Gasket or Furnace Cement -- or both?

[osimp]

Hi -
This relates to a rebuild of a VC Encore, model 2550 (cat), in use for about nine years.

I set out to replace the combustor, expecting to spend an hour or two doing it. But, although in general all the castings appear to be in good shape, I found the "refractory box" (which holds the combustor) to be falling apart and disintegrating. The secondary air probe needed replacement as well, of course. The cost of the new refractory box seemed unreasonable (>$300).

But my question has to do with sealing the fireback -- mainly the upper one -- to the back of the stove (on re-assembly). It appears to me that VC had no faith in the gasketing, as a considerable amount of furnace cement had also been used. The cement sets up rock hard, is very tenacious, and it's a real pain to remove from the gasket grooves.

Also, it appears that no gasket material was used on the left end of the upper fireback (that doesn't get clamped against other stove castings with the bolts) -- just a LOT of furnace cement was used.

So my question: What's the best approach for re-installation? What diameter rope gasketing? How much furnace cement? Etc. Seems to me a considerable amount of cement is in order -- but that means future disassembly (and clean-up) will be more difficult.

Thanks for any advice on this, your experiences, etc.

 

[DAKSY]

A total rebuild will require at LEAST two tubes of furnace cement...
For cleaning out the old stuff, I took an old slotted screwdriver & rounded the corners on my grinding wheel...
This allows you to get down into the grooves & chip out the old cement...
Any REALLY stubborn material can be removed by striking the end of the screwdriver with a hammer.
After that I used a wire wheel on a grinder to really clean out all the grooves...
MAKE SURE YOU WEAR A FACE SHIELD!
Them little wires from the wheel will pierce you in multiple locations!
I believe the only gaskets on the fireback were on the lower sections, not the upper...
The diameters for the gasket material are in you owner's manual.
If you lost it, try here:

http://www.vermontcastings.com/catalog/elements/files/2008/2000956_Encore_25501.pdf

 

[osimp]

Actually, I used a variety of other tools as well for cleaning out the grooves.

I still have the owner's manuals, one that came with the original stove (2000) and one that came with a new stove in 2009 (they're identical). The manual (and your link - thanks) address gasket sizes for moving parts (doors, etc.) but not much is said about "permanently" assembled internal castings. I've read many complaints (on-line) about VC not being forthcoming with information. VC itself refers people to their dealers who say things like "Oh, yeah, we use this stuff . . ." (while groping around in a pile of trash).

One curious thing about the original gasketing is how much wider it was than the grooves it was supposed to be "pressed down into."

My observation was that the upper fireback did have gasketing, except maybe on the left end. That's my biggest puzzle.