Why out rather than up?

[1750]

Unbelievably, it was still in the 40s this weekend and so I got to warm the place up with the Lopi.

I think it has something to do with the differential draft associated with warmer outside air, but it was tough to open the door to tend the fire without getting smoke into the room. And, this was after we had a very nice fire going, and temp measured on the top of the box was 500-600F.

It got me wondering why the path of least resistance seemed to be out into the room rather than up the hot chimney. I even intentionally built the fire toward the back of the box, but as soon as I would open the door, I could watch the smoke make its way across the top of the box and would work its way out the door if I left it open.

Any ideas? Thanks in advance for your thoughts.

Mike

ETA: I have an OAK, so I thought that should help with the draft, as well.

 

[My Oslo heats my home]

my only thought would be the cold air coming into the box may force the smoke out in that direction? I have a Jotul with a regularly decent draft, even in warmer weather, and I have never had that problem. No OAK either.

 

[ScotO]

The difference in temperature outside versus inside wasn't extreme, and that will cause very poor draft. When that happens, your chimney won't draw the smoke up the pipe. You need to either light a piece of newspaper in the stove and let it throw some heat up the pipe, put a propane torch at the flue inside your stove for a minute or two to start a draw, or build a 'top-down' fire. Do a search on here, lots and lots of people have gone through the same thing you are right now. I had it happen to me Sunday night.....

 

[1750]

The difference in temperature outside versus inside wasn't extreme, and that will cause very poor draft. When that happens, your chimney won't draw the smoke up the pipe. You need to either light a piece of newspaper in the stove and let it throw some heat up the pipe, put a propane torch at the flue inside your stove for a minute or two to start a draw, or build a 'top-down' fire. Do a search on here, lots and lots of people have gone through the same thing you are right now. I had it happen to me Sunday night.....

Thanks for your reply. If I had just started the fire, I would agree with you, but we had the fire rolling along for hours at 500-600F. The heat going up the chimney was wildly hotter than the temperature outside. I would think this alone would pull the smoke up and out through the chimney.

my only thought would be the cold air coming into the box may force the smoke out in that direction? I have a Jotul with a regularly decent draft, even in warmer weather, and I have never had that problem. No OAK either.

In the colder weather this stove usually has a great draft. Under this circumstance I'm not sure where the cold air would be coming from? I could see this if the fire was just starting and the cap of cold air in the chimney was sitting on top of the warming air in the box, but the exhaust coming out of the pipe must have been many times the temp of the air outside.

Thanks!

 

[webby3650]

Does your flue go straight up and out? Or do you have elbows? I have found that elbows will make a pretty big difference if your draft is questionable, like in warmer weather.

 

[1750]

Does your flue go straight up and out? Or do you have elbows? I have found that elbows will make a pretty big difference if your draft is questionable, like in warmer weather.

She goes straight up, webby... straight up!

 

[xman23]

Mike, The reverse draft is normally a cold start up issue. Not a 500 degree running stoves. I think your cap screen is getting pluged. The additional air flow up the chimney as you open the door can't get thru the screen. Reduce the flow with the door closed and it works.

 

[lazeedan]

How is your cap? Maybe getting a little dirty?
Dan

 

[ScotO]

I apologize, I guess I didn't read your original post very well! I agree on the cap being clogged. Sounds like that is most likely your issue, that.seems to be problematic in the shoulder seasons, especially of your wood is less than ideal (I'm not.saying that your wood isn't ideal, but that will lead to quickly clogged caps)

 

[1750]

Mike, The reverse draft is normally a cold start up issue. Not a 500 degree running stoves. I think your cap screen is getting pluged. The additional air flow up the chimney as you open the door can't get thru the screen. Reduce the flow with the door closed and it works.

How is your cap? Maybe getting a little dirty?
Dan

Thanks to you both. I'll check that. We've only had about 10 fires in this stove, so if it is plugged already, that's really concerning. Unfortunately, the chimney is on a 10/12, so it's pretty exciting to access the roof. I was hoping to be able to clean it from inside, but I guess you probably can't clean the cap from the inside?

I apologize, I guess I didn't read your original post very well! I agree on the cap being clogged. Sounds like that is most likely your issue, that.seems to be problematic in the shoulder seasons, especially of your wood is less than ideal (I'm not.saying that your wood isn't ideal, but that will lead to quickly clogged caps)

Thanks, Scotty. I'm going to check that cap. And, I bought this load of "seasoned" wood, but when I split it up a bit it seems pretty damp. I would guess that my wood is absolutely probably not ideal!

 

[webby3650]

If you have only had 10 fires does that mean its been relitively warm the whole time?

