DIY Insert Installation Advice

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Dec 14, 2015
Flagstaff, AZ
I found a nice Pacific Series Design D Insert (circa 2004) on Craigslist and I'm picking it up this weekend. In the meantime I'm trying to do all the planning for the install and maybe get parts on order.

My house was built around 1980 and has a large (at least externally) concrete block chimney. The fireplace is open, but there's a sort of trapezoidal steel liner installed with a lever at the top to open and close the flue. There's two blowers that seem to direct air into the cavity behind the liner and back out. I've never gotten any sort of smoke from the blower cavity, so I'm assuming the metal liner/flue is completely sealed up to the chimney above it and the cavity is it's own sealed airspace. There's an ash clean-out at the bottom of the chimney that I can get to from outside, but it seems to be below the floor of the fireplace and is a completely sealed concrete cavity. If I had to guess, the metal insert isn't original and the floor was built up, sealing off the ash clean out in the process.

I don't know how large the chimney space itself is and I'm assuming it's old-school. I'll have to check it from the roof, removing the existing top-cap when I do. The chimney is probably just around 20ft tall from the bottom of the fireplace (maybe).

So here's what I'm wondering:

  1. Do I attempt to remove the steel fireplace liner thing entirely or just cut out the flue flap so that I can route my chimney liner up?
  2. What do I do about the blowers? They seem pretty useless if they're just directing air around a metal shell that's a separate airspace not even connected to the rear of the stove.
  3. What about combustion air? I know this is a controversial topic, but it seems crazy to burn interior air. With the metal shell in place, I think I could merely make a hole into the cavity below (where the ash clean out opens into) and seal the whole insert to the front of the hearth. Probably not worth the effort?
  4. Any recommendations on chimney liners? I believe the Pacific Insert has a 6" outlet. I live in a pretty small town, but we do have one wood stove shop. Worth buying local, or just get something online or from Home Depot?
  5. What do you use when sealing things up? It seems like the ideal is to have the entire chimney cavity sealed at top and bottom, but how do I accomplish this when the liner itself will be hot? RTV sealant or some kind of special caulk?
Thanks in advance for the help. The knowledge and experience here is invaluable.


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I pulled out the rack for the logs and discovered there was a hatch in the floor into the ash clean out area. So I guess I need to decide whether to seal it and use room air for combustion OR seal the insert to the hearth to prevent an opening to the outside into my house.