How do I decide if I need to line a chimney?

Hi all, I have a nagging question. I have a fireplace in my basement (!!!) which has been pretty much not used. The chimey is like 12" square inside, some of the tiles look like they could have moved.
I'm putting n a wood furnace - so it should have much less heat that a fireplace: its supposed to heat the flu to around 280 degrees according to its specs, to prevent creosote.
Do I need a liner? Furnace requires minumum 8" round flue. Chimney guys ALWAYS ALWAYS ALWAYS say I need something, and I don't trust those mofos. Can the township tell me or what?
Don't want to spend another 1-2K on a liner if its totally unnecessary. The chimney has 2 flues, the other one is for a fireplace on the ground floor, which I use all the time with no problems.
Thanks,
Dean
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dean wrote:

your first call should be to your insurance company - provide them with the stove specs and they will make the decision for you.
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They said as long as its passed by the township code, I'm good.
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I just installed a wood stove...
I wanted to use my existing chimney, but was told by several people and also read several different places... That new wood stoves heat more efficiently and therefore do not send as much heat up the chimney.
Therefore it is important to have the same size chimney as the wood stove to get proper draft. Also I heard all sorts of nasty stuff about old existing chimneys and that in every case, they should be lined.
The building inspector and insurance guy went strictly by my wood stove manufacturers specs for chimney and installation requirements.
It was less expensive and better for me to install a new chimney in another location than to have my existing chimney relined.
I don't know if all this applies to a wood furnace or not? The important part is to get your insurance company to cover it, and do what is necessary to get them to cover it. That was my main concern.
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When you line a chimney, aren't you just inserting a stainless tube down the middle?
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correct - at a size specific to the required dimensions to the wood burning unit to provide adequate draft for safe burning.
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So how come that's more expensive than building a new chimney?
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dean wrote:

in building are you refering to a brick chimmney or a prefab chimney. i had a liner installed in my chimmney 30 feet for around 600.00 - this included the liner, the spark arrester, the cover for the brick chimmney and the elbow going to the stove.
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....

My woodstove puts out much MORE heat than a fireplace. YMMV Where is the 280 degrees measured? As th e flue gasses rise, they are cooled a bit and may condense at one particular spot in the chimney.

Only way you should need a liner is if the chimney is in need of repair. A competent chimney sweep can put a camera down the stack and see what it really looks like. If it is solid, all the joints intact, no reason not to use it as is. You may be able to inspect at least some of it with a flashlight and mirror.
The township may be able to tell you minimum code, but they will not have the specific requirements for every brand of stove or heater.
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When you say your woodstove puts out much MORE heat, are you talking about up the chimney or into the room? I can't imagine anything giving more heat than a fireplace going up the chimney!
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For another example, a Morso Squirrel with about 8' of 6" smokepipe: With primary draft at about 50%,

smokepipe cool enough to hold hand to it at thimble, exhaust transparent, unless ambient below ~20 deg. F.
With this unit, it's pretty hard to get temp above 350 deg F in pipe, just above stove, under any conditions. YMWV.
Fireplaces really rip when you have chimney fire.
HTH, J
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Both. My stack temperature on the stove run 400 degrees but I can crank it up even more.
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Forgot to mention, it is also a velocity thing too Fireplaces have lots more air moving with the gasses compared to an airtight stove. That is one of the thing that makes fireplaces so inefficient.
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Oh yeah, didn't think of that.
The furnace has a butterfly valve of some kind that opens up when its cold outside, to redirect some of the heat away from the heat exchanger so it goes straight up the chimney when its cold. Not sure if this is a manual thing, I don't have the installation instructions yet.
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