfire.




Yep... if I dont go the KW route here is my someday diy  list:
Raspberry Pi, pressure sensor, my existing thermocouples, GM stepper motor controlled throttle body for intake, WBO2 sensor, motorized exhaust damper etc


----------



## SpaceBus (Dec 10, 2020)

ABMax24 said:


> The way I see it a couple temp probes, a small microprocessor, and an actuator is all that's needed at the current time to control a stove and pass emissions. It shouldn't be a costly endeavor.
> 
> It could even be a manual stove with a built in automated flue damper to control draft. A very simple pressure sensor, basic microcontroller, damper and actuator would be all that's needed, and would solve 95% of high-draft related issues. It could even have a temp sensor built in to prevent an operator induced overfire.


Maybe that's cheap on the DIY end, but the R&D required to make it work for thousands of customers is a bit different. I think that's why the $10,000 figure was used.


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## BKVP (Dec 10, 2020)

SpaceBus said:


> Maybe that's cheap on the DIY end, but the R&D required to make it work for thousands of customers is a bit different. I think that's why the $10,000 figure was used.


And the tech support for the next 20+ years!  20 years ago we discussed making another type of solid fuel stoves.  So I called all my contemporaries in that same product sector and sought their opinions on a number of topics.  Unilaterally I was told "You better build into the budget a tech team for the next 20 years".  Maybe they all told me that to scare us from entering the market...maybe not.


----------



## ABMax24 (Dec 10, 2020)

SpaceBus said:


> Maybe that's cheap on the DIY end, but the R&D required to make it work for thousands of customers is a bit different. I think that's why the $10,000 figure was used.



Sure depending on the company, those used to building traditional stoves will find it a difficult and costly endeavor, those with computer/engine controls experience not so much, the components are cheap, the implementation is too for the right builder.

I think in many ways though the moral of this thread is that R&D isn't always done, the stove is built to pass the EPA test and UL certification and kicked out the door. It is far easier to build a stove that always runs a constant draft due to an automated draft control or automated inlet control than to build a standard stove that uses hard parts to attempt to compensate for varying draft conditions. Hence my 2/4 stroke comparison. I have no doubt an electronic stove would cost more, but I see 25% more being the limit, not 200-300%.


----------



## john26 (Dec 10, 2020)

sadpanda said:


> Yep... if I dont go the KW route here is my someday diy list:
> Raspberry Pi, pressure sensor, my existing thermocouples, GM stepper motor controlled throttle body for intake, WBO2 sensor, motorized exhaust damper et


Raspberry Pi may not be the best thing to use it will an analog to digital converter to make the thermocouples read it will also need an analog output preferably 4-20 ma or 0-20 ma signal.   A Velcio.net  Ace or branch  might be a better solution having some  analog I/O's and expansion ports can be added.  Allen Bradley with RS logix would be great but costly especially for the software.


----------



## begreen (Dec 10, 2020)

ABMax24 said:


> The way I see it a couple temp probes, a small microprocessor, and an actuator is all that's needed at the current time to control a stove and pass emissions. It shouldn't be a costly endeavor.
> 
> It could even be a manual stove with a built in automated flue damper to control draft. A very simple pressure sensor, basic microcontroller, damper and actuator would be all that's needed, and would solve 95% of high-draft related issues. It could even have a temp sensor built in to prevent an operator induced overfire.


Someone did that with a PE stove on this site several years ago. I've been meaning to chase that thread down to see if he is still around.


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## ABMax24 (Dec 10, 2020)

begreen said:


> Someone did that with a PE stove on this site several years ago. I've been meaning to chase that thread down to see if he is still around.



I would definitely be interested in having a read through that.


----------



## begreen (Dec 10, 2020)

ABMax24 said:


> I would definitely be interested in having a read through that.


IIRC he used 2 thermocouples and a microprocessor controlling a linear actuator. Not sure about a pressure sensor. The challenge was writing code that would cover all the variables and not short cycle or overshoot. But he seemed to be making good progress.

Here it is with an update posted a couple years ago:





						Wood stove automation using the Raspberry Pi
					

Happy New Year!  It has been a couple of years since I started working on my wood stove automation project.   Its based on Python and currently runs on a Raspberry Pi3 Model B.   I got quite far but until now I never documented any part of what I did.    Took me about a week to take pictures and...




					www.hearth.com


----------



## bholler (Dec 10, 2020)

sadpanda said:


> did not think sweeps/installers did calculations? You keep saying calculations are useless because there are too many variables to consider yet you site equations. The Slkirk Chimney and Venting Sizing handbook is full of calculations and tables... Nobody uses them?


I never said we didn't do calculations.  I do them all the time just not for natural draft appliances.  There have been many many formulas for natural draft appliances and so far only one was even remotely useful.  But in the time it took to gather all of the applicable information and run  the numbers I could easily have the stove installed and have an actual draft measurement which you would need to do anyway to confirm the math.  So why waste my time and the customers money.




sadpanda said:


> How do you know a pipe smaller than 6in can not support stove startup? Given the weight given to real world experience over science, have you ever done a 5" install? Did it also include a key damper?



I didn't say smaller than 6"couldn't support stove startup.  I said 4" on a 6" stove couldn't.  And yes I have done installs from 22" down to 2" it all depends what is needed.  And yes some 5" installs had dampers some didn't.


----------



## bholler (Dec 10, 2020)

sadpanda said:


> Honestly this is exactly what I'm driving at and why this is so damn frustrating. MFG's have put all of the risk and liability squarely on your (installers/sweeps) shoulders... Anything YOU do to try and make the installation safe and functional is ILLEGAL! How does anyone square this? I'm looking at NFI, WETT, CSIA, National Sweep Guild etc. Hell, even the EPA. Aside from making money, why force certification under conditions that do not exist in the real world?


Honestly many of the installs I do are perfectly fine without and fine-tuning of the draft.  Those that aren't are almost always easily addressed with a key damper.  So yes the conditions do exist in the real world.  I don't know what makes you think all stoves are over drafting but it simply is not true.  




sadpanda said:


> Are you comfortable with this liability? Is your local guild/CSIA/liability insurer/local fire marshal/local building inspector/federal judge? Why hasn't this alphabet soup of specials banded together and put this back on the powers that be (aka MFGs)?


If I am not comfortable with the risk or liability involved I don't do the job it is that simple.




sadpanda said:


> the Germans have decided barometric dampers are safe to use on wood burners... Math must work differently over there.


Just because something is for sale doesn't mean it is safe.


----------



## john26 (Dec 10, 2020)

sadpanda said:


> Kutzner & Weber is a German company that has a 100% automated control system that can be retrofitted to any stove. It uses temp probes, a draft inducer (if needed) a motorized intake damper and a motorized barometric damper. Can include additional fun things like integration with central HVAC, kitchen vent hood lockout (to prevent depressurization), a smoke ionizer, app control etc. Its expensive. I wanted to buy one on our last Euro trip but between trying to get it back in checked bags and wife approval, it was nixed.
> 
> So the Germans have decided barometric dampers are safe to use on wood burners... Math must work differently over there


Can't use the barometric damper  here on solid fuel  it is in page 2 of the instructions
Safety Barometric dampers should only be connected to nonpositive pressure appliances. Non-positive pressure appliances include gas, oil, and solid fuel appliances. Barometric Dampers shall be installed in the same room as the appliance it is serving. Warning: Install barometric dampers in accordance with local and national codes which may include ANSI Z223.1 (NFPA 54), NFPA 31, NFPA 211

seen this for sale at menards today from US stove company


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## jetsam (Dec 11, 2020)

A motorized barometric damper could behave responsibly if it was driven by an algorithm that had access to flue temperatures at the top of the stack and draft readings.

Not sure who's going to want to run a wire up to the top of their stack for the top temperature sensor, though.


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## Highbeam (Dec 11, 2020)

Didn’t want to feed the fire but PE stoves use a barometrically controlled secondary air feed. So when the chimney is above a certain draft, air feeds the secondary air injection system. Why not use this same type of contraption to dump air into the flue in an effort to regulate draft strength? It’s basically an internal barometric damper. No big deal.


