Backpressure. smoke, and popping lids

[erekose]

I lit up our wood stove for the first time this year and had quite a surprise.

First off it seemed a little smokier than usual and close inspection revealed some smoke was indeed leaking out. There was a decent pull of air up the chimney (sleeved and piped old fireplace), nothing less than witnesses in past seasons, nothing odd.
As I sat in front of the stove and continued to inspect it in an attempt to discover the problem the lid suddenly blew off the stove a good few inches and made me jump. I extinguished the fire and will not be re-igniting the stove until I discover the problem.

Information on the stove, etc:
The chimney is sleeved, piped, and capped, and has been for the 5+ years I've owned the house.
I had the chimney inspected and re-capped 4+ years ago as well as the old one was leaky and sub-standard.
The fireplace was not in use before by the previous owner. The bottom of the pipe was sealed.
The stove has been in use for 4+ years, and is a hand-me-down no-name cast iron stove.

As the chimney is capped I cannot see how there can be any blockage.
It was not windy last night, so I cannot see that as a problem either.

Any ideas what I should look for next?
I cannot afford a $1200+ insert and the room is too small for any stoves I have seen so far, so if I cannot resolve the situation I will probably seal the fireplace.

 

[tw40x81]

I would start with a visual examination of the chimney. When was the chimney last cleaned?

 

[erekose]

The chimney pipe was inspected 4 years ago and the pipe was clean and unused.
I've only had 10-15 fires in it since then, each no longer than 2-3 hours.

 

[tw40x81]

While it's not likely to be a creosote problem with that amount of usage, I'd still take a peek at the chimney. After 4 years you may have a critter problem, though that's unlikely too if you have a nice screen on your cap.

 

[Gooserider]

Definitely sounds like a draft problem... Inspect / clean the chimney, also check the damper on the stove, make sure it really is open when you think it is... Sometimes dampers are just sheet metal plates pressed onto a steel shaft, and they can come loose so that you move the handle to "open" but the plate doesn't actually move with it.

The more smoke is definitely saying that something isn't right in your chimney or stove exit.

Gooserider

(P.S. The standard practice says that chimneys really ought to be cleaned every year if they are used at all....)

 

[fayman]

Yeah, I agree that the chimney needs to be inspected and cleaned, regardless. Before I installed my insert, I went 3-4 years without using the fireplace. Last year my wife thought it would be a nice idea to have a fire in it. Even though it hadn't been used in 15 years, it was loaded with leaves, nuts and anything else that could sneak through the wire cap on the flue. I would've had plenty of blockage had I not brushed everything out beforehand.

 

[erekose]

Thanks very much guys.
I think an inspection / cleaning would not hurt anyway.

On the way home tonight NPR had a interesting story about chimney sweeps in Germany.
Coincidence?
:^)

 

[quads]

My opinion is a smoldering fire that "puffed". Caused possibly by not letting the fire get going good and then closing the stove draft down too soon. This smothers the fire and creates a lot of smoke/gases that can ignite suddenly. The way I understand it, this can't happen with the newer EPA stoves because you can't close them down tightly enough to smother the fire.

 

[Robbie]

"Puffed"........I agree, that is the only way the lid will pop up..........unless there is a critter in your stove trying to get out. :lol:

1. Draft not good, cold pipe etc. = smoke in house

2. lid blowing up = gas pressure trying to escape by way of least resistance.

3. sounds like your stove/pipe was cold, your fire was smoky and not going up flu (because of lack of draft because of cold air block), then gases became too much and it ignited blowing lid up........I think we've all been here, I know I have.









Robbie

 

[erekose]

Thanks so much all.
Other than the fact that I should clean my chimney, it appears I may have been the unfortunate victim of a convergence of several instances of bad luck.
Scared the crap out of us though...

 

[seaken]

Yes, this is indeed a back-puffing issue. Most common cause is wood that is not well seasoned (usually too wet - and sometimes too dry) and not enough air supply. Try giving the stove more air supply and make sure your wood is properly seasoned.

Cleaning and inspecting your chimney is always a good idea. Do it if you haven't done it in a few months. With old pre-EPA stoves we recommend inspection and/or cleaning at least twice a year. But this problem is usually caused by your fuel and the fuel to air ratio. It can be casued by wind in some cases. Not to woory, once you understand what is happening and how to control it.

Good luck,
Sean

 

[Andre B.]

I once had a barrel stove in a hunting shack the a real bad back-puffing problem, not a single puff be a continuous series at like 5 to 10 per second. Sounded like a pulse jet, which in effect it was.

Used a hammer and a large nail to add some above fire, secondary air holes and the problem went away. Would have used the rifle but the shack had more then enough ventilation.