Damper blankoff

[hydestone]

How air tight must a damper blank-off kit be when a wood stove is installed into an existing fireplace? I cannot seem to get it completely air tight...there are a few gaps where it will not seat properly due to the shaped of my existing damper frame. Should the gaps be sealed off with fire caulking or are they OK?

 

[hydestone]

Is it simply meant to be a thermal break? I.e. insulation with a plate below? Must it stop all air penetration or just the bulk of the free area?

 

[elkimmeg]

I would caulk it with 1000 degree rated caulk or higher or refactory cement in a tube.
Sealing becomes even more critical if not fully lined and not blocked of at the top.
The last thing you want is the exhaust escaping back into the living area

 

[hydestone]

Thanks ELK. I appreciate all your feedback and advice.

 

[elkimmeg]

one final word of advice do not use the red RTV caulk> It is only good to 300 degrees We had one incident in my
town already where it ignited. Did not do too much damage but scared the hell out the guy and caused minor
smoke and fumes problems in the room

What you might want to look for is a draft sealant Caulk there is a Standard called 136 Which is to draft seal and to be able to withstand 1200 degrees. One company that makes it is Boss
Boss 136 Firestop Draft Sealant tested to withstand up to 3000 degrees

Found at Home Depot
3M Fire Block Sealant FB 136

I know Rutland also makes a 136 compliant Fire stop Draft sealant as well

 

[wingnut]

I plan on using the leftover ceramic insulation from my install and packing some around the insulated pipe at the top before I cap it. Can I do the same thing at the bottom of the stack just above the smoke camber? Would this help for a better seal?

 

[Rhone]

My block-off also did not fit exactly tight particularly the left & right sides. There was about a 1/2" gap on the left in particular. I ended up stuffing it with mineral wool insulation and I mean stuffing it to be nearly rock solid. Not the best option, but better than leaving it how it was. When I redo my install & liner this year I'll see about caulking it or getting a bigger block-off.