Huffing woodstove

[Handy Andy]

  Bought a new non-catalytic Vermont castings defiant 2 years ago.  Last year, was having trouble with huffing, assumed it was because my wood wasn't dry enough.  So this year, I cut and split my wood last winter.  We had a horrible drought this summer, with temps up to about 115 degrees, and the wood I cut up was from degraded logs, not fresh.  It seems really dry. Put it in the basement, and put the dehumidifier next to it.  Vacuumed out the stove, took the top off, vac-ed out the soot, cleaned the pipe, and the cleanout on the chimney, thought I was good to go.  Now, the fire starts up good, temp goes up to 500 degrees on top of stove, and I throw the damper, to start the smoke burning.  Usually it kills the fire, after while, and I reopen the damper, get the fire going again, then at 500 I throw the damper again, and the fire will keep going, but it will die down and then flash up, causing smoke to come out the top door.  Getting the idea of how a wood burning truck works.  Can someone tell me how to get this stove to stop the huffing?  Beginning to think I should have bought the catalytic version.

[WH_Conley]

I am not familiar with your stove. I had a stove one time that had an internal damper, it was just on or off. I had pretty much the same problem you describe. Put a damper in the pipe, problem went away. I guess it was dying out and when a little fresh air came in the bottom it would just flash, kind like a mini explosion. Just as a guess it is probably not "breathing" any, has to have a continuous burn, even if it is low.

[Holmes]

  Sounds like the  gasses are igniting inside the stove. Vvvaaboom sound?  I had a Jotul that would do that. I have a catalytic com-buster now and have not had that happen with this stove.

[Handy Andy]

  Funny thing is, this only happens when the stove is cold, getting started.  Or sometimes when I want to turn the stove down, by reducing the air.  Usually once the stove is hot and working right, I can add wood and it's ok.  This morning, I cleaned out the ashes, put scraps in and started the stove up, it heated up to 500, I turned the damper to make it burn smoke, fire went black, opened up again, fire took off and came back up to 500, turned the damper again, and the fire kept burning, but it huffed about 6 times before burning right.

[beenthere]

Funny thing is, this only happens when the stove is cold, getting started.

Let the stove warm up before flipping the damper. You may be getting a false reading of 500 and the stove still isn't warm enough to "run itself" with a strong enough draw.

[Holmes]

On my stove when inside the fire box reaches 500 degrees you can engage the com-buster . That is the temp to start burning the gasses in the smoke. I still think the gasses are igniting, giving you scary little explosions in the firebox ... Holmes

[sawdust]

I had a similar problem with my Blaze king which has a catastrophic  converter. I found that I was using too small wood. It woofed so hard that it lifted the chimney off the top of the stove and set it to the side! Bigger wood so it gasses slower. I notice that they have drilled a hole in the supply damper so there is always a tiny fresh air supply. I think mine was drawing hard around the door seal until it reached a good mix and then would flash over.
Sawdust

[jdtuttle]

Here's a link with several possibilities. Look at the :"outdoor supply of combustion air"
jim
http://www.thechimneysweep.ca/2stackeffect.html

[Al_Smith]

If you just open up  the air and stack damper up a few seconds before you open the door it won't back draft on you .If you don't some stoves will huff fire like puff the  dragon .

[John Mc]

By "throwing the damper", do you mean adjusting the air inlet, or do you also have a damper in your flue above the stove? I don't have a damper at all in my flue, and don't need one... in fact, I'm told it will interfere with the proper operation of my stove (Hearthstone Pheonix, non-cat).

The huffing is usually caused by more gas being produced than there is air in the stove to burn it.  If the fire dies down, you are starving it for oxygen, so whatever you closed, you have probably closed it too far, or too soon (wood gives off a lot more gas early in it's combustion cycle).

A good place for wood stove operating tips:  www.woodheat.org

John Mc

[Al_Smith]

No stack damper ,really ? Seems odd but whatever works I guess .

[John Mc]

No stack damper ,really ? Seems odd but whatever works I guess .

Most of the newer woodstoves are better controlled by varying the air input, not the outflow through the stack.

