Downdraft Mystery

[David.Ervin]

So, we just had our two year old chimney and Heat 'n Glo Northstar swept out after a few events of smoke drafting back into the house, requiring us to throw the burning logs out on the lawn to make it stop. Sure enough, the sweep got a bunch of crud out of the chimney, so I figured that'd be the end of it. However, when we just relit the fire, I'm still getting smoke filling the living room and setting off my smoke alarms in the house. I've got an outside air kit, and when its open I can feel cold air coming in on the bottom of the fireplace, so I know that's open and working. Its almost like we're getting a downdraft somehow that's snuffing out the fire and shoving the smoke back into the house.

Any ideas?

 

[begreen]

It might be the chimney location in relation to the house? If this is a cold exterior chimney it may be more sensitive. How tall is the Northstar chimney and where is it located? How is it positioned in relation to the prevailing winds?


http://www.woodheat.org/wind-chimney.html

 

[David.Ervin]

It's on the north side of the house, and is a fair amount taller than any nearby roof. We didn't have any trouble with the northstar last year at all, and the quadrafire's chimney actually comes out right next to it (two flues, same brick-veneer chase), and has no trouble - if anything, it's a little over-drafted, and wind conditions don't seem to affect it much. As far as total height, I'd guestimate 25 feet from the top of the fireplace. I'll see if I can verify this when I get home later.

 

[jatoxico]

Check that the sweep removed and cleared all debris from the baffle and that your baffle/blanket are installed right.

 

[begreen]

Agreed. Hearing the history it sounds like the sweep may have missed something(s).

 

[David.Ervin]

Check that the sweep removed and cleared all debris from the baffle and that your baffle/blanket are installed right.

Good thinking - I wasn't home when the sweep was there, but the picture my wife took shows the baffle just pulled forward, not all the way out of the stove.

 

[David.Ervin]

I poked a camera over the edge of the baffle last night - nothing up there. We got a fire going again this morning, and if the doors are open, smoke just rolls out into the living room. When closed, I can leave the air control wide open, and it burns like it's maybe 1/3 to half way open with slow rolling flames. Usually opening the door a crack will create a roaring wind tunnel as the draft sucks in fresh air from the room, but it barely makes a difference to the flames, and we just get smoked out.

I've got a call in to the sweep to see what's next - maybe his brush didn't get all the way to the top? Maybe the screen on the cap is caked with creosote?

If it helps, here's what the chimney looks like in relation to the roof. I wish I could get a better shot of the cap itself...

 

[Grisu]

Looks like a bunch of smoke coming out your chimney. How dry is your wood? Have you ever tested it with a moisture meter by resplitting a few pieces (at room temp) and pressing the pins in the center of the fresh surface?

 

[David.Ervin]

Don't have a moisture meter (on the list). That's a fresh reload while I was out checking to verify we were actually getting stuff to go up the chimney. It's pretty common to see that when we first load up the fire in the morning. Also, it's like 11 below zero, so just breathing makes white smoke come out of my mouth and my face hurt

 

[blueguy]

Can the baffle be pushed back to the back of the stove? I could always tell when the baffle was out of place (too far forward) in my Napoleon because I would start getting smoke out the door and the fire wouldn't burn "right".

 

[Grisu]

Don't have a moisture meter (on the list). That's a fresh reload while I was out checking to verify we were actually getting stuff to go up the chimney. It's pretty common to see that when we first load up the fire in the morning. Also, it's like 11 below zero, so just breathing makes white smoke come out of my mouth and my face hurt

If that is right after reloading, yes that is common and should stop soon. The smoke has a black color to it so I did assume it was not just steam but the color of the picture could be off. It sounds like you have smoke problems even when the fire has been burning for a while:

Usually opening the door a crack will create a roaring wind tunnel as the draft sucks in fresh air from the room, but it barely makes a difference to the flames, and we just get smoked out.

That sounds like your draft is actually fine but your wood does not burn well. I would test it and/or buy some of the compressed wood logs (Envi-blocks, BioBricks, Northern Idaho Energy logs etc.) and see if you can get a good, smokeless fire going with those.

 

[Heatsource]

I'm guessing the sweep didn't really get the cap clean...

