How to best rig an OAK for basement use on a PH

[tsh2002]

Hello. I am starting to plan out putting a stove in our basement (house is a single story ranch style). We have an inside solid masonry chimney ready to go with an insulated SS liner in it. The house is pretty tight, so I prefer to use outside air. The outside air duct is already run, but it comes in at the basement ceiling then down in the masonry chimney and comes out near the floor behind the stove. I've found here on this forum and talking with various stove vendors that it shouldn't run above the stove but I cannot change that. Other than using an air gap in the OAK, are there other ways people have dealt with this? I'm tossing around some ideas such as running the intake duct down to the floor first then up to the stove, putting in an air gap as mentioned, or getting a very light non-springed damper in the OAK. Just looking for ideas and thoughts on this, thanks.

 

[Whitenuckler]

Hello. I am starting to plan out putting a stove in our basement (house is a single story ranch style). We have an inside solid masonry chimney ready to go with an insulated SS liner in it. The house is pretty tight, so I prefer to use outside air. The outside air duct is already run, but it comes in at the basement ceiling then down in the masonry chimney and comes out near the floor behind the stove. I've found here on this forum and talking with various stove vendors that it shouldn't run above the stove but I cannot change that. Other than using an air gap in the OAK, are there other ways people have dealt with this? I'm tossing around some ideas such as running the intake duct down to the floor first then up to the stove, putting in an air gap as mentioned, or getting a very light non-springed damper in the OAK. Just looking for ideas and thoughts on this, thanks.

Does the stove have a duct to attach OAK, or are you just bringing fresh air near the stove?

 

[tsh2002]

Does the stove have a duct to attach OAK, or are you just bringing fresh air near the stove?

Yes, the stove has the standard 4" intake for the OAK to attach direct.

 

[Whitenuckler]

Yes, the stove has the standard 4" intake for the OAK to attach direct.

I don't know why there is an issue with running it down? You don't have any choice unless it could come down in a wall or other room. If it looks good, and has the clearance than it is good. I'm not sure what the issues are you read about ?

 

[Highbeam]

I would rather run no OAK than connect an OAK duct that is open to atmosphere above the firebox. By making the connection to the stove in your basement you are providing two chimneys to your stove and bad things can happen when it chooses to exhaust through the intake.

 

[tsh2002]

I don't know why there is an issue with running it down? You don't have any choice unless it could come down in a wall or other room. If it looks good, and has the clearance than it is good. I'm not sure what the issues are you read about ?

The issues I've heard/read about seem to deal with the possibility of the draft reversing and going out the OAK.

 

[Whitenuckler]

I would rather run no OAK than connect an OAK duct that is open to atmosphere above the firebox. By making the connection to the stove in your basement you are providing two chimneys to your stove and bad things can happen when it chooses to exhaust through the intake.

That does not sound good. Maybe just let the air come into the room with a damper?

 

[Whitenuckler]

The issues I've heard/read about seem to deal with the possibility of the draft reversing and going out the OAK.

I didn't know about this issue. I'm glad I found about it. I have a pellet stove in my basement with OAK, but of course it has a combustion blower. Best to not connect your OAK, but bring it to the floor near the stove. A damper would be good so you can shut it off, or trim it.

 

[Highbeam]

Basement installs already have so many problems with chimney flow reversal. Hard to start fires and smoke spillage until the flue reverses direction. I know people make it work and it's best to keep the chimney warm and flowing the right way along with closing off air leaks in the home up high. The house itself can be a chimney of sorts.

 

[begreen]

What stove is this for? Some have a built-in air gap on the outside air connection to avoid reverse drafting and some don't. If the latter, the best solution is to run the outside air to within a few inches of the stove's OAK connector, leaving an airgap. In that circumstance, a shut-off valve for when the stove is not in use may be desired.

 

[EbS-P]

house is pretty tight

Can you back that up with some evidence? Tight means different things to different people. How many cfm is the kitchen exhaust is it has one?

