# Outside Air Kit - Oak - My research after investigating



## adam6979 (Dec 26, 2014)

So we had a pretty good thread going and it got closed. I was actually looking at adding an OAK to my two stoves. I have done a significant amount of research and this article best describes the flawed logic with OAK's. I will stay with drawing the inside air....

(OLD THREAD: https://www.hearth.com/talk/threads/reasons-for-an-oak.137260/page-3)

Helpful Article: http://www.woodheat.org/the-outdoor-air-myth-exposed.html


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## adam6979 (Dec 26, 2014)

This was my favorite part: "The supposed benefits of outdoor air are not supported by research results."


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## joed2323 (Dec 26, 2014)

Drill a hole and be done with it It is nonsense why you are against another small hole! The benefits far outweigh the bad... 

Getrdone


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## Wilbur Feral (Dec 26, 2014)

1) That article has been cited before, on this forum.
2)  It deals with woodstoves and fireplaces, not pellet stoves.  You might notice that neither wood stoves nor fireplaces have combustion blowers that actively pump air out of a home.  
3) Nothing in the article is referenced.  Nothing...

You can believe whatever you want - I've given up trying to help those who are beyond it.


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## fmsm (Dec 26, 2014)

Why would you want to burn heated air and replace it with cold outside air in your house?


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## acammer (Dec 26, 2014)

Yea, this is dealing with passive systems with draft based exhaust.  A pellet stove is a different animal.


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## woodmakesheat (Dec 27, 2014)

It's not even required to drill a second hole, just widen the exhaust hole a little & either modify the thimble or buy one that's already modified to allow the OAK to feed through the common opening.



	

		
			
		

		
	
 . I modified my thimble, but one can purchase a thimble that has the OAK


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## alternativeheat (Dec 27, 2014)

Pellet stoves are different than wood stoves or coal stoves. Pellet stoves force air through the combustion chamber and up the vent. Air taken from your living space with no OAK.  I've burned all three in this house and the draft situation in the house was never so pronounced as when I installed the pellet stove. I mean every single known draft in the house intensified maybe 3 fold. That is three times  the cold air replacing warm through any hole it can get in through and it was honestly felt throughout the house in the form of what can only be called wind or a breeze.. This winter I put in the OAK and that phenomenon has returned to normal.  You certainly can do as you please it's your house but I am here to tell you that OAK with a pellet stove makes a difference in My House where it was unneeded with either a wood or a coal stove..

Your stove is basically taking about ( speaking rough terms here) a block of heated air from your house roughly the size of  a  good sized closet every single minute it's operating. With in an hour depending on house size, it's cleaned your house out. And you think this is better than taking air from outside that is free ?

Some super tight houses require OAK and some stove manufacturers specify OAK on installation. There is a reason for this. Pellet stoves mechanically remove air from your breathing location.


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## bogieb (Dec 27, 2014)

One stove I HAVE to have an OAK to make the clearance to windows legal. The other stove, I added the OAK after running for a month or so without one. Much prefer with the OAK. Plenty of people don't use them and are good with that. Plenty of people have put in "significant" research before putting in OAKs. Some people have found that what "experts" tell you to do (or not to do), does not work well in their particular case.

Do what you want to your place, makes absolutely no difference to mine.


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## TimfromMA (Dec 27, 2014)

Not using OAK is the equivalent of cutting a 3 or 4 inch hole in your wall and putting a fan in it blowing out.


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## F4jock (Dec 27, 2014)

With my Harman insert I insulated around the surround and opened the old fireplace rear cleanout door that opens into the garage. I then taped a six-inch ribbon on top of the frame hanging down into the opening. When the stove is firing the ribbon is sucked into the hole almost horizontaly. To me that represents a heck of a lot of room air that would have been used for combustion and thus would have had to have been replaced from outside.


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## elevenMracing (Dec 27, 2014)

I agree with what alternativeheat said above.  I recently switched from an lp furnace in the basement that used room air for combustion to a pellet furnace in the basement with an OAK.  Ive noticed a large reduction in the amount of cold air drafting in through known leaky windows in the basement.  I've had thoughts of drilling a hole through the interior door leading to the basememt and hooking up my manometer to it and running each furnace to see if there was a measurable difference.


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## DBCOOPER (Dec 27, 2014)

bogieb said:


> One stove I HAVE to have an OAK to make the clearance to windows legal.



So Adam, why do you think an OAK would be required to reduce the exhaust clearance to a window? Perhaps the negative pressure inside the house could draw in the exhaust somewhere around the window/frame?


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## St_Earl (Dec 27, 2014)

yes. anytime i get a thread locked on a message board, i take it to mean i should start another on the exact same topic as soon as possible.

you could spend a solid week reading the search results here for OAK.


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## bags (Dec 27, 2014)

No scientific research needed. It's common sense. Quit worrying about researching about what he said,,, she said on the OAKS and spend some time looking into positive and negative air within a home. Also look into combustion air for say gas fired appliances and how they compete for air with bath fans, exhaust hoods and the like. Flues will not draft properly if they are being robbed of air by appliances, furnaces, etc; There are scientific studies on this stuff. You are just looking at the wrong ones. Get an energy audit and hook up a blower door test to your house and see how much leaky air that bad boy finds for you. You'll be surprised. Your stoves are finding them too. 

You need to understand how air moves and apply that to pellet stoves. I'll make it simple in a simple scenario. IF you have a 200 CFM blower on your stove putting out 200 CFMs of hot air but also leave a bath fan on that pulls out 150 CFMs then you are only gaining 50 CFMs of warm air. Keeping this in simple math terms here. Why do these newer high efficiency gas furnaces need outside air? So they can be efficient and not steal air from inside. A pellet stove operates much the same but only burns a different fuel. Pellets instead of gas. I've seen plenty of those furnaces pulling air from the basements because some installer took a short cut.

200 warm CFM input - 150 CFMs exhausted leaves = 50 CFM of warm air for you. With this you are burning 40 lbs. of pellets and only benefiting from 10 lbs. Trying to keep this very simple to avoid arguments and there are other factors that can be considered. Technically, each occupant in the home puts off BTU's but like I said, simple. On the flip side to quash that argument windows lose and gain too. It can get very complex but it can all be figured out in calculations.

So the bath fan stole 150 CFMs of your warm air. A pellet stove is in a sense a bath fan exhausting to a degree. It blows AIR out. Where is it getting the air it is exhausting? It's stealing it from inside your home all while pulling in cold outside air from leaks, bad weather stripping, can light housings, etc;

Lucky for us all this is still a free country and we as individuals can do what we chose to do. If you don't want an OAK and think they are a waste of time then great. I'm all for it. We can all just agree to disagree. I'm not paying for your pellets and you are not paying for mine. It's all good!


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## Skier76 (Dec 27, 2014)

My research indidates a "heated" (pun intended) debate with no agreement in sight.


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## F4jock (Dec 27, 2014)

Skier76 said:


> My research indidates a "heated" (pun intended) debate with no agreement in sight.


I'm having a hard time understanding how anyonone can argue with elementary physics. Nature abhors a vacuum. When you draw combustion air from a room and send it up the stack it MUST be replaced else the room will eventually implode. Since there is a limited volume of air in the room removing some of that air creates a very slight vacuum. Air will move into that room to fill that vaccum following the path of least resistance. This path may be from another room but ultimately the slight negative pressure the stove creates in the house MUST be equalized with an influx of air and the only place that equalizing air can ultimately come from is, wait for it, the outside. The colder outside. Now, if one takes the combustion air from the outside, as with an OAK, and returns it there, no negative pressure is created in the house and thus infiltration of cold outside air is not exacerbated. You will still have exchange of air through badly sealed windows, doors etc. but it won't be sucked into house by removal of air from within. You can't argue the physics of this, unless maybe you want to get into quantum mechanics.


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## bags (Dec 27, 2014)

That attached article isn't worth the paper it's written on IMO for various reasons. It is merely "someone else's" opinion. They talk a mean game but have no facts to back their statements either. Some research and things were stated but not cited, referenced, nor backed with proof and facts. When was it even written? Some statements are valid regarding air flow and such but nowhere is this author talking about the outside air regarding pellet stoves. I will agree many building codes are very generalized and many municipalities just follow suit out of ease and to have something on the books that someone else had an opinion about or Larry the engineer in New York signed off on. Many situations are different and you can not always apply how it reads in the rule book so to speak. There are exceptions to everything. They are talking about wood stoves and fire places. Not a pellet stove which pulls and pushes air in an entirely different manner.

Anything that requires combustion air will get it from pulling the air from somewhere. The bigger need appliances and burners usually win too. To put that article in a nut shell, Yes, sure things will get and pull air from somewhere. They even showed pictures or drawings of it theoretically. Might have been a bit off on arrow placement. Maybe not. LOL!  The main point is that an OAK reduces a pellet stove from pulling already heated inside air for combustion and replacing that lost warm air with leaky air from your homes envelope. I don't think you understand fully what some here are saying.

Just like in the article they found out the big fancy high CFM 1980's range hoods were stealing air. I feel the author's opinion is a bit dated and generalized. Many newer appliances have remedied their need to steal air. Examples are: Powered vented gas hot water heaters and furnaces supplying and exhausting their own air. Many range hoods are no longer direct vent that push air outside. Some appliances have to be vented outside or should be. Bath fans and dryer vents are two. I've seen where Jimmy Bob Billy has slung some hose to wherever on those as well. Attic spaces and basement floors seem to be a favorite.   

This article is also not referring to pellet stoves in any way, shape, nor form. Pellet stoves do control their outside air intake. This author is talking about some free ranging wild hole in the wall. I just read this after my comment above. This article has no relevance for pellet stoves. Sorry to be the bearer of bad news.


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## Don2222 (Dec 27, 2014)

adam6979 said:


> So we had a pretty good thread going and it got closed. I was actually looking at adding an OAK to my two stoves. I have done a significant amount of research and this article best describes the flawed logic with OAK's. I will stay with drawing the inside air....
> 
> (OLD THREAD: https://www.hearth.com/talk/threads/reasons-for-an-oak.137260/page-3)
> 
> Helpful Article: http://www.woodheat.org/the-outdoor-air-myth-exposed.html



1. Why put heated room air up the chimney with no OAK?

2. Why run cold damp air into the burnpot with an OAK?

Why not pull in outside air and heat it and dry it out then send it into the burn pot? ? ?

Answer is simple here!
Selkirk DT is a no brainier for me!

See my pics here
https://www.hearth.com/talk/threads...n-out-direct-or-top-vent.129497/#post-1743756


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## 3650 (Dec 27, 2014)

if you have a tight house you probably wont notice a whole lot of difference, but if your curtains blow with the wind you will wonder why you did do it sooner. At least that was my experience. I have an uninsulated 100 yo splitfaced block house with single pane windows. I could figure out why my thermostat read 80* and I was freezing. I bought one of those window units for the back room and they are self contained and therefore use outside air. I couldn't believe how warm the back room was. Then it dawned on me it had outside air. I hooked up an oak using 3" rigid aluminum dryer vent and have never looked back. The difference was amazing. On the other hand my sister has the same stove as me and her house is tighter then a bed bug in a book crack. She has no oak and her house is hot on the lowest setting most of the time.


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## bags (Dec 27, 2014)

Don,
Several OAKS do preheat the outside air first and that is better. Mine does. That said, I'd still rather have one pulling cold damp air in thru any OAK than sending my warm air out the stack. Humidity is usually down in the winter's cold air too but heating it is ideal.

3650,
All houses leak. Even the tight new ones sprayed with foam. Not a lot but they are losing heat somewhere. Otherwise you could heat it once in a great while and maintain the desired temps. Eventually, the heat would radiate out and or cold in. Some homes are worse than others and with your sister she is experiencing a lower rate of loss and her stove is pumping in more warm air than she's losing which is a good problem to have. My last place was an older drafty place and that's no fun.


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## Zebby (Dec 27, 2014)

Yep - I have an OAK direct to the firebox. 
The stove is actively pulling in a quantity of fresh air, using it in combustion, and actively pushing the hot expanded products of combustion and excess air out the vent. 
Warm/moist room air is drawn through the heat exchanger, heated and pushed back into the room.
That's the way I like it.

OAK - just do it!


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## F4jock (Dec 27, 2014)

bags said:


> Don,
> Several OAKS do preheat the outside air first and that is better. Mine does. That said, I'd still rather have one pulling cold damp air in thru any OAK than sending my warm air out the stack. Humidity is usually down in the winter's cold air too but heating it is ideal.


There are two telling statements in the last paragraphs of the cited article on the myths of outside air. Essentially they state that the entire article is premised on largely passive air feed to a system whose draft is totally based on natural chimney draft, something that essentially does not exist with a pellet stove.


