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

[ABMax24]

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]

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]

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.

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]

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.

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.

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]

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

 

[jetsam]

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.

 

[Highbeam]

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]

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]

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]

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?

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.

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.

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

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.

 

[bholler]

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]

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

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]

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.

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.


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.

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]

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]

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]

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]

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]

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.

 

[lsucet]

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.

 

[bholler]

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]

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]

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.

 

[ABMax24]

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]

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]

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.