Smoke smell from wood stove when not burning

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SudsJeff

Member
Nov 19, 2015
23
Sudbury Ontario
Hello all.
I just had a brand new Enerzone 1.6 wood stove installed in my basement rec room. The stove is vented through double wall pipe into a clay liner (6x6). The chimney was swept as part of the installation. The house is a 1970s build.

I noticed a couple of days after having a fire there was a strong smoke smell in the room. I have the main air control closed (although there is a dime sized safety hole). I also noticed a strong draft of cold air blowing out from the secondary air intake when the stove is not in use. My stove does not have a damper on this secondary air (which i guess is typical of EPA stoves?). Maybe this is normal but its pretty unpleasant. I've heard some people will install stove pipe dampers or block the secondary air with magnet or something. Any suggestions?

thanks!
 

jatoxico

Minister of Fire
Aug 8, 2011
4,218
Long Island NY
You are getting down draft most likely due to the basement install. With the stove off warm air is rising in the house and is lost to the outside usually through the attic. This is the so called stack effect. The negative pressure created (especially in the lowest part of the house) allows cold air to come down the chimney.

If you have any obvious points of leakage like a poorly sealed attic door it may help to seal it up. If you can close the door to the basement when the stove is off it might help but this can be a difficult problem to solve. How tall is the chimney?
 
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SudsJeff

Member
Nov 19, 2015
23
Sudbury Ontario
You are getting down draft most likely due to the basement install. With the stove off warm air is rising in the house and is lost to the outside usually through the attic. This is the so called stack effect. The negative pressure created (especially in the lowest part of the house) allows cold air to come down the chimney.

If you have any obvious points of leakage like a poorly sealed attic door it may help to seal it up. If you can close the door to the basement when the stove is off it might help but this can be a difficult problem to solve. How tall is the chimney?
Thanks for the reply. I failed to mention my setup is an exterior brick chimney with the clay liner. I haven't taken a measurement yet, but I would say about 30-40 ft (the basement of a split level house going above the higher split). Down draft makes sense since its very tricky getting the stove lit without getting smoke in the room (admittedly this is probably contributing to that smoke smell). I have to use one of those low smoke fire starter things before I even think about putting kindling in there.
 

jatoxico

Minister of Fire
Aug 8, 2011
4,218
Long Island NY
Thanks for the reply. I failed to mention my setup is an exterior brick chimney with the clay liner. I haven't taken a measurement yet, but I would say about 30-40 ft (the basement of a split level house going above the higher split). Down draft makes sense since its very tricky getting the stove lit without getting smoke in the room (admittedly this is probably contributing to that smoke smell). I have to use one of those low smoke fire starter things before I even think about putting kindling in there.
Cold exterior chimney makes it that much worse. I too fight the stack effect on occasion since my stove is in a walk out basement. I sometimes have to pre-warm the flue with a piece of newspaper or I'll smoke my self out. One day as a newb we had bad atmospheric conditions and I started up some paper figuring I'd just overwhelm the down draft. Bad idea, ended up with full on reverse draft (fire was fed by air from chimney not room).

Possible solutions could include adding an insulated liner to try to keep the chimney as warm as possible but that could be an expense with no guarantee of working. If there is a cleanout or anything that could be allowing cool air into the system seal it. Do whatever you can to keep the chimney warm while eliminating rising warm air in the house.

Two concerns or points;
One that the smell you are getting is "smoky". I can feel the air but it doesn't smell of creosote. Was the chimney well cleaned before the install? Are you burning dry wood?

Two be sure to add a CO detector. You know the draft can reverse so it's possible it can occur after the chimney cools but when you still have a decent sized coal bed.
 
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SudsJeff

Member
Nov 19, 2015
23
Sudbury Ontario
Cold exterior chimney makes it that much worse. I too fight the stack effect on occasion since my stove is in a walk out basement. I sometimes have to pre-warm the flue with a piece of newspaper or I'll smoke my self out. One day as a newb we had bad atmospheric conditions and I started up some paper figuring I'd just overwhelm the down draft. Bad idea, ended up with full on reverse draft (fire was fed by air from chimney not room).

Possible solutions could include adding an insulated liner to try to keep the chimney as warm as possible but that could be an expense with no guarantee of working. If there is a cleanout or anything that could be allowing cool air into the system seal it. Do whatever you can to keep the chimney warm while eliminating rising warm air in the house.

Two concerns or points;
One that the smell you are getting is "smoky". I can feel the air but it doesn't smell of creosote. Was the chimney well cleaned before the install? Are you burning dry wood?

Two be sure to add a CO detector. You know the draft can reverse so it's possible it can occur after the chimney cools but when you still have a decent sized coal bed.
Great points! Apparently it was cleaned. I do have a cleanout, and it is a loose fitting metal plate that slides up and off. I will see if I can improve the seal there. Ahh the dry wood. That's a whole other post (rant). I purchased 5 cords of "dry" oak. It was not dry (my moisture meter was reading high 30s). Instead i am burning some old birch (3 years) that is in the teens for moisture. And yes we have a CO detector and a wifi enabled smoke detector.

