Newbie with a Fisher Grandma Bear question

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spistols

New Member
Nov 23, 2021
3
Georgia
Am new as new can be to wood stoves and their hookup. Moved into a retirement cabin recently that came with a Fisher Grandma Bear. After using the stove 2x, the next few days, I get a smell of burnt wood in the room, where the stove is. When I get close to the stove, I feel a draft coming from the places highlighted in yellow and where the yellow arrows are.

No fireplace/chimney service place is available to come out till late December to look at it. So, I bought stove/oven black high heat caulk, but am reluctant to caulk all of the places up in case there is more to the issue.

In summary, I have drafts bringing a burnt smoke smell back into the room, after all is cooled down and not in use on the stove pipe connections, and where it goes into the wall in some type of collector contraption thing. If it means anything, this stove is vented into the same chimney as the fireplace on the 1st floor, which is not operated as a gas only fireplace, but has the option of wood burning as well.

Please help a newbie out.

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begreen

Mooderator
Staff member
Nov 18, 2005
96,312
South Puget Sound, WA
Is the stove on an independent flue in the same chimney as the fireplace or sharing a single flue? Hopefully, it is connected to its own independent flue. It's illegal to share a common flue.

Is this a basement installation? If so, it may be a negative pressure zone. If the fireplace chimney terminates at the same height as the separate flue pipe coming up from the stove, then it may be pulling in smoke from the fireplace. Or it may be that the draft is reversing in the cold flue. That is common with basement installations. One basic test for this would be to open a nearby window an inch. Does the cool air leak in the yellow marked area stop or lessen?

Don't caulk the stove pipe. It's going to need to be pulled to inspect the installation. It would be best to not use the stove without understanding what is happening. The fixture that the stovepipe is connected to is called a thimble. In this case, it is a heat-shielding thimble. A professional sweep can determine if it is properly installed and connected to the chimney flue.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,668
NE PA
The pipes are backwards, the crimped male end should face down.

Each joint requires 3 screws.

Have chimney inspected to make sure they are not connected to the same flue and chimney is clean and safe for use.
 

John Bramhall

Member
Nov 28, 2014
7
Bend, Oregon
Is the stove on an independent flue in the same chimney as the fireplace or sharing a single flue? Hopefully, it is connected to its own independent flue. It's illegal to share a common flue.

Is this a basement installation? If so, it may be a negative pressure zone. If the fireplace chimney terminates at the same height as the separate flue pipe coming up from the stove, then it may be pulling in smoke from the fireplace. Or it may be that the draft is reversing in the cold flue. That is common with basement installations. One basic test for this would be to open a nearby window an inch. Does the cool air leak in the yellow marked area stop or lessen?

Don't caulk the stove pipe. It's going to need to be pulled to inspect the installation. It would be best to not use the stove without understanding what is happening. The fixture that the stovepipe is connected to is called a thimble. In this case, it is a heat-shielding thimble. A professional sweep can determine if it is properly installed and connected to the chimney flue.
 

John Bramhall

Member
Nov 28, 2014
7
Bend, Oregon
Basement installations are prone to what is called the STACK EFFECT. Warm air leaking out a higher location in the home may cause the chimney to provide a negative flow to replace the air escaping on a higher floor. Is there a window open somewhere on a higher floor?
 

spistols

New Member
Nov 23, 2021
3
Georgia
No windows open on higher floor. I am pretty sure there are two flues, as I see two at the top of the chimney. The first floor has a fireplace, but it is all gas, with gas logs, no wood burning- if this means anything. I am getting a smell in the basement of burnt wood, even though I fired up the wood stove 2x in October. I opened up the basement window, but did not notice any draft in or out of the "yellowed" areas.

