High Temperature Silicone Sealant

I was told by the Selkirk guy to seal around the chimney where it exits the thimble with high temperature silicone sealant. What is the general exterior temperature of a Class A Stainless Steel Chimney in normal use? Do I need any special silicone caulk because I am seeing regular silicone caulk with maximum temperature ranges up to 204°C. The Rutland High Temperature Caulk only increases that to 260°C; it would appear that they are doing the "Lure to catch fishermen." I have yet to see any sort of high temperature sealant that can be used outdoors and remains flexible that is significantly higher in temperature than normal silicone sealant.

 

I have been told to just use 100% silicone.

 

Here's one........Hi-Temp Red Silicone Caulk-57500 - The Home Depot

 

I think that's the fire caulk they use at work.

 

Any red "high temp" silicone will work, 500-600*f IIRC
Most hardwares or automotive parts stores will have it

 

I can put my hand on Class in normal use...can't keep it there too long though.

 

Here's another.............Gasket Makers : Permatex® High-Temp Red RTV Silicone Gasket

 

Yet another...........Rutland Products High Heat Silicone (76) - High Heat Sealants & Patches - Ace Hardware

 

As I said, the Rutland is only 260°C; regular silicone is 204°C. I would have to travel 65 km to get the Rutland so may just as well use the local available silicone caulk.

 

Yes, but those little tubes would mean buying many of them.

 

Again, that is only a bit higher in temperature than what I can get at Lowe's Home Improvement. If the outside of the chimney is not going to be that hot; meaning over 204°C, then I can just go with regular silicone.

 

How much do you plan to put on?
The Rutland is rated at 500 degrees.
Use one of the other even higher rated ones if you don't think that little tube will be enough.

 

That handles up to 343°C, 139°C above regular caulk; however, it is also pricey and you have to have it shipped, so there is the shipping fees to add to the ~$18.00 cost.

 

You can pretty much get any of the hi-temp stuff locally.
Really.
Go to an auto parts store.
Oh, and don't skimp on your safety......you're almost done.
Be safe.

 

I appreciate all the feedback. It appears that I can use the regular silicone caulk rated to 204°C without worries.

 

I was lumping Lowes in the hardware category, not a great one, but...

 

I have to fill a gap around the outside of the chimney where the horizontal pipe meets the tee; have not measured the gap but I am thinking a cartridge in a caulking gun will be needed. Then there is the inside gap as well that needs to be filled.

 

Yes, when it comes to hardware, Lowe's is dismal. It seems they are moving to everything in blister packs with limited selections. I could not even find the eyebolts they use to sell when I was working on my tractor carrier.

 

When silicone fails from heat it doesn't burst into flames so this isn't really a safety issue but a maintenance issue.

Red silicone looks dumb IMO, I would rather use black or grey RTV rated to 600 degrees F (we aint in Canada). On the outside of Class A, you should see any higher than 200 degreesF with any regularity so the silicone options from Lowes should be fine.

I use regular GE2 100% silicone (available in grey or clear) on my class A pipes to seal the storm collar. No troubles.