In the meantime, to prevent smelly cold air from rushing in the house, do you think I should plug that secondary air intake. Its a fairly large 1x3 rectangle under the stove. Or perhaps getting a stove pipe damper installed? We dont make fires everyday but use the room everyday.

thanks
 

begreen

Mooderator
Staff member
Nov 18, 2005
83,600
South Puget Sound, WA
Basement installations can be tricky. This location is often a negative pressure zone. Exhaust fans, clothes dryers and competing appliances make the situation worse when they are running. To help alleviate the problem the stove pipe should have the minimum of bends and run straight up through the house. If that is not possible then eliminate 90º turns in the stove pipe by replacing them with a softer bend made up of 2-45º elbows. Connect to an insulated liner in the chimney. And add an outside air supply to the stove. http://woodheat.org/all-about-chimneys.html

To improve the seal on the cleanout, run a bead of silicone around the edge of the door and then close the door on the bead. Let it setup for at least a day.
 
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Woody Stover

Minister of Fire
Dec 25, 2010
12,160
Southern IN
The stack effect will be exacerbated if the point at which the air is leaving the house is higher than the top of the stack. If the smell is coming down the clay liner, though, as I think it may be, a liner to the top is definitely going to help stove performance, and may help with the smell. For sure, a thorough cleaning of the clay liner and smoke chamber will help. But with a liner to the top ("positive connection") you can seal around it with mineral wool insulation, top and bottom, to minimize air being drawn down between the liner and the clay tile. It sounds like you have a "direct-connect," where the chimney goes into the clay liner a short distance, then stops. Sealing between the chimney and the clay liner at that point would keep air from coming down to some degree. Is the chimney pipe going into a fireplace, or can you get a pic of how the connector pipe is connected to the clay liner? Can you tell if the smell is actually coming out of the stove, or from the area where the connector is going into the clay liner?
 
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SudsJeff

Member
Nov 19, 2015
23
Sudbury Ontario
The stack effect will be exacerbated if the point at which the air is leaving the house is higher than the top of the stack. If the smell is coming down the clay liner, though, as I think it may be, a liner to the top is definitely going to help stove performance, and may help with the smell. For sure, a thorough cleaning of the clay liner and smoke chamber will help. But with a liner to the top ("positive connection") you can seal around it with mineral wool insulation, top and bottom, to minimize air being drawn down between the liner and the clay tile. It sounds like you have a "direct-connect," where the chimney goes into the clay liner a short distance, then stops. Sealing between the chimney and the clay liner at that point would keep air from coming down to some degree. Is the chimney pipe going into a fireplace, or can you get a pic of how the connector pipe is connected to the clay liner? Can you tell if the smell is actually coming out of the stove, or from the area where the connector is going into the clay liner?
Interesting ideas. The double wall stove pipe connects to a wall thimble and a section of stainless steel pipe which enters the opening in the clay liner. To my knowledge the installers did not seal the section of stainless pipe against the clay liner. I will check tonight around that thimble. I just assumed since I could feel the air pushing through that secondary air intake that it must be coming from that. My profile picture is the stove in question. thanks!
 

SudsJeff

Member
Nov 19, 2015
23
Sudbury Ontario
Basement installations can be tricky. This location is often a negative pressure zone. Exhaust fans, clothes dryers and competing appliances make the situation worse when they are running. To help alleviate the problem the stove pipe should have the minimum of bends and run straight up through the house. If that is not possible then eliminate 90º turns in the stove pipe by replacing them with a softer bend made up of 2-45º elbows. Connect to an insulated liner in the chimney. And add an outside air supply to the stove. http://woodheat.org/all-about-chimneys.html

To improve the seal on the cleanout, run a bead of silicone around the edge of the door and then close the door on the bead. Let it setup for at least a day.
I am beginning to wonder why the installers didn't install a liner kit. I had assumed that that would be required since it was a clay liner. They said the overall diameter of the clay liner was within the area requirements for a 6 inch stove pipe and was in good condition. While I may have saved some $ on the install. I now may need to call them back to fix this issue.
 
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begreen

Mooderator
Staff member
Nov 18, 2005
83,600
South Puget Sound, WA
They may have been correct as far as meeting the flue requirement as specced by the stove mfg., but not necessarily code correct. They may also not have been aware that there is a reverse-draft problem. Another possible issue is room in the chimney for a 6" insulated liner. The liner problem does have work arounds if there is enough room for a pre-insulated liner.

Even after fixing the liner, the negative draft issue may persist when the stove is not running. If so, this is more of a house issue. Exhaust fans and leakage in the upper floors due to a bedroom window cracked open, recessed ceiling lights or an unsealed attic door can also contribute to the problem. A damper in the pipe probably won't solve the issue. They are designed for safety reasons to not completely block off the airflow.
 

mellow

Resident Stove Connoisseur
Jan 19, 2008
5,072
Salisbury, MD
If your existing terracotta met the requirements it is probably too small for a liner to go down(5.5" insulated might fit?), more than likely they will have to bust out that terracotta to fit a 6" insulated liner down.

One trick you could try and see if it helps, with the stove cold, pickup some of that stretch wrap used for shipping on a big roll, try sealing up the stove and see if the smell goes away.
 
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SudsJeff

Member
Nov 19, 2015
23
Sudbury Ontario
Can you tell if the smell is actually coming out of the stove, or from the area where the connector is going into the clay liner?
So it turns out the cold air was blowing in from the connector at the clay liner. It was not sealed. I used some stove cement to make a good seal. Then packed the area with some insulation. Problem solved. Thanks to everyone who helped with this one!
 
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