Suggestions for wood furnace

[jpgeis08]

I just built a new ranch home in 2021 and had a masonry chimney installed for my wood furnace. Chimney is located internally in home and is 27 ft from thimble to outlet at the top and is lined with 8x12 clay liner. I just purchased a new Drolet Heat Commander, still waiting for it to arrive. I tried hooking up my old wood furnace (energy king 480) from the old house while waiting for the new one to show up and get a draft reading on the chimney. It seems like this thing is going to draft waay to much, especially for the new Heat Commander since you can't choke down the air on the 2020 ones. I get readings of 0.03 before lighting, once warmed up and burning it reads 0.15, and i can choke down with key damper to about 0.06-0.08.

My questions:
-Can i use key damper on the new one? -Manufacturer specifically states not to
-Should i use the barometric damper? Much debate on creosote buildup with this route
-I'm fearful the chimney liner that was installed is too big. Will installing a 6" liner reduce the draft? Most of the time I think of bigger chimney having low draft concerns...that is definitely not the case with mine. I hate to install a liner in a brand new chimney, but am willing if this is the best option and will help moderate the draft.
-Are there ways to cut air back on the new ones to keep them from "running away"

 

[kennyp2339]

Short end answer although the manufacture states no damper, thats because the furnace was tested at a specific draft and anything less then that draft will put the certification in jeopardy of polluting more. Use your head, most of these tests are at .05wc ft while running on high, the closer you can get to getting to manufactured testing spec the better off you are... you may need (2) key dampers.
I'd shy away from a baro, it cools the chimney gasses to much and could lead to messy build up much faster then regular build up.

 

[brenndatomu]

masonry chimney installed for my wood furnace. Chimney is located internally in home and is 27 ft from thimble to outlet at the top and is lined with 8x12 clay liner.

Oops...class A stainless chimney pipe would have been better...and you are WAAAY over sized...Heat Commander (and all modern wood furnaces call for a 6" flue (28 sq in) you have 96 sq in, almost 4X.

It seems like this thing is going to draft waay to much, especially for the new Heat Commander since you can't choke down the air on the 2020 ones. I get readings of 0.03 before lighting, once warmed up and burning it reads 0.15, and i can choke down with key damper to about 0.06-0.08.

You will find that it overdrafts when the intake damper is open, and then the draft will completly fall on its face when the furnace gets up to temp and goes into its clean burn mode (not alot of waste heat going up the flue to keep it warm and drafting) It will also tend to allow creosote buildup because you will not be able to keep it warm enough, especially clear to the top.

Can i use key damper on the new one? -Manufacturer specifically states not to
-Should i use the barometric damper? Much debate on creosote buildup with this route
-I'm fearful the chimney liner that was installed is too big. Will installing a 6" liner reduce the draft? Most of the time I think of bigger chimney having low draft concerns...that is definitely not the case with mine. I hate to install a liner in a brand new chimney, but am willing if this is the best option and will help moderate the draft.

A hard no to the key damper, yes to the barometric. Well, you could install a KD just as a secondary, or emergency backup damper, but I wouldn't bother.
I have a 27' chimney too...it drafts very well, but I have an insulated SS liner in it too.
And yes, I think you better plan on an insulated SS liner.

 

[jpgeis08]

Oops...class A stainless chimney pipe would have been better...and you are WAAAY over sized...Heat Commander (and all modern wood furnaces call for a 6" flue (28 sq in) you have 96 sq in, almost 4X.

You will find that it overdrafts when the intake damper is open, and then the draft will completly fall on its face when the furnace gets up to temp and goes into its clean burn mode (not alot of waste heat going up the flue to keep it warm and drafting) It will also tend to allow creosote buildup because you will not be able to keep it warm enough, especially clear to the top.

A hard no to the key damper, yes to the barometric. Well, you could install a KD just as a secondary, or emergency backup damper, but I wouldn't bother.
I have a 27' chimney too...it drafts very well, but I have an insulated SS liner in it too.
And yes, I think you better plan on an insulated SS liner.

Inside dimensions are like 6.75" by 11.25". I would have to bust out the clay tiles to put an insulated SS liner in (again...painful to do on a new chimney but just want this thing to run smooth and safely). did you have to do this to install yours?

 

[brenndatomu]

did you have to do this to install yours?

No, mine was 12 x 12"
Yeah that stinks to have to bust out a fairly new flue...you could try snaking in an uninsulated liner, see how that works out...but an insulated liner will always perform better, stay cleaner, and be safer.

 

[woodey]

Inside dimensions are like 6.75" by 11.25".

I have the exact sized clay liner and have no problems with draft, but my chimney is closer to 38ft.

 

[john26]

I have the same size clay tile, 36' total flu. I cheated used 5.5 insulated two Ts and one 90 in the basement drafts well, I do have a manual damper but usually run it open to 3/4 open. Thermocouple on the outside of the liner just below the cap I read between 115 and 150 F when burning. I have checked a few times be removing the cap on the T fluffy light brown build up but not too heavy after 2 months.

 

[jpgeis08]

Do you all like the rigid liner or the flexible liner? My flue is is a straight shot so I think I could do either. I put a flexible liner in my last house that I was renting. It worked well, just seems like maybe it was a bit more difficult to get spotless than a smooth, rigid liner would be.

 

[john26]

I had to use flex my chimney had slight curve in it, it had to curve around the smoke shelf for the fireplace above. My 2 inserts both have flex , I prefer the heavy wall flex its more durable and cleans like rigid but more expensive and heavier to handle. 1 insert has heavy wall the other and the furnace has thin wall.