----------



## john26 (Dec 11, 2020)

Highbeam said:


> Didn’t want to feed the fire but PE stoves use a barometrically controlled secondary air feed. So when the chimney is above a certain draft, air feeds the secondary air injection system. Why not use this same type of contraption to dump air into the flue in an effort to regulate draft strength? It’s basically an internal barometric damper. No big deal.


The difference is Pacific Energy is not mixing room temperature air with flue gasses in the chimney like a barometric damper.  Looks to me like Pacific Energy has addressed the problem of overdraft and fixed it with simple solution.  Maybe some time of barometric or automatic draft regulator  could be installed in the OAK or intake of the stove much like PE with their secondary's.  I think the whole argument against the barometric is inducing cooler air in the chimney system lowering gas temps.  I have seen other methods that do the same thing manually to lower draft.  For example a hole in the bottom of a T with an adjustable Sheetmetal tab over it.  Did it work?   Yes  Is, it safe?  Well he never had a chimney fire that I know of but I think 90% of us here would never do that.  I know I would not.


----------



## bholler (Dec 11, 2020)

john26 said:


> The difference is Pacific Energy is not mixing room temperature air with flue gasses in the chimney like a barometric damper.  Looks to me like Pacific Energy has addressed the problem of overdraft and fixed it with simple solution.  Maybe some time of barometric or automatic draft regulator  could be installed in the OAK or intake of the stove much like PE with their secondary's.  I think the whole argument against the barometric is inducing cooler air in the chimney system lowering gas temps.  I have seen other methods that do the same thing manually to lower draft.  For example a hole in the bottom of a T with an adjustable Sheetmetal tab over it.  Did it work?   Yes  Is, it safe?  Well he never had a chimney fire that I know of but I think 90% of us here would never do that.  I know I would not.


Well said


----------



## brenndatomu (Dec 11, 2020)

jetsam said:


> A motorized barometric damper could behave responsibly if it was driven by an algorithm that had access to flue temperatures at the top of the stack and draft readings.
> 
> Not sure who's going to want to run a wire up to the top of their stack for the top temperature sensor, though.


Sounds like asking for problems to me...would have to be designed so that it has a built in failsafes...what happens when the power goes out...or the motor pukes, etc?


john26 said:


> I have seen other methods that do the same thing manually to lower draft. For example a hole in the bottom of a T with an adjustable Sheetmetal tab over it. Did it work? Yes Is, it safe? Well he never had a chimney fire that I know of but I think 90% of us here would never do that. I know I would not.


Having a BD, I would not want to use this method...the BD is CONSTANTLY adjusting to keep the draft at your setting...a static hole is just asking for trouble IMO.


jetsam said:


> Not sure who's going to want to run a wire up to the top of their stack for the top temperature sensor, though.


True...and temp is still only part of the equation...depending on the chimney, the proper temp may, or may not give you the correct draft.


john26 said:


> The difference is Pacific Energy is not mixing room temperature air with flue gasses in the chimney like a barometric damper.





john26 said:


> I think the whole argument against the barometric is inducing cooler air in the chimney system lowering gas temps.


The temp of the makeup air really doesn't matter...the BD only opens as far as it needs to hit the draft you have it set for...a little bit if the makeup air is really cold, or a lot more if its warm air. Kinda like running the temp on your water heater higher...the length of your hot shower can be longer, because you are mixing in less of the hotter water.


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## bholler (Dec 11, 2020)

Highbeam said:


> Didn’t want to feed the fire but PE stoves use a barometrically controlled secondary air feed. So when the chimney is above a certain draft, air feeds the secondary air injection system. Why not use this same type of contraption to dump air into the flue in an effort to regulate draft strength? It’s basically an internal barometric damper. No big deal.


As long as the air is preheated in the firebox it shouldn't cause a problem.  I could see an extra tube with no holes feeding an internal baro working well.


----------



## john26 (Dec 11, 2020)

brenndatomu said:


> Sounds like asking for problems to me...would have to be designed so that it has a built in failsafes...what happens when the power goes out...or the motor pukes, etc?


Spring loaded return closing the damper off from make up air


brenndatomu said:


> The temp of the makeup air really doesn't matter...the BD only opens as far as it needs to hit the draft you have it set for...a little bit if the makeup air is really cold, or a lot more if its warm air. Kinda like running the temp on your water heater higher...the length of your hot shower can be longer, because you are mixing in less of the hotter water.


I understand its not cold air unless on an outdoor furnace but its still cooler than the flue temps.  The Barometric damper would be a non issue if you could mix air the same temp as the flu gas or 250F or hotter into the chimney.  One problem with this is drafting through the stove back to square one.    Now if the stove had an outer jacket to preheat the air feeding the barometric it would help still it would be hard in my opinion to hit 250F and now you are losing efficiency on the stove and loosing heat that would normally transfer into the space being heated.
I mixed air on a large air handlers  building return and outside make up air it doesn't take much to drop discharge temps.  To be honest I cheated a lot in cold weather and ran outside make up air well below the specified 20%


----------



## jetsam (Dec 11, 2020)

brenndatomu said:


> Sounds like asking for problems to me...would have to be designed so that it has a built in failsafes...what happens when the power goes out...or the motor pukes, etc?
> 
> Having a BD, I would not want to use this method...the BD is CONSTANTLY adjusting to keep the draft at your setting...a static hole is just asking for trouble IMO.
> 
> ...



If you have a computer on your stove watching the draft, you probably have it watching the intake air too.  Run it off a small battery, charge the battery with a TEG.  We only need a few watts here to stay ahead of a RISC board, sensors, motors, and cable and charging losses.

You can reduce motor wear (and battery usage) by simply having a predefined wait between adjustment runs.  In case of motor failure or battery power loss,  put a little failsafe spring on the intake and the damper- the intake springs shut, the damper springs open.  

Hardware costs on top of the stove are pretty low. The most expensive items are the battery, the TEG, and the computer, none of which should break $50 even at retail prices. You could drive the price and power requirements of the computer way down by switching from off the shelf hardware to a custom RISC SOC- which would mean a consortium of stove manufacturers agreeing on some kind of standard there, which probably isn't a real possibility.

 Obviously I have a thousand ideas and questions about how that would actually get implemented, but I feel like there's a path to a product that isn't overly complex and works reliably there.


----------



## jetsam (Dec 11, 2020)

john26 said:


> The difference is Pacific Energy is not mixing room temperature air with flue gasses in the chimney like a barometric damper.  Looks to me like Pacific Energy has addressed the problem of overdraft and fixed it with simple solution.  Maybe some time of barometric or automatic draft regulator  could be installed in the OAK or intake of the stove much like PE with their secondary's.  I think the whole argument against the barometric is inducing cooler air in the chimney system lowering gas temps.  I have seen other methods that do the same thing manually to lower draft.  For example a hole in the bottom of a T with an adjustable Sheetmetal tab over it.  Did it work?   Yes  Is, it safe?  Well he never had a chimney fire that I know of but I think 90% of us here would never do that.  I know I would not.



In theory you could feed the barometric damper above the flue collar with heated room air (pulled through the stove in a separate intake, airtight to the firebox).  Obviously you need some new holes and a new tube in the stove, but there's no moving parts to break.


----------



## bholler (Dec 11, 2020)

jetsam said:


> In theory you could feed the barometric damper above the flue collar with heated room air (pulled through the stove in a separate intake, airtight to the firebox).  Obviously you need some new holes and a new tube in the stove, but there's no moving parts to break.


Yes then the only issue needing addressed is what happens in the event of a chimney fire


----------



## jetsam (Dec 11, 2020)

bholler said:


> Yes then the only issue needing addressed is what happens in the event of a chimney fire



The damper should close as draft increases, making it about the same as a stove with no baro in that extreme case, no?  Or does it still let some dilution air in at full close?


