VC Winter Warm Insert Small refractory question

[HearthReader]

Am installing a used Vermont Castings Winter Warm -Small insert. Looking down from the chimney outlet, I can see a gap between the refractory block and the backplate and throat. As a result, I'm afraid that there will be leakage up thru that gap that will short-circuit the catalytic combustion. The combustor that same with the unit looks like it was overheated and distorted some, and I have a new one on order. That will help the combustor refractory plate fit more tightly and make less backward pressure on the whole assembly, but I think there will still be a small gap (1.2 inch). The gap is the brighter white in the photo.

One idea I have is laying a piece of gasket across the gap (above the gap, not down in it) and tacking it down to the the plate on the right with refractory gasket cement. The second photo has it laying across the gap in much the way I would do it. It doesn't interfere with the damper plate laying back across the area when open.
Any idea if this will work?

 

[certified106]

I would be hesitant to put any kind of stove cement on refractory material as it is very sensitive and fragile. I can't get a good look at the first picture but it look as the refractory material sits back underneath the steel lip. If this is the case I wouldn't worry about it as the smoke has to pass through the catalyst before it could leak through the refractory gap. Smoke will always follow the path of least resistance so as long as your draft is good I doubt you would have much flue gas passing through there if any. I know my refractory material doesn't have any significant seal around it and just sits loosely over the top of my cat.

If you can expound on the pictures a little bit more it might help to understand how the stove works. Is the steel you see on the right side of the picture the damper and does the catalyst sit in the middle of the stove under the refractory housing?

 

[HearthReader]

Thanks for the response - here's a diagram from the manual showing gas flow in the stove. The red arrow shows the angle of view. The metal plate visible is part of the firebox behind the damper (blue line). The yellow line is the top of the refractory. The red dot is over the gap and would be the piece of gasket in cross-section if I put it there. As you can see, when the damper is closed, the hot gases exit the back of the firebox and are pulled downward through the catalyst, and then come back up on either side of the catalyst to reach the stovepipe. As such, the gap where it appears would let gases bypass the whole catalyst.

Note that I would only tack it to the metal plate with glue, not onto the refractory.

 

[HearthReader]

Installing a nice new cat seems to have fixed most of the problem 0 the former owners overheated the original cat and it distorted, which resulted in the refractory mount being a little askew. The new cat lets everything close up tight, resulting in very little gap up top (still 1/8", but I'm told that won't matter). Thanks for the responses.