Possible Defiant Encore Overdraft Problem

[kwburn]

I installed a model 2190 Defiant Encore catalytic (used, with new cat) this week and have burned it twice so far. Both fires tended to get away from me temp-wise with griddle temps with cat engaged staying in the 750-900 range and no ability to bring them down. The owners manual recommends 750 as the max normal operating temperature. Primary air lever was set to minimum. I confirmed air control functioning properly with a mirror and a flashlight allowing me to see the primary air flap fully opening and closing with the side control lever (and opening does increase fire activity). After the first fire I wrote it off as having to get to know the stove, but after this one something is not right. All gaskets and door handles should be good to go, although I will test them tomorrow when the stove is cold.

Here is the setup. Stove is venting into fireplace via an 8" positive flue connection kit sealed at damper and extending all the way up to the first flue tile. Chimney is a 30 foot 8x12".

My concern is overdraft due to the height of the chimney. The stove will operate fairly normally adding 1 split at a time but anything more than that and temps will shoot up. Installing an inline damper will be virtually impossible due to the exhaust pipe setup if thats going to be a suggestion.

I know there is another air intake under a cover on the back of the stove (secondary air?). I don't remember if adjusting that is possible or even recommended. It is not mentioned in the owners manual that I see.

 

[begreen]

It does sound like there is potential for overdraft. What size splits are you burning? How dry is the wood?

 

[kwburn]

while i wouldnt call it a kindling fire, the splits have been on the long and skinny side (kind of like a thick branch that has been split in half) and about 5 or 6 at a time (firebox about half full). certainly not beefy splits though. i guess i wasn't looking to challenge the stove with big thick stuff until i got to know it better.
average 1-2 year seasoned and ready to burn.

would your suggestion be to burn thicker stuff to try slowing down the burn?

 

[begreen]

Yes, small stuff will burn faster and hotter. Good for kindling and small fires, but not regular burning unless it's all you have. Try a good sized (6") split or two and let us know how it works.

 

[kwburn]

further inspection of the stove this morning found a half inch length of the swing out ash pan gasket pinched under the ashpan. so technically extra air was getting in through there. i repaired it and will fire up again tonight. we have a family event to head to know so i'll try later and see if any improvement and post results. fingers crossed.

 

[Gooserider]

It doesn't take much extra air to really make an Encore crank, and especially coming in from the ashpan a small gap will DEFINITELY make a big difference.

I found that on my 2550 Encore Cat, there is enough slop in the ashpan hinge that it is easy to close the door slightly askew if you aren't careful to wiggle it into place as you close it. If I don't get it right, I have just enough of a gap that I fail the "dollar bill test" over about a 3" length on the bottom of the door. This allows enough extra air in that I will seriously overcook the stove.

You have a tall stack, but it's way oversized, marginally a code violation. I'm going into a 25' tall 6" stack, and have no problem controlling the stove. I'm willing to bet that once you find and fix any and all gasket issues you will have no problem.

Gooserider

 

[kwburn]

fixing the one obvious spot on the ash pan gasket improved things quite a bit but there is still room for improvement. air on lowest setting is still giving me griddle temps creeping into the 800's with anything more than a couple logs. so i'm going to go ahead and replace the ash pan gasket. i thought it was fine but upon better inspection some areas do look too compressed. my wife pointed out that it's not like me to have not just done it after putting so much other work into the stove and she's right.

it's good to know a little extra air can be causing my problems and that there is still hope to get this figured out.

 

[webbie]

Quick test solution trial...

get a rock or similar non-combustible and insert it in the flue pipe (maybe a couple rocks) in order to try and choke it off. That stove is approved with a 6" flue, so making it a big smaller should not create any problems. Insert these through the bypass so you can get them out later!

If this helps somewhat, then you can either use the rocks or install an actual turn damper in the pipe and set and forget this turn damper (perhaps change it during "warm" season) - so it retards the draft.

 

[kwburn]

ok, more improvement as of last night. it's getting there

changed the ash pan gasket. goose is right, that is not a great design and tough to seal. i really had to tighten up the handle to make the right side make decent contact. the stove burned much more controlled last night (highest it got was around 750 on low air at one point when several thin splits were burning) although i still haven't loaded it up. after it was well established i dropped a single nice sized log onto the hot coal base and it burned perfectly at 600 degrees for a couple hours when i went to bed. before changing the gasket, the fire always burned hot on the right side of the stove which now makes a lot of sense since i think the ash pan was leaking air on that side.

i know there is still some room for improvement so after another experimental fire when it gets colder if i still need more control i'll do the ROCK trick. thats a great idea considering i can't get a damper plate installed. VC may need to change the owners manual to read "Stove cannot be burned open with the optional screen when rocks are used to damper an 8" stovepipe". LOL.