Factory Insulated Chimney Pipe on ZC Fireplace

[DIYrod]

Hello. This is my first post but I've already learned a lot by reading the many Hearth Forums. It's great to see different perspectives for solving the various installation challenges. I'll try to be as specific as I can. Hope my post is not too long!

I am installing a Regency H2100 Hearth Heater (HH) in a vacation cabin. It has a rear exhaust and will be mounted in front of a ZC wood burning fireplace. My plan is to use an adjustable 90 degree connector on the back of the the HH to connect a 6" SS flexible liner with insulation wrap. It will be inside an existing ZC chimney flue with a 22' run to the top.

Until recently, I assumed the existing chimney pipe system was the typical air cooled double walled system that is normally used for ZC fireplaces and is discussed in many of the forum threads. But, after removing the Top Cap, it now looks like the existing chimney is made of 3' long factory insulated sections. The chimney pipes seem to be double walled with 14" OD x 9" ID and with 2.5" of insulation between the inner and outer walls. The pipe sections are capped (but not sealed) on each end. There are small vent slots that allow minimal breathing between the insulated pipe sections. But, the last section on top has a ring cap that pretty much seals off the insulation. And, the Top Rain Cap is simply clamped onto the 14" OD.

I assume this insulated chimney system is better than the air cooled versions but I'm not sure what kind of top plate assembly is needed. My local dealer recommends a Factory Built Homesaver Guardian 6" Adapter 14940, with a storm collar, Top Clamp and a Guardian Cap. It is a popular assembly for air cooled chimneys, but the 14940 adapter is designed to allow the needed air flow for air cooled chimney systems. I guess it will work but I'm concerned about the adapter allowing cold air flow between the wrapped 6" liner and the 9" ID inner pipe. Can I use the 14940 adapter and stuff insulation between the 6" liner and the 9" flue to stop the cold air from sinking into the ZC firebox and then into the cabin?

Vent slots with the sealing ring cap sitting to the side

Sealing ring cap installed over the vent slots

Existing Top Rain Cap

 

[begreen]

Welcome. If possible, skip the adjustable 90 coming off of the stove and use either a capped tee, or a fixed 90 elbow. This should be a stainless steel fitting.

I don't see any harm in stuffing some Roxul (not fiberglass) around the liner, though the cool air leakage could be minimal here. Additionally you could install a damper sealing block-off plate and stuff Roxul down below too.

 

[DIYrod]

Thanks for the fast reply. I've not found any other postings related to the type of insulated chimney pipe that I have. How common is it?

Well, I already purchased the SS adjustable 90 because I was planning to adjust it to about a 60 degree angle and then bend the flex liner the other 30 degrees inside the ZC firebox. If I use the adjustable 90, do I need to tape the seams that are in the 90 to reduce any smoke leakage? And, should the adjustable 90 be wrapped with the insulation wrap?
Another option I might have is to use a standard SS appliance connector that I already have. But it would mount to the back of the HH horizontally and then I would need the flex liner to bend 90 degrees inside the ZC firebox to line up with the horizontal connector. I've not worked with a flex liner so I don't know how flexible they are or how much of a bend radius is possible. I certainly do not want to damage the liner by bending it too much.

Do you think I should proceed with the dealers suggested Factory Built Guardian system with the 6" Adapter no. 14940? (I do like the fact that it is UL Listed.) Or, is there a better way to solve my top plate issue?

I do have some 1" Kaowool Cerachem blanket. Could I use it instead of the Roxul for stuffing around the liner? I plan to stuff it around the top and bottom of the liner.

Am I correct in assuming that my finished chimney system will be better than the usual air cooled system? There will be no air cooled chamber (as the original chimney was designed), but I'll end up with a 3 wall chimney system with 3" of insulation. (2.5" if insulation in the existing chimney pipe plus 1/2" on the liner.)

I'm real anxious to finish my install and fire up the Hearth Heater. We just got several inches of snow last night but I know summer is coming soon. This has been a 6 month process because I had to remove a raised hearth to allow room for the Hearth Heater, I then refaced the old fireplace with cultured river rock and mounted a new 8' mantle that I finished out of a 200 lb cedar log.

 

[begreen]

Tape won't stand up to the heat. If you can find one, maybe get a fixed 45 deg elbow instead. Kaowool is good stuff, it would be fine to use. There is redundant insulation here and it should be very safe. Actually, I see no need to insulate the liner in this system, but it won't hurt if you want extra peace of mind.

It sounds like you are up in the Sierras. What altitude is this?

 

[DIYrod]

Tape won't stand up to the heat. If you can find one, maybe get a fixed 45 deg elbow instead. Kaowool is good stuff, it would be fine to use. There is redundant insulation here and it should be very safe. Actually, I see no need to insulate the liner in this system, but it won't hurt if you want extra peace of mind.

It sounds like you are up in the Sierras. What altitude is this?

We're in Big Bear, CA at about 7000'.

I'll try to trade the adjustable 90 for a 45. Will I be able to bend the flex liner 45 degrees inside the ZC firebox?
I am curious, what would be wrong with using the adjustable 90?

 

[begreen]

They are not as tight and can come apart at the seams.

 

[DIYrod]

They are not as tight and can come apart at the seams.

Thanks for the help. I think I have the information I need to finish my install. I'll try to post a picture when I'm done.