Resolute backpuffing - Help request.

[ostrya]

I've been heating our home with a Vermont Castings Resolute for the third seasons now since we've moved in. This year, though the stove's started to belch smoke back into our living room. My wife and I are finding a bit unpleasant to say the least. I've burned wood for heat for at least eight years and have used four or five different stoves in different heating situations, so am not totally green although I can't seem to pin down the source of this problem. I've read and followed the literature from Vermont Castings but this hasn't prevented the problem. Any suggestions?

For background:
We noticed that the stove wasn't burning like it had in previous years.
After getting up to temp in updraft mode for 10-15 minutes I'd switch to downdraft but upon doing that it was hard to keep the griddle temp high enough for a clean thorough burn even with the thermostat set quite far in the open position (I liked to keep the griddle between 450-550deg) Backpuffing was common after about 15 minutes in downdraft mode. The puffs were sudden whooshes of flame in the firebox which pushed smoke into the room through any openings in the stove.

The manual suggests this backpuffing is a low draft issue caused by either warm outside air temperature or windy conditions. although it seems to happen even during cold nights and low wind conditions.
Based on previous forum seaches I figured the firebox was oxygen starved then the gasses would ignite suddenly when air became available. Maybe the air inlets were clogged? I cleaned the interior by vacuuming all air ports both inside and out, made sure the horizontal flue section was clean. I had already brushed the vertical flue (which yielded more creosote than normal) so knew it wasn't buildup that was the issue. While vacuuming out the stove I did notice ash in the air inlets so I now shovel ash from the firebox more often. I fired it up and thought this had resolved the issue. The stove began to respond well to normal thermostat adjustments and hold a fire in downdraft mode (burning at 4-500 deg on the griddle top). Immediate back puffing didn't seem to be a problem.

Now I've noticed that the back puffing begins to happen half way through a burn cycle - after about 3 hours in downdraft mode and while th griddle temp has been consistent at 450-550deg.

Not sure what's going on. Any thoughts appreciated.

Other info that may be pertinent:
Upon buying the house we had the 8" clay flue lined with 6" ss flex and insulated. After cleaning this fall I noticed that the insulation appears to have compacted or slid down at least 8 feet. Am having the installer come to remedy this asap. I'm not sure if it's the cause but it's my most likely suspect as of now.
I've noticed some cement chips falling from joints and the casting around griddle seems to have be bowed up enough to interfere with smooth opening of the top (ugh! stove rebuild necessary?)
I replaced lid, door, and window gaskets a little more than one year ago.
fuel is white ash, sugar maple, beech and been split stacked for about two years and under cover
stove ser no. 067688

 

[ostrya]

Hi Folks,
I'm still having this problem but am a bit surprised no one has any thoughts. I dunno if everyone's stumped or just doesn't care to respond. In any event, we're considering a new stove as I'm not sure where else to turn but would hate to get rid of this one if it's something that could be resolved otherwise. Since the last post I have had more insulation poured between the liner and flue - took a full bag or more - not sure where the old stuff escaped to! One other observation is that the backpuffing often follows a bouncing and rattling of the intake flap...
I wonder if it would it be worth having it pulled apart and rebuilt?

 

[begreen]

Sorry about that, things got busy before Christmas. Welcome.

Assuming the wood is ok, as a test have you tried shooting for a higher griddle temperature? Maybe 500-600? But I would also check the wood, by splitting it in half and checking the moisture on the freshly split face of the wood.

 

[Jack33]

I have years of experience with this stove so I'll give it a shot. First, whenever I had back puffing issues it was either a clogged chimney, clogged stove, or lots of wind driving air down the chimney. Whenever gas ignited in the stove it would literally pop the griddle up a few inches and go bang, so I'll assume that is not your issue.

Have you cleaned out the back of the stove between the outer cast and inner fire back? There is a flat cover with 2 allen head screws in it to access the area. This is the area under the damper when it is open. It will crust up no matter how dry your wood is. I would always clean this out twice during the heating season. If you have never removed these tiny screws, I would heat the stove up before trying to loosen them. Another problem is the cement that bonds and seals the fire back area. While the cover is off stick a flash light inside the stove pointed towards the rear intake ports, close the damper and doors to the stove. Look down behind the damper and see if you can see the light. If the light is shinning through, this means that intake air is escaping into the flue and the flue exhaust can escape into the intake air and back into the house.