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## F4jock (Dec 27, 2014)

3650 said:


> if you have a tight house you probably wont notice a whole lot of difference, but if your curtains blow with the wind you will wonder why you did do it sooner. At least that was my experience. I have an uninsulated 100 yo splitfaced block house with single pane windows. I could figure out why my thermostat read 80* and I was freezing. I bought one of those window units for the back room and they are self contained and therefore use outside air. I couldn't believe how warm the back room was. Then it dawned on me it had outside air. I hooked up an oak using 3" rigid aluminum dryer vent and have never looked back. The difference was amazing. On the other hand my sister has the same stove as me and her house is tighter then a bed bug in a book crack. She has no oak and her house is hot on the lowest setting most of the time.


Combustion air has to come from somewhere to equalize pressure or the house would have imploded and your sister exploded.


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## checkthisout (Dec 27, 2014)

The article is for wood stoves which use natural draft and are thus not equipped with a blower.

In that case, the article probably makes some accurate points but does not provide any references to any sources of information used to make the conclusions.

In a lot of cases sure, an OAK probably isn't that big of a deal because the stack effect that comes from heating the house (higher pressure generated by hot air rising the ceiling) is probably a larger loss than a draft generated by a wood-burning stove and may, as the author stated (without citing any sources) may actually cause problems during high winds.

In the case of a pellet stove, sure, some people probably have such leaky, poorly insulated houses that a closed loop combustion circuit won't make any noticeable difference. In other words there are bigger fish to fry before installing an OAK. However, installing the OAK certainly wouldn't hurt and would be the final step in the making the system as efficient as possible.

As others have stated, there is a reason high-efficiency Natural Gas appliances have closed combustion systems and also why pellet stove manufacturers can spec a lower exhaust-to-window clearance if an OAK is used.

If you don't believe an OAK helps out in terms to using less fuel to heat your particular building then explain why countless engineering studies have shown otherwise.

This is a fun discussion but lets keep it civil. Hearth.Com is one of the few internet forums I frequent where people don't flame each other, as frustrating as it can be when someone on the internet is wrong.....


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## checkthisout (Dec 27, 2014)

And as a side note, I wish I had done better research on available products and used that Sel-Kirk direct-temp stuff during my install. The beefier pipe would have looked cooler and the design  preheats the intake air.


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## TimfromMA (Dec 27, 2014)

Combustion air has to be replaced from somewhere.


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## BUBIBEAR (Dec 27, 2014)

I can not understand why anybody who can read ,would continue to bother with subject . If the stove company states in the instructions that. OAK IS MANDITORY WITH THIS STOVE . What is your problem . Quit wasting everyone s time. Show some smarts . Do not buy the stoves that require an  OAK .


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## Rearscreen (Dec 27, 2014)

Makes me wonder about science. My new sweetheart has had stoves all of her life. Then I entered her life. She said her house is always drafty in the winter. I said do you have an OAK? She was unaware that woodstoves can do this. I installed one and she can't believe the drafts are gone. But I will reread the article and try to convince myself....


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## F4jock (Dec 27, 2014)

Rearscreen said:


> Makes me wonder about science. My new sweetheart has had stoves all of her life. Then I entered her life. She said her house is always drafty in the winter. I said do you have an OAK? She was unaware that woodstoves can do this. I installed one and she can't believe the drafts are gone. But I will reread the article and try to convince myself....


The article focuses on one sector of stoves. Please read the last three paragraphs.


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## FTG-05 (Dec 27, 2014)

I had three non-negotiables when installing my wood stove this last summer and fall:

- Safety.  This meant no corners cut.  This meant no corners being discussed to be cut.  This meant that stove manufacturer and NFPA requirements were just that: requirements, not wishes or hopes to have or "I'm the expert" (let's not go there).  Without safety, all else is irrelevant.  In short:  RTFM.  Then follow it.

- Englander 30-NC wood stove.  Best stove for the money, excellent company customer service reputation and it has a huge glass window so that my wife could see the flames.  Ok ok, you're probably right:  the first two just happened to come along for the ride, the third was the real "non-negotiable".  Ok, so what, sue me!

- OAK.  You want to me to go to all that trouble to heat air not once, but twice??? Are you out of your mind?  Get the fork outta here!











Any questions?


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## woodmakesheat (Dec 27, 2014)

I measured the OAK intake airflow of my stove on heat setting 7 of 9. It measured 600 lfm using a calibrated anemometer. The inside diameter of the OAK is about 1.92 inches. A little math and you have ~12-13 CFM. Not sure if this adds to the conversation, but I'm an engineer so I like to measure things. 

The biggest benefits of the OAK for me are 1) the moisture in my house is retained better than it was with the woodstove that drew air from the inside of the house and thus sucked cold dry air into the house from the outside. My humidifier is working less that it did when I used the wood stove for heat. Granted it's been moist so far this year, so this is still not completely verified 2) The power has died here 2x already this year since I installed the pellet stove and not even a slight scent of smoke was emitted into the house from the pellet stove as it burned itself out. This may have worked just as well drawing inside air, but having the system isolated from the living space and a greater delta T between intake and exhaust is nice insurance.

I have no issue with what's in the article - fighting the draft demons on a windy day or a day where a huge inversion existed was always a concern with the woodstove. The 1st year I had the woodstove I got the most heinous sinus infection ever. I contemplated clearing my sinuses with a .38 it was so awful. Dry air contaminated with stove spillage didn't help and may have helped trigger said sinus issues. But I don't agree with the certainty of the article re: can it be said that an external intake is always better or worse with a woodstove - I don't see how one could ever make such a definitive statement after burning wood for a few years. I do know that I'll take a pellet stove any day of the week over a wood stove when it comes to indoor air pollution and aching sinuses. I also know the article is not relevant to a pellet stove's forced, guaranteed negative pressure combustion chamber.


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## F4jock (Dec 27, 2014)

FTG-05 said:


> I had three non-negotiables when installing my wood stove this last summer and fall:
> 
> - Safety.  This meant no corners cut.  This meant no corners being discussed to be cut.  This meant that stove manufacturer and NFPA requirements were just that: requirements, not wishes or hopes to have or "I'm the expert" (let's not go there).  Without safety, all else is irrelevant.  In short:  RTFM.  Then follow it.
> 
> ...


Hey. If you want to suck hot air out of your home for combustion use and cold air in to replace it so your stove works harder it's up to you. You ARE heating air twice. The air you bring into the room frim outside and the air you exhaust from the room for combustion instead of recirculating it but if you want to reinvent physics maybe you should write a paper and you and Sheldon Cooper can present it.


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## F4jock (Dec 27, 2014)

woodmakesheat said:


> I measured the OAK intake airflow of my stove on heat setting 7 of 9. It measured 600 lfm using a calibrated anemometer. The inside diameter of the OAK is about 1.92 inches. A little math and you have ~12-13 CFM. Not sure if this adds to the conversation, but I'm an engineer so I like to measure things.
> 
> The biggest benefits of the OAK for me are 1) the moisture in my house is retained better than it was with the woodstove that drew air from the inside of the house and thus sucked cold dry air into the house from the outside. My humidifier is working less that it did when I used the wood stove for heat. Granted it's been moist so far this year, so this is still not completely verified 2) The power has died here 2x already this year since I installed the pellet stove and not even a slight scent of smoke was emitted into the house from the pellet stove as it burned itself out. This may have worked just as well drawing inside air, but having the system isolated from the living space and a greater delta T between intake and exhaust is nice insurance.
> 
> I have no issue with what's in the article - fighting the draft demons on a windy day or a day where a huge inversion existed was always a concern with the woodstove. The 1st year I had the woodstove I got the most heinous sinus infection ever. I contemplated clearing my sinuses with a .38 it was so awful. Dry air contaminated with stove spillage didn't help and may have helped trigger said sinus issues. But I don't agree with the certainty of the article re: can it be said that an external intake is always better or worse with a woodstove - I don't see how one could ever make such a definitive statement after burning wood for a few years. I do know that I'll take a pellet stove any day of the week over a wood stove when it comes to indoor air pollution and aching sinuses. I also know the article is not relevant to a pellet stove's forced, guaranteed negative pressure combustion chamber.


You'll soon find that being an engineer hereon can sometimes be frustrating . . . .  but as you, I and others have been trying to say, while some of this may be relevant to a wood stove it does not apply to pellet stoves!


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## Bridgeman (Dec 27, 2014)

So yea, OAK  instalation seems logical and certainly has passionate defenders on this site. The question I have is where is white paper study by a recognized authority that gives hard numbers that proves the point? I have looked and I don't think it exist. I agree it makes common sense and an there is a compelling argument that it saves money and pellets.  The point is this, is there hard science to back or disprove the need for an OAK? If there is such a thing post the link and put this discussion to rest. I have a feeling that because of the infinite variability of conditions and installations this would a very difficult thing to study. I personally have a Harman in a center chimney instalation with no liner or OAK and the thing works great. If I could get a definitive answer that I would save X amount of pellets with an OAK I would go through the trouble of drilling down into the brick and out a getting fresh air for combustion. I have a few technical issues with running very cold vent pipe in my furnace room that has held me back. So show me the hard numbers and convince me it is worth the trouble. No BS back of the envelope stuff from you engineers either. The majority of that stuff just an opinion with made up numbers to prove your point.


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## woodmakesheat (Dec 27, 2014)

If it's too difficult, I wouldn't do it. In fact I didn't do it with my woodstove (even though manuf. highly recommended it) due to same issue - drilling through slate and mortar to get into the basement just didn't seem like it was worth the effort.


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## OhioBurner© (Dec 27, 2014)

Bridgeman said:


> So yea, OAK  instalation seems logical and certainly has passionate defenders on this site. The question I have is where is white paper study by a recognized authority that gives hard numbers that proves the point? I have looked and I don't think it exist.



I'd be curious as well. Unfortunately the last thread got closed as we were just about getting to some real numbers... chickenman posted up some info that their stoves were tested in lab conditions and found 10% fuel savings. So in those conditions we have some good numbers. Of course our home conditions will be greatly different and probably half or less (just guessing) the savings seen compared to lab conditions. Would be nice to learn more about the actual lab testing conditions... how many cfm were being used, insulation, temp differences inside and out, etc.

I'm probably not going to 'notice' a 5% improvement unless I'm studying numbers, but figure it is there (I hope). What I mean is I won't notice a difference of 5% in the hopper, or even on the thermometer since my room temperatures vary a lot already. Heck 5% wouldn't even be the difference of 1 notch of the heat setting on the stove. Some people with tighter houses can probably notice the induced drafts more than I, my house is too leaky that whether I'm pulling an extra 20cfm or whatever of drafts for combustion air probably isn't noticeable. I'm waiting until it gets colder though to retest to see if the difference is substantial enough to notice... colder drafts and also stove running hotter means more volume of air in those drafts. If I recall properly, my combustion blower maxes out at 80cfm and so far I've been no where near max output.

The one thing I'll point out again to those that keep stating your just wasting your already heated air up the flu not using an OAK, or its like cutting a hole in your wall and putting a fan on it blowing outside, there is at least one big difference. That heat isn't just all wasted being blown through a hole out the wall or up the chimney. Your passing it through a heat exchanger on its way outside. A big chunk of all that heat you think is being wasted is being recovered. And likewise, the colder air you think your keeping out of your home by ducting it into the stove directly also lowers temperatures and passes those effects to your home through a heat exchanger. Of course heat exchangers are not 100% efficient, so there should be some small gains in favor the OAK, just don't expect that you'll save half of your fuel cost, maybe more like a few percent. Depending on how many btu's it takes to heat your home, and how much hassle and cost to put your OAK in, the difference could be substantial or it could take it a chunk of the heating season just to pay for the OAK install. Of course there are other advantages other than financial too (humidity, backdrafting, etc). Home heating is going to very greatly from one situation to another.

Edit> also I forgot to think to design something to close off the OAK when I put mine together. Seems a small issue I've found since switchign to OAK is that it still circulates a little air  when the stove is off. The stove gets pretty cold and I'm probably wasting some btu's there, so need to stuff a rag or something over the OAK intake I guess for now.


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## adam6979 (Dec 27, 2014)

I think all the reply's that are given have been great and educational. I agree that the article wasn't good on face value and certainly did not include references. This is where the forums are useful. Real life examples are 10X greater to me than a "study" or "research says". The fact that most of you have said an OAK is important and so far no one has said that you do not need one says they are needed. This is the reply's I was looking for and I think adds value to this site Thank you again for all the information and I too will install an oak and post the results I see.


