I spoke with a dealer for the Jotul c350 fireplace insert, that I am planning to buy, yesterday and question his advise. I was asking about where the stainless liner passes through the old damper. My damper is only 5 inches wide and the tube is six, plus, I believe that the area is supposed to be sealed around the pipe. He said that they always just smoosh the pipe to an oval, pass it through and count on the seal at the top of the chimney. It sounds bogus (he seemed like the type to just wing it). I was also wondering if combustion air on these types of stoves ever comes from the chimney vs. the room? Thanks for your help, I want my install to be correct (I won't be going back to that guy) whether I do it myself or hire it out,
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KaptJaq
Minister of Fire
From what I have seen:
There are round/oval/round segments made for passing through narrow damper openings. With these you know you are keeping the proper volume inside the pipe. That said, many competent installers do "ovalize" the round pipe to fit through the narrow opening with no problem.
The best install will have a block-off plate near the old damper opening. If it is an interior chimney you can get by with just the top sealed (and insulation above the heated area of the house) but you will loose some heat going up the old flue and warming the masonry. If that masonry is all internal the heat will slowly radiate into the house with little net loss. If it is an external chimney I would use a block-off plate and a fully insulated liner.
If you do not want to use room air for combustion air ask about an OAK (outside air kit). Having it draw air from the chimney is potentially dangerous.
These are what I have seen, I'm sure others will add their opinions...
KaptJaq
Edited for clarity...
There are round/oval/round segments made for passing through narrow damper openings. With these you know you are keeping the proper volume inside the pipe. That said, many competent installers do "ovalize" the round pipe to fit through the narrow opening with no problem.
The best install will have a block-off plate near the old damper opening. If it is an interior chimney you can get by with just the top sealed (and insulation above the heated area of the house) but you will loose some heat going up the old flue and warming the masonry. If that masonry is all internal the heat will slowly radiate into the house with little net loss. If it is an external chimney I would use a block-off plate and a fully insulated liner.
If you do not want to use room air for combustion air ask about an OAK (outside air kit). Having it draw air from the chimney is potentially dangerous.
These are what I have seen, I'm sure others will add their opinions...
KaptJaq
Edited for clarity...
Installers want it easy, especially if the sales rep has given you a fixed quote. It's not uncommon to ovalize the liner to get it past the damper, but it must be done carefully. Liners are thin metal that can tear. It's pretty common to skip the block-off plate, especially in a competitive quote. It's optional, though it can make a nice difference if the chimney is exterior and somewhat short. Regardless, be sure that the chimney is thoroughly cleaned, including the damper shelf area before installing the liner.
Can you describe the chimney? Height? Interior or exterior chimney?
Can you describe the chimney? Height? Interior or exterior chimney?
Ashful
Minister of Fire
Squishing a 6" single wall pipe from 6" diameter to fit a 5" opening will only reduce the cross-sectional area from 28.3 to 27.1 square inches. Not too bad. Worse if you use double-wall or insulated pipe, and MUCH worse if you start going less than 5". For example, at 4" it shrinks to 24.2", and at 3" it shrinks to 19.7".
Thanks for all the input. It is an interior chimney that passes through the master suite on it's way up. Do you think that not insulating it will help create some heat in the masonry? I was leaning towards insulating it to keep down the creosote potential (though I always burn dry hardwoods), but if the residual heat will help in the bedroom upstairs, perhaps I won't. I was looking at the double wall flex pipe with the smooth interior, but someone spoke disparagingly of it. It seems like a smart move when it comes to cleaning and buildup. Thanks again for the help everyone!
Oh, and now that I think of it, perhaps the smart thing to do is to just insulate the top of the chimney opening around the tube to keep the heat in. Thanks again
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