 

[David.Ervin]

I'm guessing the sweep didn't really get the cap clean...

This is what I'm going with. I tried an experiment of holding a lit piece of paper in the stove, right at the front where the smoke would usually go up over the baffle and out the chimney. As far as I can tell, its not going up at all, and I got a face full of smoke. We've got a call in to the sweep who - surprise! - hasn't returned it yet, as well as a call to the local dealer who's got us scheduled for an inspection on Monday. Hopefully we get this knocked out between one or the other of them.

Can the baffle be pushed back to the back of the stove?

Good thought, but it's in there all the way. Even took it out and put it back myself to be sure.

 

[Bagelboy]

Chimney is definetly high enough. My bet is there is blockage of some sort!

 

[Heatsource]

get yourself a soot eater, it will clean the cap from inside

 

[blades]

Learned a long time ago that wire mesh at the top of the flue is going to be a problem somewhere during the season. There are better spark arresting types of caps that do not load up like screen. Nature of the beast even with really good wood.

 

[73blazer]

Good thinking - I wasn't home when the sweep was there, but the picture my wife took shows the baffle just pulled forward, not all the way out of the stove.

That's quite a bit more creosote than I've ever gotten out of my North Star. I sweep every year and all I get is mabey a handful of brown/black superfine dust. I think your wood probably needs tested to see if it's under 20%, I've noticed my Northstar doesn't burn good at all if wood is over 20%MC. Also, I put a little rutland magnetic thermometer on the pipe behind the top grate, it helps get more consistent temps and burn out of the unit. When I load up I let it get up to 5 or 600 on that before closing it down most of the way and I'll have good secondary burn for hours after that. Also, when cleaning, my cap does get crudded up more than any other part of the chimney, I take it completely apart so it's a long flat piece of louvered sheet metal and I take a wire brush to both sides, then re-assemble. And yes, the baffle board and blanket need to be all the way back against the back.

 

[Schmev]

It might be the chimney location in relation to the house? If this is a cold exterior chimney it may be more sensitive. How tall is the Northstar chimney and where is it located? How is it positioned in relation to the prevailing winds?

View attachment 154411
http://www.woodheat.org/wind-chimney.html

This is almost exactly my setup! Draft isnt too bad though.

 

[AK13]

I had an issue with my insert smoking worse than usual and draft seemed low. It was the spark arrestor. The chimney liner was very clean except for the top foot where it pokes out of the chimney and the spark arrestor was all gunked up. I brushed it clean and draft was noticeably improved and the smoking with the door opened stopped.

 

[David.Ervin]

It was the spark arrestor

I'm really hoping this is what it turns out to be, since it should be an easy fix. I'm not looking forward to the prospect of renting a huge ladder and climbing up there in the dead of winter if I have do DIY this, though.

 

[begreen]

Do you have a pair of good binoculars? I could spot my clogged cap with them. If it's clogged the sweep should come back and clean it. That's part of the job.

 

[Heatsource]

I'm really hoping this is what it turns out to be, since it should be an easy fix. I'm not looking forward to the prospect of renting a huge ladder and climbing up there in the dead of winter if I have do DIY this, though.

soot eater, soot eater, soot eater
you can clean the cap from the comfort of your living room, check it out!

 

[English BoB]

Try letting the fire burn hotter before shutting down the air supply. Let more of the smoke out of the fireplace.

Bob

 

[David.Ervin]

We've got a tech from the nearest dealer coming by this afternoon to see what's up.

soot eater, soot eater, soot eater

If the diganosis is anything along the lines of "clogged whatever", this is probably happening on the way home from work.

 

[David.Ervin]

We got the tech out who checked over all the intake and baffle related stuff, then on closer inspection with binoculars, concluded the chimney cap was still clogged up! We called back the sweep while the tech was there, and they agreed to come back to make the climb up to the top and get it actually clean this time.

Sweep just left (brought two guys this time), and retrieved another bunch of creosote from the flue, along with scrubbing the cap from the outside. I suspect they just didn't run the brush all the way to the top last time. We've got enough draft to get that "freight train" roar when you light off some paper in the stove again, and I'll get a good hot fire going this evening to confirm the problem is solved.