Outside Air Kit - Oak - My research after investigating

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.

Combustion air has to be replaced from somewhere.

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 .

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....

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....

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

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?

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.

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.

- 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 forking out of your mind? Get the fork outta here!











Any questions?

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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.

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.

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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!

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.

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.

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.

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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.

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..

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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.

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

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.

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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.

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.

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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.

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.

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

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.

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.

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I reject your reality and substitute my own.

TimfromMA said:

I reject your reality and substitute my own.

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There's a lot of that going around!

I thought this was resolved last week...

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.

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

I read the linked article, it is correct grammatically.

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