----------



## bholler (Dec 11, 2020)

jetsam said:


> The damper should close as draft increases, making it about the same as a stove with no baro in that extreme case, no?  Or does it still let some dilution air in at full close?


The a barometric damper opens as draft increases.  Current ones still leak when closed but that could be addressed.  But in the event of a chimney fire draft will skyrocket and the damper will open wide supplying more air to the fire.


----------



## Highbeam (Dec 11, 2020)

jetsam said:


> The damper should close as draft increases, making it about the same as a stove with no baro in that extreme case, no?  Or does it still let some dilution air in at full close?



Regular barometric would go wide open trying to increase air pressure in the flue. Feeding oxygen to the chimney fire. 

Really though, that’s the same thing that the secondary air systems do now. 

Chimney fires seem like a bad idea, I recommend nobody have one.


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## lsucet (Dec 11, 2020)

In case of chimney fire a BD, if you are around it can be capped, unlike many secondary burn stoves that the access to those multiple intake air are difficult to reach and possibly many owners of them not even know where are located. Please I am not saying that a BD or any other components are okay to use, just saying.


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## bholler (Dec 11, 2020)

lsucet said:


> In case of chimney fire a BD, if you are around it can be capped, unlike many secondary burn stoves that the access to those multiple intake air are difficult to reach and possibly many owners of them not even know where are located. Please I am not saying that a BD or any other components are okay to use, just saying.


Yes if you are around and if you know you are having one.


----------



## john26 (Dec 11, 2020)

Highbeam said:


> Regular barometric would go wide open trying to increase air pressure in the flue. Feeding oxygen to the chimney fire.
> 
> Really though, that’s the same thing that the secondary air systems do now.
> 
> Chimney fires seem like a bad idea, I recommend nobody have one.


I had one  once I shut my key damper  and intake to furnace and it went out quick.


----------



## Highbeam (Dec 11, 2020)

john26 said:


> I had one  once I shut my key damper  and intake to furnace and it went out quick.



If it ever happens, and I am aware of it, that’s my plan too. Shut everything as tight as I can and grab my essentials as I call the FD. 

It’s good to have a plan but we just don’t hear about it too often on this forum or from burning enthusiasts.


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## ABMax24 (Dec 11, 2020)

I don't understand the logic of putting in a barometric damper and pumping either room temperature or stove heated air up the chimney. I feel like this is akin to driving with the accelerator pedal to the floor and controlling the vehicle speed with the brakes.

It's seems so much simpler, safer and efficient to either automate a stove to compensate for overdraft or to make an automated flue damper.


----------



## begreen (Dec 11, 2020)

Highbeam said:


> Didn’t want to feed the fire but PE stoves use a barometrically controlled secondary air feed. So when the chimney is above a certain draft, air feeds the secondary air injection system. Why not use this same type of contraption to dump air into the flue in an effort to regulate draft strength? It’s basically an internal barometric damper. No big deal.


The PE EPT is feeding that air right into the combusting wood gas, not downstream after combustion.


----------



## Highbeam (Dec 11, 2020)

begreen said:


> The PE EPT is feeding that air right into the combusting wood gas, not downstream after combustion.



Understood. The same type of device that barometrically feeds that air to the secondary manifold could be used to feed air directly to the flue just like a barometric damper does.


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> I don't understand the logic of putting in a barometric damper and pumping either room temperature or stove heated air up the chimney. I feel like this is akin to driving with the accelerator pedal to the floor and controlling the vehicle speed with the brakes.
> 
> It's seems so much simpler, safer and efficient to either automate a stove to compensate for overdraft or to make an automated flue damper.


I really like the idea of an automated pipe damper but it takes away from the simplicity of most stoves by adding a level of electronics.  A barometric damper bring run off of preheated air is very simple and would address the issue if it could be made to close in the event of a chimney fire.


----------



## begreen (Dec 11, 2020)

Highbeam said:


> Understood. The same type of device that barometrically feeds that air to the secondary manifold could be used to feed air directly to the flue just like a barometric damper does.


Essentially it is a barometric damper also, just a very different location and a much smaller air feed.


----------



## ABMax24 (Dec 11, 2020)

bholler said:


> A barometric damper bring run off of preheated air is very simple and would address the issue if it could be made to close in the event of a chimney fire.



I strongly disagree, regardless of  air pre-heating or not the intent of a BD is to reduce flue temps to reduce draft, on a tall chimney like mine (36ft) water vapor will be condensing at the top of the stack before the draft is brought back within specs.

If the air is preheated enough to prevent creosote it is also too hot to be effective in reducing stack temps, which means its ineffective in reducing draft.


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> I strongly disagree, regardless of  air pre-heating or not the intent of a BD is to reduce flue temps to reduce draft, on a tall chimney like mine (36ft) water vapor will be condensing at the top of the stack before the draft is brought back within specs.
> 
> If the air is preheated enough to prevent creosote it is also too hot to be effective in reducing stack temps, which means its ineffective in reducing draft.


No a bd is not meant to reduce draft by reducing flue temps.  It reduces draft by introducing dilution air.  This weakens the vacuum.  Yes currently it also reduces the flue temps because the dilution air is cool.  It would be just as effective with hot air


----------



## john26 (Dec 11, 2020)

ABMax24 said:


> If the air is preheated enough to prevent creosote it is also too hot to be effective in reducing stack temps, which means its ineffective in reducing draft.


Maybe I am missing something.  Is draft reduction in the chimney the goal?  or draft reduction in the stove?  With a barometric is the draft reduced in the chimney or just the stove?  Wouldn't the barometric draw air from the room it is in maintaining  pressure in the chimney just reducing pressure in the stove?


----------



## bholler (Dec 11, 2020)

john26 said:


> Maybe I am missing something.  Is draft reduction in the chimney the goal?  or draft reduction in the stove?  With a barometric is the draft reduced in the chimney or just the stove?  Wouldn't the barometric draw air from the room it is in maintaining  pressure in the chimney just reducing pressure in the stove?


If you reduce draft in the chimney you reduce the suction placed on the stove.


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## ABMax24 (Dec 11, 2020)

bholler said:


> No a bd is not meant to reduce draft by reducing flue temps.  It reduces draft by introducing dilution air.  This weakens the vacuum.  Yes currently it also reduces the flue temps because the dilution air is cool.  It would be just as effective with hot air



Then you are going to need a huge volume of dilution air to reduce vacuum. Essentially what that is doing is using the friction within the chimney to reduce draft due to high flow rates, on a 6" or 8" chimney those volumes are going to be many times the volume the stove generates in flue gases.

As an experiment of this I pulled the cleanout cap on the tee of my chimney to see how much air gets pulled in while burning, It's a lot, I wouldn't be surprised to find the volume of air being drawn in the opening to measure in the hundreds of CFM.

I already believe I put too much hard work into processing wood just to go up the flue in the form of hot gases, I'll have no part in deliberately sending more up the stack.


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## ABMax24 (Dec 11, 2020)

john26 said:


> Maybe I am missing something.  Is draft reduction in the chimney the goal?  or draft reduction in the stove?  With a barometric is the draft reduced in the chimney or just the stove?  Wouldn't the barometric draw air from the room it is in maintaining  pressure in the chimney just reducing pressure in the stove?



Reducing draft in the stove is all that's needed, of course reducing chimney draft has the same effect, but definitely isn't needed if you can reduce draft only on the stove.

Realistically you wouldn't even need to reduce draft on the stove, ideally there would be a mechanism to maintain constant airflow into the stove regardless of draft, then draft doesn't matter as long as there is enough to light the stove. That would be the holy-grail of stove control.


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> Then you are going to need a huge volume of dilution air to reduce vacuum. Essentially what that is doing is using the friction within the chimney to reduce draft due to high flow rates, on a 6" or 8" chimney those volumes are going to be many times the volume the stove generates in flue gases.
> 
> As an experiment of this I pulled the cleanout cap on the tee of my chimney to see how much air gets pulled in while burning, It's a lot, I wouldn't be surprised to find the volume of air being drawn in the opening to measure in the hundreds of CFM.
> 
> I already believe I put too much hard work into processing wood just to go up the flue in the form of hot gases, I'll have no part in deliberately sending more up the stack.


