Periodic smoke blowback in my woodstove


  #1  
Old 10-25-13, 08:09 AM
K
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 6
Received 0 Votes on 0 Posts
Unhappy Periodic smoke blowback in my woodstove

I've seen several posts on this and have my suspicions, but the exact situation is this: I have a wood stove with a straight steel stovepipe, situated in an alcove brick recess (not against a wall), it fires up beautifully and works fine, until... Suddenly we'll look behind us and smoke is billowing out of the blower vent and around the door, out of the blue. We just moved in, and it's happened twice now (out of about five or six uses of the stove). Two nights ago, no problem. Last night was windy, with snow/rain; there's a cap on top, seems clean, etc. The pipe extends about three and a half feet above the roof where it exits, but it doesn't actually rise much above the peak point of the roof (if at all; may be just shy of clearing it). Not nearly as high as the pipe for my oil-burning furnace, which has one of those triangular, turning caps on it (they call it a "whistler" around here). Pressure differentials in the house are a problem—if we turn on the attic fan, it immediately starts sucking air out of the wood stove, so we learned quickly not to try and clear the smoke that way. Opening a window as a preventative measure isn't really an option since it's cold country in the winter. I suspect that wind and atmospheric conditions are occasionally pushing the smoke back down the stove pipe, but don't know how to fix the problem. Will extending the pipe to bring it well clear of the roof ridge help? Maybe a little vortex or something forming as the wind comes across the roof ridge (a pure guess, I'm not an engineer). When it happens it makes the wood stove unbearable, flooding house with smoke, have to open all the windows and doors to clear it, which defeats the purpose of the fire. We need this stove to work; can't afford to heat the house with oil all winter! Help this newbie, please!
 
  #2  
Old 10-25-13, 08:50 AM
W
Member
Join Date: Nov 2008
Location: Canada
Posts: 634
Received 0 Votes on 0 Posts
I have a woodstove, but have never had this happen to me. I have heard of it though. Hopefully someone on here has a suggestion as I could see this being a fairly serious safety issue if you go to bed at night with the stove burning. Carbon monoxide when you're sleeping isn't a good thing.
 
  #3  
Old 10-25-13, 09:43 AM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
A couple of questions:
1. "Suddenly we'll look behind us and smoke is billowing out of the blower vent and around the door,"
Blower vents are not connected to the combustion chamber so smoke should never be blowing out. Am I interpreting what you said correctly?
2. Does the stove pipe exit near the peak or more towards the edge? If over by the edge then the vortex you suspect may well be the problem. A picture of the inside and outside might help. But I'm not an engineer either.
3. Attic fans, also called whole house fans (house to attic) are a big problem. Not only can they backdraft your wood stove, but they can backdraft your oil heater. Even if you are confident you will remember to not run the fan when the heat or stove is running, someone else might not remember and CO is very bad.
4. I assume the stove pipe is a double walled approved chimney??

Be sure to have a CO detector, although I would never bet my life on one.
Bud


http://www.doityourself.com/forum/el...-pictures.html
 
  #4  
Old 10-25-13, 10:52 AM
M
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 48,141
Received 403 Votes on 359 Posts
The top of the chimney is supposed to be 2' higher than the surrounding roof/peak. If I remember the formula correctly, chimneys on the lower end of a roof have to be 2' higher than anything within 4'
Does the stove pipe have a cap on it? sometimes a cap will stop or slow down the winds ability to blow back down the chimney.
 
  #5  
Old 10-25-13, 11:33 AM
K
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 6
Received 0 Votes on 0 Posts
It does have a cap on it, actually. Not sure if it's plus-2 for anything within 4 feet; I'll be climbing up to take another look (with a tape measure) as soon as the snow is gone and it's safe.
 
  #6  
Old 10-25-13, 11:46 AM
K
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 6
Received 0 Votes on 0 Posts
It looks like it's coming out of the same vents as the blower, but that may be an appearance created by the volume of smoke escaping around the door, which has good gaskets btw (or might smoke get sucked into the fan itself, and be recirculated through the blower?)...

The pipe exits at what would be the edge, except for the fact that there's a sunroom on the opposite side of the brick, so it's around halfway, counting the sunroom, which was part of the original construction as far as I can tell. There's less of a slope on the sunroom roof than the main roof, which may be meaningless and none are highly sloped, but it's a convoluted roof configuration, all in all.

Thanks for the tip on the fan; the furnace is in the basement (if that matters) and we have CO2 detectors, but we'll take your advice to heart. (It's a handy thing in the summertime, in our land of no air conditioning, I'll give it that.)

It is an "official" chimney stovepipe, yes. Hopefully I can get a few snaps over the weekend and offer 'em up for consideration. Thanks for your insight, one and all!
 
  #7  
Old 10-25-13, 12:05 PM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
Just one more point on that big fan, we see them often here in Maine. One of the dreaded situations is fan on in the evening to help bring the house temp down after a hot day. They do a good at that. However, left running, you go to bed or out somewhere, and the house cools below the set temp on the stat and suddenly you have the fan and the furnace running at the same time. Just FYI.

The "convoluted roof configuration" makes it difficult to anticipate air flow problems. My personal first choice would be extending the chimney. But let's see what the pictures show.

You are correct, that smoke from the vent may just be a result of the fan pulling it in. I suspect you will get future opportunities to watch it in action.

Bud
 
  #8  
Old 10-25-13, 12:11 PM
K
Member
Thread Starter
Join Date: Oct 2013
Location: USA
Posts: 6
Received 0 Votes on 0 Posts
I suspect as much myself, alas. Thanks for the tip on the fan; duly noted.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: