Short run exhaust pipe installation for P35i insert.

[CBL]

First post guys so go easy on me.

I've been doing research and shopping around for a pellet insert for quite sometime. I've lurked here for awhile and this website has been a great resource for doing that. I've honed it down to a Harman P35i insert.

I was reviewing the installations instructions and it shows two methods of into an existing fireplace. One where the whole length of the chimney is lined with SS pipe,Then the other one where only a short run of pipe is used up until the first flue tile, then the area around the damper plate is insulated and the chimney is capped to keep the pipe protected.

With the short run pipe installation Harman suggests, there's no mention minimum or maximum chimney heights where it can be applied. I spoke to my city building inspector about it and he mentioned he would generally be good with it as long as it's approved by the manufacturer. I called Harman and asked them if there any specifics about this type of installation it and they couldn't give me an answer either as it varies within installations and told me to speak with a local dealer. I plan on visiting one over the weekend to ask about it. But wanted to know what the experts on here thought....My chimney is on the newer side (built in 1990) and it's in pretty good shape. Its a 2 floor colonial home and the flue is probably about 30' high give or take. Thoughts? I did attach the page in the manual for better reference.

Thanks for the help

 

[DAKSY]

The main issue with this type of install will be future maintenance. The fly ash which would normally be expelled from the full length & out the chimney top, will now fall back around your short section. It will build up until it falls into the liner, if you let it go that long. If you DO decide to periodically slide the insert out to clean that area, how will you keep the built up fly ash from falling back into the fireplace cavity once the block-off plate is pulled? Believe me when I say that it won't just drop to the floor. It will go ALL OVER the place...Others may chime in here...

 

[Lake Girl]

For my peace of mind, I think I would run the exhaust the full length of the chimney with termination at the top. No chance of smoke filtering into the house and no accumulation of ash within the chimney space. It would be frustrating to have to change later and redo install IMO.

Welcome to the forum - pics when you're all set up

 

[CBL]

Ah... Yes. I see what you are saying, a full linear it is.

Speaking of liners, what the consensus on with insulating a chimney linear before installation?

 

[john193]

One more vote for a full liner to the top. I personally don't see a reason to insulate a chimney liner. I have a rancher with about 18 feet of SS liner. I believe the harman terminates to a 4 inch opening at the exhaust. Given the length you need, I'd go with 4 inch pipe.

 

[DAKSY]

Ah... Yes. I see what you are saying, a full linear it is.

Speaking of liners, what the consensus on with insulating a chimney linear before installation?

If you insulate the top - under the cap plate & the bottom - over the block-off plate, you will end up with virtually the same effect as insulating the entire height. The standing column of air between the insulations will act as an insulator as well. There has been some discussion on the woodstove side about certain manufacturers REQUIRING that the liners be insulated, so you may want to check that when you make your purchase.

 

[Lake Girl]

Wouldn't the exhaust pipe leech some heat to the chimney tile so it would act as a heat sink? Especially with insulating under cap and block off plate?

 

[fmsm]

I'll chime in on my P35i installation. 4" pipe to a block off at the top and an insulated block off at the flu, I also recently had an OAK kit installed and am glad that I did. Had I realized when I. Ran the liner I would be doing OAK I might have run it next to the exhaust liner and through the block off plate aiming it at a different direction and level from the exhaust. The dealer will probably tell you not to bother with the OAK, DO NOT listen to him!

My 2 cents.....

 

[mrjohneel]

I exhaust my p35i to the top but Harman recommends that the MAXIMUM vertical pipe is 30 feet so you have to take that into consideration. My fireplace is located in the middle of the house so I could not have my OAK through an outside wall. Because I ran my exhaust to the top, I could place my OAK up the same flue but terminate it well below the end of the exhaust. Good luck. It's a good stove.