 

[webby3650]

How tall is the flue?

 

[xman23]

Some guys get by with a screen on the cap. Mine was plugged halfway thru the first season. It was a gooey mess when i got up there. A 1/4 inch mesh wasn't going to work. Removed the screen 12 years ago. That said the gooey cap has gotten better each year as the oak I burn got seasoned. To do the top down cleaning I remove the last top section and clean it and the cap on the ground. The brush won't work on the cap or screen. I clean the cap with fireview glass cleaner.


10 fires and plugged maybe a record, but it's possible. It maybe hard to see from the ground as it's all hanging from the screen on the inside.

 

[coldkiwi]

Did you open the bypass before you opened the door

 

[Backwoods Savage]

Unbelievably, it was still in the 40s this weekend and so I got to warm the place up with the Lopi.

I think it has something to do with the differential draft associated with warmer outside air, but it was tough to open the door to tend the fire without getting smoke into the room. And, this was after we had a very nice fire going, and temp measured on the top of the box was 500-600F.

It got me wondering why the path of least resistance seemed to be out into the room rather than up the hot chimney. I even intentionally built the fire toward the back of the box, but as soon as I would open the door, I could watch the smoke make its way across the top of the box and would work its way out the door if I left it open.

Any ideas? Thanks in advance for your thoughts.

Mike

ETA: I have an OAK, so I thought that should help with the draft, as well.

Mike, I agree with some of the suggestions given and yes, it is possible to plug a cap with that few number of fires. As you sadly found out, when buying wood, it is best to buy it at least a year before you need it. The sellers all say it is "seasoned" but it is extremely rare that the wood is ready to burn. The main reason is that most times the wood gets split just before delivery and wood just won't dry worth a hoot until it has been split then stacked out in the wind to dry.

What really caught my eye though was your statement that you were opening the firebox door when the stove top was at 500-600 degrees. That is no doubt why you got the smoke. That also is why we never open our firebox door until the stove top is down to at least 350 degrees and usually lower than that. Before opening the door, we give it full draft. For a cat stove this also usually means you open the bypass. Wait at least a minute then before opening the firebox door and even in the 40 degree outdoor range you should not get any smoke in the house.

Hope this helps and good luck to you.

 

[1750]

If you have only had 10 fires does that mean its been relitively warm the whole time?

No, it's at a cottage that has just been roughed in. We've only been there on weekends.

How tall is the flue?

It's about 15 feet above the firebox. About 5 feet out of the roof.

Some guys get by with a screen on the cap. Mine was plugged halfway thru the first season. It was a gooey mess when i got up there. A 1/4 inch mesh wasn't going to work. Removed the screen 12 years ago. That said the gooey cap has gotten better each year as the oak I burn got seasoned. To do the top down cleaning I remove the last top section and clean it and the cap on the ground. The brush won't work on the cap or screen. I clean the cap with fireview glass cleaner.


10 fires and plugged maybe a record, but it's possible. It maybe hard to see from the ground as it's all hanging from the screen on the inside.

I have to look at taking the double-wall sections down from the inside. I don't think there's a sliding section, so I'm not sure how that will work. I will have to get on the roof to look at the cap. As I've taken the advice given here and burn smaller, hotter fires, I think this has improved.

Did you open the bypass before you opened the door

This stove doesn't have a bypass, coldkiwi. (Lopi Republic 1750)

Mike, I agree with some of the suggestions given and yes, it is possible to plug a cap with that few number of fires. As you sadly found out, when buying wood, it is best to buy it at least a year before you need it. The sellers all say it is "seasoned" but it is extremely rare that the wood is ready to burn. The main reason is that most times the wood gets split just before delivery and wood just won't dry worth a hoot until it has been split then stacked out in the wind to dry.

What really caught my eye though was your statement that you were opening the firebox door when the stove top was at 500-600 degrees. That is no doubt why you got the smoke. That also is why we never open our firebox door until the stove top is down to at least 350 degrees and usually lower than that. Before opening the door, we give it full draft. For a cat stove this also usually means you open the bypass. Wait at least a minute then before opening the firebox door and even in the 40 degree outdoor range you should not get any smoke in the house.

Hope this helps and good luck to you.

Thanks for the thoughtful response, Backwoods. This stove doesn't have a bypass, but I do give it full draft before opening the firebox door, and do that very gradually. I was surprised that the smoke works its way toward the door, so I played with that variable quite a bit. It didn't seem to matter how long i waited, or how slowly I opened the door. That smoke was determined to come into the house!

I'm curious why the smoke from the cooler stove (i.e., below 350F) doesn't come into the house, but the smoke from the hotter stove does. It would seem like the hotter the stove, the better the draft. (This admittedly could be completely wrong!)

