I need help with smoke being drawn out of stove when heat pump kicks in.

syd3006 · Mar 2, 2015

I have a problem that I'm sure some of you folks could give me advice on. I have a "Century Hearth" wood stove, it works well, have had it for 8 winters and it has performed adequately, have had to do nothing more than replace a few fire bricks, replace the door and glass gaskets and painted it twice.
The problem is that when it is very cold and my heat pump kicks in especially if there is a smoldering fire in the wood stove, it will draw smoke out from around the wood stove door. I think the heat pump unit is drawing air from the rooms and not cold air returns. I had my oil furnace replaced with the geo thermal shortly after I had my wood stove installed so I don't know if it would have done the same thing with the oil furnace.
I usually don't run the geo thermal unit and wood stove at the same time but in very cold and windy weather I would like to as the house is drafty.
If anyone has a suggestion I would appreciate it, I asked the guy that installed the heat pump but haven't heard back from him.

DougA · Mar 2, 2015

If you crack open a window near the stove when this is happening, does the smoke stop coming into the house?
Was there a heat exchanger added to the geothermal unit or any other outside air intake?

syd3006 said:
I think the heat pump unit is drawing air from the rooms and not cold air returns

The cold air returns should be getting their air from the rooms, so not sure what you are meaning.

mellow · Mar 2, 2015

Sounds like you have a tight house, see if that model stove can have an Outside Air Kit hooked up to it, you need to draw your combustion air from outside as your house is tight and appliances are fighting for availible air.

toddnic · Mar 2, 2015

Yep....an Outside Air Kit (OAK) should take care of your problem. Your house is tight and your HVAC is pulling air from whatever source is available, including your woodstove chimney.

Tenn Dave · Mar 2, 2015

I often run my heat pump as my stove fire burns down during shoulder season and never have a smoke problem. My house is newer construction and pretty tight. My stove does not have an OAK. Sounds like your heat pump system is out of balance. Since heat pumps do not use combustion to create heat, they merely circulated extracted heat.

DougA · Mar 2, 2015

toddnic said:
your HVAC is pulling air from whatever source is available

Maybe not. If it's a geothermal/electric system, there may be an air exchanger but since there is no combustion, there should be no air being exhausted from the heater, just re-circulating air. If there is an air exchanger, it needs adjusting. That's why I asked the questions in my post. More info is needed.

Boiler74 · Mar 2, 2015

Tenn Dave said:
I often run my heat pump as my stove fire burns down during shoulder season and never have a smoke problem. My house is newer construction and pretty tight. My stove does not have an OAK. Sounds like your heat pump system is out of balance. Since heat pumps do not use combustion to create heat, they merely circulated extracted heat.

This. Your air is out of balance. The return air is sucking more than your supply side can provide. Do you have bedrooms closed off? Registers shut? Maybe supply registers in the basement with no returns, and the basement door is closed? The supply side and return side on the heat pump need to be balanced. It's possible you are leaking air into unconditioned space through unsealed ducts too. Lots of info out there on the web about furnaces drawing negative pressure in the house.

begreen · Mar 2, 2015

Exactly right. We had another case of this a month or so ago. The stove was in a MIL apt sharing a common HVAC system with the main house. The apt had too large of an air return. When running the HVAC would create negative pressure in the apt and pull smoke from the flue joints. Blocking off the return to the apt immediately solved the problem. I suggested they have their HVAC mechanic install another return in the main house to alleviate the problem, but apparently he deferred.
https://www.hearth.com/talk/threads/wood-stove-in-two-suite-home.138030/#post-1857761

Oldman47 · Mar 2, 2015

Another possibility is if you have an out of balance heat recovery type heat exchanger on that geothermal. With the geothermal running that heat exchanger pair of fans will also be running and might affect the home's internal pressure.

bholler · Mar 2, 2015

regardless of the specifics you need to get a good hvac guy out to figure out why you are getting negative pressures in the area of the stove. Some one really needs to be there to figure it out and then properly fix it. The other thread that begreen posted we were able to help him figure out the problem but he didnt fix it properly he just covered up the return which could cause many other problems. Call a hvac guy

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I need help with smoke being drawn out of stove when heat pump kicks in.

syd3006

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DougA

Minister of Fire

mellow

Resident Stove Connoisseur

toddnic

Minister of Fire

Tenn Dave

Minister of Fire

DougA

Minister of Fire

Boiler74

Burning Hunk

begreen

Mooderator

Oldman47

Minister of Fire

bholler

Chimney sweep

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