Damper Blockoff Plate

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victor

Member
Sep 11, 2008
18
Maryland
I read elsewhere on the forum about installing a damper blockoff plate and am planning on doing so myself. Is there ever any problem with sealing the chimney off at the top and bottom and getting condensation inside?
 
On a pellet stove?

Eric
 
victor said:
Yes, a fireplace insert pellet stove. I plan on running the pipe the whole way up the chimney. Thanks.

If you are installing a new liner all the way to the top, you should be installing a cap at the termination point. Then run the new liner through that cap. I don't think that you need to block off the old damper. I did the same thing with my insert but instead of blocking off the damper with a metal plate I installed some mineral wool insulation on either side of the new flue liner.

You should off coarse check with the installation instructions.
 
victor said:
Yes, a fireplace insert pellet stove. I plan on running the pipe the whole way up the chimney. Thanks.

No damper on the exhaust. PERIOD

Eric
330-876-0200
 
Eric:

Thank you for your reply but I think we might be talking about two different things here. I don't want to put a damper inside the insert pellet stove exhaust pipe.

What I want to do is to replace the fireplace damper with a piece of 3/8" steel plate with a 3-1/2" hole in it for a flex pipe for the insert stove exhaust. I'll have the plate cut at a local metal shop and just lay it on the shelf where the original damper plate sat. This way it will be easily removeable if I need to. The hole for the pipe will be slightly larger than the 3" exhaust pipe to make it easier to get manuevered through and I'll fill the gap with insulation. My thinking is that if I just take the damper out and leave the opening where the fireplace damper is (about 5" x 30") I would lose a lot of heat up the chimney. I'll put a top plate on the chimney cap and seal it, so there won't be a draft in the chimney itself, the exhaust pipe from the stove will run the whole way up the chimney and through the top cap. It seems a lot of heat will be lost through convection up the chimney and through the masonry. Is there a problem with sealing the chimney cavity off from both top and bottom?
 
Yes we were. What you are talking about is a blanking plate. It takes the place of the damper. I am sorry. I heard before that someone tried to put a damper, such as you would do to a wood stove on a pellet stove. That will not work.

No problem with sealing it off at both ends.

Eric
 
That's the set up I have with my pellet stove.
Brick build Chimney
The top is sealed off with a nice top plate and has only an opening for flex pipe with rain cup on top of it..
Original Damper plate on fire place taken out and replaced with a plate which has opening for the 3" flex pipe.
Works fine for me and I do no anticipate any problems or issues.
 
Imo if you get the kit with the top plate
and cap, there's no need to block off the
bottom where your damper used to be.
Top plate doesn't allow any draft down
the chimney and it's just needless extra
work to make a bottom block off plate
if you have the same kit I used.

The way my brother sealed it up there with concrete
anchoring screws and stove cement, that sucker
isn't letting in any draft whatsover.
 
zeta said:
Imo if you get the kit with the top plate
and cap, there's no need to block off the
bottom where your damper used to be.
Depends on your chimney construction. If it's an interior chimney I'd agree that two blocking plates might be overkill. But if it's an exterior chimney then you'll get a cooler column of air due to the exposure to the exterior of the house.

I have a center chimney contemporary Cape and it's never cool to the touch -- my neighbor has his chimney on the outside wall of the living room and his chimney feels cool or cold during the winter. They're usually not insulated to prevent heat/cold transmission.
 
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