Stove puffs smoke

[David Wayne]

Hey guys, I have a Brunco wood furnace in my basement. Chimney runs from basement floor up through center of house (two story) & when I load it up it will puff smoke out the spinn draft on the loading door. I have used this same furnace for 20 yrs & in the past the only time it did this was an indication that the chimney needs cleaned. This year I moved the furnace to the other side of the chimney to get more in the center of the house for better heat distribution, I use it as a stand alone, rather than a add on to my LP furnace, with its own plenum & duct work. The stove pipe is the same length run,& everything else is the same as it has been for yrs. I store 4-5 cords of wood in the basement same as always so I know it is dry. I alway have run the bottom draft at 1/2 open & top draft at 1/2 to full open. This year I have had to close the top off completly when it gets to smoking. I need to figure this out,my LP has not been hooked up for 3 years now so this is my heat.
And yes the chimney & pipe are clean. Any ideas?

Thanks Dave

 

[tatra805]

the only thing i can think of is draft and thus the chimney.

Is this new place more airtight than the previous one?
A pipe can be closed off preventing draft at any place
somewhere in the middle = dirty chimney
at the top = a birdnest or santa claus trying to get in
at the bottom = a sealed room

So it is not because the chimney is clean that you have a guarantee for good draft, as you had no problems before i assume the piping is ok and then i only can think about the inlet airside.

If you keep the doors of the room open, does it do the same?

 

[David Wayne]

Same drafty old house, just moved furnace a few feet. This place is far from airtight. Looked up chimney with mirror, its open, removed pipe their clean.
bought a new brush for chimney will scrub it better. The old brush is pretty well worn, but the chimney is 8x12 & the stove outlet is 7" so the little bit on the sides shouldnt be affecting it but I will clean again anyway. Like I said its all the same setup it has been for 20 yrs.

Dave

 

[Rookie1]

Wow has anybody had Santa stuck in their chimney before?

 

[David Wayne]

Maybe I should have added that the stove doesn't do this all the time. Mainly about 10 minutes after we stoke it for the night I'll start smelling smoke and have to close the top draft.

Dave

 

[wdchuck]

Stack effect until the wood gets going.

Is the chimney lined? If its masonry, and is unlined, then hairline cracks may have formed, and it will have an effect on your draft. I've run into a similar situation, and after running a liner of sorts down, 6" black pipe, just to see what would happen, there is a difference, my draft has improved to what it was a few years ago when I first installed the wood furnace. I'll be installing a stainless liner after this winter, or removing the old chimney completely and running a stainless/insulated chimney all the way up.

I've used the mirror/spotlight inspection method also, and even with cleaning and dry wood, hot burning, the inside of the chimney has taken a beating, so its only use is as a chase for a liner now.

Sounds like my two story corn crib is similar to yours.

There is plenty of good advice on how to make a woodburner work better in this forum.

 

[David Wayne]

Good advise is right,& not just on woodburners.
The chimney is masonery with the clay type liner, I tore the old chimney down all the way to the basement & laid up a new one back around 1988. When tearing down the old chimney I just picked up the bricks with no need for a hammer untill I was two feet down into the attic!

My stove seems to be building unburnt gasses, when it gets to puffing & I open the door a crack it will ignite & shoot fire arond the door. I have heard of OWB doing this. My wood this year is mostly dead elm (red) & I wonder if stoking it at which time I close the draft to 1/2 open, maybe the wood is trying to burn faster than it can get air. Since this is mainly when it puffs.

Dave

 

[kstill361]

Make sure the stove pipe is slightly uphill going to the chimney not level, elbows can mess with the draft. Close that top draft on the feed door, no reason for it to stay open, use it to clear the smoke before opening the door. You get that gas explosion because you open the door too fast before the smoke clears and the sudden rush of fresh air ignites the gases. Do you have a chimney cap? you could be getting downdraft.

 

[tatra805]

i had exactly the same problem today with my 602 which i finally installed this afternoon.

situation:

when opening the air supply after having it closed down when the wood was in high-burn mode the 602 spit out a puff of flames through the air inlet.

I could repeat this effect time after time.

The 602 has a 125mm outlet which goes into a 200mm chimney with only 1meter of 125mm piping between stove and chimney.

Draft of the chimney is high, if not too high. It was very windy this afternoon and the stove was almost a howling wolf at anything more than 1/4 open.

What i noticed:

at the moment of opening the air inlet the pressure or draft in the chimney peaks for a moment. This sucks in a huge amount of air into the burning chamber. then almost instantly the draft drops dramatically till things level out.