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## adam6979 (Dec 27, 2014)

OhioBurner© said:


> Edit> also I forgot to think to design something to close off the OAK when I put mine together. Seems a small issue I've found since switchign to OAK is that it still circulates a little air  when the stove is off. The stove gets pretty cold and I'm probably wasting some btu's there, so need to stuff a rag or something over the OAK intake I guess for now.




I have thought about this too. With the strong wind here (often 40-50mph in the winter and 20-30 in the spring/fall) I wanted to find a way that I could close it off manually when wanted.


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## checkthisout (Dec 28, 2014)

OhioBurner© said:


> That heat isn't just all wasted being blown through a hole out the wall or up the chimney. Your passing it through a heat exchanger on its way outside. A big chunk of all that heat you think is being wasted is being recovered..



This is not correct. Imagine for a moment you don't have an OAK and there is no fire burning in your pellet stove but the combustion blower and convection fan are running.

Sure, the room air being pulled inside the stove passes across the heat exchanger and then goes out the exhaust but since the air temperature on both sides of the heat exchanger is equal, no heat transfer can occur.

What this means is that all heat coming off the heat exchanger is being produced by the burning fuel and now more fuel must be burnt to replace the heated air that is being pulled from the building and blown outside.



OhioBurner© said:


> Seems a small issue I've found since switchign to OAK is that it still circulates a little air when the stove is off. The stove gets pretty cold and I'm probably wasting some btu's there, so need to stuff a rag or something over the OAK intake I guess for now.



Yeah, mine came with a little butterfly valve in the wall pass-through that you can open and close as needed.


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## Zebby (Dec 28, 2014)

adam6979 said:


> The fact that most of you have said an OAK is important and so far no one has said that you do not need one says they are needed.



Well, technically Breckwell only says the OAK is necessary on my stove for mobile home installation. In fact, they omitted a tube connecting the back panel of my stove to the firebox inlet.
This seems to suggest that the manufacturer doesn't think they are needed.
If you as the owner choose not to add the OAK, that is your decision.

Maybe you've got a gassy dog, in which case exchanging the air in the room with fresh air might be a good thing.

I stated in the first (closed) thread that there are a number of factors (and variables) involved in the "equation".
I don't want to waste time trying to set up or evaluate that equation and I don't have the measuring equipment, so I went with my knowledge and did what made sense to me.
My decision was that I wanted the OAK, and I also installed an inexpensive automotive manifold heat hose inside the stove to make the connection that Breckwell left out.
I have the combustion air circuit effectively separate from the room air. It just makes sense to me.
If the stove was not against an exterior wall, or otherwise difficult to install, I probably would not have added the OAK.


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## OhioBurner© (Dec 28, 2014)

checkthisout said:


> This is not correct. Imagine for a moment you don't have an OAK and there is no fire burning in your pellet stove but the combustion blower and convection fan are running.
> 
> Sure, the room air being pulled inside the stove passes across the heat exchanger and then goes out the exhaust but since the air temperature on both sides of the heat exchanger is equal, no heat transfer can occur.
> 
> What this means is that all heat coming off the heat exchanger is being produced by the burning fuel and now more fuel must be burnt to replace the heated air that is being pulled from the building and blown outside.



Yes, if you were to run the stove blower with it being off then it would basically be like an exhaust fan in the bathroom. But this is not how we run a stove. There is a temperature difference during normal operation. And that difference is slightly greater when you are using room air for supply, hence the heat exchange I mentioned.


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## checkthisout (Dec 28, 2014)

OhioBurner© said:


> Yes, if you were to run the stove blower with it being off then it would basically be like an exhaust fan in the bathroom. But this is not how we run a stove. There is a temperature difference during normal operation. And that difference is slightly greater when you are using room air for supply, hence the heat exchange I mentioned.


What if the room air temperature and outside temperature are the same?


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## F4jock (Dec 28, 2014)

You guys are making my head explode! You do not NEED an OAK but the physics of the situation doesn't change because you do or do not want one: If you draw combustion air FROM the room and exhaust it to the OUTSIDE it MUST be replaced and the only place that replacement air can ultimately come from is OUTSIDE where it's cold or you wouldn't have the stove running in the first place! If you draw combustion air FROM outside and exhaust it TO outside with an OAK you do not exacerbate cold air infiltration to the room from outside. You figure the rest out! There is no way that this reality can be changed no matter what you think or what is written where unless you have a source of bottled, compressed air you can discharge into your house. You can debate the NEED for an OAK relative to better combustion all you want, and frankly that is also pretty much a given, but you can NOT change the physics of air movement.

EDIT: And for the record, cold air generally contains slightly more oxygen than warm air, thus better supporting combustion. Once again, physics, and physics does not change because of opinion.


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## TimfromMA (Dec 28, 2014)

F4jock said:


> You guys are making my head explode! You do not NEED an OAK but the physics of the situation doesn't change because you do or do not want one: If you draw combustion air FROM the room and exhaust it to the OUTSIDE it MUST be replaced and the only place that replacement air can ultimately come from is OUTSIDE where it's cold or you wouldn't have the stove running in the first place! If you draw combustion air FROM outside and exhaust it TO outside with an OAK you do not exacerbate cold air infiltration to the room from outside. You figure the rest out! There is no way that this reality can be changed no matter what you think or what is written where unless you have a source of bottled, compressed air you can discharge into your house. You can debate the NEED for an OAK relative to better combustion all you want, and frankly that is also pretty much a given, but you can NOT change the physics of air movement.
> 
> EDIT: And for the record, cold air generally contains slightly more oxygen than warm air, thus better supporting combustion. Once again, physics, and physics does not change because of opinion.



I reject your reality and substitute my own.


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## F4jock (Dec 28, 2014)

TimfromMA said:


> I reject your reality and substitute my own.


There's a lot of that going around!


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## moey (Dec 28, 2014)

I thought this was resolved last week...


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## TimfromMA (Dec 28, 2014)

Bottom line. 
OAK is only required when the stove manufacturer and building codes say it is but it always recommended. Put it in or dont. I really don't care.


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## Keifer2669 (Dec 28, 2014)

Well said by F4jock.... The people who don't want to use an oak try so hard to justify it to themselves! Which is fine.  Enjoy the drafts, and wasting more $ to heat ur home


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## johninwi (Dec 28, 2014)

I read the linked article, it is correct grammatically.

Counterpoints
https://chimneysweeponline.com/hooa3.htm


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## Wilbur Feral (Dec 28, 2014)

F4jock said:


> You guys are making my head explode!


Amen on that!  I'm done with this one and hereby vow to not argue for or against an OAK for at least 24 hours.  And I now feel compelled to make a charitable contribution to the physics departmment at the local high school, 'cause clearly it has become a subject that is not adequately taught to far too many people.


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## F4jock (Dec 28, 2014)

Keifer2669 said:


> Well said by F4jock.... The people who don't want to use an oak try so hard to justify it to themselves! Which is fine.  Enjoy the drafts, and wasting more $ to heat ur home


But if that makes them happy who are we to keep intruding!


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## F4jock (Dec 28, 2014)

Wilbur Feral said:


> Amen on that!  I'm done with this one and hereby vow to not argue for or against an OAK for at least 24 hours.  And I now feel compelled to make a charitable contribution to the physics departmment at the local high school, 'cause clearly it has become a subject that is not adequately taught to far too many people.


And I'm with you. I'm done with this thread. And as well as the physics department I'm going to see if the English department has any courses on logic that I can support . . .


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## 3650 (Dec 28, 2014)

My oak is direct outside to firebox and that is probably not as efficient as the kind that use the chimney pipe as a heat exchange. If i could afford the high dollar type I would certainly have it. I say this because my experience in sub zero cold snaps is not all that great. I have noticed that when its like -20 out my stove doesnt seem to throw near the heat it should and I blame this on the extreme cold temps entering the firebox. I actually get frost on my oak at these temps. The heat exhange type would certainly be the way to go If you have the coin.


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## TimfromMA (Dec 28, 2014)

3650 said:


> My oak is direct outside to firebox and that is probably not as efficient as the kind that use the chimney pipe as a heat exchange. If i could afford the high dollar type I would certainly have it. I say this because my experience in sub zero cold snaps is not all that great. I have noticed that when its like -20 out my stove doesnt seem to throw near the heat it should and I blame this on the extreme cold temps entering the firebox. I actually get frost on my oak at these temps. The heat exhange type would certainly be the way to go If you have the coin.



One could argue that using your exhaust vent to preheat OAK air will cool exhaust gasses causing an increase in creosote buildup.


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## F4jock (Dec 28, 2014)

TimfromMA said:


> One could argue that using your exhaust vent to preheat OAK air will cool exhaust gasses causing an increase in creosote buildup.


And observe that cooler air contains more oxygen thus supporting better combustion but. . . .


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## FTG-05 (Dec 28, 2014)

F4jock said:


> Hey. If you want to suck hot air out of your home for combustion use and cold air in to replace it so your stove works harder it's up to you. You ARE heating air twice. The air you bring into the room frim outside and the air you exhaust from the room for combustion instead of recirculating it but if you want to reinvent physics maybe you should write a paper and you and Sheldon Cooper can present it.



I could be wrong, but you might want to read my last bullet point once more.  

Just a thought!


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## F4jock (Dec 28, 2014)

FTG-05 said:


> I could be wrong, but you might want to read my last bullet point once more.
> 
> Just a thought!


Read it several times. Unclear. At least to me sounds like no OAK but *shrug*.


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## meisen (Dec 28, 2014)

johninwi said:


> I read the linked article, it is correct grammatically.
> 
> Counterpoints
> https://chimneysweeponline.com/hooa3.htm


Hey John,
We lived in Madtown for 9 years! Miss it some but loving the milder winters here on the East Coast. 

Everything I read in your link was to do with wood stoves so is that not an apples and oranges comparison? Even if there was some evidence based data on there it's unclear if it truly applies to pellet appliances. Except maybe in a power outage scenario where spillage is a concern. I think the OAK question is made a little more complex when youtalk in terms of in a passive draft device. Glad I don't have to do that much thinking.


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## bags (Dec 28, 2014)

meisen said:


> Hey John,
> We lived in Madtown for 9 years! Miss it some but loving the milder winters here on the East Coast.
> 
> Everything I read in your link was to do with wood stoves so is that not an apples and oranges comparison? Even if there was some evidence based data on there it's unclear if it truly applies to pellet appliances. Except maybe in a power outage scenario where spillage is a concern. I think the OAK question is made a little more complex when youtalk in terms of in a passive draft device. Glad I don't have to do that much thinking.


The original article cited and attached was about wood burners also. John just attach another contradicting the one that this thread was opened with. And that has been the main point driven home here a gazzilion times that it has almost zero relevance being used with pellet stoves for starters. The second is positive and negative pressures and the happy campers watching their trouser bottoms swirl in the breeze while riding the Lazy Boy in front of their pellet stoves without OAKs hooked up.


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## bags (Dec 28, 2014)

I'll try one more angle here. Your house with a nice warm pellet stove blowing is a *hot cup of coffee*. The outside is an* ice cold glass of water*. Ya with me here?
Good.
What happens when you mix the two? *You wind up with some luke warm week azz coffee*. Agree? Who likes that crap? This is exactly what happens (in a sense) with your living room as the cold air infiltrates your home and IT WILL thru numerous air leaks you have not even realized were included for free with the nice new crib (aka: house). The hot coffee will get watered down with the cold outside water. It is that simple. It really, really is. Now who wants to debate about how great cold watered down coffee is great?

OK, now the OAK sort of works like a sealed restrictive funnel letting the right amount of cold water drip into your HOT coffee and keeps the glass of cold water from being poured in real fast. This way the hot coffee does not burn your mouth and you are not drinking cold watered down week azz coffee. Not being a smart azz, but think about it for a moment. This is about as KISS as I can get with this bizarre and perplexing OAK issue.


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## checkthisout (Dec 28, 2014)

What if I have an outdoor boiler? This boiler uses outside air to feed the combustion, heats the water then puts it into a heat exchanger in my house.

Ok?

You would have a hard time convincing me that running a duct from the combustion inlet on my boiler to the inside of my house so that it pulls the combustion air out of my house would be a good idea or that it wouldn't make any difference in the amount of heat required to warm my house.


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## checkthisout (Dec 28, 2014)

TimfromMA said:


> One could argue that using your exhaust vent to preheat OAK air will cool exhaust gasses causing an increase in creosote buildup.



Maybe? Or the heated air would help increase combustion temperatures so that less creosote forms in the first place.

You gotta clean the chimney anyway, lest Santa Claus not bring you any presents.


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## FTG-05 (Dec 28, 2014)

F4jock said:


> Read it several times. Unclear. At least to me sounds like no OAK but *shrug*.