No not at all.  When dealing with low draft a tiny gap in an area on a pipe joint can make .01" of difference in draft.


----------



## Highbeam (Dec 11, 2020)

ABMax24 said:


> Then you are going to need a huge volume of dilution air to reduce vacuum. Essentially what that is doing is using the friction within the chimney to reduce draft due to high flow rates, on a 6" or 8" chimney those volumes are going to be many times the volume the stove generates in flue gases.
> 
> As an experiment of this I pulled the cleanout cap on the tee of my chimney to see how much air gets pulled in while burning, It's a lot, I wouldn't be surprised to find the volume of air being drawn in the opening to measure in the hundreds of CFM.
> 
> I already believe I put too much hard work into processing wood just to go up the flue in the form of hot gases, I'll have no part in deliberately sending more up the stack.



If the draft demand is satisfied by non firebox air then your hot firebox gasses aren’t being sucked out prematurely.That’s the point. 

Outside air connection to your stove and/or barometric damper means you are not dumping conditioned air. 

Finally, 36’ is ridiculous. I’m more concerned with a stove designed for a normal 12’ chimney when your install requires 20’. The stove should easily accommodate that normal range.


----------



## SpaceBus (Dec 11, 2020)

Highbeam said:


> If the draft demand is satisfied by non firebox air then your hot firebox gasses aren’t being sucked out prematurely.That’s the point.
> 
> Outside air connection to your stove and/or barometric damper means you are not dumping conditioned air.
> 
> Finally, 36’ is ridiculous. I’m more concerned with a stove designed for a normal 12’ chimney when your install requires 20’. The stove should easily accommodate that normal range.


36' is just a two story home with a basement...


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> Reducing draft in the stove is all that's needed, of course reducing chimney draft has the same effect, but definitely isn't needed if you can reduce draft only on the stove.
> 
> Realistically you wouldn't even need to reduce draft on the stove, ideally there would be a mechanism to maintain constant airflow into the stove regardless of draft, then draft doesn't matter as long as there is enough to light the stove. That would be the holy-grail of stove control.


Or you could just set the draft properly and then air input would be constant.  And a small leak in a gasket wouldn't cause a big issue.


----------



## begreen (Dec 11, 2020)

SpaceBus said:


> 36' is just a two story home with a basement...


Yes, my SIL's house is two tall stories (10 ft ceilings) and a full standup attic. Basement to chimney top is probably over 40 ft and 30'+ from the first floor fireplace.


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> Then you are going to need a huge volume of dilution air to reduce vacuum. Essentially what that is doing is using the friction within the chimney to reduce draft due to high flow rates, on a 6" or 8" chimney those volumes are going to be many times the volume the stove generates in flue gases.
> 
> As an experiment of this I pulled the cleanout cap on the tee of my chimney to see how much air gets pulled in while burning, It's a lot, I wouldn't be surprised to find the volume of air being drawn in the opening to measure in the hundreds of CFM.
> 
> I already believe I put too much hard work into processing wood just to go up the flue in the form of hot gases, I'll have no part in deliberately sending more up the stack.


And pulling that tee cap reduced your draft on the stove to zero.  Or close to it.  You would be sending the same amount of heat up the stack regardless.


----------



## john26 (Dec 11, 2020)

ABMax24 said:


> Reducing draft in the stove is all that's needed, of course reducing chimney draft has the same effect, but definitely isn't needed if you can reduce draft only on the stove


I understand that 
draft between the baro and the chimney outlet would remain close to the  original  draft so when the temp in the flu drops due to the dissolution of hot gasses the overall draft will drop some.  The reduction of draft through the stove is made up by draft through the baro damper this causing the draft between the baro and the chimney outlet to be close to original draft.


----------



## bholler (Dec 11, 2020)

SpaceBus said:


> 36' is just a two story home with a basement...


Yeah my old 2 story houses chimney was 38 from crock to top.  That is why I had 2 key dampers.


----------



## bholler (Dec 11, 2020)

This is very basic chimney physics.


----------



## bholler (Dec 11, 2020)

john26 said:


> I understand that
> draft between the baro and the chimney outlet would remain close to the  original  draft so when the temp in the flu drops due to the dissolution of hot gasses the overall draft will drop some.  The reduction of draft through the stove is made up by draft through the baro damper this causing the draft between the baro and the chimney outlet to be close to original draft.


Absolutely correct.


----------



## ABMax24 (Dec 11, 2020)

Highbeam said:


> If the draft demand is satisfied by non firebox air then your hot firebox gasses aren’t being sucked out prematurely.That’s the point.
> 
> Outside air connection to your stove and/or barometric damper means you are not dumping conditioned air.
> 
> Finally, 36’ is ridiculous. I’m more concerned with a stove designed for a normal 12’ chimney when your install requires 20’. The stove should easily accommodate that normal range.



But if you use outside air you cool the flue increasing creosote accumulation, if you use inside air you are wasting the valuable energy you spent heating with the stove in the first place, same goes for using preheated air from the stove as was mentioned a bunch of posts back.

I agree a 20' chimney shouldn't require any special treatment to work right, stoves should be built to accommodate this. 



bholler said:


> Or you could just set the draft properly and then air input would be constant.  And a small leak in a gasket wouldn't cause a big issue.



I agree, a flue damper does this well. But as is the topic of this thread, flue dampers are questionable under various codes and certifications. I know in the Province of Quebec they are not permitted at all.



bholler said:


> And pulling that tee cap reduced your draft on the stove to zero.  Or close to it.  You would be sending the same amount of heat up the stack regardless.



Yes I know it reduces draft to essentially zero.

My point is a barometric damper on a chimney like mine will be allowing massive amounts of air into the chimney, either from outside causing a massive creosote buildup, or inside requiring more cold outside air to be heated to replace it, or robbing heat from the stove through a pre-heater as was proposed earlier.

Pulling air from inside or from a pre-heater is where the additional heat is being wasted up the flue.


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> But if you use outside air you cool the flue increasing creosote accumulation, if you use inside air you are wasting the valuable energy you spent heating with the stove in the first place, same goes for using preheated air from the stove as was mentioned a bunch of posts back.
> 
> I agree a 20' chimney shouldn't require any special treatment to work right, stoves should be built to accommodate this.
> 
> ...


But if you weren't robbing that heat to preheat the dilution air an equal ammout of air would be sucked up the chimney out of the stove.  So no increased heat loss.


----------



## ABMax24 (Dec 11, 2020)

bholler said:


> But if you weren't robbing that heat to preheat the dilution air an equal ammout of air would be sucked up the chimney out of the stove.  So no increased heat loss.



Not if you are using a flue damper, or restricting the inlet air to the stove.


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> Not if you are using a flue damper, or restricting the inlet air to the stove.


If you are running the same stack temp the heat loss would be the same


----------



## SpaceBus (Dec 11, 2020)

The same amount of air will always be drawn up the flue. Under high draft situations more air is drawn in a shorter time and then it slows down later when draft reduces. There are only so many BTU in a load of wood and it needs the same amount of air if it burns fast or if it burns slow.


----------



## ABMax24 (Dec 11, 2020)

bholler said:


> If you are running the same stack temp the heat loss would be the same



Depending on excess air in that flue gas. Stoves in an overdraft scenario have more excess air than a stove with the proper draft.

If you have 2 chimneys at the same temperature one with 25% excess air leaving the stove and one with 100%, the stove with 100% excess is loosing far more heat up the stack, which is the stove in overdraft conditions.


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> Depending on excess air in that flue gas. Stoves in an overdraft scenario have more excess air than a stove with the proper draft.
> 
> If you have 2 chimneys at the same temperature one with 25% excess air leaving the stove and one with 100%, the stove with 100% excess is loosing far more heat up the stack, which is the stove in overdraft conditions.
> 
> View attachment 269087


How much more?  Does that small ammout of lost heat.  Which honestly would only be a couple percent really justify the cost complexity and maintenance involved in adding electronically controlled damper or air intake?  I don't think so at all.