 

[Fsappo]

I've acutally gotten the old style VC stoves to back puff like that by adding very dry wood to a very hot bed of coals. Rapid smoke build up and ignition would do it. The suggestion about cleaning the seconadry combustion area is a solid one. Depending on how old the stove is, it may be time for a rebuild to make sure all the hidden passages that the old VC stoves were famous for are all clear.

 

[Troutchaser]

Hmmmm...
I'd love to see more suggestions if anybody has them. I've added 3ft. of pipe (on icy roof) to help with draw. 21 feet straight up now. I seem to be getting the secondary combustion going nicely; however, the stove actually begins to re-heat after a couple of hours with a bunch of gas explosions inside the box. Then all settles out again after maybe an hour or two. Sounds like the same type scenario posted with this thread.

Secondary going- stove temp 600deg.
one hour - stove temp. 575deg. explosions starting.
two hours - stove temp. 600 deg. with gas firing all over inside the box. Flue temp. increasing.
three hours- stove temp. 500 deg. stable low burn

8 1/2 hours after loading stove top is 200deg. with nice coals for start-up. Yes, I can smell something in the house. Not too bad, but something. I have been taking the air down in stages and leave it with air mostly closed off. Any air at all and I've got pretty good flaming (not explosions).

We've discussed pressure issues, wind issues, outside temp. issues, and wood issues before. I'm kinda stumped and tend to just let it play out. But I'm guessing all this points to draft and why it is lost. Should the air stay open slightly and we live with shorter burn times?

 

[Battenkiller]

I'm pretty new to the VC Vigilant, and I'm still learning its idiosyncrasies. I get the occasional smoky smell as well, but I've been attributing it to smoke-scented outside replacement air being drawn into the basement. I have experienced the flapping air intake on one occasion (no backpuffing then), but the only once caught the old gal belching smoke. It was a small explosion that occurred after I let smoke build up in the chamber them shut the bypass without opening the primary air first. Got a nice little pop and some sparks out of the secondary air intake hole that woke me up pretty good. This may have happened at other times I didn't see (stove is in the basement, so I don't notice everything it does), but on most of the other occasions, I went outside and there was a strong smoky smell outside.

I am only worried about the safety issue. I've already let more smoke into the house by absent-mindely forgetting to close the griddle top while starting a fire than I'd ever get from backpuffing.

 

[summit]

Hi Folks,
I'm still having this problem but am a bit surprised no one has any thoughts. I dunno if everyone's stumped or just doesn't care to respond. In any event, we're considering a new stove as I'm not sure where else to turn but would hate to get rid of this one if it's something that could be resolved otherwise. Since the last post I have had more insulation poured between the liner and flue - took a full bag or more - not sure where the old stuff escaped to! One other observation is that the backpuffing often follows a bouncing and rattling of the intake flap...
I wonder if it would it be worth having it pulled apart and rebuilt?

take out the combustion chamber, completely go over it, then replace... clean out the comustion chamber air inlet as well.

 

[ostrya]

Thank you for the responses. Somehow I missed them until now (1/2 year later!) but I thought I'd follow up in case it might be helpful to others...
I burned it for the rest of last year in updraft mode and stayed warm. As was suggested here, a local stove shop recommended pulling off the interior firebox components to clean out and inspect for ash buildup.
I just did this and there was a good amount of ash in there. The cement was crumbling as well. I assume this was the issue but I have yet to install it and get it going. I also ended up removing the tie rods and pulling the whole stove apart to re cement all joints and it's curing now. I can't wait to have it humming along, burning like it should.
If you're having a similar problem I'd recommend at least pulling out the fire back and sides to check for ash clogging the long air paths.

 

[markleyh]

I really wish you luck with that Resolute and hope my experience doesn't happen to you. We had the same backpuffing problem with a Defiant Encore and found the flue path to be blocked in several areas. Ash would build up on top of the catalytic converter, but also ash downstream from the cat in the area you discovered. Of course, we discovered this only with a complete tear-down. A VC factory-trained tech rebuilt the stove and recemented all the joints, but ever after that we had major problem with air leaks and overfiring. Warped 2 firebacks and three throats, had the thing take off in the middle of the night twice and not shut down with all ports closed... Finally bailed out and am soooo happy with the Fireview.

If you have air leaks after the rebuild, they can be hard to find, but watch for signs of overfiring once you start burning.

Good luck and happy Winter!