Defiant Encore - Catalytic and heating problems

[Petertay]

We have happily used a Defiant Encore for 14 years: from November to March it burns 24 hours a day.

But a problem has developed: We let the griddle temp come up to 500 degrees, then push the lever to engage the (new) combuster. The problem is that the stove then begins cooling, and we have to open the lever to heat it up again. Why won't it hold the temp or even get warmer when we open the "thermostat" lever?

In order to minimize your questions, here is what I can tell you:
We begin each day by letting the fire get good and hot.
8-inch Metalbestosl chimney goes through the wall directly behind the stove, then up for 10 feet. It is free-standing in the cold air with a cap.
I suspect the chimney is too cold and doesn't draw well. Sometimes smoke just rolls out the top and falls to the ground. But the problem I'm writing about is new: the stove has worked well all these years.
Air intake is a conversion kit, so it draws outside air.
Fuel is large well-dried oak or locust.
All gaskets seem okay, but some have not been replaced in a few years. How would that matter? Ash pan gasket is tight (or it would allow the fire heat up, which doesn't happen).
I replaced the fireback (with factory kit) two years ago because the damper area had become warped. The stove guts were vacuumed and rebuilt, paying proper attention to all the places that needed stove cement. A new fibre housing for the combustor was included with the kit. New cotton batts replaced old ones at this time.
We tried using the new variety combustor (the kind with a mesh). Same problem. We went back the regular honey-come variety. Same problem either way.

Any ideas on why the stove won't heat up with the combuster in operation? Thanks in advance.
--Peter

 

[Heat Miser]

The thermostat and/or control cable could be damaged and is affecting the air intake door on your stove. On my 2005 VC Defiant catalytic there is also a secondary air combustion probe inside the refractory box under the catalytic element. It controls the secondary air inlet and it could also have a problem when the cat is engaged and not properly regulating the burn. It's probably best to call up Vermont Castings and see what they have to say about the issue.

 

[Petertay]

Thanks for the suggestions. The primary air valve opens and closes when the thermostat lever is moved, so that seems okay.

But the secondary air inlet, I forgot about that. I pulled the probe out and the stem seems real short; maybe burned off. Another observation: The stove was hot when I took the cover off the secondary air inlet, and the shutter was closed. After I pulled the hot probe out and looked at it, it was cool when I shoved it back in. The shutter was closed. Perhaps this was not the best way to test it, but it seems the shutter remains closed whether it is hot or cool. So it needs to be replaced.

A gasket replacement kit is also on the way, so we'll see how it goes when that work is doneese items have been replaced. Meanwhile, we appreciate your help.

--Peter

 

[downeast]

Once an owner gets past the out-of-the-box quality control problems with the CFM Encore, it is a great heater.
There are plenty of parts that can deform and wear for air leaks and air control; you've done most of the fixes.
The secondary air probe does wear: replace it. Do ALL the gaskets, including the door ceramic 'glass', pipe exit, cat damper, ash pan. Yes, that damned ash pan assembly bolts into the base, check that gasket and bolts. Get a smoke "pellet bomb" from a dealer for a leak check. It was suggested here to use an air compressor to "blow out" the stove and see where air exits from seams: cast stoves have furnace cement sealing the seams which dries out over time. Only Morso uses fiberglass gaskets for seams (may be others also).
Some here will push the "flue problem"; could be, but you've had the same flue system for years working fine.
Finally, the Service Manual for your Encore 0028 is here somewhere online in .pdf ; the Encore 2550 Service Manual is available from CFM sometimes depending on who and how you speak with. Those Service Manuals are very well done and complete with schematics and tips and tricks for repair and rebuilding. You have already done much more than most.
Experience: 3 VC Encores since 1989. The worst were the two made after 1995: the buyout of Vermont Castings by CFM Majestic.

 

[seaken]

Hi Peter,

It is not unusual to have to go higher than 500 degree griddle temp before the cat will ignite. Try 550, then 600, all the way to 700. I've had catalytics that wouldn't lite off before griddle temps were 700 degrees. And yes, Downeast is right - replace that secondary probe. In fact, get two. For 24/7 burners, like yourself, that probe may need to be replaced every two years. Check it twice a year, when you clean your cat.

 

[webbie]

10 feet of chimney with a TEE is way short. Common guidelines say to subtract 5 feet of effective chimney height for each 90 degree turn, so the height of your chimney is about 5 feet! Combine that with being outside, and you are bound to have problems.

I know it worked before, but your troubleshooting will be easier if you forget about that. You were just lucky. There are never two days when the draft and weather conditions are exactly the same.

So raising the chimney as much as possibly is my advice.

 

[Petertay]

Thanks, Guys, for the help.
About the chimney: As I mentioned it is a Metalbestos --triple-wall stainless. It is rarely warm to the touch. Do you think enclosing it in a chase would help it keep a better inside temp, or does the built-in insulation keep it as warm as possible?
--Peter

 

[webbie]

The built in insulation does most of the job, although enclosing it may slightly help. Mostly it needs to be taller.