[Handy Andy]

  When I start a fire, I always have the air lever set for the most combustion air.  The damper I mention is the door you close when you want the stove to start burning the smoke.  There is a big ceramic thing in the back of the stove with a few about 1/4" holes, and the smoke goes through those holes, and when the ceramic is hot enough, the smoke burns, creating heat.  When it is working, the stove pipe gets cooler, you can put a hand on it without getting a burn, so the thing does work. I have a stove pipe thermostat on the top door of the stove, it's shaped like a griddle, and the directions say to get the stove up to 500, on that thermostat, and close the damper.  But it seems like it takes a while to get the ceramic block hot enough to work right.  Once it's hot, can add wood with no problem.

[WH_Conley]

Look at your parts manual and see if that thing is not part #90 on the exploded view. The defiant is sold as a convertible stove. If that is what you are talking about with the holes, the converter is in place. I know nothing about catalytic stoves, never burned one. Also, check "damper adjustment", wouldn't be the first thing that ever left the factory that needed a little fine tuning. That is to say nothing of normal wear.

[beenthere]

  When I start a fire, I always have the air lever set for the most combustion air.  The damper I mention is the door you close when you want the stove to start burning the smoke.  There is a big ceramic thing in the back of the stove with a few about 1/4" holes, and the smoke goes through those holes, and when the ceramic is hot enough, the smoke burns, creating heat.  When it is working, the stove pipe gets cooler, you can put a hand on it without getting a burn, so the thing does work. I have a stove pipe thermostat on the top door of the stove, it's shaped like a griddle, and the directions say to get the stove up to 500, on that thermostat, and close the damper.  But it seems like it takes a while to get the ceramic block hot enough to work right.  Once it's hot, can add wood with no problem.

Now, you started out in your OP saying you had a non-catalytic stove. What you just described is what I have and the bee-comb like ceramic thing is referred to as the catalytic burner. Treat it with great care, and carefully vacuum the fly ash out of it or it will not draw air through it. I strongly suspect that is your problem. No hot gases are passing through that ceramic after-burner. I had the same problem.

[Handy Andy]

  Beenthere, there are 2 models of this stove, the one with the catalytic converter, and the one they call"non catalytic", but they both burn smoke. I used my shop vac on it when it was cold before firing it up last time.

[SwampDonkey]

No stack damper ,really ? Seems odd but whatever works I guess .

None on my furnace and at my uncle's none on his stove pipe, it's controlled by the stove outlet with a slider knob and damper on the side with a slider. On my shop stove I do because it's a really old design with just a low tech damper plate.

[Holmes]

 Vermont castings has a combination stove ,cat and non cat is this that stove? It seems you have a catalytic you are engaging. If you add wood to a cat stove and do not use the proper sequence of operation ,disengage then re-engage the cat  when the stove gets hot enough you will get the problem you are having.  Holmes

[John Mc]

It certainly does sound as though what you are describing is engaging the catalytic converter. (Vermont Castings does sell a stove that can be run as a cat or non-cat stove). You do NOT want to engage the converter until the converter is up to the appropriate temperature. Failure to operate this properly can muck up your converter. I don't have a lot of experience with cataylitic stoves, but I believe once the catalytic converter is solidly up to temperature, it tends to stay that way, even when adding more wood (as long as you dont't let things really burn out between charges of wood.

I suspect either you are just switching over to catalytic burn too early, or in the worst case, you have done that early switch often enough that the catalytic converter is contaminated or clogged (or maybe partly clogged). This MIGHT be why you got away with it the first year, but now as the contamination has built up, you are having problems.

[WI Fire]

I have a VC Defiant Encore, 20 + years old. I use it in early fall, early spring, and occasionally in deep winter. I have replaced the catalyst block twice, and also taken it out and done the vinegar cleaning once. I don't part with it, because with the bimetallic strip temp. control, it's been superb. I likewise believe the chimney must be well heated, and the stove up to temp before moving to catalytic mode. I have seen flames 'puffing' similar to a backdraft if the temp. control on the right side of the stove is too far closed.

The other thing, is chimney length which influences draft. I have a good interior 30 plus foot run. If your draft is not good, you could also influence the starving effect.