----------



## brenndatomu (Dec 11, 2020)

bholler said:


> No a bd is not meant to reduce draft by reducing flue temps.  It reduces draft by introducing dilution air.  This weakens the vacuum.  Yes currently it also reduces the flue temps because the dilution air is cool.  It would be just as effective with hot air


I have experimented with room air for the BD, vs air from direct connect OAK...the damper opens less, to do the same job, when using the OAK.


----------



## bholler (Dec 11, 2020)

brenndatomu said:


> I have experimented with room air for the BD, vs air from direct connect OAK...the damper opens less, to do the same job, when using the OAK.


Yes I am sure cooler air does reduce draft a bit more than heated air.  But using cool air presents more serious problems in most cases.


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## ABMax24 (Dec 11, 2020)

bholler said:


> How much more?  Does that small ammout of lost heat.  Which honestly would only be a couple percent really justify the cost complexity and maintenance involved in adding electronically controlled damper or air intake?  I don't think so at all.



Judging by that chart I posted 5-10%. But it wouldn't have to be electronic, a manual flue damper could do the same thing, no?

I do like the idea of electronic control. But fundamentally I'm opposed to barometric dampers, to me almost any other solution is better than that.


----------



## brenndatomu (Dec 11, 2020)

bholler said:


> But using cool air presents more serious problems in most cases.


I'm sure it does...my comment was directed toward your earlier statement that "it would be just as effective with hot air"


----------



## bholler (Dec 11, 2020)

brenndatomu said:


> I'm sure it does...my comment was directed toward your earlier statement that "it would be just as effective with hot air"


Ok so my statement there wasn't  accurate.  But heated air will still be very effective and won't cool the fluegases


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> Judging by that chart I posted 5-10%. But it wouldn't have to be electronic, a manual flue damper could do the same thing, no?
> 
> I do like the idea of electronic control. But fundamentally I'm opposed to barometric dampers, to me almost any other solution is better than that.


Can you show us where you got that chart?  I really don't think it is referring to what you think it is referring to


----------



## ABMax24 (Dec 11, 2020)

bholler said:


> Can you show us where you got that chart?  I really don't think it is referring to what you think it is referring to



It's a chart for natural gas appliances, I can't find one for wood. But gives an approximate idea of heat loss in regards to stack temperature and excess combustion air.

This is very similar to the stack-loss method used to calculate wood stove efficiency.






						Combustion Efficiency and Excess Air
					

Optimizing boilers efficiency is important to minimize fuel consumption and unwanted excess to the environment.




					www.engineeringtoolbox.com


----------



## bholler (Dec 11, 2020)

ABMax24 said:


> It's a chart for natural gas appliances, I can't find one for wood. But gives an approximate idea of heat loss in regards to stack temperature and excess combustion air.
> 
> This is very similar to the stack-loss method used to calculate wood stove efficiency.
> 
> ...


Yeah that chart is talking about extra air in the combustion chamber for natural gas.  Not at all referring to air introduced into the smoke stream


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## ABMax24 (Dec 11, 2020)

bholler said:


> Yeah that chart is talking about extra air in the combustion chamber for natural gas.  Not at all referring to air introduced into the smoke stream



Yeah I was talking about extra air in the firebox from overdraft, in particular the secondary tubes. Not extra air added to the flue.

But I see where I went wrong, I got mixed up in the mess of posts.


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## SpaceBus (Dec 12, 2020)

Maybe the better thing to do would be to approach the legislature to try and legalize key dampers for installs that require it. Perhaps make the wording of the law require a certified sweep to come out and do measurements? We are already talking about a niche of a niche, so maybe it doesn't even matter.


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## john26 (Dec 12, 2020)

would this work if you had an oak kit to install it on?





						3" Barometric Damper
					

3" Stainless Steel Barometric Damper,4" Stainless Steel Barometric Damper



					www.pelletstoves.com
				



never mind draw through stove would be the same


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## begreen (Dec 12, 2020)

FWIW,  I notice that the Jotul F500v3 manual specifically recommends adding a butterfly damper to the stovepipe if the draft is strong.


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## Todd (Dec 12, 2020)

begreen said:


> FWIW,  I notice that the Jotul F500v3 manual specifically recommends adding a butterfly damper to the stovepipe if the draft is strong.


Same with the F45 manual


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## orlkc (Dec 13, 2020)

Todd said:


> Same with the F45 manual



I looked at the hearthstone manuals -- same.  The older 8022  version talks about installing a damper if the draft measures more than 0.1" wc.  I also looked at the newer EPA 2020 version (8024) and I see the same recommendation.  The wording changed slightly, but not the overall message.


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## begreen (Dec 13, 2020)

All stove manuals should include information like this considering how many houses have over 25' chimneys.


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## BKVP (Dec 13, 2020)

begreen said:


> All stove manuals should include information like this considering how many houses have over 25' chimneys.


How many?  %?


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## SpaceBus (Dec 13, 2020)

I'm also curious. 20'+ is pretty easy on a two story house. Our cheap little saltbox has a 24' flue so to my perspective they seem common. Most houses I've lived in have been of modest price and also two story. I know objectively that ranch style homes are common and popular, but I have no first hand experience.


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## begreen (Dec 13, 2020)

BKVP said:


> How many?  %?


It would depend on the region, maybe 50% or more in regions that wood heat? Ranch style houses seem to be a bit more common out west. FWIW, I have never lived in a one-story home except for one cold winter in a shack in New England. 

In 1973, one-story homes made up 67% of new-home construction. That declined to 43% in 2006, before reversing course and rising to 46% in 2011, said Stephen Melman, director of economic services for the National Association of Home Builders, citing U.S. Census information.





						One-Story vs. Two-Story Dream Home? Are You Ready to Decide?
					

Choosing between a 1-story and a 2-story plan can be difficult. We look at the pros and cons of each to help you decide which one works best for your family.




					www.theplancollection.com


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## john26 (Dec 13, 2020)

I have a two story with two chimneys one is 29'3" the other is 19'3"   29'3" has some over drafting 19'3" is hard to establish a draft with a new fire but that may be the insert.


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## brenndatomu (Dec 13, 2020)

We have one that is ~27' and one that is ~18'.
Might be interesting to do a poll thread of heights...
<15'
15-20'
20'-25'
25'-30'
30-35'
35'+


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## bholler (Dec 13, 2020)

Now mine is either 19 or 21 feet I can't remember.  My old house was about 38


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## john26 (Dec 14, 2020)

So I experimented with my Lope freedom that runs on the 29' chimney last night.    We had a few warm days here so I checked door gaskets with a dollar all was good.  I then added a second fire brick above the baffles centered in the stove in line with the flu outlet blocking 9" of the smoke path.  This stove has a bypass so start up was unchanged after I established a good fire (bypass closed) I started cutting back the air.  I noticed the controls are touchier but the fire seemed slow down more at low burn very lazy flame down low but still good secondary's.  The secondary flames seemed to linger and swirl more in the fire box more glowing on the secondary tubes.  I did notice a little more soot on the window in an odd 3 circular pattern.   I reloaded round 9.m.  and cut the air back all the way.  I reloaded at 4:30 a.m. this morning more coals than normal.  a few logs intact just as coals usually they are broke down a lot more.   The window seemed vary typical of over night burn some had burnt off from last night but was spread more evenly across the window.
I know this will probably void the UL listing and maybe an EPA violation punishable by death but I do think my burns did extend some  maybe 1 hr?  The wife says she will let the fire go until I get home "its hot in here"  her I deal temp is 80F.  The air was fully cut back at 5a.m.  I did use a light weight pumice brick I may replace the rest of them in the baffle with pumice type.


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## Nate R (Dec 14, 2020)

brenndatomu said:


> Might be interesting to do a poll thread of heights...
> <15'
> 15-20'
> 20'-25'
> ...



I agree, that might be interesting to know how it's distributed. 

