Installing a liner in fireplace for a pellet insert

[New Hampshire Jim]

My son bought a Harman Accentra Pellet insert for his existing fireplace. We plan to install a 4 In. liner in the chimney. I have a few questions that I hope you can help us with. The chimney is about 20 feet tall and is lined with an 8 by 8 inch liner. and comes down to a 3 In by 18 inch damper. We have the instruction book from Harman and It Is a little confusing as It states we will have to block off the chimney with a metal plate and then add insulation on top of this. as stated above we will use a 4 In flex pipe and I think we can squish this to fit through the 3 in wide damper and then round It out again to fit on the back of the stove. I can see stuffing the Insulation around this to block any cold air from coming In but for the life of me I cannot see how or where the metal plate should be. The top of the chimney will be covered and cemented down. Any advice on how this should be done.Should we just forget the plate and call It Done
Thanks In Advance
Stay Warm My Friends
Jim Hourihan
Plaistow NH

 

[DAKSY]

We stuff the damper area with unfaced fiberglass &
we also stuff around the liner at the top (under the top plate).

 

[BrotherBart]

How to here:

https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/

 

[Pellet-King]

My top plate where the cap is, Is siliconed sealed to top of flue, my pipe comes down thru the damper to my stove, cause my top flue is sealed I have no cold air or draft down chimney, If there is then It get's heated by the rear of stove and pipe

 

[New Hampshire Jim]

Thanks all your answers will help and are appreciated
Jim

 

[Nicholas440]

I made a template out of a sheet of cardboard and fit it into my damper opening, then I traced it onto an aluminum sheet 3/32 inch thick, and cut it fit the opening. I then cut the hole in the aluminum plate which the flex pipe would fit though. I took 2 small brass handles and attached them to the aluminum plate which allowed me to just push it up in place easily, and it fit tight as a glove. I then used rtv silicone caulk and sealed the edges all the way around it. My damper opening was slightly larger than 3 inches, so I didnt have to squeeze the vent to fit it in. The top of my chimney has a stainless steel plate which is cut and formed with edges bent downward, this is also silicone caulked and pressed in place on top.

Overall it works great, no cold drafts come down, no water, and Im pleased. Originally my installer had only put a 7 foot flex pipe in the chimney, just a stub and put a rain cap at the top but we found that due to the volume of cold air inside that liner was difficult at times for the comubstion blower to adequately push up and out, and I often had a puff of smoke come back down on start up. I changed that to a full flex pipe all the way up, 17 feet, and no more puffs of smoke now.


You should be in good shape, just make a block off plate, put some insulation up in there if you wish, we did that to mine, then just run your vent up and out, or down from the top and in.


Good luck

 

[Xena]

Similar to Pellet-Kings set up, our top plate (up at the cap)
is sealed to the top of the flue with concrete anchoring screws
and silicone. No cold draft is able to get down the chimney.
I know some people make a block off plate down in the area
where the chimney damper used to be. With the secure
top plate we installed there was no need for this as this setup
is quite stealth.

 

[vvvv]

Similar to Pellet-Kings set up, our top plate (up at the cap)
is sealed to the top of the flue with concrete anchoring screws
and silicone. No cold draft is able to get down the chimney.
I know some people make a block off plate down in the area
where the chimney damper used to be. With the secure
top plate we installed there was no need for this as this setup
is quite stealth.

without the bottom plate, the warm air can migrate up the chimni where it will find cold brix * condense. I'd stuff bottom with fglass or kwool & cover with al foil to minimize air penetration

 

[richkorn]

My flue area is just packed with insulation around the 4" flex liner. That's all you need.

 

[vvvv]

My flue area is just packed with insulation around the 4" flex liner. That's all you need.

must be magic fiberglass that air cant pass thru? :lol:

 

[richkorn]

My flue area is just packed with insulation around the 4" flex liner. That's all you need.

must be magic fiberglass that air cant pass thru? :lol:

No - just the same insulation used to stop the air from passing through the walls of my house.

 

[Xena]

without the bottom plate, the warm air can migrate
up the chimni where it will find cold brix * condense. I'd stuff bottom with
fglass or kwool & cover with al foil to minimize air penetration.

The chimney is on an inside wall so
no cold bricks in there.

Stove has been set up this way
since Nov. 2005. No problems yet
so I'm not worried.

 

[vvvv]

without the bottom plate, the warm air can migrate
up the chimni where it will find cold brix * condense. I'd stuff bottom with
fglass or kwool & cover with al foil to minimize air penetration.

The chimney is on an inside wall so
no cold bricks in there.

Stove has been set up this way
since Nov. 2005. No problems yet
so I'm not worried.

YA BUT HOW MUCH OF CHIMNI IS EXTERIORIZED or within cold alltc space? so2 be cold