back puffing from VC encore catalytic

[mgriz]

I have a VC encore catalytic which is giving me a lot of trouble puffing up through the top griddle. the gases seem to build up in the stove and then ignite every 4-5 minutes causing a small burst and bumps the griddle up. The stove has an 8" rear flue that runs 2' horizontally into a T connector with 8" flex pipe which then reduces to a 7" pipe all the way up my chimney (about 30' total). Burning dry seasoned wood, the pipe was recently cleaned, cat is in good condition. Is the reduction from 8" to 7" pipe causing a congested area where the gases build, thus causing the back puffing?

 

[STOVEGUY11]

Could be. You could take the oval 8" flue collar off and put a 6" round on and meet that up to the 7" liner

 

[begreen]

The Encore should be ok with 7". It can be run with 6" as long as the front door isn't opened. Is the stove nice and hot before the cat is engaged? Is there a good bed of smaller pieces of wood being laid down on the hot coals before the larger chunks are added? As a test, maybe try waiting a little longer after a refill before engaging the cat?

 

[FireWalker]

I had this problem with my Duchwest XL Cat stove. The problem is more pronounced in fall and spring when running at lower air settings. Small hot fires for shoulder seasons, you will have to give up trying to get loooooong burn time this time of year. I believe there to be nothing wrong with your setup, I believe it to be your (and my old one) stove design. The puff occures when combustion gasses build up and ignite in the firebox and have no place to go because the bypass damper is closed. Come winter you will find very low damper settings (long burn) will initiate puffing, open the damper more.

 

[downeast]

All of the above suggestions. Hey this is fun since I've got to be in for awhile.
Plus-- Remember that it takes awhile ~ 15 to ~ 20 minutes for the stove to get up to a cat temperature after loading. Then you engage the bypass damper to allow the flues gases to pass thru the cat, giving the cat enough time to "light off" ( not the tech term ). Again it is usually another 15 to 20 minutes to get the stove top thermometer back up to 500 F to 650 F. Then -and only then - the air or temp control can be turned down. That's why most stove makers went to non-cats: extra care and tending. Non-cats are more similar to the older non-EPA stoves.
In a word: if you don't light off the cat it will not perform . Try it. And use a timer to remind yourself.

Another factor: this time of year is tough on flues. Low fires, low barometric pressure create less draft.
Also: you may have backpuffing because of wind eddying down the pipe even with a chimney cap. Got a high ridgeline over the pipe? Nearby trees. All stoves and flues backpuff from time to time.

 

[bmwbj]

Here Here, I had the same thing happen to me the other night, with my intrepid II. I know it not the right time of year
and outside temps for a long "cat" burn, But I tried it anyway --- and sure enough it back puffed.
I resolved it by opening up the primary air all the way, opening up the bypass, then running the stove with the door open and
a screen installed as to not over heat the stove. The wife likes it running with the door open anyway ---- looks and sounds more
romantic she say...LOL

It just has not been cold enough here to run the stove properly.

 

[mgriz]

Could be. You could take the oval 8" flue collar off and put a 6" round on and meet that up to the 7" liner

I need the oval to fit through my damper in my fireplace. I could replace it with a 6" oval, but it's a big job to pull the 7" stainless pipe out from the top to get at the 8" flex.

 

[mgriz]

The Encore should be ok with 7". It can be run with 6" as long as the front door isn't opened. Is the stove nice and hot before the cat is engaged? Is there a good bed of smaller pieces of wood being laid down on the hot coals before the larger chunks are added? As a test, maybe try waiting a little longer after a refill before engaging the cat?

I know about the possible use of the 6" pipe, but I thought the fact I had 6" to 8" to 7" might cause a problem. After adding new wood to a bed of good hot coals, I leave the damper open until the new wood is hot and then engage the cat. using a mix of split and unsplit (3") wood, all well seasoned but not crazy dry. I am baffled and ready to get rid of the stove.

 

[mgriz]

I had this problem with my Duchwest XL Cat stove. The problem is more pronounced in fall and spring when running at lower air settings. Small hot fires for shoulder seasons, you will have to give up trying to get loooooong burn time this time of year. I believe there to be nothing wrong with your setup, I believe it to be your (and my old one) stove design. The puff occures when combustion gasses build up and ignite in the firebox and have no place to go because the bypass damper is closed. Come winter you will find very low damper settings (long burn) will initiate puffing, open the damper more.

I have a liner all the way up my chimney (35') and the draft is very good, almost too good. I have the primary air control only open 1/3 and the stove still burns around 500+. I have a drafty house, so once fall hits I burn the stove at regular temp and don't try to run it slower. If I try to open the damper even a little more I find the stove runs away from me.

 

[FireWalker]

When you say it runs away from me, is the bypass damper open or closed?

 

[mgriz]

runs away even with the bypass closed. I am ready to throw it out in the garage and get a jotul (f500)or hearthstone (pheonix or bennington). any stove suggestions.

 

[FireWalker]

My Duchwest is rusting away in my garage. I may still hook it up when I play in the shop.

Somewhere there is an air leak on your stove. With the bypass closed you should be able to smother the fire with the main air supply closed. Thats when you get a big backpuff.