Here's the list without the attempt at humor:

I had three non-negotiables when installing my wood stove this last summer and fall:

- Safety.

- Englander 30-NC wood stove.

- OAK.


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## meisen (Dec 28, 2014)

So one last thing before this gets closed...it seems the main point the anti-OAK-in-pellet stove crowd makes is that using cooler air in the combustion chamber is less efficient...ie it's more work (ie less heat is available for heating) for the stove to hear that air.

Has anyone actually verified that this is the case? Is it really that big a difference? What, intake at 10 or 20 vs 70 degrees inside temps? A modest difference. What is typical combustion temp? I'm reading 450+ off my burnpot, I'm sure it's hotter as the meter maxxes. So does higher oxygen, lower-moisture content air typical of winter really force the stove to work significantly harder to heat the air?

I'm betting it doesn't. Plus you are still having to heat that air as some point to get it to 70.  My old, drafty house seals it for me without further ado. Is that the question that needs answering though?


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## OhioBurner© (Dec 28, 2014)

checkthisout said:


> What if the room air temperature and outside temperature are the same?


Then we wouldn't be running the stove?



F4jock said:


> You guys are making my head explode! You do not NEED an OAK but the physics of the situation doesn't change because you do or do not want one: If you draw combustion air FROM the room and exhaust it to the OUTSIDE it MUST be replaced and the only place that replacement air can ultimately come from is OUTSIDE where it's cold or you wouldn't have the stove running in the first place! If you draw combustion air FROM outside and exhaust it TO outside with an OAK you do not exacerbate cold air infiltration to the room from outside. You figure the rest out! There is no way that this reality can be changed no matter what you think or what is written where unless you have a source of bottled, compressed air you can discharge into your house. You can debate the NEED for an OAK relative to better combustion all you want, and frankly that is also pretty much a given, but you can NOT change the physics of air movement.



I don't think anyone is debating that what you are saying there isn't true.

Edit> Not sure if I made it clear earlier but I support the use of OAK especially where its easy to install . Mine wasn't a great solution and probably would not have done the OAK except that it was required in my case.


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## checkthisout (Dec 29, 2014)

OhioBurner© said:


> Then we wouldn't be running the stove?
> .



What if it ran out of pellets while I was gone and it's 50 degrees outside and inside my house?


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## TimfromMA (Dec 29, 2014)

checkthisout said:


> What if it ran out of pellets while I was gone and it's 50 degrees outside and inside my house?



If it ran out of pellets, it would be off.


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## alternativeheat (Dec 29, 2014)

I think you will find the people who have trouble heating their houses with a pellet stove when it's -30 deg outside will do so because it's -30 deg outside and probably have hit the threshold of the stoves heating capability. It takes a lot of heat to heat a house with that kind of penetrating cold going on. Some furnaces or boilers even run non stop in that kind of cold. I know when it turns cold here it takes about 3 days for the real cold to start doing it's thing and we get down to about 0 around here not -30. The first day of a cold snap is barely felt in the house, the heat source runs a little harder. But by the third day it starts get so your cranking on it, using more fuel etc. If the wind blows hard out there that's another element to consider. Now in my case though I can't really compare this OAK phenomenon in cold as mine is in my chimney picking up relatively warm air by comparison.

I think you will find that the light yellow part of a wood flame is around 1000degC or 1800deg F, measured directly in side the flame. It's unlikely 30 deg differences in in coming air will matter much. In fact cold air might turn that flame even a slightly hotter brighter yellow as it supports more oxygen than hot air ( if the OAK doesn't frost up and restrict flow, in which case a heat tape might be a good thing).


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## F4jock (Dec 29, 2014)

FTG-05 said:


> Here's the list without the attempt at humor:
> 
> I had three non-negotiables when installing my wood stove this last summer and fall:
> 
> ...


Ah. Thanks. More better!


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## Lake Girl (Dec 29, 2014)

F4jock said:


> Ah. Thanks. More better!






F4jock said:


> And observe that cooler air contains more oxygen thus supporting better combustion but. . . .



Where does this come from?  Hubby, the fire fighter says the same thing - Honeywell study from the 1950s but can't find it on-line.


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## DBCOOPER (Dec 29, 2014)

The cooler air at the surface is more dense and as such contains more o2. Its the opposite of being at a higher altitude.


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## F4jock (Dec 29, 2014)

Lake Girl said:


> Where does this come from?  Hubby, the fire fighter says the same thing - Honeywell study from the 1950s but can't find it on-line.


Cold air is more dense than warm air thus there are more oxygen molecules per unit volume.


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## Lake Girl (Dec 29, 2014)

Charles's law?  Since the Hubby was a diver, well acquainted with Boyle's - pressure and volume inversely related.  It's the temperature part of the equation and it's effect I'm after.  

Nasty headache interfering with brain function today  Just wish I could say it was celebrating the holidays too much but not the case...


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## F4jock (Dec 29, 2014)

Lake Girl said:


> Charles's law?  Since the Hubby was a diver, well acquainted with Boyle's - pressure and volume inversely related.  It's the temperature part of the equation and it's effect I'm after.
> 
> Nasty headache interfering with brain function today  Just wish I could say it was celebrating the holidays too much but not the case...


If I remember correctly, Charlie was talking about the volume of a gas being directly proportional to temperature at a constant pressure. Here we're talking about density so while the percentage of oxygen is constant no matter the temperature the amount per unit volume is greater.


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## CaptSpiff (Dec 29, 2014)

Zebby said:


> ... <Breckwell> omitted a tube connecting the back panel of my stove to the firebox inlet.
> <snip>
> I also installed an inexpensive automotive manifold heat hose inside the stove to make the connection that Breckwell left out.



I was told the "gap in the OAK path" you describe was a safety decision in case the OAK became clogged. Many trailer home installs are done with the OAK "drilled & dropped" down thru the trailer floor boards without proper critter guard. Great place to store supplies & make a nest.

Also, someone mentioned frost on the outside of the OAK tube. This is from the warm moist room air, and I solved that by wrapping foil coated pipe wrap around the flex tube. Also solved the small water puddle that would form when the frost melted. I've never heard of an OAK frosting over and blocking airflow.


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## acammer (Dec 29, 2014)

It's a fact that colder air promotes combustion as it contains more o2 per unit due to density.  Us hot-rodding guys know that well- we spend all sorts of money trying to cool the intake air going into our engines.  With cooler, denser air, you can add more fuel (which is the important point for this argument) as well as better control detonation (which is the more important argument in the engine performance application).  The ~70*F difference of intake air nor the slightly more enriched O2 content of the colder air probably have much of an impact on the firebox output temp, but a 70*F difference of air turning over in your house 10+ times a day is gonna be noticeable.


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## New Hampshire Jim (Dec 29, 2014)

A few years ago I was installing a Harman Advance pellet stove to replace a wood stove. I got some help from my son the Mechanical  Engineer. At the time we were debating the benefits of Installing an OAK. This Is what we came up with. All Measurements are rounded and approximate

House Is a 1400 Square foot 2 story cape X 8 foot ceilings = 12,000 cubic foot 
Combustion blower Is 80 CFM X 60 Min. =4800 cubic feet of air moved per hour
So every 2 1/2 hours without an OAK you will be sucking all the air inside your house that you just spent big bucks to heat up and replacing It with outside air be It 20 Deg. or -20 deg. that will find all the nooks an crannies In your house.

With an OAK all the combustion air will come from the outside
Since the reason for putting In the stove was to make us roast toasty and save a few bucks the OAK was installed and the pipe wrapped with 3 In.X1/2 In. neoprene boiler pipe wrap I got at home depot.

It was also pointed out to me that all the new cars have OAKs that are ducted to bring in the cold air In front of the radiators  as this air Is denser and makes more Horse Power
Jim


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## F4jock (Dec 29, 2014)

New Hampshire Jim said:


> A few years ago I was installing a Harman Advance pellet stove to replace a wood stove. I got some help from my son the Mechanical  Engineer. At the time we were debating the benefits of Installing an OAK. This Is what we came up with. All Measurements are rounded and approximate
> 
> House Is a 1400 Square foot 2 story cape X 8 foot ceilings = 12,000 cubic foot
> Combustion blower Is 80 CFM X 60 Min. =4800 cubic feet of air moved per hour
> ...


As do the cold air intakes installed on my high performance '90 Stillen 300ZX Twin Turbo and '69 Vette LT 1. Unfortunately you will find that, at times in this thread, physics takes a back seat to "I found it on the internet so it must be true."


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## bcarton (Dec 29, 2014)

I can't wait to get an OAK installed, because cold air comes in through the bath vent like it never did before and everyone hates it.  It'll have to wait until summer, because I need to drill through a brick hearth to do it properly.


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## michpelletburner (Dec 29, 2014)

I myself look at it this way, in most cases the oak is a super easy install and doesn't cost alot to put in. And what are the negative effects of having a oak, i don't for see any. I mean no chance for negative pressure inside the house, there isn't air from outside being pulled in through cracks and cool dense oxygen rich air is really good for combustion ( hence why your car pulls air from outside the engine compartment). Will the stove cause negative pressure? who knows it depends on how tight your house is and what other machines are exhausting air. I just feel the oak is a no brainier if its not to hard to install and may have positive effects with no negatives. My stove has had a oak from day one so i have no experiance without one, so to each his own i just think in my opinion its a good idea.


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## michpelletburner (Dec 29, 2014)

I also doubt that the stove not using a oak is "stealing" tons of heat from your house, but i bet the cold air being drawn in from all the cracks is affecting temperature.


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## New Hampshire Jim (Dec 29, 2014)

Hmm With all the gear heads on this forum I was just wondering when we will see someone try to hook up a NOS fogger to there OAK for faster starts and some REAL HOT temperatures. And the bragging. My stove puts out 600 H.P. what will yours do.
Tongue In cheek


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## SteveG518 (Dec 29, 2014)

I just can't understand how people can argue against an OAK. Take heated air from the house and push it outside only to let new COLDER air in through any and every leak in the house, or take outside air and have a max of what 20* difference come out of your stove to heat your pressure equalized house? Is this really still a serious debate? HONESTLY?

What ever happened to common sense?


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## acammer (Dec 29, 2014)

Lets quantify this a little bit more.  If a non-OAK'd stove has a 100CFM combustion blower, that's 144,000 cubic feet of air that has to be pulled inside and heated.  Let's say it's 70*F inside, and 0*F outside.  1 cubic foot of air requires 1.274 BTU to heat from 0*F to 70*F (specific heat of .0182BTU per cubic foot per degree).  1.274BTU x 144,000 cubic feet a day is 183,456 BTUs of additional heating a day, 22lbs of pellet fuel (8,250BTU/lbs), $2.78 ($5/40lb bag of pellets).

So on a cold day, a non-OAK'd stove could cost you a few extra bucks a day.  Even if you go conservative and figure a 4 month heating season with half that loss ($1.50/day x 120 days) you've paid $180 extra to heat that outside air, almost an extra ton of pellets!  For those of us in cold climates with longer heating seasons it's even more.  That's not insignificant at all, there is really money to be saved there.


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## F4jock (Dec 29, 2014)

New Hampshire Jim said:


> Hmm With all the gear heads on this forum I was just wondering when we will see someone try to hook up a NOS fogger to there OAK for faster starts and some REAL HOT temperatures. And the bragging. My stove puts out 600 H.P. what will yours do.
> Tongue In cheek


Well. . . .I DID install High Speed Bumper Bolts on mine. . . .


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## SteveG518 (Dec 29, 2014)

f4jock, Don't forget about that cheesy inline electric supercharger fan in your OAK!!


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## acammer (Dec 29, 2014)

New Hampshire Jim said:


> Hmm With all the gear heads on this forum I was just wondering when we will see someone try to hook up a NOS fogger to there OAK for faster starts and some REAL HOT temperatures. And the bragging. My stove puts out 600 H.P. what will yours do.
> Tongue In cheek



I love tuning and tweaking the pellet stove, I look at it like tuning a carburetor (or EFI now that I have a stove with digital fuel/air trims instead of damper) in slow motion, with a window into the combustion chamber.  I don't have any nitrous on my stove, but once it's out of warranty I might do a little burn-plate/air flow modification - I guess that's cylinder head work in my other hobby!


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## Tonyray (Dec 29, 2014)

SteveG518 said:


> I just can't understand how people can argue against an OAK. Take heated air from the house and push it outside only to let new COLDER air in through any and every leak in the house, or take outside air and have a max of what 20* difference come out of your stove to heat your pressure equalized house? Is this really still a serious debate? HONESTLY?
> 
> What ever happened to common sense?


we have a 90 yr old barely insulated 2 story house and without an Oak it would almost be pointless to have a pellet stove with no OAK.
Be glad you have one and don't fret much about those that don't... they will argue till the cows come home cause change is easier said than done. but if someone we're to put one in for free and do all the work,
many would go for it in a heartbeat.


