New member wood burner to furnace

[Jbarrett86]

Hello all!
My name is John and I run a company out of Michigan called Breathe Easy. I am an HVAC contractor and we focus on indoor air quality. I got a call from a customer saying her carbon dioxide levels were very high in her home. I stopped by and her levels are indeed extremely high and actually the highest Ive seen to date. Im posting here b/c she has a wood burner attached to her furnace and I have 0 experience with this setup. I can say for sure that she, at a bare minimum, needs a combustion air vent in this room along with a few other things that I can rememdy but this setup just looks wrong to me. I appologize for lack of pics but I can get more. The furnace and water heater exhaust to another location and are not tied to the wood burner. With this install, I dont see how the furnace would not pull from the wood burner as she just has a manual damper on the supply line going to the plenum. Im also reading she should really have a back draft damper and the wood burner should be at least 10 ft away from the furnace. There is no room to move the wood burner 10ft away so I was wondering if anyone could give me any help at all on this? I am just way out of my area of expertise here but I really want to help this person out if at all possible. I would really appreciate any advice anyone could give me. Thank you so much!

 

[EatenByLimestone]

I just want to clarify that the issue is carbon dioxide and not carbon monoxide?

If the wood burner isn’t running, do the CO2 levels return to normal? Is there any sort of fresh air going to the utility room?

 

[Jbarrett86]

I just want to clarify that the issue is carbon dioxide and not carbon monoxide?

If the wood burner isn’t running, do the CO2 levels return to normal? Is there any sort of fresh air going to the utility room?

Yes carbon dioxide. I found out she actually doesnt have a carbon monoxide detector.. but told her to not run the wood burner until I got back for more testing. I do suspect there would be some carbon monoxide as well if I had to guess with the wood burner going.

There is no fresh air at all going to the room. I told her to leave her wood shute open for the time being. The CO2 stays high but I suspect its because all of the equipment in there with no fresh air in the room has started to supply that to the rest of the home as the company that installed the furnace has large holes in the filter rack and its not even sealed so all of the air is going around the filter..

The issue here is I really feel even with a combustion air vent run to this room, it wouldnt fix how this is installed. Im just not 100% sure what the right way is so she can get clean air

 

[EatenByLimestone]

It sounds like the woodstove is drawing so much combustion air that it’s reversing the draft on the regular furnace/water heater. But if that was the case, the rest of the house wouldn’t be filling with carbon dioxide.

Has this been a long term problem or something that just started? You might want to check to see if there are other things that could be drawing the air out of that room. Bathroom fans, kitchen vents, and even a lack of air sealing on the upper floors causing the house to act like a chimney.

 

[EatenByLimestone]

You mentioned the furnace and water heater do not use the same flue as the woodstove. Are they attached to a chimney and natural draft or are they power drafted out the side of the house?

 

[Jbarrett86]

It sounds like the woodstove is drawing so much combustion air that it’s reversing the draft on the regular furnace/water heater. But if that was the case, the rest of the house wouldn’t be filling with carbon dioxide.

Has this been a long term problem or something that just started? You might want to check to see if there are other things that could be drawing the air out of that room. Bathroom fans, kitchen vents, and even a lack of air sealing on the upper floors causing the house to act like a chimney.

They exhaust out through the roof further down and natural draft. This is new to me with a new customer. Im honestly not sure how long its been going on. Im assuming its been a problem for a while. Its in a basement and its a smaller space and the door shut to this area.

 

[EatenByLimestone]

Is the furnace and water heater flue clear of obstruction?

Shutting down the woodstove and monitoring air quality will rule that out as an issue. My thought is there must be a stronger draw outside that room if the carbon dioxide is being pulled outside of that room.

Find that draw and I think you’re on your way to solving the issue.

 

[brenndatomu]

By the age of the furnace n stuff this appears to be an older house, certainly not too tight..seems weird to me that the co2 would go up, but not the CO?

 

[stoveliker]

She doesn't have a CO detector.
CO will be up as well.

 

[Jbarrett86]

Yeah Im about positive the CO is up too. I went over to do testing but my equipment was still out for calibration so I just went out to get some info. Was really surprised she didnt already have a CO detector. Im going back this week to do further testing but did tell her to not run the wood burner, and she now has her wood shute open to get some outside air in there as well.

Does this install look ok though can anyone tell me that? Im thinking I will need a damper to close off the wood burner from the furnace when the wood burner is not in use so its not pulling when wood is smoldering. But even if I do a combustion air vent in here and put a damper in and everything, is this install safe? Another thing to note is she has 0 return runs in the basement only a few supply runs. I also felt like that could be a potential issue as well.

Also, wondering is she supposed to run the furnace fan and the wood burner fan at the same time or just the wood burner on its own? It has its own blower and I cant help but think if both blowers are running at the same time if that would cause issues. I didnt ask that when on site but thought to ask that here just in case.

 

[EatenByLimestone]

I have the feeling no 2 installs like this are going to be the same. It may take some time and monitoring to really sort it out.

Good on you for taking it on!

 

[stoveliker]

A damper won't be air tight and thus won't resolve back flow issues.

 

[brenndatomu]

There needs to be returns, at least to the basement, preferably right to the furnace(s)
This could be the whole problem right there...pulling a negative pressure on the basement

 

[Jbarrett86]

There needs to be returns, at least to the basement, preferably right to the furnace(s)
This could be the whole problem right there...pulling a negative pressure on the basement

Exactly what I was thinking. I think she has multiple issues here. I think with returns in basement, backdraft and dampers along with a combustion air venting that should take care of everything. Also planning on mortaring that exhaust in for the woodburner.