school me on chimney pipe

[iamquaker]

ok so i just purchased a used Avalon 945 raineer insert model. with the 45 degree pipe exit out the top. its in great shape and will be ready to go after a cleaning and some paint.

question is on the chimney pipe. i currently have a brick fireplace and i will run the pipe up the existing brick chimney that is about 12" square inside. i have a tight neck to get past in the old flu its only about 4" wide.

one stove shop told me to get a flex pipe and squish it thru the thin opening, another stove shop told me to use a hammer drill and bust out the old brick till i can get the 6" pipe thru with no problems.

what do you all think?

 

[BrotherBart]

It that 4" constriction firebrick or is it the steel/iron frame for the fireplace damper?

 

[Gooserider]

Not knowing that particular insert - (I don't memorize stove specs...) is it pellet or cordwood, and what is the nominal pipe size on it? Squishing flex pipe is generally not a great idea unless you are talking a very small amount of squish, usually under an inch or so. I wouldn't want to squish a 6" pipe to fit a 4" gap... Over squishing risks damaging the integrity of the pipe (the seams tend to open up) not to mention the problems of restricting the draft area excessively and the problems it poses for cleaning and inspections.

OTOH, modifying the firebox has it's own issues. Generally it's considered OK to remove the damper flaps, and probably OK to cut out or remove the damper frame itself. Modifying the brickwork is often seen as more questionable, but is sometimes OK. I'd suggest talking to your local code enforcement person about what he'd feel most acceptable given your situation. It's very hard to tell over the net when we can't see just what you have to deal with. NOTE, if you modify the firebox, code requires you to permanently attach a warning label to the inside of the box stating that it has been modified and is no longer safe to use as a conventional fireplace. Your local stove shop should be able to get you one of these labels.

Gooserider

 

[jjbaer]

ok so i just purchased a used Avalon 945 raineer insert model. with the 45 degree pipe exit out the top. its in great shape and will be ready to go after a cleaning and some paint.

question is on the chimney pipe. i currently have a brick fireplace and i will run the pipe up the existing brick chimney that is about 12" square inside. i have a tight neck to get past in the old flu its only about 4" wide.

one stove shop told me to get a flex pipe and squish it thru the thin opening, another stove shop told me to use a hammer drill and bust out the old brick till i can get the 6" pipe thru with no problems.

what do you all think?

I did a combination of three things: 1) squished my 6" pipe just a wee bit, 2) cut away part of the cast iron damper (the non-movable part that the damper seats against) and 3) I removed one-half of a few bricks. But then I repacked the area where I pulled the brick from with some high temp cement to make sure nothing was exposed. I have an outside chimney however so even if removing a brick increased temps it does so on the part of the chimney whose other side is exposed to the outside air (insert "no risk of fire"). Also, except for the 1 inch of pipe that passes through the damper area, my entire length of pipe is fully insulated with 1/2" insulation (even the foot or so of pipe from the damper to the stove connector) to guarantee nothing would ever burn the house down...

 

[webbie]

As mentioned, either will do. Personally, I would rather remove the damper plate, perhaps grind a little (4.5 inches would be nice), and use slightly oval pipe. You can purchase pipe already ovalized for this.

That is a great stove - the unit with the 45 degree flue. I think maybe they stopped making it, but it was my favorite.

According to current NFPA codes, your chimney is over sized for that 6" pipe, which means you should run a 6" liner pipe all the way up to the top of the chimney - as you will see from other threads here, that will work better and be easier to clean (and much safer). If you are in a very cold climate and the fireplace is exterior...or if the tiles are in very poor condition, you should also consider insulating the liner.