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## F4jock (Dec 29, 2014)

SteveG518 said:


> f4jock, Don't forget about that cheesy inline electric supercharger fan in your OAK!!


And I got that special in-hopper device that increases pellet burn temperature by 200 degrees. Just screw it into the hopper and let the pellets vaporize as they pass through it! Only $19.95! (Plus processing and handling.)


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## acammer (Dec 29, 2014)

F4jock said:


> And I got that special in-hopper device that increases pellet burn temperature by 200 degrees. Just screw it into the hopper and let the pellets vaporize as they pass through it! Only $19.95! (Plus processing and handling.)



Like the old magnet on the fuel line to straighten the fuel molecules for enhanced economy!?


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## SteveG518 (Dec 29, 2014)

All im saying is that its crazy for people to even argue about that subject. 

f4jock, PS I installed that hopper device and now my girls in her bikini all winter. Worth every penny in P&H 


but honestly on a serious note; yes if you want one, install one and feel the benefits. If not, leave it be and continue to spend the extra $ to heat the house. Wish I was made of money too....


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## Bridgeman (Dec 29, 2014)

I have one last comment on this OAK thread. The average air exchange rate in a standard home with closed windows and doors in this country is about half the air in the house every hour. Look it up, that's a fact. The rate is determined by the difference of tempature between inside, outside and wind speed. So air exchange is happening anyway. It's not like you heat your air and it hangs around the place. How does that effect things? I guess you can say not having an OAK would increase the air exchange rate.  Perhaps we are sitting in a breeze of cold air from outside anyway and stealing a little to run our space heaters that radiate heat off the stove and the contents of the room?
If the savings was so clear there would be a hard number out there. I'm sure there a heads exploding across North America at this point. The search for truth has casualties on occasion.


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## F4jock (Dec 29, 2014)

Bridgeman said:


> I have one last comment on this OAK thread. The average air exchange rate in a standard home with closed windows and doors in this country is about half the air in the house every hour. Look it up, that's a fact. The rate is determined by the difference of tempature between inside, outside and wind speed. So air exchange is happening anyway. It's not like you heat your air and it hangs around the place. How does that effect things? I guess you can say not having an OAK would increase the air exchange rate.  Perhaps we are sitting in a breeze of cold air from outside anyway and stealing a little to run our space heaters that radiate heat off the stove and the contents of the room?
> If the savings was so clear there would be a hard number out there. I'm sure there a heads exploding across North America at this point. The search for truth has casualties on occasion.


Sorry but "a little" can be quantified by the capacity of the combustion blower. (See post above.) and it's more than "a little." Also, I challenge the "fact" of that much passive hourly air exchange, especially in this day of tightly insulated homes. Blower capacity and temperature differential are provable, quantifiable facts. I can EXACTLY calculate the air turnover the combustion blower causes and thus, given the temperature differential between inside and outside air and the BTU of pellets, the EXACT amount of money your lack of an OAK costs YOU. All you can quote is some nebulous average that is based on what, exactly? My house? Your house? Whose house?

Average air turnover is something that, no offense meant, you believe to be true because you read it on the internet. I'm an Engineer x2; chemical and mechanical. I deal in facts. I can prove my case. Prove yours!


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## Tonyray (Dec 29, 2014)

SteveG518 said:


> All im saying is that its crazy for people to even argue about that subject.
> 
> f4jock, PS I installed that hopper device and now my girls in her bikini all winter. Worth every penny in P&H
> 
> ...


burning the US Hardwoods right now..


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## Bridgeman (Dec 29, 2014)

There are multiple govement funded studies by actual scientist that show the air exchange rate in all types of buildings. Residential buildings are not sealed space. Air flows in and out at a surprising rate. There are a few exceptions and newer is generally less leaky. Every two hours all the heated air is gone in most homes. If it didn't we would need air exchangers in our home to be healthy.(some new homes do)
 How do you calculate the radiant heat component in your calculations? All that hot air is heating up objects too. I use very efficient radiant heaters at work that use massive amounts of interior air and the space is very comfortable. 
I just don't think it's as simple as a calculation as it seems. It defies logic to think I would cut my pellet needs by a third. I think there is a small savings but it's not clear that it is.  My opinion is that the savings is overstated.
 The engineers that work with me often need guidance on what to calculate not how. It's big picture thing. No offense intended here either.


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## F4jock (Dec 29, 2014)

Bridgeman said:


> There are multiple govement funded studies by actual scientist that show the air exchange rate in all types of buildings. Residential buildings are not sealed space. Air flows in and out at a surprising rate. There are a few exceptions and newer is generally less leaky. Every two hours all the heated air is gone in most homes. If it didn't we would need air exchangers in our home to be healthy.(some new homes do)
> How do you calculate the radiant heat component in your calculations? All that hot air is heating up objects too. I use very efficient radiant heaters at work that use massive amounts of interior air and the space is very comfortable.
> I just don't think it's as simple as a calculation as it seems. It defies logic to think I would cut my pellet needs by a third. I think there is a small savings but it's not clear that it is.  My opinion is that the savings is overstated.
> The engineers that work with me often need guidance on what to calculate not how. It's big picture thing. No offense intended here either.


I can factually refute every one of your arguments including the radiant heat question, which BTW, is extremely easy to rebut, but it's apparent that your mind is made up so rather than waste more of our collective time I'll just let you figure it out.


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## Zebby (Dec 30, 2014)

Curious about posters using the combustion blower cfm rating as the standard to calculate air exchange in a heated space. 
Assuming the stove is running, the exhaust consists of products of combustion, excess air and a small amount of unburnables (ash).
All of this except the ash is expanded to a larger volume by being at a much higher temperature than the ~70 degree F indoor air used without an OAK. 
I assume the air actually taken from the source to be of a smaller volume than that which the combustion blower sends out, therefore a calculation of air exchange via a hot stove should be based on intake air volume. 

I know it is still a substantial amount being drawn into the firebox, and therefore taken out of the heated space, just not quite as much as the combustion fan cfm would suggest.
Anybody got thoughts on that? Is the difference between firebox intake volume and exhaust volume considered not significant? Or are people just using combustion blower cfm to simplify the discussion?

Using 20 degree cold air and 400 degree hot air, the latter seems to be greater in volume by 86% by Charles' law. V2/V1 = T2/T1  in degrees K at constant pressure. A pellet stove is not as simple as expansion of plain air, admittedly.


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## F4jock (Dec 30, 2014)

Zebby said:


> Curious about posters using the combustion blower cfm rating as the standard to calculate air exchange in a heated space.
> Assuming the stove is running, the exhaust consists of products of combustion, excess air and a small amount of unburnables (ash).
> All of this except the ash is expanded to a larger volume by being at a much higher temperature than the ~70 degree F indoor air used without an OAK.
> I assume the air actually taken from the source to be of a smaller volume than that which the combustion blower sends out, therefore a calculation of air exchange via a hot stove should be based on intake air volume.
> ...


You have to calculate based on intake at ambient because that is the volume the blower is moving. Output = input plus a bit because as well as blower CFM you have stack draft due to heat thus you have a slight negative pressure in the firebox / stack. Volume difference us due to expansion of the same amount of air. Just takes up more space.


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## acammer (Dec 30, 2014)

I second that F4jock, we're talking about intake air, at ambient, which would be the difference if you were pulling from inside vs. outside.  Exhaust will be a much higher volume due to the heat.  Everything was somewhat arbitrary in the air turnover calculation I laid out earlier, just food for thought, ball park figures to give a talking point and a better feel for how much of a difference we're talking about.

The argument still stands even in light of a residential structure turning it's air over every other hour without the negative pressure of an appliance on it - if you add that 100CFM pull on all those leaks you're increasing the turn-over rate by that much more.


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## zrtmatos (Dec 30, 2014)

I replaced a pellet stove with 34K output and no OAK with a stove that had slightly more output, 38K but installed an OAK with it. Big difference in cutting down air leaking in through an adjacent room to the stove. This room has newer windows and the leaks of air found their way in without the OAK. I can attest to it working. I probably could have not changed stoves and just installed an OAK. Just do the OAK install in the first place.


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## F4jock (Dec 30, 2014)

acammer said:


> I second that F4jock, we're talking about intake air, at ambient, which would be the difference if you were pulling from inside vs. outside.  Exhaust will be a much higher volume due to the heat.  Everything was somewhat arbitrary in the air turnover calculation I laid out earlier, just food for thought, ball park figures to give a talking point and a better feel for how much of a difference we're talking about.
> 
> The argument still stands even in light of a residential structure turning it's air over every other hour without the negative pressure of an appliance on it - if you add that 100CFM pull on all those leaks you're increasing the turn-over rate by that much more.


Mass balance FTW.


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## Lake Girl (Dec 30, 2014)

Trying to find the gas laws that apply to this situation to show increased efficiency of burn using cold air ...

http://www.chemteam.info/GasLaw/GasDensity.html
Air is a mixture of 21% oxygen gas and 79% nitrogen gas (neglect minor components and water vapor). What is the density of air at 30.0 °C and 1.00 atm?

Comment: For both solutions, we need the "molecular weight" of air:

MW(air) = (%O2 x MWO2) + (%N2 x MWN2)
(0.21 x 32) + (0.79 x 28) = 29 g/mol

*Solution #1:*

1) Use PV = nRT and assume 1.00 L:

(1.00 atm) (1.00 L) = (n) (0.08206) (303 K)
n = 0.0402185 mol (of air at 303 K)

2) Calculate grams of air:

0.0402185 mol times 29 g/mol = 1.17 g
3) Determine density:

1.17 g / 1.00 L = 1.17 g/L

Same equation but using -20C:
1x1=n (.08206) (253.15K)
n=.0478235

.0478235 x 29 g/mol = 1.3868 g
1.3868g/1.00L = 1.3868 g/L

Brain still hurts so someone else can take it from here...


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## F4jock (Dec 30, 2014)

Lake Girl said:


> Trying to find the gas laws that apply to this situation to show increased efficiency of burn using cold air ...
> 
> http://www.chemteam.info/GasLaw/GasDensity.html
> Air is a mixture of 21% oxygen gas and 79% nitrogen gas (neglect minor components and water vapor). What is the density of air at 30.0 °C and 1.00 atm?
> ...


And at colder temperature the molecular density also reduces water vapor entrainment thus allowing even more oxygen and other molecules BUT you're unfortunately wasting your time as there is a tendency to deny the physics of the situation and replace it with what is "felt" to be right.


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## Zebby (Dec 30, 2014)

CaptSpiff said:


> I was told the "gap in the OAK path" you describe was a safety decision in case the OAK became clogged. Many trailer home installs are done with the OAK "drilled & dropped" down thru the trailer floor boards without proper critter guard. Great place to store supplies & make a nest.



My OAK has a screen to prevent critters larger than 1/4 inch from entering. I'll have to cover the opening in warmer weather to prevent bees, spiders, etc. making homes though.

Safety decision?
But if the continuous OAK path were to become clogged, no/reduced air entering would make the owner seek a cause for poor stove performance. 
The gap in the OAK would allow the stove to take in room air in violation of mobile home codes, and the stove would continue working.
Which is the more safe condition?


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## Zebby (Dec 30, 2014)

F4jock said:


> You have to calculate based on intake at ambient because that is the volume the blower is moving. Output = input plus a bit because as well as blower CFM you have stack draft due to heat thus you have a slight negative pressure in the firebox / stack. Volume difference us due to expansion of the same amount of air. Just takes up more space.



Sorry if I'm being a PITA on this.....but my combustion blower is on the hot side of the firebox, so why would it's cfm (cubic feet per minute) rating not then apply to the volume of heated exhaust gas?
If it was mass airflow, then I'd see that (intake air mass + mass of carbon from the burning wood = exhaust mass).   

I admit that I wasn't so good at compressible flow and I know you must be, especially having jet engine theory experience.

Thanks


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## acammer (Dec 30, 2014)

Zebby said:


> Sorry if I'm being a PITA on this.....but my combustion blower is on the hot side of the firebox, so why would it's cfm (cubic feet per minute) rating not then apply to the volume of heated exhaust gas?
> If it was mass airflow, then I'd see that (intake air mass + mass of carbon from the burning wood = exhaust mass).
> 
> I admit that I wasn't so good at compressible flow and I know you must be, especially having jet engine theory experience.
> ...



The intake volume doesn't change as the intake air temperature doesn't change - the temperature and volume change is happening at the combustion event inside the stove, after the intake.  That's why the exhaust volume is higher than the intake volume.


