Combustion air for new insert - can I take from chimney?

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Fourthbean

New Member
Oct 17, 2021
17
N. Texas
I purchased an old slammer insert and we’ve since decided not to install it but rather get a smaller epa fireplace insert. Thank you for the advice yesterday!

I’d like to feed it fresh outside air for burning but there is no void in the chimney other than up. There is a crawlspace but I think I’d have to core through brick or cement to get there.

Is it a stupid idea to run a 6” insulated liner for exhaust but also another smaller one for intake 25’ up to grab fresh air from there? Our existing chimney is approximately 12x12” so if I couldn’t fit a 4/5” tube I’m sure I could do a pair that would be large enough?

This is the unit we are looking at currently.

 

Fourthbean

New Member
Oct 17, 2021
17
N. Texas
Picture of the chimney for fun:

4F1E1D4D-AE3B-414C-A970-15616E1F0C35.jpeg
 

begreen

Mooderator
Staff member
Nov 18, 2005
90,417
South Puget Sound, WA
The 1800i is not setup for an outside air supply. There wouldn't be a place to connect to the stove. Also, there is a risk of draft reversal with the intake air higher than the stove intake.
 

Fourthbean

New Member
Oct 17, 2021
17
N. Texas
Oops, must have read the wrong manual.

I have heard about draft reversal being a thing even with inlet down at ground level. I guess it would be even worse with my hair brained idea?
 

EbS-P

Minister of Fire
Jan 19, 2019
1,451
SE North Carolina
1800i is not setup for an outside air supply
My new one does. It has knockouts on the right or left side. But it does not appear to be an air tight connection. The OAK connects to the outer jacket while the air intakes are on the bottom center. Given that I don’t think it’s really worth it you have a tight house or are in a negative pressure zone for what ever reason.
With a second vent going up it’s just going to start drafting warm room air out.
 
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begreen

Mooderator
Staff member
Nov 18, 2005
90,417
South Puget Sound, WA
My new one does. It has knockouts on the right or left side. But it does not appear to be an air tight connection. The OAK connects to the outer jacket while the air intakes are on the bottom center. Given that I don’t think it’s really worth it you have a tight house or are in a negative pressure zone for what ever reason.
With a second vent going up it’s just going to start drafting warm room air out.
Interesting. The manual goes out of its way to downplay the use of an OAK.
 

EbS-P

Minister of Fire
Jan 19, 2019
1,451
SE North Carolina
Interesting. The manual goes out of its way to downplay the use of an OAK.
Given the design it feels like this was an after thought to satisfy a code/regulation requirement. I that said it get make up air as close the the air inlet as possible.
 

Riteway

Member
Jul 27, 2020
125
Kitsap County, WA
Any particular reason why you think you need outside air? Your mention in your previous post that your house is large and the open fireplace drafts well, so it seems like you'd be in good shape as-is.
 

PaulBunyun

Member
Oct 15, 2019
44
Michigan
I have seen maximum run length for some of the OAK piping set by manufacturers. You might want to contact the the manufacturer and your local inspector to get their opinion. That goes without saying some of the draft effects others have already mentioned. For that simple fact alone I would advise against what you proposed. Is there no way to get the OAK to go out an exterior wall.
 

Fourthbean

New Member
Oct 17, 2021
17
N. Texas
Any particular reason why you think you need outside air? Your mention in your previous post that your house is large and the open fireplace drafts well, so it seems like you'd be in good shape as-is.
Only reason is efficiency. Yes our house is plenty leaky to replace used air unfortunately :).

I’ve been doing more reading and it seems even the experts aren’t liking plumbing an intake to the outside for safety concerns which is matching what I’m seeing here. Could be this insert had the option to meet the code requirement in some places but they really don’t feel it’s needed.
 

Fourthbean

New Member
Oct 17, 2021
17
N. Texas
I have seen maximum run length for some of the OAK piping set by manufacturers. You might want to contact the the manufacturer and your local inspector to get their opinion. That goes without saying some of the draft effects others have already mentioned. For that simple fact alone I would advise against what you proposed. Is there no way to get the OAK to go out an exterior wall.
After some additional reading and the direction found here I’m just going to let it use room air for combustion. Should be 10x less than what our open fireplace used. Likely we won’t notice it now.

Thanks all!
 
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begreen

Mooderator
Staff member
Nov 18, 2005
90,417
South Puget Sound, WA
Given the design it feels like this was an after thought to satisfy a code/regulation requirement. I that said it get make up air as close the the air inlet as possible.
Yes, you could be right. There are states that insist on OAK for new installations.
 

EbS-P

Minister of Fire
Jan 19, 2019
1,451
SE North Carolina
Yes, you could be right. There are states that insist on OAK for new installations.
I took a second closer look at the OAK intake and it’s ok once the blower get out in place. Not at all a sealed intake but it’s design is intentional and reasonably thought out. Side knockouts are boxed and isolated from the jacked. Installing the blower restricts the front intake some bit it’s still very open to where the primary and secondary intakes are. Secondary air intake is about 3-4x the area of the largest primary air setting. Just an FYI