How does one measure that? is it from the floor level the stove is on, or the exit height of the stove? I mean, that's a ~ 2 foot difference, but when you start talking about minimum stack height, that can matter.


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## john26 (Dec 14, 2020)

My measurements are the actual length of the liners.


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## brenndatomu (Dec 14, 2020)

Nate R said:


> I agree, that might be interesting to know how it's distributed.








						How tall is your chimney? A poll...
					

This came up in another thread...curious how many people have short, normal, or extra tall chimneys... Vote for as many as you have (or use) up to 3.




					www.hearth.com


----------



## Hoytman (Dec 18, 2020)

sadpanda said:


> ... Just give us the formulas / reference tables like everything else.   The formula for calculating theoretical draft is simple enough.  Adjust for local average winter ambient temperature, type of flue pipe and installation method and BOOM we are in the ball park.   Two k-type thermocouples, a data logger and a manometer can all  can be had for peanuts on Amazon.  Heck even wide band O2 sensors are standard fare for the average automotive enthusiast if we want to go full EU emissions geek.  Do the calcs, add in a couple of monitored test burns for fine tuning/user training/validation and voila!   We have a fully commissioned, safe, functional installation that keeps the EPA dweebs happy.
> 
> 
> Why is this so hard?
> ...


Can you provide the formulas you mentioned? I need them to calculate theoretical numbers... because I have the manometer and getting ready to buy thermo couples and maybe even O2 censors to get my geek on.
Would have already had this but we had a date with corona for a minor set-back.

Now I’m going to read the rest of the thread.


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## Hoytman (Dec 18, 2020)

bholler said:


> A 4" pipe on a 6" stove will not have enough volume on startup and will smoke back into the house.  Draft measurement is only one part of the equation.  You also have to have the correct volume.
> 
> Why should key dampers be avoided???   If you are using it to bring draft into spec you would not have smoke spillage at all when you open the door.
> 
> ...


I just wonder how many guys that have the old Fisher stoves with 8” breech reduced to 6” have encountered smoke into the room on start-up? Coaly is one that has discussed this many times...reducing the pipe and liner size on these stoves for increased draft.


----------



## bholler (Dec 18, 2020)

Hoytman said:


> I just wonder how many guys that have the old Fisher stoves with 8” breech reduced to 6” have encountered smoke into the room on start-up? Coaly is one that has discussed this many times...reducing the pipe and liner size on these stoves for increased draft.


I actually think they work best on 7".  I have had customers who has issues running on 6" but others who it worked fine for.

One key thing is a larger flue does not mean more draft.  The draft is the same but volume and velocity change


----------



## Hoytman (Dec 18, 2020)

moresnow said:


> Old big green machines are brining huge bucks at auction right now because of this very reason. Stupid expensive service calls for what is quite simply... Goofed up eeeeelectronic gadgets/gizmo's that are causing crazy down time in a mother nature limited time frame. Noooo good.


goofed up? Nope!! More like designed in.


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## Hoytman (Dec 18, 2020)

These automated dampers at the top of the chimney that keeps getting mentioned...has already been done on the other end of the system...it’s called Hitzer, D.S. Machine, Blaze King, Vermont Castings, and others...in the form of bi-metallic thermostats...and in at least two cases with no longer made Quadra-fire computer automated stoves controlling incoming primary and secondary air. I forget the particular model.

On the subject of barometric dampers it has been explained to me to view them as pressure sensitive two-way valves on the chimney side of the system that responds to push (down draft situations) and pull ( high wind situations) in order to maintain a given draft range or pressure within the system. Hard enough to think about their use in a coal or gas situation let alone worrying about wood burning and cooling flue gases forming creosote. Not taking a side on whether they should be used for wood, but you muddy the water, so-to-speak, when you start worrying about room air compromising flue temps versus the BD doing it’s job of maintaining proper chimney pressures and therefore proper draft range. That’s how it was explained to me and it seems much easier to think about it and understand it’s proper function in those terms...at least for me.


----------



## bholler (Dec 19, 2020)

Hoytman said:


> These automated dampers at the top of the chimney that keeps getting mentioned...has already been done on the other end of the system...it’s called Hitzer, D.S. Machine, Blaze King, Vermont Castings, and others...in the form of bi-metallic thermostats...and in at least two cases with no longer made Quadra-fire computer automated stoves controlling incoming primary and secondary air. I forget the particular model.
> 
> On the subject of barometric dampers it has been explained to me to view them as pressure sensitive two-way valves on the chimney side of the system that responds to push (down draft situations) and pull ( high wind situations) in order to maintain a given draft range or pressure within the system. Hard enough to think about their use in a coal or gas situation let alone worrying about wood burning and cooling flue gases forming creosote. Not taking a side on whether they should be used for wood, but you muddy the water, so-to-speak, when you start worrying about room air compromising flue temps versus the BD doing it’s job of maintaining proper chimney pressures and therefore proper draft range. That’s how it was explained to me and it seems much easier to think about it and understand it’s proper function in those terms...at least for me.


Close but it is only a one way valve.  It it set to only let a certain ammout of vacuum to the stove.  If the chimney has to much suction it opens reducing the suction on the stove.  It doesn't change the actual draft in the chimney just the draft that reaches the stove.   It stays closed (but leaks) when draft is low


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## sadpanda (Dec 24, 2020)

Hoytman said:


> Can you provide the formulas you mentioned? I need them to calculate theoretical numbers... because I have the manometer and getting ready to buy thermo couples and maybe even O2 censors to get my geek on.
> Would have already had this but we had a date with corona for a minor set-back.
> 
> Now I’m going to read the rest of the thread.


I linked all of formulas and spreadsheets in previous posts

Datalogger I've been using for temps: Amazon product


----------



## sadpanda (Dec 24, 2020)

bholler said:


> One key thing is a larger flue does not mean more draft.  The draft is the same but volume and velocity change



Yes...  And THAT is why its so DUMB to only focus on draft and to only be given draft recommendations...  We are having  VOLUME issues.

I believe the solution is very simple.  MFGs just need to publish CFM requirements instead of the sporadic and vague 'draft recommendation'.  Let the sweeps/end users break any/all EPA laws required to achieve safe/optimum operation.


----------



## sadpanda (Dec 24, 2020)

brenndatomu said:


> I have experimented with room air for the BD, vs air from direct connect OAK...the damper opens less, to do the same job, when using the OAK.



Was the stove on OAK or just the BD?

Draft is a measure of differential pressure.  Barometric damper is a differential valve...

Assuming your stove is not hooked to outside air, the stove slightly depressurizes the room and make up air comes from outside air infiltrating your home via windows/leaks.  

Having the BD taking air from the same room as the appliance means both are fighting for this same makeup air.  Remember, chimney draft works because flue temp/height relative to AMBIENT or outside air.  Your house functions as virtual damper...

However, if stove AND the BD are getting outside air, neither is fighting the resistance of cracks/seals etc.  In this situation, YES temperature plays a part just not a huge one.   Playing with my excel sheet, decreasing average flue temp by 80F delivers a 0.01" WC and 22 CFM reduction (6in pipe, 15ft, 32F ambient, 500>420F).   Assuming avg flue temp is kept above condensation point, the only possible point of creosote formation should be right at the BD inlet.


----------



## bholler (Dec 24, 2020)

sadpanda said:


> Was the stove on OAK or just the BD?
> 
> Draft is a measure of differential pressure.  Barometric damper is a differential valve...
> 
> ...


And how do you propose flue gas temps are kept above the condensation point when dumping unknown ammounts of outside air into the stack just past the stove?


----------



## AndrewU (Dec 24, 2020)

Hope you don’t mind a brief interruption of the technical discussion. 

Pretty sure I should be fine, but can you all comment on my likely draft before I do my first test fire. Stove is a BK Ashford 30.2, perfectly straight run of 18’ collar to cap.  Elevation about 150-180’ ASL.  2 story house, chimney is more than 10’ horizontally from the peak, so with an 8/12 pitch chimney extends about 9-9.5’ from the roof (8’8” code minimum).  Duravent brand double wall chimney with a telescoping double wall black pipe connecting the stove to the class A chimney (elevated hearth so only 4’ from collar to ceiling box).