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## F4jock (Dec 30, 2014)

acammer said:


> The intake volume doesn't change as the intake air temperature doesn't change - the temperature and volume change is happening at the combustion event inside the stove, after the intake.  That's why the exhaust volume is higher than the intake volume.


Thank you!


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## bags (Dec 30, 2014)

Also IF your OAK was completely clogged meaning zero air I'd say you would be experiencing a poor burn scenario. They should be sealed as to not leak any cold air between the exterior intake and delivery to the burn. Not always the case and I am sure some installs would allow air to be sucked in regardless. Mine is sealed with very secure hose clamps and high temp silicone.

PITA if I need to pull it apart? No. A quick simple roll of a razor knife cuts silicone really quick and easy in a few seconds. I am all about NOT having leaky air jacking my program up. I found an adjustable door sill that had a nice long gap this fall. Couldn't see it at all from anywhere until I laid on the floor doing some caulking and was pissed when I spotted it. I was wondering why I felt a cold draft and some itsy bitsy bugs seemed to be found inside by this door. DUH! High use door that's 4 years old so I assume non stop stepping on the threshold or sill readjusted it over time.


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## F4jock (Dec 30, 2014)

Zebby said:


> Sorry if I'm being a PITA on this.....but my combustion blower is on the hot side of the firebox, so why would it's cfm (cubic feet per minute) rating not then apply to the volume of heated exhaust gas?
> If it was mass airflow, then I'd see that (intake air mass + mass of carbon from the burning wood = exhaust mass).
> 
> I admit that I wasn't so good at compressible flow and I know you must be, especially having jet engine theory experience.
> ...


Please see acammer's reply above.


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## F4jock (Dec 30, 2014)

Zebby said:


> My OAK has a screen to prevent critters larger than 1/4 inch from entering. I'll have to cover the opening in warmer weather to prevent bees, spiders, etc. making homes though.
> 
> Safety decision?
> But if the continuous OAK path were to become clogged, no/reduced air entering would make the owner seek a cause for poor stove performance.
> ...


If you want to screen your intake more finely you can upsize the intake (Easy calculation if you know combustion blower capacity.) to be sure that you can pass enough air with a given percent of the size mesh you choose clogged, reduce it to the OAK diameter and inspect the screen daily. Best of all worlds.


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## woodmakesheat (Dec 30, 2014)

Zebby said:


> Curious about posters using the combustion blower cfm rating as the standard to calculate air exchange in a heated space.
> Assuming the stove is running, the exhaust consists of products of combustion, excess air and a small amount of unburnables (ash).
> All of this except the ash is expanded to a larger volume by being at a much higher temperature than the ~70 degree F indoor air used without an OAK.
> I assume the air actually taken from the source to be of a smaller volume than that which the combustion blower sends out, therefore a calculation of air exchange via a hot stove should be based on intake air volume.
> ...



I think this is a good question, so I decided to measure my stove's actual input CFM.  I did a more accurate measurement of my CPM-10 running full tilt (9/9) which is about 36k BTU/hr input. This time I removed the OAK tube from the back of the stove so I could measure the airflow entering the stove @ a standard temperature (70F) and through an easy to measure rigid pipe.

Input Airflow: 820 LFM
Pipe diameter: 1.75", Cross-sectional Area = 0.0733 sq ft.

Inlet Airflow = 820 ft/min * 0.0733 ft^2 = *60.1 CFM*

This is for a stove that is on the low end of BTU output.

Assuming proportional airflow, a large stove like the P61A input probably flows about 100 CFM running full tilt.

You could assume that a typical stove on a cold day is drawing about 60-80 CFM.

Agree/Disagree?


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## 709GADE (Dec 30, 2014)

If you have an HRV in your home, which removes stale warm air and returns fresh partially heated air, do you think an OAK is needed? I have a rather new home that has an HRV and this is my first season with a pellet stove. I had the company that I bought the stove from install it and the technician said an OAK is not needed in my house.  Do you agree?


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## woodmakesheat (Dec 30, 2014)

709GADE said:


> If you have an HRV in your home, which removes stale warm air and returns fresh partially heated air, do you think an OAK is needed? I have a rather new home that has an HRV and this is my first season with a pellet stove. I had the company that I bought the stove from install it and the technician said an OAK is not needed in my house.  Do you agree?



In my opinion, an OAK is never _required _unless the manufacturer says it is. Oh the other hand, an OAK is always _preferable_.


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## acammer (Dec 30, 2014)

woodmakesheat said:


> In my opinion, an OAK is never _required _unless the manufacturer says it is. Oh the other hand, an OAK is always _preferable_.



Agreed.  I also think your CFM calculation looks right.


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## Zebby (Jan 1, 2015)

woodmakesheat said:


> I think this is a good question, so I decided to measure my stove's actual input CFM. I did a more accurate measurement of my CPM-10 running full tilt (9/9) which is about 36k BTU/hr input. This time I removed the OAK tube from the back of the stove so I could measure the airflow entering the stove @ a standard temperature (70F) and through an easy to measure rigid pipe.
> Input Airflow: 820 LFM
> Pipe diameter: 1.75", Cross-sectional Area = 0.0733 sq ft.
> Inlet Airflow = 820 ft/min * 0.0733 ft^2 = 60.1 CFM
> ...



Sounds good. 
My initial assertion was that air volume being drawn out of the house with no OAK (and thus replaced by drafty inflow) should not be 1 to 1 with combustion blower rated cfm, as some comments have suggested. 
It's a trivial issue, I admit, but the devil's in the details. I'm one of those kind of guys. 
If you'd be so inclined, and when you have a little time, could you take volume measurements of both inlet air @ 70 and vent gasses?

Thanks.

p.s.   I just found , , and  in with the smilies.


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## F4jock (Jan 1, 2015)

Zebby said:


> Sounds good.
> My initial assertion was that air volume being drawn out of the house with no OAK (and thus replaced by drafty inflow) should not be 1 to 1 with combustion blower rated cfm, as some comments have suggested.
> It's a trivial issue, I admit, but the devil's in the details. I'm one of those kind of guys.
> If you'd be so inclined, and when you have a little time, could you take volume measurements of both inlet air @ 70 and vent gasses?
> ...


You're assertion is essentially incorrect. Now it's up to you to find out why. I suggest your local high school physics dept.


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## Zebby (Jan 1, 2015)

F4jock said:


> You're assertion is essentially incorrect. Now it's up to you to find out why. I suggest your local high school physics dept.


Ok, I'll look into it some more.
Thanks


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## F4jock (Jan 1, 2015)

Zebby said:


> Ok, I'll look into it some more.
> Thanks


Try asking about this term for starters: Mass Balance


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## woodmakesheat (Jan 2, 2015)

Zebby said:


> Sounds good.
> My initial assertion was that air volume being drawn out of the house with no OAK (and thus replaced by drafty inflow) should not be 1 to 1 with combustion blower rated cfm, as some comments have suggested.
> It's a trivial issue, I admit, but the devil's in the details. I'm one of those kind of guys.
> If you'd be so inclined, and when you have a little time, could you take volume measurements of both inlet air @ 70 and vent gasses?
> ...



I am not sure my anemometer can accurately measure the flow of the hot gasses since I don't have a way to cleanly insert the probe into the exhaust. The temperature of the probe in the exhaust stream makes a difference in getting an accurate number. Also not sure the probe would be happy in those temperatures and contamination levels. I would agree that the nameplate rating of blower is not an accurate method of determining the actual inlet flow of a stove - it's a ballpark method one uses if no other information is available (altitude, temperature, pressure drops in system, contribution from combustion products) Having measured the actual input flow to my stove (under standard conditions!) though, we now know actual airflow + any leakage (which is relatively low in my new stove) into the stove from the house, which is what we care about in this thread. Also as stated, air in = air out.


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## Lake Girl (Jan 2, 2015)

woodmakesheat said:


> I think this is a good question, so I decided to measure my stove's actual input CFM.  I did a more accurate measurement of my CPM-10 running full tilt (9/9) which is about 36k BTU/hr input. This time I removed the OAK tube from the back of the stove so I could measure the airflow entering the stove @ a standard temperature (70F) and through an easy to measure rigid pipe.
> 
> Input Airflow: 820 LFM
> Pipe diameter: 1.75", Cross-sectional Area = 0.0733 sq ft.
> ...



Does your meter tolerate colder conditions?  Would be interesting to see what the measurement would be through outside inlet...


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## woodmakesheat (Jan 2, 2015)

Lake Girl said:


> Does your meter tolerate colder conditions?  Would be interesting to see what the measurement would be through outside inlet...



It can, but it needs a correction factor based on the temperature. Also I realized that I don't seal the inlet tube to the pipe on the stove. The pipe on the stove sticks out like 8 inches and I have the hose slid all the way over that and butted against the back wall of the stove so I'm not worried greatly about air seeping (also stove runs 24/7), but it could affect the flow readings a little. I'm sure there'd be a pressure drop due to the hose and screen, there are mathematical ways to estimate this that would be close enough IMO.


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## daffonce (Jan 2, 2015)

Look you need an oak so the flames dont suck all the oxygen out of the room causing you to suffocate i have thrown all physics out the window now too.


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## bags (Jan 2, 2015)

daffonce said:


> Look you need an oak so the flames dont suck all the oxygen out of the room causing you to suffocate i have thrown all physics out the window now too.


There is no way anyone will suffocate with nor without the use of an OAK. Homes are not that tight to begin with. That's like saying you have to leave a window or door cracked year round so you get your needed oxygen. Your statement is confusing to me. What is it you are trying to say? The point you are making is?


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## St_Earl (Jan 2, 2015)

i detect sarcasm.


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## bags (Jan 2, 2015)

St_Earl said:


> i detect sarcasm.


I did too but that fun stuff tends to fly over heads. I get it and that's why I have an OAK. I can be about as sarcastic as they come. Reread my drive it home post about the people gasping for O2 above. Now I'm really *cornfused*. LOL! Who said beating a dead dog can't be fun. Sick, but fun if you're a little twisted.

Disclaimer: No animals were harmed in the above statement. Do not try this at home.


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## Former Farmer (Jan 2, 2015)

I did not notice any regards to humidity levels in the house.  If you have to humidify air in your house, an OAK is a definite benefit versus pulling more dry air into the house and trying to keep the humidity levels where you want.


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## PWash (Jan 2, 2015)

+1 point to anyone who can list the laws of thermodynamics, and +2 points for anyone who knows that those laws don't really apply to stoves.


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## daffonce (Jan 2, 2015)

I know the 4 laws of thermo. The biggie that applies is energy cant be created nor destroyed and also the zeroth law.


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## TimfromMA (Jan 2, 2015)

How many point for liking my OAK and not giving a rats butt about the laws of thermodynamics..


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## F4jock (Jan 2, 2015)

TimfromMA said:


> How many point for liking my OAK and not giving a rats butt about the laws of thermodynamics..


Actually lots because, if I remember them correctly, the four laws have little to do with the subject under discussion in this thread.


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## Lake Girl (Jan 2, 2015)

bags said:


> There is no way anyone will suffocate with nor without the use of an OAK. Homes are not that tight to begin with. That's like saying you have to leave a window or door cracked year round so you get your needed oxygen. Your statement is confusing to me. What is it you are trying to say? The point you are making is?




That would be a throw up your hands, hit your head against the wall, frustrated response ... a wee bit of sarcasm, you bet!


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## F4jock (Jan 2, 2015)

Lake Girl said:


> That would be a throw up your hands, hit your head against the wall, frustrated response ... a wee bit of sarcasm, you bet!


Suffocate? Never! We all know your eyeballs would explode first!


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## PWash (Jan 2, 2015)

TimfromMA said:


> How many point for liking my OAK and not giving a rats butt about the laws of thermodynamics..


Thats maybe the smartest answer but it means you arent playing the game and therefore you dont get any pts.  

heres an arguement worth +1 pt:  Not using an oak means that inside air is used and that air has less oxygen available for the fire because people have been breathing in the house.

heres an arguement worth +2 pts:  CFM physics of cold air acceleration and turbo vortices, mass flow volume rate; hot air stays in the house and also QED.

Also no points given for real facts, but obviously your scorecards may vary.


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## F4jock (Jan 2, 2015)

PWash said:


> Thats maybe the smartest answer but it means you arent playing the game and therefore you dont get any pts.
> 
> heres an arguement worth +1 pt:  Not using an oak means that inside air is used and that air has less oxygen available for the fire because people have been breathing in the house.
> 
> ...


-1 for possible misuse of the term QED. We need an official ruling.


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## FTG-05 (Jan 2, 2015)

F4jock said:


> -1 for possible misuse of the term QED. We need an official ruling.



