Smoke from woodstove drafting down flue into basement

[Exmasonite]

Looking for some help and suggestions.

So, have been burning wood pretty consistently for 2-2.5 weeks and have noticed a problem: i am getting a lot of smoke in my basement. Let me explain:

House: 2 story log home with full basement. Woodstove on 1st floor, piped into chimney (clay tile lined chimney only). Chimney has 2 flues... one for the woodstove and the second for the fuel oil burner in the basement. Fuel oil burner does baseboard heating (seldom used) and hot water.

Stove, btw, is an old Merlin 3 (new zealand stove made in 1990's, one of first EPA approved stoves, still on list).

So, i have noticed an intermittent haze/smoky smell in basement. It waxes and wanes. I have been burning pretty much 24/7.

Today, there was a much thicker "haze" in the basement than before.... i attributed to wind conditions, etc. Came home from work and CO detector on first floor was beeping at "32". Aired out house, all is well. Basement isn't smoky this evening but have also stopped fire.

I ran into this problem a little bit last year but wasn't sure if it was odor from woodstove or boiler (since i was running boiler more last year). This year, boiler has been seldom on.

The smoke is comng out of the bypass port on the boiler outflow pipe (running from boiler into chimney) The boiler tech who came out to service boiler says I can't cover this port. I figure i have 1 of a few options for this haze/smoke:

1) Somehow the stove smoke is being drawn down boiler flue... possibly due to tight house and draw of air to stove is creating negative pressure in basement

2) Smoke from stove is blocking the flue action of the boiler flue and the fumes are from the boiler (which cycles on a few times a day for hot water).


I had a sweep out to the house to do the chimney a month or so back. I called him up and he thinks the first option is most likely. He'd like to put a 3' flue cap extender on one of the flues to fix the problem ($250 installed). Here are my questions:

1) Is this the right fix? Is there anything else I should be looking at?

2) If the flue extender is the right fix, which flue should i "extend": the woodstove or boiler flue?

Thanks in advance and hope this makes sense.

 

[jatoxico]

It's a poser. To make the best decision I think you should be sure what the smoke is. The smell of wood and oil smoke are not very alike. Any oily residue? Try white glove test on metal or glass. Also does the stove have a full liner or is it possible there are gaps in the clay liners?

My 2 cents;

If wood smoke down draft, add extender.

If oil smoke pressure prob. Can add air kit to boiler.

 

[begreen]

Are the flue tops for the two flues close to the same height? If so, raise the wood stove flue by 12-18" and this issue should stop.

 

[Exmasonite]

jatoxico-

You know, i'm a bit of a neophyte in that regard. I will say that i THINK it's wood smoke. I say that for several reasons:

1) It smells like regular "smoke" to me... as in wood smoke. Not sure i know what fuel oil smoke is like.

2) when boiler tech was out last year, he noted slight creosote/wood smoke build up in boiler flue pipe

3) have found some of the heaviest smoke when the boiler hasn't been on for HOURS

Chimney is simple tile lined... no full liner. Would like to do that but no $$ for that now. Wonder how tough it'd be to diagnose a problem in the tiles but would like to rule that out before dropping $$ on an extender that doesn't fix the problem

BG-

Flue tops are exact same height at top of chimney... there's a metal cover over top with a cagearound the sides to protect from rain... but i wonder if that cap is restricting air/smoke flow and contributing to problem

 

[jatoxico]

Every house I've ever lived in has had oil heat so had my share of puff backs etc. Oil smoke is pretty distinctive and I think you would know it was not wood. So lets assume its wood smoke. Does this happen when the weather is very cold or only when outside temps are cool but not cold? If you are certain the smoke is coming through the flue regulator then off hand it does sound like a down draft issue.

 

[remkel]

Sounds to me like your house is using the boiler flue as it's source for makeup air from the stove. I had this problem at one time. Now that my flue has been extended another 4' or so I no longer have the issue. I also connected an OAK to my wood stove which I also believe is helping to control the amoung of makeup air that has to come into the house.

 

[Exmasonite]

jatoxico-

I think the problem is worse when it's warmer out... case in point, today and yesterday here in CT. Had left the stove on a very long, low burn while we were off at work. The CO monitor was actually beeping at 41 today so no more burning in the woodstove for now.

So, assuming this is a downdraft issue, a flue extender on the wood stove flue is the way to go? Stove predates OAK and such.

 

[Mad Tom]

Like BeGreen said, raise your stove pipe.

 

[jatoxico]

jatoxico-

I think the problem is worse when it's warmer out... case in point, today and yesterday here in CT. Had left the stove on a very long, low burn while we were off at work. The CO monitor was actually beeping at 41 today so no more burning in the woodstove for now.

So, assuming this is a downdraft issue, a flue extender on the wood stove flue is the way to go? Stove predates OAK and such.

Sounds like it. When you can swing it add the full liner. Good luck and post your results.