ETA: I have an OAK for it too.


----------



## Highbeam (Dec 24, 2020)

AndrewU said:


> Hope you don’t mind a brief interruption of the technical discussion.
> 
> Pretty sure I should be fine, but can you all comment on my likely draft before I do my first test fire. Stove is a BK Ashford 30.2, perfectly straight run of 18’ collar to cap.  Elevation about 150-180’ ASL.  2 story house, chimney is more than 10’ horizontally from the peak, so with an 8/12 pitch chimney extends about 9-9.5’ from the roof (8’8” code minimum).  Duravent brand double wall chimney with a telescoping double wall black pipe connecting the stove to the class A chimney (elevated hearth so only 4’ from collar to ceiling box).
> 
> ETA: I have an OAK for it too.



Your chimney sounds excellent. Hopefully you have a roof brace since the chimney sticks up so high. 15’ minimum height and you’re at 18’. Should be great.


----------



## AndrewU (Dec 24, 2020)

Highbeam said:


> Your chimney sounds excellent. Hopefully you have a roof brace since the chimney sticks up so high. 15’ minimum height and you’re at 18’. Should be great.



Yes, roof braces were used.  We did hire a fireplace guy to do the roof work.  I can do a lot myself, but I don’t do roof work.  Especially with an 8/12 pitch.


----------



## stoveliker (Dec 24, 2020)

sadpanda said:


> Yes...  And THAT is why its so DUMB to only focus on draft and to only be given draft recommendations...  We are having  VOLUME issues.
> 
> I believe the solution is very simple.  MFGs just need to publish CFM requirements instead of the sporadic and vague 'draft recommendation'.  Let the sweeps/end users break any/all EPA laws required to achieve safe/optimum operation.





sadpanda said:


> Draft is a measure of differential pressure.  Barometric damper is a differential valve...



There is some truth in that draft is not the right terminology. But draft is also not differential pressure.








						Draft in Chimneys
					

Scientific American is the essential guide to the most awe-inspiring advances in science and technology, explaining how they change our understanding of the world and shape our lives.




					www.scientificamerican.com
				



copied from a pdf, so some spelling issues, but readable. From 1869 ...!

What matters is the total airflow through the system, as you recognize. However, flow is created by a driving force and a resistance in the system. Those are the knobs one can tune.

Given that the impedance in a (proper) chimney is negligible when compared to the impedance of the stove, what matters is the pressure difference in the chimney (the driving force), and the impedance (resistance) of the stove. The first is the engine for the system operating, and the latter is the bottleneck limiting the flow.

These two aspects determine the flow. (And yes, the temperature of the flue gases affects the pressure difference created in the chimney.)

Focusing on flow may therefore be correct, but it's a *derived* quantity. One cannot "dial in" a flow. One can dial in a chimney length.  Flow is the volume of gas at a certain pressure and temperature which goes through a cross sectional area per second ... see how complicated that gets if mfg's would tell you "x cubic foot per minute at 300 F"? How'd the average customer do that...).

As the impedance of the stove is not controllable (beyond the tuning of the air inlet - and that has been controlled by the mfg by limiting your options to (almost) closed and "xx square inch open"), what remains is  the "engine" that gets the system going: i.e. the pressure difference. 

For a given stove (and when reading a manual with mfg instructions, the stove is "given", i.e. won't change), a certain range of pressure difference created by the chimney will allow the stove to operate. As that range is to a large extent determined by the chimney length, with outside temps, local geography, wind conditions, etc, being *perturbations* (only, even if sometimes substantial) on this chimney length, AND with the length being easily prescribed while the perturbations cannot be dictated, ... as all that, the manufacturers do focus on chimney length.  To make the length a decent proxy for the driving force they need, they tell you not to put 90 degree elbows, and a horizontal length of more than xx ft.

Do the chimney (length, geometry) right, and yes, the system will work. 

Finally, to have manufacturers prescribe lengths that in fact will make customers happy despite the (sometimes substantial) perturbations of uncontrollable local circumstances, manufacturers will add a safety margin into their calculations.

So, forgive my lecturing - it's a personal flaw - but I think this discussion so far somewhat misses the point (driving force and resistance rather than derived quantities), and I hope the above explains the "why" of chimney length prescriptions - it is simply the most deterministic knob a mfg can dictate to make sure things work.


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## Isaac Carlson (Dec 24, 2020)

A lot of the things you mention are because of user error.  You need to learn about anything you are going to use BEFORE using it.  So many people install a wood stove and try to burn any wood they can find.  They don't know about it works or what maintenance to do.  And some of them just don't care.  The rest just don't know and are oblivious to the fact that everything in the world needs maintenance.

There are draft tables and chimney size/area charts.  It is all available Online or from some stove installers.


this one is  metric, but you can convert it.


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## john26 (Jan 13, 2021)

I was wondering if anyone has a picture or used a draft limiter form Pacific Energy?  The more I read about the EBT, my understanding is that the stove has a  small allowable amount of air flow on the secondary's normally.  When the draft increases it sucks open the small baffle allowing extra air in the secondary manifold like a boost mode  then closes  down again as the fire decreases slowing draft back down.    Is my under standing of this correct?





						Fireplace Parts
					

Pacific Energy Parts  has the largest supply of replacement parts for Wood burning Freestanding Stoves and Wood Burning Fireplaces in the world.  Keep your home heated safely using genuine Pacific Energy Fireplace Parts. Rapid Shipping!



					pacificenergyfireplaceparts.com


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## MR. GLO (Feb 20, 2021)

sadpanda said:


> TL;DR
> 
> Getting additional draft is easy: add more pipe.  Reducing draft is wrought with compromise and with current restrictions is _*technically *_impossible. The overdraft problem is virtually universal; even with a flat roof, any two story house will have a stack taller then mfg recommendations. This is illogical, poses eminent danger and should be rectified with extreme prudence
> 
> ...


jotul lists draft.


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## bholler (Feb 20, 2021)

MR. GLO said:


> jotul lists draft.


Every manufacturer will provide a draft spec if asked.  Most also have technical manuals that are much more detailed


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## DBoon (Feb 21, 2021)

This might have already been answered in this post, but practically speaking can anyone tell me where to find information on:

Realistic draft reductions due to horizontal runs or elbows?
Realistic draft reductions due to size of chimney pipe (friction loss of smaller pipe versus larger pipe)?
Realistic draft reductions due to chimney caps?
Realistic draft reductions possible with a pipe damper?
I know that I am going to have a problem with a 27' chimney on a new install, but it would be nice to be able to calculate the extent of the problem I'll have relevant to the stove I will install.


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## bholler (Feb 21, 2021)

DBoon said:


> This might have already been answered in this post, but practically speaking can anyone tell me where to find information on:
> 
> Realistic draft reductions due to horizontal runs or elbows?
> Realistic draft reductions due to size of chimney pipe (friction loss of smaller pipe versus larger pipe)?
> ...


There is no way to give you realistic numbers for those things.  They all play off of each other and changing one variable will change the effects of all of those things.  As will house pressures outside barometric pressure temp etc.  At 27' I would just plan on 2 key dampers


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## begreen (Feb 21, 2021)

john26 said:


> I was wondering if anyone has a picture or used a draft limiter form Pacific Energy?  The more I read about the EBT, my understanding is that the stove has a  small allowable amount of air flow on the secondary's normally.  When the draft increases it sucks open the small baffle allowing extra air in the secondary manifold like a boost mode  then closes  down again as the fire decreases slowing draft back down.    Is my understanding of this correct?


The EBT A and B are explained here.





						Sweep's Library - Pacific Energy's Extended Burn Technology
					

Here's a look at Pacific Energy's EBT technology, as used on several Summit, Neo and Alderlea wood stoves



					hearth.com


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## john26 (Feb 21, 2021)

begreen said:


> The EBT A and B are explained here.
> 
> 
> 
> ...