After official review, the ruling on the field stands!  15 yard penalty and automatic first down!


[and no, i have not been watching too much football!]

To keep it on point:  I've got OAK installed for 30-NC, despite what the installer wanted, recommended or otherwise.


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## F4jock (Jan 2, 2015)

FTG-05 said:


> After official review, the ruling on the field stands!  15 yard penalty and automatic first down!
> 
> 
> [and no, i have not been watching too much football!]


I'm appealing to the comissioner and there's no such thing!


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## bags (Jan 2, 2015)

Wonder how many pages we can get to on this OAK discussion before it gets OAK'ed? Over And Killed. Isn't page 6 about the time we start talking about cars, Dr. Phil, and football?


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## F4jock (Jan 2, 2015)

bags said:


> Wonder how many pages we can get to on this OAK discussion before it gets OAK'ed? Over And Killed. Isn't page 6 about the time we start talking about cars, Dr. Phil, and football?


I won't tell 'em if you won't.


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## FTG-05 (Jan 2, 2015)

bags said:


> Wonder how many pages we can get to on this OAK discussion before it gets OAK'ed? Over And Killed. Isn't page 6 about the time we start talking about cars, Dr. Phil, and football?



I think the last time it got nuked was when we got sidetracked on the merits of OAK-modded J79's vs. non-OAK'd J79's.  But I could be dreaming.

Ok, seriously, I don't understand why this is such a big mystery or even why it's even a controversy - at all!

It's a simple concept:  Do you want to heat the air in your home once or twice?  The only other possible issue is the one of safety wherein the stove manufacturer requires it for certain installations (i.e. 30-NC for mobile home applications).  Someone please explain why this is so controversial, please!


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## F4jock (Jan 3, 2015)

FTG-05 said:


> I think the last time it got nuked was when we got sidetracked on the merits of OAK-modded J79's vs. non-OAK'd J79's.  But I could be dreaming.
> 
> Ok, seriously, I don't understand why this is such a big mystery or even why it's even a controversy - at all!
> 
> It's a simple concept:  Do you want to heat the air in your home once or twice?  The only other possible issue is the one of safety wherein the stove manufacturer requires it for certain installations (i.e. 30-NC for mobile home applications).  Someone please explain why this is so controversial, please!


Simple: Feelings over physics.


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## Wilbur Feral (Jan 3, 2015)

FTG-05 said:


> Ok, seriously, I don't understand why this is such a big mystery or even why it's even a controversy - at all!



F4Jock nailed it.  Feelings over facts (and knowledge of physics).

I took a couple of days away and it still rages on...


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## moey (Jan 3, 2015)

Put a fan in your window blowing out in the winter. Do you think it will help with heating your house?


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## bags (Jan 3, 2015)

Moey's getting real, real short and sweet.


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## checkthisout (Jan 5, 2015)

If your eyes do this when you turn your pellet stove on, you might need an OAK.


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## checkthisout (Jan 5, 2015)

I wouldn't worry about inlet air temperature affecting the cleanliness of combustion on your stove.

You can just open the damper a tad more if you notice any difference in flame performance.


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## checkthisout (Jan 5, 2015)

In MOST stoves there is more air being drawn from the house than just through the actual combustion air inlet.

There is a significant amount of air flowing in through the glass wash and through the hopper if, both of which pull from inside the house.

The _other than MOST_ stoves have gasketed hoppers and ducts that lead to the combustion air inlet for the glass wash.


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## checkthisout (Jan 5, 2015)

Zebby said:


> Curious about posters using the combustion blower cfm rating as the standard to calculate air exchange in a heated space.
> Assuming the stove is running, the exhaust consists of products of combustion, excess air and a small amount of unburnables (ash).
> All of this except the ash is expanded to a larger volume by being at a much higher temperature than the ~70 degree F indoor air used without an OAK.
> I assume the air actually taken from the source to be of a smaller volume than that which the combustion blower sends out, therefore a calculation of air exchange via a hot stove should be based on intake air volume.
> ...



Bernoulli's equation is probably the tool to use rather than the ideal gas law?


----------



## adam6979 (Jan 26, 2015)

moey said:


> Put a fan in your window blowing out in the winter. Do you think it will help with heating your house?


Well in all fairness it would make the pellet stove run longer before reaching temp I guess that could help heat the cold spots from them cycling quicker....


----------



## Noname (Nov 24, 2016)

I know this is an old thread with much debate but here's my experience. House was gutted and remodeled out in the country and not much wind break, 60 yrs old on a slab but pretty efficient from the windows to insulation. Unfortunately it's isnt perfect. I have a Winslow pi 40 sat into an old but awesome looking brick fireplace. I was getting the draft and air leaks that people were speaking of so I rented a 2" boring bit and heavy duty hammer drill, bored through 15" of wall and threaded 2" flexo pipe for exhaust work from advance auto which cost $16 and connected to the stove. I siliconed where the pipe and brick are on the outside and siliconed in place a 3" drain cover over the pipe for bugs and mice which I got at lowes for $3. As I type this THERES no draft what so ever as compared to before and the glass is as clean now as this morning when I cleaned it, which it would be greying up a bit by now. It's in the 30's and my stove is on 1 and its 74 in a 1950 sq ft house. I can't say the stove is burning any better but I can say the house is a few degrees warmer from front to back due to no drafts. Total cost including the drill rental was about $70.


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## Don2222 (Nov 24, 2016)

Noname said:


> I know this is an old thread with much debate but here's my experience. House was gutted and remodeled out in the country and not much wind break, 60 yrs old on a slab but pretty efficient from the windows to insulation. Unfortunately it's isnt perfect. I have a Winslow pi 40 sat into an old but awesome looking brick fireplace. I was getting the draft and air leaks that people were speaking of so I rented a 2" boring bit and heavy duty hammer drill, bored through 15" of wall and threaded 2" flexo pipe for exhaust work from advance auto which cost $16 and connected to the stove. I siliconed where the pipe and brick are on the outside and siliconed in place a 3" drain cover over the pipe for bugs and mice which I got at lowes for $3. As I type this THERES no draft what so ever as compared to before and the glass is as clean now as this morning when I cleaned it, which it would be greying up a bit by now. It's in the 30's and my stove is on 1 and its 74 in a 1950 sq ft house. I can't say the stove is burning any better but I can say the house is a few degrees warmer from front to back due to no drafts. Total cost including the drill rental was about $70.


Now that you have a fresh air pipe, you can stuff the damper shelf and all around the flue liner with 100% fire proof Roxul insulation to prevent that nice heated warm room air from going up the chimney$$


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## Noname (Nov 24, 2016)

No chimney to worry about. We hacked it off during the remodel and roofed over it so no heat loss. The old metal damper is still in there and closed up.


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## tlc1976 (Nov 24, 2016)

I first tried my stove with no OAK.  It would barely run.  It could get so little air that opening the air intake damper did nothing.  I would get a steady stream of smoke not from the pipe joints I sealed, but from the factory pipe joints.  So I sealed every single possible overlap and rivet hole on the interior pipe.  Then I ran it and finally no more pipe smoke, but a few hours later it errored out and all the smoke sucked back in the house through the hopper.  All piping was done meeting every requirement and I have 6 ft of rise outside so there should have been good draft.  So I said enough of this foolishness and I installed an OAK (homemade with flanges from work, 2" automotive solid and flex pipe.)  No more issues, runs perfectly to this day at any setting, full control of intake damper.  Night and day difference.  House is about 30 years old but I learned it was built very well.  I was skeptical at first because my old house is just a few years older and was draft galore even when I moved in 17 years ago (used to have to put blankets over the windows).  I can only imagine how airtight newer houses are.  But I did date someone in 2003 who had to open a bathroom window in order to run the fireplace.

So anyway my experience made me a firm believer in an OAK.  Makes sense, it's the most surefire way to balance the air debt created, do it once and forget it.  So later if you go through and seal up all the air leaks or replace the leaky windows in your house, no worries.

Also you have to heat the air that comes in regardless, so might as well do it at the source.  Having the air intake at the appliance makes that the coldest spot, so that's where you put the heat.  Same logic to why heat registers and radiators are usually under windows.  One might think it's counterintuitive, but you take care of the coldest spot first.


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## alternativeheat (Nov 25, 2016)

On my P61 I used metal dryer vent flex hose.


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## bogieb (Nov 25, 2016)

Noname said:


> I know this is an old thread with much debate but here's my experience. House was gutted and remodeled out in the country and not much wind break, 60 yrs old on a slab but pretty efficient from the windows to insulation. Unfortunately it's isnt perfect. I have a Winslow pi 40 sat into an old but awesome looking brick fireplace. I was getting the draft and air leaks that people were speaking of so I rented a 2" boring bit and heavy duty hammer drill, bored through 15" of wall and threaded 2" flexo pipe for exhaust work from advance auto which cost $16 and connected to the stove. I siliconed where the pipe and brick are on the outside and siliconed in place a 3" drain cover over the pipe for bugs and mice which I got at lowes for $3. As I type this THERES no draft what so ever as compared to before and the glass is as clean now as this morning when I cleaned it, which it would be greying up a bit by now. It's in the 30's and my stove is on 1 and its 74 in a 1950 sq ft house. I can't say the stove is burning any better but I can say the house is a few degrees warmer from front to back due to no drafts. Total cost including the drill rental was about $70.



Welcome to the forum Noname!

Yeah, many people comment that they don't need an OAK because their house is leaky so none of their appliances will struggle for ari. My house was leaky (it's better now although it is still fairly leaky as I get work done on it), and that is why I installed an OAK. Took away the majority of drafts that I felt when the stove was running. Did it help my stove breathe better? Nope, but did make my house more comfortable to live in.


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## OhioBurner© (Nov 25, 2016)

My house is still plenty leaky with OAK, really it made no difference in temperature or perceived drafts unfortunately.


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## Tonyray (Nov 25, 2016)

without an OAK, aren't you using the "air going back to the stove" that you paid to heat.?


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## OhioBurner© (Nov 26, 2016)

To a certain degree, yes. Whether or not that makes any noticeable difference will depends on a few things. Right now, with my stove off most of the time, it's actually cooling my house slightly via natural chimney effect since the stove is a heat exchanger and pulling in outside air, warming it, and then venting up the chimney. If I was really ambitious I'd go out and plug up the intake every time but I'm not that ambitious and know I'd end up firing up the stove forgetting about it half the time lol.


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## BUBIBEAR (Nov 26, 2016)

OhioBurner© said:


> To a certain degree, yes. Whether or not that makes any noticeable difference will depends on a few things. Right now, with my stove off most of the time, it's actually cooling my house slightly via natural chimney effect since the stove is a heat exchanger and pulling in outside air, warming it, and then venting up the chimney. If I was really ambitious I'd go out and plug up the intake every time but I'm not that ambitious and know I'd end up firing up the stove forgetting about it half the time lol.


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## BUBIBEAR (Nov 26, 2016)

I don't have enough time to bother with this .Total misinformation .


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## Pete Zahria (Nov 26, 2016)

OhioBurner© said:


> Right now, with my stove off most of the time, it's actually cooling my house slightly via natural chimney effect ...


Here is another experiment.
Go outside and feel the little amount of air coming out of your
chimney with the stove off.
Now go back to it when the stove is on.
All that rushing air coming out of your chimney
was replaced with an equal amount of cold air coming into the house..

Dan


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## bags (Nov 27, 2016)

Noname said:


> I know this is an old thread with much debate but here's my experience. House was gutted and remodeled out in the country and not much wind break, 60 yrs old on a slab but pretty efficient from the windows to insulation. Unfortunately it's isnt perfect. I have a Winslow pi 40 sat into an old but awesome looking brick fireplace. I was getting the draft and air leaks that people were speaking of so I rented a 2" boring bit and heavy duty hammer drill, bored through 15" of wall and threaded 2" flexo pipe for exhaust work from advance auto which cost $16 and connected to the stove. I siliconed where the pipe and brick are on the outside and siliconed in place a 3" drain cover over the pipe for bugs and mice which I got at lowes for $3. As I type this THERES no draft what so ever as compared to before and the glass is as clean now as this morning when I cleaned it, which it would be greying up a bit by now. It's in the 30's and my stove is on 1 and its 74 in a 1950 sq ft house. I can't say the stove is burning any better but I can say the house is a few degrees warmer from front to back due to no drafts. Total cost including the drill rental was about $70.



I am all for OAK's because they work. Glad you see the results. You'll get that $70 bucks back in short order cost wise and that's no including the extra comfort.


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## OhioBurner© (Nov 27, 2016)

Pete Zahria said:


> Here is another experiment.
> Go outside and feel the little amount of air coming out of your
> chimney with the stove off.
> Now go back to it when the stove is on.
> ...