 

[tsh2002]

Basement installs already have so many problems with chimney flow reversal. Hard to start fires and smoke spillage until the flue reverses direction. I know people make it work and it's best to keep the chimney warm and flowing the right way along with closing off air leaks in the home up high. The house itself can be a chimney of sorts.

The concept makes sense, but I'm not sure how different this would be than to a single level home with no basement. Would the intake duct need to run under the floor? Wouldn't that have similar issues, or does a second level (basement, and main level and/or a second level on top of that ) make that much difference? I agree there would be several factors, we're hoping to make this work since the chimney is mostly inside so hopefully it stays as warm as possible.

 

[tsh2002]

What stove is this for? Some have a built-in air gap on the outside air connection to avoid reverse drafting and some don't. If the latter, the best solution is to run the outside air to within a few inches of the stove's OAK connector, leaving an airgap. In that circumstance, a shut-off valve for when the stove is not in use may be desired.

Thanks, I think this is probably what I will do to start with and see how it goes. We are planning on getting the Woodstock Progress Hybrid for this one.

 

[tsh2002]

Can you back that up with some evidence? Tight means different things to different people. How many cfm is the kitchen exhaust is it has one?

The house is only 5 years old and had decent insulation and sealing done when it was built. We do have a kitchen exhaust vent which I am showing is 380 cfm. Plus I do know that running the dryer will also pull air, etc. There was a blower door test done at construction, too, it says 65 cfm infiltration rate.

 

[GG Woody]

Air gap for sure, only needs to be an inch or so, lots of ways to accomplish this.

 

[begreen]

I think the PH will need the air gap. Note that basements often end up as negative pressure zones. Just leakage through an attic door, or out of upstairs vents (bath, dryer, kitchen) can cause this. Sometimes it takes a whole house ventilation system or a heat-recovery ventilator (HRV) to balance this out. Check the draft with no stove installed by holding an incense stick or smoke next to the chimney thimble. If the draft quickly pulls it up the chimney, that is a good sign.

 

[Highbeam]

I think the PH will need the air gap. Note that basements often end up as negative pressure zones. Just leakage through an attic door, or out of upstairs vents (bath, dryer, kitchen) can cause this. Sometimes it takes a whole house ventilation system or a heat-recovery ventilator (HRV) to balance this out. Check the draft with no stove installed by holding an incense stick or smoke next to the chimney thimble. If the draft quickly pulls it up the chimney, that is a good sign.

While you’re smoking, run over to the oak stub and see which way it’s flowing too.

And yes on a single story home you go down into the floor or out the wall. Not up above the firebox.

 

[tsh2002]

While you’re smoking, run over to the oak stub and see which way it’s flowing too.

And yes on a single story home you go down into the floor or out the wall. Not up above the firebox.

Just getting back to this, finally. We just got the stove (Woodstock PH) and I'm now looking at getting the stack pipe & OAK connected.

I checked and I have a decent draft going up the flue, and there is a steady supply of air coming in from the outside air stub as well. There's about 7 inches between the back shield of the stove to the chimney face, so I'm thinking of putting together some metal ducting similar to the attached drawing, to give sort of an "air gap" with a small vent that will open to the room air, my thought is that I would be able to better control the air to/from the room and avoid having excess outside air entering the room. Also, the outside air stub comes in the room at about 8 inches lower than the inlet on the back of the stove, hoping this might also help as well since any air leaving the stove going backwards would have to go down, before going up?

I'm curious if having the vent in my drawing open to the room would suffice as an "air gap". I'm still not sure I understand the conditions that would cause the stove to run in reverse, i.e. wind outside, stove running super low, etc?

Thanks again for the help!

 

[EbS-P]

So is your closable outside air vent there to make up for the fact that the oak terminates above the stove which is generally not allowed.

Edit read closer. It is.

I’m not sure I think that the best way. Why doe you need and OAK?

 

[tsh2002]

So is your closable outside air vent there to make up for the fact that the oak terminates above the stove which is generally not allowed.

Edit read closer. It is.

I’m not sure I think that the best way. Why doe you need and OAK?

Correct, since this is in a basement we do not have a way to terminate the outside air below the stove.