I assume this is caused by the bottleneck of the 125mm piping.

Now when this burst of air enters the burning chamber it mixes and ignites and those gasses need more than a 125mm pipe so they puff through the air inlet. (remember that at that exact moment the draft drops, so almost no draft)

If i understand my situation correctly i should reduce the draft of the 200mm chimney in order to keep the pressures leveled out.

As an experiment i opened the chimney cleaning/service door (which is in my cellar 3,5 meter below the stove ) to allow part of the draft to suck air from there.

Result: no more puffing, no more howling and a much better regulating of the burn rate.

I know this is a bad idea as the exhaust gasses can enter the cellar an become a Cmonoxide trap. But it confirms my theory that i have too much draft.

Identical chimney for my F8 and there i never have a puff, never any problems with draft or whatever. chimney is 200mm, F8 has outlet of 185mm; so much less difference.

My conclusion: check for bottlenecks

 

[David Wayne]

Make sure the stove pipe is slightly uphill going to the chimney not level, elbows can mess with the draft. Close that top draft on the feed door, no reason for it to stay open, use it to clear the smoke before opening the door. You get that gas explosion because you open the door too fast before the smoke clears and the sudden rush of fresh air ignites the gases. Do you have a chimney cap? you could be getting downdraft.

Yes pipe is uphill, two 90 elbows, no cap never have had one.I will try to post a pic. tomorrow of the chimney as it exits the house, no trees or anything around. I didnt open the door or I think I would be hairless. Just crack it about 1/2". I have always used the top draft more than the bottom, been useing this furnace for 20 yrs with no problem this way & no build up in the chimney. I may be wrong, but I have read many times that wood burns 80 percent as a gas & 20 percent as a solid (opposite of coal) & for the most efficient burn draft should be set accordingly. Chimney draw is good, I can shovel up some bark & (wood dirt) throw it in the stove & smoke will not come out the open door. Even without bypassing the secondary burn chamber. Only after loading & turning back for the night.

I have added an extra cold air return to the duct system to gain CFM across the furnace & up into the house. This will make the furnace a little cooler but not enough to shut the blower off. I dont think this would have any effect anyway.

Dave

 

[dwinch53]

Hey guys, I have a Brunco wood furnace in my basement. Chimney runs from basement floor up through center of house (two story) & when I load it up it will puff smoke out the spinn draft on the loading door. I have used this same furnace for 20 yrs & in the past the only time it did this was an indication that the chimney needs cleaned. This year I moved the furnace to the other side of the chimney to get more in the center of the house for better heat distribution, I use it as a stand alone, rather than a add on to my LP furnace, with its own plenum & duct work. The stove pipe is the same length run,& everything else is the same as it has been for yrs. I store 4-5 cords of wood in the basement same as always so I know it is dry. I alway have run the bottom draft at 1/2 open & top draft at 1/2 to full open. This year I have had to close the top off completly when it gets to smoking. I need to figure this out,my LP has not been hooked up for 3 years now so this is my heat.
And yes the chimney & pipe are clean. Any ideas?

Thanks Dave

Dave, you said that you moved the furnace to the other side of the chimney, are you using the same flue as before? does your gas furnace share the same flue...If this is a diff flue then before is it the same size as the other one? DW opcorn:

 

[David Wayne]

Gas furnace doesnt share flue, it is sidewall vent. And yes wood burner is using the same one it has always used. Didnt have any problem last night wich is good, but I hate trying to solve problems that are not consistent. The only thing I did different is not load up with the deadwood. I always burn seasoned wood,but the elm I have has been dead for several yrs.

Dave

 

[hotrod1950f1]

I have the same problem with my Royal stove if I do not let the new load of wood get burning good and hot before I close the strove back up. It doesn't seem to matter how hot te bed of coals is that remains when I load the stove.

 

[David Wayne]

Just wanted to thank everyone for their help & give an update.
I have cleaned the chimney 3 times in the last 2 weeks with the new brush, still smokes once in a while. I also moved the stove back to its original location just to eliminate that as a possibility.Yesterday I bought a good flashlight & looked down from the top & see more creasote than the mirror from the ground shows,so I scrubbed the pizz out of it & got a 5 gallon bucket full (32' chimney). Didnt get all of it though, the brush wont break it loose. 7x11 brush & ID of flue is 6x10. I have one of those expandable sweeps on a rope that I am going to try to weld steel on to scrape the sides better. I think(hope) this will solve my problem.
Thanks again
David