Retrofit a Block Off Plate?

[mkirschner]

Greetings, this is my first post. Excellent site, and I wish I'd found it before having our insert installed!

Quick background: Quadra-Fire 2700I wood burning insert installed professionally this January. Full stainless flex liner, single story interior chimney.

Seems to have excellent draft, and we really like it a lot so far.

But, after reading around here, I've become a bit obsessed with a couple of things.

One is installing a block off plate to squeeze out a bit more efficiency. Question: Can this be done easily as a retrofit? The main issue being maneuvering the flex liner through the hole after temporarily unbolting it, without removing the insert. I haven't tried unbolting it yet to see, thought I'd ask first.

The second thing is insulation. It doesn't seem to be necessary for draft in our case, but the safety aspect (and theoretically reduced creosote buildup) is appealing. Obviously this would be a pour-in type of insulation and would require having the block-off plate installed first. This seems like a more ambitous undertaking, as it involves breaking the seal on the top, mixing pour-in insulation, etc.

Any thoughts or comments would be appreciated.

Thanks,
Mitch

 

[zzr7ky]

Hi -

The block off plate depends on the shape of the chimney throat so it's pretty much custom/retro fix every time. It could be made in 2 sections each with a 'U' that overlap to form the pass through clearance.

If you don't see buildup when cleaning and have no draft issue I'd skip insulating it. It's not like it's a 25' chimney out in the wind right?

I would put the block off plate in.

ATB,
Mike

 

[CarbonNeutral]

Mine:

 

[weatherguy]

Carbon, do you use silicone to hold the pieces together? I plan on doing one this summer.

 

[CarbonNeutral]

Hi temp silicone, plus some sheet metal screws. I think I also used tapcons into the fireplace brick as well.

 

[weatherguy]

Hi temp silicone, plus some sheet metal screws. I think I also used tapcons into the fireplace brick as well.

Thanks, I wasnt sure if I could do it without taking the liner off but looks like I can. I may ask a couple more questions when the time comes.
thanks again

 

[mkirschner]

Thank you everybody for the replies. I'm now resolved to add a block off plate well before next Fall. I'll post back photos after it's done.

Thanks again,
Mitch

 

[Hogwildz]

Silicone good for the perimeter of the plate. Bad for around the liner itself.
It won't be there long, and will stink to high heaven.
Use rope gasket around the liner to fill the gap in the plate, or if its say a small gap, you can try some furnace cement.
Anything on the larger gap size, and the cement will fall out. Rope gasket works like a charm. (Thanks Brother Bart).

 

[tickbitty]

Bumping this thread. Was not worried about block-off plate but chimney has dropped a little crud onto back of the insert that doesn't thrill me, and I figure the block off plate is recommended anyway... so... looks like the best thing for us would be to do a two pc one like the one illustrated here, does anyone else have additional pics or tips for that? If you do two pcs, and seal it with caulk, do you do kaowool or etc on top too? Thought I recalled seeing someone else on here that did. Would really rather not tapcon into the brick... wondering how else to keep it up though.
I don't have a lot of tools, could I hand cut the sheet metal, or use a dremel?

 

[Retreadsme]

I prefer to anchor drip rail around the chimney throat forming a ledge, then cut a single piece shelf to lay into that perimeter ledge and screwing it together. I find trying to form the flanges around the block-off plate to perfectly match the chimney throat is far too time consuming and I'm not satisfied with the fit. (just me though) I put ceramic blanket on top of the plate (you'll get various opinions about added value on that) and run a bead of Dap brand High Heat Mortar around the wall edge of the drip rail just to make sure all probable leaks are sealed. (there are various opinions about the need for this also) I cut an oblong hole 1/2" bigger than the flex pipe (N-S) and 1/4" bigger (E-W) after measuring 4 times (I'm old so have to double check my checks) and cutting once.
That's just my way, everyone has "their way".
The drip rail needs to be the "old style" heavy duty, not the cheapo big-box store stuff. I use 18 ga steel instead of the big-box 22-26 ga stuff for the plate. (everyone has an opinion on that too)
Just to top off the install if it is on an exterior wall or set-out fireplace, I line the 3 walls of the original brick firebox with ceramic blanket for minimum heat sink affect. Please have appropriate breathing protection while handling ceramic fiber blanket, bat, board until it is contained.

 

[vvvv]

wonder how wrapping kwool with al foil & jamming it in would work

 

[begreen]

Here are some good instructions. You should at least have a set of tin snips or make a pattern out of cardboard that fits perfectly including the folded attachment edges. Then have a sheetmetal shop do the cutting and bends for you.

https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/

Here are some other examples with pictures:
https://www.hearth.com/econtent/index.php/forums/viewthread/11697/
https://www.hearth.com/econtent/index.php/forums/viewthread/9630/P15/
https://www.hearth.com/econtent/index.php/forums/viewthread/47057/

 

[tickbitty]

Here are some good instructions. You should at least have a set of tin snips or make a pattern out of cardboard that fits perfectly including the folded attachment edges. Then have a sheetmetal shop do the cutting and bends for you.

https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/

Here are some other examples with pictures:
https://www.hearth.com/econtent/index.php/forums/viewthread/11697/
https://www.hearth.com/econtent/index.php/forums/viewthread/9630/P15/
https://www.hearth.com/econtent/index.php/forums/viewthread/47057/

Thanks very much! That bottom one with the rigid insulation and two-pc plate was the one I was looking for/remembering. I don't want to take the stove out, or the liner out of the stove, so this might not be that easy (or that pretty) but I think I can work something out. Thanks again.