Green Mountain 40 Odor

[Billwardii]

Installed a GM 40 late last winter (2023) after flue inspection, new stove pipe install, etc. The GM 40 replaced an old Wonder Coal we had in the house but we have not used wood heat since 2020. The GM initial burns went well, other than it seemed it is impossible to reload with some smoke. However, we noticed a fairly regular sooty/creosote smell during use and afterwards. My wife was pregnant at the time and very sensitive to smells so we decided to use another heat source. I noticed it too, but not as much.

Fast forward to last week. Started off with low-slow burns. Smoke still escapes when reloading (waiting until only hot coals are left before reloading seems to remedy that issue) and we are back to strong sooty/creosote odors during firing and a day or two after an active fire goes out. I just don't remember that smell with other stoves, even the old wonder coal. Last night the temp was in cat range, I engaged it and went to bed. In the middle of the night the sooty smell was very strong, but I imagine part of that was because the fire had died down and the cat was still engaged?

Does anyone have any thoughts or suggestions?

 

[neverstop]

Installed a GM 40 late last winter (2023) after flue inspection, new stove pipe install, etc. The GM 40 replaced an old Wonder Coal we had in the house but we have not used wood heat since 2020. The GM initial burns went well, other than it seemed it is impossible to reload with some smoke. However, we noticed a fairly regular sooty/creosote smell during use and afterwards. My wife was pregnant at the time and very sensitive to smells so we decided to use another heat source. I noticed it too, but not as much.

Fast forward to last week. Started off with low-slow burns. Smoke still escapes when reloading (waiting until only hot coals are left before reloading seems to remedy that issue) and we are back to strong sooty/creosote odors during firing and a day or two after an active fire goes out. I just don't remember that smell with other stoves, even the old wonder coal. Last night the temp was in cat range, I engaged it and went to bed. In the middle of the night the sooty smell was very strong, but I imagine part of that was because the fire had died down and the cat was still engaged?

Does anyone have any thoughts or suggestions?

on the smoke spillout. what is your chimney setup? rear exit, #of elbows, total height, insulated pipe, etc. these stoves require a lot of draft compared to other stoves and as I've been told by hearthstone "if you get smoke rollout on reloads then your draft is insufficient".

on the sooty smell. does it smell like smoke or does it kind of smell different like slightly sweet? the soap stone can retain moisture and if the stove isn't used frequently or if the wood is wet i've noticed that the stove can drip black liquid. when the stove gets hot that liquid can evaporate and that smell is slightly sweet, somewhat similar to a BBQ.

 

[Billwardii]

Thanks for the insight, neverstop

Regarding the smoke, the stove vents out the top, straight run of 2' single wall, 6" pipe (with plans to replace with double wall this year), elbows and runs 1' towards the thimble. Curiously, we had to attach a 6" to 5" adapter to go through the thimble with a piece of 5" pipe. The chimney is ceramic flue liner, laid up within concrete chimney block, approx. 25' tall.

The sooty smell has a sweetness to it, and the liquid that drips has the same or virtually the same smell as we are experiencing. The first burns we stay diligent about keeping that liquid cleaned up! But perhaps the soapstone have are not completely 'baked out' after a 3/4 good fires?

 

[tabner]

It took me several Fire/Cool Down/Fire cycles before the black water drip completely stopped. And that black liquid definitely had a strong smoke/creo odor to it. So it could still be that baking out. When the stove was not going (like all summer), i could get creosote smells in the house, but that was when it heated up outside and i got some negative draft going since my stove is in the basement, unlikely that's your problem.
My other thought is some backpuffing? My GM60 would backpuff at times, and when it did that a small amount of smoke would puff out of all the stovepipe seems, and stink the house up like smoke for half an hour. Not sure if you're seeing any of that?

 

[neverstop]

Thanks for the insight, neverstop

Regarding the smoke, the stove vents out the top, straight run of 2' single wall, 6" pipe (with plans to replace with double wall this year), elbows and runs 1' towards the thimble. Curiously, we had to attach a 6" to 5" adapter to go through the thimble with a piece of 5" pipe. The chimney is ceramic flue liner, laid up within concrete chimney block, approx. 25' tall.