Weird to say, but am trying to get a chimney sweep company to come and look, but in my area, there are either none available or that call back, or one that is extremely high in my eyes- $400 to clean and inspect. Not sure what chimney cleaning goes for these days.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,668
NE PA
No windows open on higher floor. I am pretty sure there are two flues, as I see two at the top of the chimney. The first floor has a fireplace, but it is all gas, with gas logs, no wood burning- if this means anything. I am getting a smell in the basement of burnt wood, even though I fired up the wood stove 2x in October. I opened up the basement window, but did not notice any draft in or out of the "yellowed" areas.

Weird to say, but am trying to get a chimney sweep company to come and look, but in my area, there are either none available or that call back, or one that is extremely high in my eyes- $400 to clean and inspect. Not sure what chimney cleaning goes for these days.
Is there another heat source running in the basement vented outside, like an oil burner, gas water heater, or any other vented appliances exhausting air from the basement or home? Clothes dryer, kitchen or bath fans? Radon blower? Something exhausting out of the home that wasn't running when it was warmer when it worked?
What type gas appliance is in the fireplace upstairs? Vented using indoor air exhausting up the chimney, or vent free? Was it going when you had no problem with the stove in October? Is the basement door open, connecting both levels?

I ask because as it gets colder, the chimney and stove will work better.

All items above create a lower pressure area in the vicinity of the stove. When cold air outside is in the chimney, it drops down easily becoming the air intake for the house. A mechanical blower can overpower the chimney easily and smell after the stove is out. Any appliance exhausting out will depressurize the home, higher atmospheric pressure outside pushes in wherever it can.

With stove cold, open intake air damper, shake out a match or use incense stick to see if smoke is pushed back into room. Lighting some twisted up paper to warm the chimney should start the draft rising. Check with the smoke test at intakes to see if draft reverses. When chimney is warm, smoke should draw into stove easily.
 

coaly

Fisher Moderator
Staff member
Dec 22, 2007
4,668
NE PA
When you understand what makes the stove work, you will be able to troubleshoot problems and have an understanding of how to control the stove.

Hot exhaust gasses lighter than outside air rise up the chimney. This creates a low pressure area in chimney, pipe, and stove. This is measured as draft. This lower pressure allows atmospheric air pressure to PUSH into the stove intake. This feeds oxygen to the fire to make it burn. The chimney becomes the engine that runs the stove. The hotter the rising gasses, and colder outside the chimney, the stronger the draft. Any leaks into the stove, pipe, or chimney allows the higher pressure to leak into the vent system cooling it. This reduces draft by cooling the rising gasses. Minor leaks were pipes go together are not critical. An opening into chimney such as an open clean out into chimney cool the rising gasses too much.

Once you get the draft correct, and stove works as it should, the temperature of the rising gasses becomes important. Not only for the operation of stove getting air inside, but for creosote formation. A magnetic pipe thermometer is need on the stove pipe before the chimney connection. The thermometer will read the surface temperature, which is about 1/2 the actual internal temp. The object is keeping the internal temperature to the top of chimney above 250*f while smoke is present. Below this critical temperature, water vapor from combustion condenses on flue walls allowing smoke particles to stick. This is creosote. This is why an insulated flue is much better so it stays hotter inside with less wasted heat left up the chimney, making the stove more efficient with additional heat to radiate inside.

Pipe thermometers are graduated in zones for proper burning temperature. Notice the pipe thermometer starts at the low burn zone about 250*. This is actually about 500 internal, assuming the internal flue gasses will cool back down to 250* before they exit the top. Since all chimneys cool differently, the burn zone will be from 250 to about 450. Above that will be a hot zone, showing extra heat left up is waste dropping efficiency. Without the thermometer on the pipe you are guessing.

Open dampers 2 to 3 turns when starting. As stove comes up to temperature, slowly close air dampers down a turn and monitor pipe temp. Close more as thermometer reaches about 350. This should run about that temp with dampers open 1 turn or less. Set air for heat output desired. Do not let pipe temp below 250* while smoke is present. That is as low as you can burn cleanly. In the coaling stage there is no smoke and temperature can drop extending burn time. Open air again when loading on coals to get back up to the burn zone above 250* as quickly as possible. You will learn where the cruise temperature is where it likes to run.