Thank you I read through it a few times and few threads on here with The Chimney Sweep I have a much better understanding of it now.  If I could only adapt one to my Lopi LOL.


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## DBoon (Feb 22, 2021)

bholler said:


> I would just plan on 2 key dampers


I certainly respect your knowledge and experience in this regard, bholler, but it is puzzling why there is no data available from anywhere that states what draft restriction one key damper will provide under some type of standard operating conditions. In fact, there doesn't seem to be very much data on just about anything relating to chimney drafts, just sort of an "about this" approach and a bunch of rules of thumb. As a technical person, I'd really like to see the math.


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## bholler (Feb 22, 2021)

DBoon said:


> I certainly respect your knowledge and experience in this regard, bholler, but it is puzzling why there is no data available from anywhere that states what draft restriction one key damper will provide under some type of standard operating conditions. In fact, there doesn't seem to be very much data on just about anything relating to chimney drafts, just sort of an "about this" approach and a bunch of rules of thumb. As a technical person, I'd really like to see the math.


There is no data because there are simply too many variables with a natural draft appliance.


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## Highbeam (Feb 22, 2021)

And not all key dampers are the same. Some have big holes!


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## coaly (Feb 23, 2021)

DBoon said:


> This might have already been answered in this post, but practically speaking can anyone tell me where to find information on:
> 
> Realistic draft reductions due to horizontal runs or elbows?
> Realistic draft reductions due to size of chimney pipe (friction loss of smaller pipe versus larger pipe)?
> ...


The Wood Burners Encyclopedia by Jay Shelton is an excellent book that gives tons of technical info in an easy to read and understand manner. They go cheap on eBay and by far the best book I use. This book was listed as further reading in every Fisher manual that came with a stove! It's like manufacturers don't want customers to know these things making themselves dangerous today.

Your question is asking for resistance coefficients of chimney components.

There are pages that explain the variables.
There are  4 parameters that change total flow. (Temp difference between flue gasses and outdoor air, chimney height, chimney diameter, and whole system resistance coefficient)

After adding up the resistance values compiled from the first very important table (I give examples below) you then use the total system resistance coefficient in a table that calculates flow at given temperatures of the chimney size. The curve shows at what temps the flow will be.

This is how resistance values are calculated;
An open fireplace or open door stove uses inlet resistance as 2.
At the other extreme, if an air damper is air tight, its resistance would be infinite.
Everything else is given a resistance value in between.

Starting with the stove itself, different size stoves with air wide open has an air inlet damper effective resistance. Meaning door closed, air wide open. The air intake opening is the most resistance in the system.
As an example, a small stove with 6 inch outlet can be 10-40. Larger stoves with larger air opening can be 5-20.
This is the resistance coefficient of the stove itself with air damper wide open.

The items you questioned;
Each component is given an estimated range since there are large variations of resistance of various kinds of caps, pipes and elbows due to different surface smoothness, gradualness of curves, shapes of caps etc.

Round elbow, 45* --------- 0.2-0.7
Round elbow, 90*---------- 0.5-1.5
Tee or Breeching ---------- 1.0 - 3.0
Straight pipe
4 inch------- .08  - .12 per foot
6 inch ------- .05 - .08 per foot
8 inch ------- .04 - .06 per foot
Chimney top
Open --------------------------0.0
Spark Screen-----------------0.5
Rain / Wind Caps------------0.5 - 3.0
Pipe Damper
Open--------------- ---------- negligible
Closed ------------------------5-20

Notice this shows the inlet damper wide open with the resistance through stove can be about the same as a closed flue pipe damper. Modern dampers have no regulated opening when closed, they are very tight compared to antique dampers made for a calculated opening when closed.

These numbers can be used to estimate the overall capacity of a venting system, but are perhaps more useful for estimating the effect of contemplated changes to an existing system.

What a horizontal pipe does (pitched upward at least 1/4 inch per foot) is adds to the pipe resistance without adding to the total height of system. So using the tables with resistance vertical and chimney temp differential horizontal, the curve changes due to less height at the higher resistance.  A century ago it was common to put the stove as far away from chimney as possible. So calculating 50 feet of pipe resistance without gaining height, you see how much draft was needed to overcome the added resistance.

There may be computer programs now to calculate flows better, but I'm old school still using the paint method to figure out square footage of radiation surface area.


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## MR. GLO (Feb 23, 2021)

brenndatomu said:


> I've been saying for years that half the problems people come here with are due to wet wood...the other half are draft issues....and I am just shocked that you almost never see anybody suggest checking the draft (in the stove forums) or somebody says, "they checked it when they put it in...back in September"...say what?! They checked the draft with no fire, and when it was 60* out?!


I would like to see a video of somone checking a draft on a stove during the entire burn process..   I cant find any.   I know the damper will change your draft but I heard others using magnets over the secondary air hole, but I don think this would change the draft readings.  Has anyone tested the magnets?


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## begreen (Feb 23, 2021)

MR. GLO said:


> I would like to see a video of somone checking a draft on a stove during the entire burn process..   I cant find any.   I know the damper will change your draft but I heard others using magnets over the secondary air hole, but I don think this would change the draft readings.  Has anyone tested the magnets?


Putting magnets over the secondary intake should be a last effort, after others fail. Doing so will upset the designed combustion balance in the firebox. Cutting off the boost air first and if necessary reducing the primary air a bit more is better for keeping the clean burning characteristics of the stove.


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## john26 (Feb 23, 2021)

On my Lopi I reduce the secondary air inlet in the low setting from 3/8" to 3/16" and it drastically changed the way the insert performed.  I tried 2 fires with it it smoldered with little to no secondary flame, window turned very black quickly but burned time was extended some but not enough to justify a smoke dragon.


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## DBoon (Feb 25, 2021)

Thanks for the info, Coaly. I've found some other on-line resources as well using some of the key words you mentioned and I'll be diving into this a little more over the weekend.


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## ABMax24 (Feb 25, 2021)

Drilling holes and creating orifices' to reduce airflow isn't as intuitive as it seems. take a 1/2" and 1" hole for example, the 1" hole has 4 times the area, and roughly 4 times the flow of the 1/2". I think this is where a lot of people go wrong in doing this.

I've played around with restricting air to the secondary tubes a lot, quite frankly more than any sane person should. I have got reasonable results, and managed to get my stove to operate semi-normally on a 36ft stack. That being said it was still more sensitive to outside air temps than any other stove I have run.

I'm now a big believer in flue dampers, it reduces the vacuum on the stove to that a normal height chimney. They can also be adjusted to suit the current draft situation, and allow the primary and secondary airflows to be balanced with each other.

My stove is now setup as it came from the factory, the ICC Ultrablack damper in my flue works well, although it did require a little more restriction to deal with my excessive stack height.


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## Trevor Tahclep (Dec 25, 2021)

john26 said:


> I was wondering if anyone has a picture or used a draft limiter form Pacific Energy?  The more I read about the EBT, my understanding is that the stove has a  small allowable amount of air flow on the secondary's normally.  When the draft increases it sucks open the small baffle allowing extra air in the secondary manifold like a boost mode  then closes  down again as the fire decreases slowing draft back down.    Is my under standing of this correct?
> 
> 
> 
> ...


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## Isaac Carlson (Dec 25, 2021)

Outside temps have more of an effect on draft than most people would think.  The same with flue temps.


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## brenndatomu (Dec 25, 2021)

Isaac Carlson said:


> Outside temps have more of an effect on draft than most people would think.  The same with flue temps.


Yup, HUGE!


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## BKVP (Dec 25, 2021)

Forecast for Wed at 9F in Walla Walla.   It's awesome we have some snow and cold.  Need the snowmelt in Spring.


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## Isaac Carlson (Dec 25, 2021)

Our chimney pulls harder as the temps drop, which automatically pulls more are through the same size opening, which tends to keep the house about the same temperature.  BUT, that's a function of stove size, chimney, and house leakage.


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