The sooty smell has a sweetness to it, and the liquid that drips has the same or virtually the same smell as we are experiencing. The first burns we stay diligent about keeping that liquid cleaned up! But perhaps the soapstone have are not completely 'baked out' after a 3/4 good fires?

if the wood has a high moisture content or if it's been high humidity outside and the stove isn't being run 24/7 i've had that smell come from mine during the middle of the season.

the chimney sounds like it's not to the specifications laid out in the stove manual. the 5" adapter on the horizontal section combined with the clay flue liner are most likely causing your smoke spillage issues. if the clay liner is a 8x12" then that means the cross sectional area is 3x that of the specified 6" ID liner. that will cause the flue gases to slow down. also, since the clay is uninsulated that will also be a hit to performance.

 

[Billwardii]

It took me several Fire/Cool Down/Fire cycles before the black water drip completely stopped. And that black liquid definitely had a strong smoke/creo odor to it. So it could still be that baking out. When the stove was not going (like all summer), i could get creosote smells in the house, but that was when it heated up outside and i got some negative draft going since my stove is in the basement, unlikely that's your problem.
My other thought is some backpuffing? My GM60 would backpuff at times, and when it did that a small amount of smoke would puff out of all the stovepipe seems, and stink the house up like smoke for half an hour. Not sure if you're seeing any of that?

Thanks, Tabner,
Perhaps the soapstone is still not baked out enough, the weather has not been conducive for a long fire with temps in the 40's one day but jumping to the 60s the next. It's been a start, stop, open the windows kind of fall. And the soapstone is charred up pretty good in the mornings rather than clean which makes me think there is a lot of smoke rolling around the firebox as it dies down in the middle of the night with the temps dropping and the cat engaged. Thankfully, no backpuffing, but I have had that when I had a chimney obstruction or reduced capacity. What conditions made your GM 60 backpuff?

 

[Billwardii]

if the wood has a high moisture content or if it's been high humidity outside and the stove isn't being run 24/7 i've had that smell come from mine during the middle of the season.

the chimney sounds like it's not to the specifications laid out in the stove manual. the 5" adapter on the horizontal section combined with the clay flue liner are most likely causing your smoke spillage issues. if the clay liner is a 8x12" then that means the cross sectional area is 3x that of the specified 6" ID liner. that will cause the flue gases to slow down. also, since the clay is uninsulated that will also be a hit to performance.

Neverstop,
You may have it figured out. The wood is dry, but the problem may be with the chimney set-up. I knew it could be an issue before purchasing after looking at the specs beforehand, but as it is only the 8" square clay liner I was hoping it wouldn't be an issue or not much of one. But like the house, it is not insulated lol.

 

[KDubU]

Ideally you need to install a liner in the chimney as that will help I think.

 

[wetwood4life]

like the house, it is not insulated lol

We've had constant problems with smoke rollout on our 2 year old install. Hearthstone Castleton into Class A pipe. Someone here pointed out if you have a drafty house whose gaps/cracks add up to more than your chimney area, then your house will act like a chimney and fight the real chimney's draft. You might want to get some air sealing up in the attic.

 

[begreen]

We've had constant problems with smoke rollout on our 2 year old install. Hearthstone Castleton into Class A pipe. Someone here pointed out if you have a drafty house whose gaps/cracks add up to more than your chimney area, then your house will act like a chimney and fight the real chimney's draft. You might want to get some air sealing up in the attic.

Good tip. Leaky second story windows, attic vents, etc. definitely can cause the house to act like a chimney creating negative pressure on the floor(s) below.

 

[Billwardii]

Ideally you need to install a liner in the chimney as that will help I think.

That would probably solve a lot of problems all the way around, thanks KDubu

 

[Billwardii]

We've had constant problems with smoke rollout on our 2 year old install. Hearthstone Castleton into Class A pipe. Someone here pointed out if you have a drafty house whose gaps/cracks add up to more than your chimney area, then your house will act like a chimney and fight the real chimney's draft. You might want to get some air sealing up in the attic.

It is a fairly drafty farmhouse we are fixing up and that makes a lot of sense, that it is fighting the chimney draft. It is ballooned framed with the second story shut off, but that area of the house is the traditional definition of "climate controlled," the old timers were tough lol

 

[Billwardii]

Good tip. Leaky second story windows, attic vents, etc. definitely can cause the house to act like a chimney creating negative pressure on the floor(s) below.

Thanks begreen! I think you guys have been able to answer all my questions! In short: I should have built a small cabin with a new chimney.