Thanks to all of you for your thoughts on my original question.

Mike

 

[coldkiwi]

I did not know the 1750 did not have a bypass..I know it makes a big difference on the freedom when opening the door

 

[begreen]

Could be the cap screen is starting to plug. This can happen quickly if the wood is damp or if a lot of newspaper or cardboard is used to start the fire. Try opening the air control all the way, then open door slowly.

 

[Backwoods Savage]

No, it's at a cottage that has just been roughed in. We've only been there on weekends.
It's about 15 feet above the firebox. About 5 feet out of the roof.
I have to look at taking the double-wall sections down from the inside. I don't think there's a sliding section, so I'm not sure how that will work. I will have to get on the roof to look at the cap. As I've taken the advice given here and burn smaller, hotter fires, I think this has improved.
This stove doesn't have a bypass, coldkiwi. (Lopi Republic 1750)
Thanks for the thoughtful response, Backwoods. This stove doesn't have a bypass, but I do give it full draft before opening the firebox door, and do that very gradually. I was surprised that the smoke works its way toward the door, so I played with that variable quite a bit. It didn't seem to matter how long i waited, or how slowly I opened the door. That smoke was determined to come into the house!

I'm curious why the smoke from the cooler stove (i.e., below 350F) doesn't come into the house, but the smoke from the hotter stove does. It would seem like the hotter the stove, the better the draft. (This admittedly could be completely wrong!)

Thanks to all of you for your thoughts on my original question.

Mike

Mike, I too have been curious about this but I guess never curious enough to seek the real answer. I just have noticed it though the years and sort of just took it in stride to not open that door when the stove is hot. The few times we have, we didn't like the outcome.

 

[Milton Findley]

The smoke goes to where it thinks the chimney is.

 

[Gark]

Stoves are meant to be left closed until well after they have burned the entire load. Timing is important - wait until the flames are long gone and there is only a medium bed of coals left (1 or 2 inches left depending on what species is going in next) before another load. The stove will have cooled down some. You said that you open the stove with the top at 500 to 600, that may be when the fuel is outgassing heavily (smoking). Coals leftover from a burn cycle put out very little smoke. Also, can your OAK be closed? If the OAK intake port is on a windy side of the house it could stuff more air into the firebox than a lazy draft could handle (when the stove door is open). JMHO.
Any exhaust fans/clothes dryer running? Windows/doors open on the leeward side of the building?

 

[rideau]

Why are you opening the door when the stove is still producing lots of heat?

And Gark's right...if you wait until the load is burned down to coals, there is really no smoke to come out the door.

That said, some with smoke seepage issues close their air intake completely before opening the door, which they find forces the stove to use the door as air inlet, thus preventing air/smoke exiting the door.



unorthodox, but it has worked for some.

 

[1750]

Why are you opening the door when the stove is still producing lots of heat?

And Gark's right...if you wait until the load is burned down to coals, there is really no smoke to come out the door.

That said, some with smoke seepage issues close their air intake completely before opening the door, which they find forces the stove to use the door as air inlet, thus preventing air/smoke exiting the door.



unorthodox, but it has worked for some.

Usually I am opening the stove when it's still hot to load it up for the overnight burn. Sometimes, admittedly, I'm just opening it up because I want to.

The question was academic as much as practical. I didn't understand why what was happening was happening, and thought maybe someone here would.

I've shut the air-intake down to create the situation you describe (it's even in Lopi's manual), but it still resulted in smoke coming into the room rather than up the chimney, which is even more of a mystery to me. You'd think those conditions would be adding to negative pressure in the box, making it even less likely smoke would come into the room.

Thanks for your thoughts.

 

[1750]

The smoke goes to where it thinks the chimney is.

There is undoubtedly wisdom here, Milton.

Stoves are meant to be left closed until well after they have burned the entire load. Timing is important - wait until the flames are long gone and there is only a medium bed of coals left (1 or 2 inches left depending on what species is going in next) before another load. The stove will have cooled down some. You said that you open the stove with the top at 500 to 600, that may be when the fuel is outgassing heavily (smoking). Coals leftover from a burn cycle put out very little smoke. Also, can your OAK be closed? If the OAK intake port is on a windy side of the house it could stuff more air into the firebox than a lazy draft could handle (when the stove door is open). JMHO.
Any exhaust fans/clothes dryer running? Windows/doors open on the leeward side of the building?

The OAK is on the windy side of the house, though I've closed it and I haven't noticed a difference. No fans or dryers yet. It will be interesting to see if those have an effect. The place is supposed to be tight, so I hope it does!

Thanks for your input.