Add a steel plate or no?

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Tjm

New Member
Feb 25, 2021
69
Western NY
Cutting my smoke shelf out of heatform… front done still have to cut the top. Plan was to bend a steel plate with a flat back and triangular flag off each side to reseal the hole and make a sort of chase. Installer doesn’t mind but he really thinks it’s unnecessary as the blaze king Sirocco we’re putting in there already has a convection chamber up the back so it really doesn’t put off much heat in the back both from a safety standpoint and also from keeping my heatform vents functional. Of course I think the 45 degree elbow on the back of the stove will be single wall? His vote is just to cut out the top and fill the cavity with insulation. Thoughts?

Interior chimney with (I think) 6” of block behind the heatform and plenty of combustibles touching chimney. Going with a 6” insulated liner.
19.5 ft chimney from the top of the stove. Just poured the crown! No more weird chimney pipe extension!

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bholler

Chimney sweep
Staff member
Jan 14, 2014
26,212
central pa
Cutting my smoke shelf out of heatform… front done still have to cut the top. Plan was to bend a steel plate with a flat back and triangular flag off each side to reseal the hole and make a sort of chase. Installer doesn’t mind but he really thinks it’s unnecessary as the blaze king Sirocco we’re putting in there already has a convection chamber up the back so it really doesn’t put off much heat in the back both from a safety standpoint and also from keeping my heatform vents functional. Of course I think the 45 degree elbow on the back of the stove will be single wall? His vote is just to cut out the top and fill the cavity with insulation. Thoughts?

Interior chimney with (I think) 6” of block behind the heatform and plenty of combustibles touching chimney. Going with a 6” insulated liner.
19.5 ft chimney from the top of the stove. Just poured the crown! No more weird chimney pipe extension!

View attachment 283053 View attachment 283054 View attachment 283055
Your heatilator vents will still be functional yes. They will suck air in the vents it will come out that big hole into the chimney and that heat will be wasted. Unless you were able to put the block off plate above the cut area which would be a real pita.
 

kennyp2339

Minister of Fire
Feb 16, 2014
6,124
07462
I'd leave the whole and install a sheet metal underneath with insulation between the sheet metal and parts of the old heat form, this will limit and residual heat that comes up off the stove from going up the metal chase and being absorbed into the masonry.
 

Tjm

New Member
Feb 25, 2021
69
Western NY
They definitely plan to block off the chimney. Not sure if above or below the cut area. Kind of assumed above. They don’t use a plate but just insulation i think at the top and bottom. Maybe I’m wrong but I wasn’t too concerned about heat flowing up the chimney with it being inside the house thinking it would radiate most of it upstairs. That was my thought anyway. More concerned with safety and if I could keep any small amount of heat going to our frigid mudroom behind where the heatform vents go.
 

Tjm

New Member
Feb 25, 2021
69
Western NY
Bholler - I was thinking of using the same thickness as I cut out ( 3/16) but I think in the past you said 1/8 or something thinner would be fine? Do you agree with dealer that it won’t see high temps back there with the convection air chamber on the back of the stove? Maybe I can ask that they use a double wall elbow to transition to the liner.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
26,212
central pa
Bholler - I was thinking of using the same thickness as I cut out ( 3/16) but I think in the past you said 1/8 or something thinner would be fine? Do you agree with dealer that it won’t see high temps back there with the convection air chamber on the back of the stove? Maybe I can ask that they use a double wall elbow to transition to the liner.
Really high temps no. But enough temp to cause a convective current sucking air up the chimney to be cooled then drop back down.

I typically just use 20 gauge galvanized.
 
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