I am using an OAK as our home is very tight and well insulated (including the basement), I'd rather try to let the stove breath as much as possible and we do have things that can pull air such as two dryers, kitchen hood, bathroom exhaust, etc.

 

[EbS-P]

Correct, since this is in a basement we do not have a way to terminate the outside air below the stove.

I am using an OAK as our home is very tight and well insulated (including the basement), I'd rather try to let the stove breath as much as possible and we do have things that can pull air such as two dryers, kitchen hood, bathroom exhaust, etc.

My guess is that the basement will be a low pressure zone. That means any open vent will be pulling in cold air.

A manual control of the vent how will it work? Open while burning? Or when it’s going out? Closed when the stove is cold? How many hours a day will it be burning during the winter.

Sounds like an adjustable HRV would be better.

Have you run the stove without the OAK?

 

[GG Woody]

Just getting back to this, finally. We just got the stove (Woodstock PH) and I'm now looking at getting the stack pipe & OAK connected.

I checked and I have a decent draft going up the flue, and there is a steady supply of air coming in from the outside air stub as well. There's about 7 inches between the back shield of the stove to the chimney face, so I'm thinking of putting together some metal ducting similar to the attached drawing, to give sort of an "air gap" with a small vent that will open to the room air, my thought is that I would be able to better control the air to/from the room and avoid having excess outside air entering the room. Also, the outside air stub comes in the room at about 8 inches lower than the inlet on the back of the stove, hoping this might also help as well since any air leaving the stove going backwards would have to go down, before going up?

I'm curious if having the vent in my drawing open to the room would suffice as an "air gap". I'm still not sure I understand the conditions that would cause the stove to run in reverse, i.e. wind outside, stove running super low, etc?

View attachment 344815

Thanks again for the help!

I think that you're on to something...
I think you could close the top of your "closeable vent" permanently, but open the bottom of that stack all the time. If the stove chooses to draw that outside air it can, and if somewhere else in the house needs make up air it may draw through there. Maybe plug it in the off season?
However, I'm not sure if any of this is legal (probably isn't), or if a chimney sweep would like that it could easily be plugged and turned into what it is not supposed to be. Much like people plug their combustion air intakes in their mechanical rooms.

 

[tsh2002]

My guess is that the basement will be a low pressure zone. That means any open vent will be pulling in cold air.

A manual control of the vent how will it work? Open while burning? Or when it’s going out? Closed when the stove is cold? How many hours a day will it be burning during the winter.

Sounds like an adjustable HRV would be better.

Have you run the stove without the OAK?

To be determined on this vent idea, probably open it when burning (which we do plan on having this stove running 24/7 during the burning season), and close it during the off season or when not needed, etc. I didn't know much about HRVs, just looked and will keep that in mind, too.

Haven't tried running it yet without an OAK as it's new, but could always try that I suppose.

Thanks!

 

[EbS-P]

To be determined on this vent idea, probably open it when burning (which we do plan on having this stove running 24/7 during the burning season), and close it during the off season or when not needed, etc. I didn't know much about HRVs, just looked and will keep that in mind, too.

Haven't tried running it yet without an OAK as it's new, but could always try that I suppose.

Thanks!

I’d test it with no OAK. Then I would add an HRV then I’d mess with an OAK as a last resort.

If your house is tight you need fresh air. It’s best to get to choose where and how it gets inside.

 

[tsh2002]

Here's what I've come up with so far, and giving it a try. Used some 10x3 furnace duct and two 4" starter collars on each side, with a 2x10 vent on top that adjusts/closes, as it fits perfectly behind the PH stove with the minimum required clearance of 7". My thought is IF (and it's a big if to me), it started running in reverse for whatever reason, the smoke would come out the vent and hopefully set off my smoke alarm that is nearby and alert we have an issue. This also allows it to draw inside air if needed, but so far I'm seeing more than adequate outside air (there's some cold air actually pushing out the vent). Plus, so far we have an excellent draft and the PH stove seems to breathe more than I thought it would, which in this case might be a good thing. I like this for now so that I can easily monitor things, time will tell. Thanks again for all of the feedback on this.