Chimney conversion from gas to wood

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counts86

Member
Nov 11, 2014
9
Steamboat Springs, Co
Hello everyone and thanks in advance for your help.

I have an existing chimney that I believe was wood at one point. The reason I think it was wood is that the chimney above the ceiling is 8" triple wall. I have a label and found a match. in an old wood stove installation catalog from 1983. At some point, the stove was converted to gas at which point they dropped 6" double wall class B venting down the entire length of the chimney which is about 35'. I want to convert back to wood as I just found a nice Jotul F CB 3 and I installed a gas furnace for my primary heat source. I had originally assumed that the class b vent only went from the gas stove to the ceiling box and that I would only need to replace that class B section. However, I now know that I need to get rid of the entire length of class b all the way to the rain cap.

This is where my questions comes in;

1) I can't figure out how the class b is supported. I can twist it and it just spins including the rain cap. I had thought that it was locked into the ceiling support box but it doesn't seem to be. I also can't lift it up. Is the rain cap supporting it? I haven't been able to access the top yet because I'm waiting for a friend with ropes and harnesses. The roof is a 45 degree pitch.....

2) Is the ceiling box correct for the 8" triple wall? I can't tell if it's locked into the ceiling box or if it is just resting on the box. If I can figure out how to remove the class B, I need to transition from the 8" triple wall to 6" double wall all the way to the stove (I can't do single because of stove to wall clearance) and I don't know how to do this.

Thanks everyone!

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Last edited:

begreen

Mooderator
Staff member
Nov 18, 2005
96,455
South Puget Sound, WA
The chimney pipe probably twist-locks into the ceiling support box which is what is supporting it. After undoing the guy strap outside, try rotating the pipe counter-clockwise. It's likely that the ceiling support box will not mate properly with modern DuraTech or DuraPlus class A chimney pipe. If so, it will also need to be replaced. Try calling DuraVent tech support to verify.
 

counts86

Member
Nov 11, 2014
9
Steamboat Springs, Co
The chimney pipe probably twist-locks into the ceiling support box which is what is supporting it. After undoing the guy strap outside, try rotating the pipe counter-clockwise. It's likely that the ceiling support box will not mate properly with modern DuraTech or DuraPlus class A chimney pipe. If so, it will also need to be replaced. Try calling DuraVent tech support to verify.
Begreen, thanks for the reply. I have a call into Duratech but they haven't gotten back to me yet. I will follow up with them today.

I am able to twist the pipe counterclockwise though. If I lift slightly I can twist the pipe counterclockwise several rotations and nothing happens. It just free spins....
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,455
South Puget Sound, WA
Begreen, thanks for the reply. I have a call into Duratech but they haven't gotten back to me yet. I will follow up with them today.

I am able to twist the pipe counterclockwise though. If I lift slightly I can twist the pipe counterclockwise several rotations and nothing happens. It just free spins....
At this point the chimney pipe may be free and just resting on the edge of the support box. Can you lift it upward now?
 

kennyp2339

Minister of Fire
Feb 16, 2014
6,707
07462
Its probobaly night the right answer you want to hear, but at a minimum you want to dis-assemble the whole chimney, all pipes, inspect the ceiling support box, inspect the chimney pipe for any damage at a minimum.
Personally for me, I would not use a metal chimney thats possibly 36yr old +, I'd rip out and install new, but a thorough inspection to make sure all metal inside the triple wall is intact, no rot, all clips, twists, locks are in working order would make it ok to re-use as is. Another consideration is making sure the inner liner on the triple wall is in good condition, if the previous owner before it was converted to gas used a metal brush to clean, the chimney could be compromised.
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,455
South Puget Sound, WA
I think he is committed to replacement. The old air-cooled chimney is probably rated at 1700º and not the currently required 2100º HT rating. The folks at DuraVent can verify the rating of the DCR chimney.
 
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moresnow

Minister of Fire
Jan 13, 2015
2,083
Iowa
The stove is also designed for 6 inch I believe.
 

kennyp2339

Minister of Fire
Feb 16, 2014
6,707
07462
I think he is committed to replacement
Thats not what it interpreted, I was under the assumption that OP just wants to remove the class B vent thats from the gas stove to the top of the chimney cap. I hope I'm wrong with that.
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,455
South Puget Sound, WA
However, I now know that I need to get rid of the entire length of class b all the way to the rain cap.
Hope so too, this is what led me to think so. Best to see what DuraVent's techs say. But I agree, it looks like this should be a tear out.
 

counts86

Member
Nov 11, 2014
9
Steamboat Springs, Co
Thanks everyone for the feedback. I was indeed trying to be cheap and re-use the existing triple wall. However, I spoke with Duravent and this is the 1700 degree pipe. Given the age of the pipe, temperature rating and the potential draft problems with the 8" from the ceiling upward, I agree that this has to be a tear out. It looks like I'll be hooking up the old gas stove for this winter......The CB 3 will have to wait until I'm committed to spending a ton of money on pipe.

Thanks everyone!
 
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