I'm familiar with how they work, thanks. And right now my stove is 4F cooler that the room, but not enough to cause me to worry about it. This year I've basically switched the pellet stove to secondary, for use when it's below freezing, so it's mostly been off so far. Luckily I at least insulated the OAK pipe, something many forget about, since it is a rather long (in my case at least) pipe made out of aluminum with lots of little ridges (think about it like many more square feet of 'heat exchanger').



BUBIBEAR said:


> I don't have enough time to bother with this .Total misinformation .


If you're going to call someone a liar you better have the facts to back up the claim. Realize I've not called anyone a liar, and support OAK use, just playing devils advocate that the improvements are only slight and in some cases not perceivable. Some people just like to exaggerate that they'll use 1/2 the fuel because they are running an OAK. I'm hoping maybe at the end of the season it'll equate to a bag or two of fuel for me saved, even if I can't readily feel the difference.


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## Pete Zahria (Nov 27, 2016)

OhioBurner© said:


> I'm familiar with how they work, thanks.


cool.


OhioBurner© said:


> Some people just like to exaggerate that they'll use 1/2 the fuel because they are running an OAK.


which is also an exaggeration...


Dan


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## Tonyray (Nov 27, 2016)

Pete Zahria said:


> cool.
> 
> which is also an exaggeration...
> 
> ...


before we got and OAK, we would sit on the floor at times and feel the cool draft crawling along the floor.
PROB air going back to the stove].
that ended when we installed the OAK.. That's my total expirience with/without an OAK.


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## doghouse (Nov 28, 2016)

To OAK or to not OAK.  I understand the differing of opinions people have.  I OAK because I understand the benefits.  What I don't understand is that people say that their homes are leaky and drafty and do nothing about it.  Imagine the benefits if they sealed up their homes.


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## Pete Zahria (Nov 28, 2016)

doghouse said:


> To OAK or to not OAK.  I understand the differing of opinions people have.  I OAK because I understand the benefits.  What I don't understand is that people say that their homes are leaky and drafty and do nothing about it.  Imagine the benefits if they sealed up their homes.


It may be, that everyone doesn't have the resources to do it.
If you burn an extra ton of pellets that runs you a couple of hundred bucks.
That doesn't buy one replacement window. Or entry door.
Sure there are a lot of things you can do that "help" and many have already
done those... but can't do all the stuff necessary to do the whole deal the way it should be done,
to save that 200 bucks.
Just a thought.

Dan


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## bogieb (Nov 29, 2016)

doghouse said:


> To OAK or to not OAK.  I understand the differing of opinions people have.  I OAK because I understand the benefits.  What I don't understand is that people say that their homes are leaky and drafty and do nothing about it.  Imagine the benefits if they sealed up their homes.


I can only work so fast on my house. I have replaced all but 2 windows, all the doors (and installed storm doors), the roof, all insulation and sheetrock to exterior walls (including plugging up the 9" gap from the plywood to the top of the wall) - except for the 2 walls in the kitchen and 1 tiny closet.

I have insulated my unfinished basement, reinsulated and resheetrocked the garage, sealed up numerous other areas.

My big area of leakage is now the ceiling to the main floor as that is all acoustical tile instead of sheetrock. I also need to enhance insulation in my 2.5' tall (at the tallest) attic.

I have been here 3 years and work 2 jobs. If you want to come help me do the physical labor of demolition and installation as well pay for more materials for further improvements at the same time - you  are welcome to


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## tlc1976 (Nov 29, 2016)

Insulating the OAK pipe is something I'm thinking of doing.  There were times last winter when it was -20F or so, and I had frost on the outside of the pipe in the house.  Kept a towel on the floor behind the stove to catch the drips when the frost melted.


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## Mt Bob (Nov 29, 2016)

tlc1976 said:


> Insulating the OAK pipe is something I'm thinking of doing.  There were times last winter when it was -20F or so, and I had frost on the outside of the pipe in the house.  Kept a towel on the floor behind the stove to catch the drips when the frost melted.


Same thing out here,didn't want to insulate,kinda defeats having the incoming air preheated a little,so I put a y valve at the wall connection,if I see frost forming,I flip the lever and use house air for a bit.


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## dozerdean (Nov 29, 2016)

They sell a oak & exhaust that is combined together that heats ur outside air as it enters ur stove. Trust me a  oak does make a difference!!


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## Tonyray (Nov 29, 2016)

tlc1976 said:


> Insulating the OAK pipe is something I'm thinking of doing.  There were times last winter when it was -20F or so, and I had frost on the outside of the pipe in the house.  Kept a towel on the floor behind the stove to catch the drips when the frost melted.


Have been down to zero degrees and never saw any ice or frost on my OAK.. Wonder why some people do get that condensation and others don't..


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## Mt Bob (Nov 29, 2016)

Tonyray said:


> Have been down to zero degrees and never saw any ice or frost on my OAK.. Wonder why some people do get that condensation and others don't..


Hi Tony.Don't know imagine id has to do with humidity.Never happens to me unless it is colder than -15.But having the valve on mine,sometimes I use inside air just to change some air inside the cabin.


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## Tonyray (Nov 29, 2016)

bob bare said:


> Hi Tony.Don't know imagine id has to do with humidity.Never happens to me unless it is colder than -15.But having the valve on mine,sometimes I use inside air just to change some air inside the cabin.


ok.. prob condensation or humidity...


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## tlc1976 (Nov 29, 2016)

That was the only time I saw it, -20F or colder.  Typically winter has low humidity in the house, but when you've got that kind of extreme temperature difference (and I'm sure the velocity of that cold air coming in makes it even colder yet), it will find moisture somewhere.


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## fedtime (Nov 30, 2016)

Here in Nova Scotia, there is another very good reason to have an OAK - radon gas.  Having something in your house that creates a negative pressure increases the risk that radon gas will be pulled into your basement more efficiently.  With the OAK, that risk is reduced.  I have radon remediation as well as OAK kits on both stoves (basement and main floor) any my radon numbers are well below risk level.  Not a risk in all areas, but it is for some.


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## bogieb (Nov 30, 2016)

Even with low humidity in my house (~25% in the dead of winter) I get frost on my OAKS. I have wrapped insulation around them


fedtime said:


> Here in Nova Scotia, there is another very good reason to have an OAK - radon gas.  Having something in your house that creates a negative pressure increases the risk that radon gas will be pulled into your basement more efficiently.  With the OAK, that risk is reduced.  I have radon remediation as well as OAK kits on both stoves (basement and main floor) any my radon numbers are well below risk level.  Not a risk in all areas, but it is for some.



That is a great reason - Radon is also a concern for some areas of new England (and most of NH). Never even thought of that since I don't know if either of my houses had/ have radon, and don't care to test. (and please, no safety police getting on my case - I have no kids, no family and no friends, so  it's just me breathing the air here).


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## Ifixjetz1 (Nov 30, 2016)

What does one do when the Stove is in the middle of the room? Its hard to Install a OAK where my stove is located without tearing down drywall


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## Lake Girl (Nov 30, 2016)

Ifixjetz1 said:


> What does one do when the Stove is in the middle of the room? Its hard to Install a OAK where my stove is located without tearing down drywall


Any option of running it down and out?  May have to resize up if it is a long run.  What kind of stove?


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## Ifixjetz1 (Nov 30, 2016)

Its a castle serenity located on the Downstairs level on a cement slab.


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## Lake Girl (Nov 30, 2016)

Up and along the floor joists but likely that would require pulling drywall unless there are sections of the basement that are unfinished or have a suspended ceiling.  I am judging you are currently running the stove?  How is it performing?

ps ... do recall someone posting a system that brought outside air into basement on exterior wall that had a U configuration extending toward the floor.  Will see if I can find the thread...


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## Mt Bob (Nov 30, 2016)

Ifixjetz1 said:


> Its a castle serenity located on the Downstairs level on a cement slab.


Replace your flue system with selkirk direct temp.


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## OhioBurner© (Dec 1, 2016)

doghouse said:


> To OAK or to not OAK.  I understand the differing of opinions people have.  I OAK because I understand the benefits.  What I don't understand is that people say that their homes are leaky and drafty and do nothing about it.  Imagine the benefits if they sealed up their homes.


Oh I am doing something about it, but only a drop in the bucket really. To seal up my house would probably require gutting the entire thing, something I'll never do in part because I don't plan on staying in this house, and well because the walls are finished nicely inside and out. It'd be different story if it was in desperate need of cosmetic update as well. I did gut the last two rooms that were quite old plaster walls, half of the upstairs of the old section of the house didn't even have any insulation on the roof so that was my priority. I was getting a lot of air infiltration into the common wall between the old house and the new addition. That is basically now an interior wall right through the center of the house. Cold air was blowing right in there and circulating through the whole house basically. I found one small section where two roofs meet at funny angle that left a large cavity between that had vented soffit, that vented straight into that wall the runs through center of the house. I sealed up the venting but there is still air getting in there could be getting in between where the roofs meet at various points, kind of hard unless I am going to rip up almost brand new standing seam metal roof. I can't wait to dump this place and maybe design my own efficient home.


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## Pete Zahria (Dec 1, 2016)

Tonyray said:


> Wonder why some people do get that condensation and others don't..


More humidity.
My place is so dry there is nothing to frost up!

Dan


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## GT_Sharp (Dec 3, 2016)

Would just like to mention that I finally put in an OAK on my shop stove (Castile Serenity) that I fabbed from various metal leftovers and I love it! Makes a noticeable difference. Must just be better to blow hot  air out the cracks than suck in cold air,


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## mtrentw (Nov 21, 2018)

I've had an accentra insert for 6 years.  Ran it two years before installing an OAK.  Decided on an OAK in 2016 and it seemed better, but not quantifiable.  This season, after cleaning, I noticed it wasn't burning right.  After pulling it out again, I discovered I pinched off my homemade OAK on reinstall.  Decided to just run without it.  Major difference in draft and temperature in the house.  It used to heat up 3 rooms, now it only kept one warm.  Decided this morning to reinstall my OAK.  World of difference.

But the plural of anecdote is not data, so as a professional mechanical engineer who has worked in HVAC and industrial district heating plants, I started to play with some numbers to see if I could get to the bottom of it.

Using assumption of 0 degree OAK intake air vs. 70 degree room air and assuming the combustion fan pulls about 75 CFM, I figure the stove needs to produce an additional 5,670 BTU per hour to heat the outside air coming in the home (or reduces stove heating capacity.)  That being said, the stove with an OAK would need to burn a few more pellets to pre-heat the 0 degree outside air to be an equivalency.  But, with all puts and takes at an assumed 80% efficiency, I still figure the OAK saves about 1,200 BTU per hour or 28,000 BTU for a full day run, so that would be about 3 pounds per full day run savings.

I don't care much about the miniscule savings, but I absolutely am convinced an OAK kit is the way to go based on drafts and family comfort.  The fact that I've got some numbers to back me up makes me feel better.

Trent


"We can't solve problems by using the same kind of thinking we used when we created them."
-Albert Einstein


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## Don2222 (Nov 21, 2018)

mtrentw said:


> I've had an accentra insert for 6 years.  Ran it two years before installing an OAK.  Decided on an OAK in 2016 and it seemed better, but not quantifiable.  This season, after cleaning, I noticed it wasn't burning right.  After pulling it out again, I discovered I pinched off my homemade OAK on reinstall.  Decided to just run without it.  Major difference in draft and temperature in the house.  It used to heat up 3 rooms, now it only kept one warm.  Decided this morning to reinstall my OAK.  World of difference.
> 
> But the plural of anecdote is not data, so as a professional mechanical engineer who has worked in HVAC and industrial district heating plants, I started to play with some numbers to see if I could get to the bottom of it.
> 
> ...


Hi Trent
You do not have to compromise by using an OAK with incoming air at 0 degrees! I will not do that!
I use the Selkirk DT or Direct Temp venting with a 3rd wall to bring that outside air in and down to the stove around the hot flue pipe to dry And preheat the incoming outside cold and/or damp air!! Thus increasing the whole system efficiency by 10% 
This works very well for me and my friends who have installed it!!


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## mtrentw (Nov 22, 2018)

Hi Trent
You do not have to compromise by using an OAK with incoming air at 0 degrees! I will not do that!
I use the Selkirk DT or Direct Temp venting with a 3rd wall to bring that outside air in and down to the stove around the hot flue pipe to dry And preheat the incoming outside cold and/or damp air!! Thus increasing the whole system efficiency by 10% 
This works very well for me and my friends who have installed it!!

I'd love to have concentric intake, but the insert and flue pipe is already there and installed, so it'd be too much to retrofit at this point.  Next stove for sure will be this way.


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