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[robash9608]

I built my furance about a year ago and I've been having problems with the firebox going under pressure. I've got a 146 cfm fan mounted on the door. It's a double pass flue design with 6in square tubing as the flue. The chimney is about 6 ft high. Seems like i might have a draft problem, you can look at the top of the chimney and see the smoke puffing and also the smoke discharges back through the blower. I've been burning 1 year seasoned oak firewood.  Any thoughts of why this would happen??

[Guru]

I would start by cleaning the chimney.  If the chimney isn't insulated it will collect creosote and close the opening.

[willieG]

i am thinking the same as guru. if your double pass flue is collecting and starting to plug in the corners you may be creating a draft slow down and causing back draft and this is sucking enough fresh oxygen down the flue to ignite the gas in the flue and causing puffing out the door and smoke rings out the stack

a good cleaningn is in order for starters

[MattyNH]

Sounds like your stack could be plugged. Not sure where you live..But on warm days or late spring I avoid throwing in wet/green wood..Doesnt run enough..What I found that helps out with creasote is Ash Trol-MC by CB..My stack is 20FT up..Havent had a prob with stack plugging up..2nd season using it..Let me know how you make out..

[robash9608]

The chimney is clean, thats the first thing that I did when I started to have the problem. I have burned green wood and it seemed not to have the problem as bad. Just wondering if the wood is to dry?

[BFB Builder]

Sounds like we are having similar problems with diffrent results. My stove also huffs and puffs mine does this for about 5 min 15-20 min after I stoke. She  also creates excessive smoke. see the post Smoke troublefor the fix I am trying I will keep evoryone informed how it goes.

[robash9608]

I extended my flue down about 8 inches from the bottom of the firebox and still continue to have the same problems.. I have noticed that if I stack the wood on the sides of the firebox, (not in the flowpath of the fan) I don't have the problem. Does this indicate that I might need a larger fan??

[willieG]

I extended my flue down about 8 inches from the bottom of the firebox and still continue to have the same problems.. I have noticed that if I stack the wood on the sides of the firebox, (not in the flowpath of the fan) I don't have the problem. Does this indicate that I might need a larger fan??

im going out on a limb here and say yes..when you stack your wood in teh path of the fan you cause it to burn (or smolder) more rapidly and this is causeing more gas (instead of flame) now with what you describe as a double path  chimney this must mean you have at least 3 or four elbows in your exhaust pipe. each one of these elbows takes away from your chiney draw. so you need more air to push it out. also this may be causing yoru "going under pressure" if this in fact means your stove is back drafting (sucking air down the chimney)  and  then having a mini explosion in the fire box that causes the smoke and gasses to exit where ever they can (around door gaskets and blower seals)

so it  looks like bigger fan or less wood?

[robash9608]

Thanks Willie