Gas heater Cat III Thimble Insulation?

[Gopherboy6956]

Hey All - Quick question - just installed my heater - got the vent sealed with some good high temp silicone, but what do you guys do around the thimble? Just insulate as normal? Use a can of spray foam in there?

Thanks!

 

[fitter30]

Your install manual or manufacture would have that info. Probably would depend on type of combustible your putting through it. Ceramic insulation is good for 1900°f.

 

[Gopherboy6956]

Its tough because all of their documentation refers to the entire Saf-T vent system, not the thimble alone. I can't find anything in there that references the clearance or insulation allowed types around the thimble, just the pipes themselves. Waiting on Selkirk Corp support to get back to me.

 

[4x4Pete]

I understand that the thimble is designed to hold the required clearance to combustibles and insulation as well. Insulation can let heat pass through it without combusting but if it is touching wood or another combustible, it could cause a fire. . No combustibles or insulation is allowed inside between the telescoping barrier and the vent piping, air space only. What purpose would the thimble have if you need to keep additional space around it? It should provide the required clearance. Let us know what Selkirk says.

 

[PoorUB]

but what do you guys do around the thimble? Just insulate as normal.

I always insulated it with fiberglass as that is what the building used.
I suppose you could foam it. The thimble is there to provide clearance to combustibles, so what ever insulation you have available should be fine.

 

[Gopherboy6956]

I always insulated it with fiberglass as that is what the building used.
I suppose you could foam it. The thimble is there to provide clearance to combustibles, so what ever insulation you have available should be fine.

As you can see in my picture my rough opening is a little larger than the thimble, which Is why I thought foam - I wanted to really fill in those gaps.

But you're right - tonight I felt the metal on the side of the thimble while it was running and it was perfectly cool to the touch - so probably no issues with any kind of insulation.