New install- pellet vent into 6" or 8" all fuel SS chimney?

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dpwoods

Member
Jan 1, 2009
10
Northern MN
I've been enjoying a Harman P61 in an old drafty farmhouse for the past 4 winters. My current install is a through the wall vent with 5' of vertical vent inside the heated space. This is northern MN, a 10,000 heating degree day climate.
The existing house is being replaced by a new house that should be enclosed in the next couple of weeks. This will be a two story house on a hydronic slab with some lofty ceilings on the second floor. The pellet stove is making the move, too. I like the ambiance of the open flame and want a second backup source of heat. I installed a 4" pvc outside air source under the slab to the stove space.
That brings me to the chimney question. During a power outage, a small genny or a deep cycle battery/inverter will be able to keep the pellet stove operating for a couple days. I also have a Fisher woodstove available that would be able to keep me going indefinitely in the case of an ice storm like we had in southern MN last year (seems like the weather is getting more interesting). I plan to install either a 6" or 8" stainless steel all-fuel chimney that would have about a 21' rise through the second floor and roof. 99.5% of the time, the P61 vent would be adapted to vent into the bottom of this pipe to vent vertically through the roof. The Harman manual lists a similar option, shown in the attachment below.
What size stainless chimney should I be looking at? The entire flue run will be inside the heated envelope of the house till it passes through the roof. The Fisher has a 6" flue outlet. Due to lots of glass on the south side, a through the wall vent for the pellet stove isn't an option.

Harman chimney vent.jpg
 
Once you see the price of the 8" Class A, you're gonna crap. Go with 6" & everything will be less expensive. Either way, when you attach your P61A to the Class A you're gonna want to run a 4" liner from the pellet vent/ClassA adapter to the top. Easier to clean & less wear & tear on the combustion blower. Also, that diagram is not the way you want to go, IMHO. I'd run the Class a vertically from a ceiling support box & adapt the pellet vent there. That way should you want to pull the Harman & revert to cord wood, you'd need minimal connector pipe.
 
The beauty of a hydronic slab is it will take along time to get all the heat out of it. We enjoy ours even though its in the basement as it tempers out the day and night temps. You going with electric or other for the system? The need to have a power source for heat goes from hours to days. Better get things closed up as the freeze warnings are getting more frequent. Good luck
 
Thanks for the reply, Daksy. I was hoping 6" would be sufficient, that is what the Fisher has for a flue outlet. Stainless pipe is pricey in all sizes, but the price of 8" is an attention getter! My concern was having enough draft for either the Harman or the Fisher. You mention using a liner (I'm assuming 4" for the pellet pipe) will be less wear and tear on the combustion blower. Is that because I will be trying to lift smoke and fly ash so far vertically? Your are correct about the install, the diagram I included in my post is from the Harman manual. A clip from a Supervent document below shows what I am planning for the install.
Chimney.jpg


Bioburner, the boiler will be high efficiency propane. Off peak electric used to be a good deal in this area, but prices have increased to the point where it is no longer competetive. The thought behind a hydronic floor is that I'm not married to one type of heat source. Wood and pellets are other options, depending on where fuel prices go. Up is my guess........... This house has lots of south glass to soak up sunshine during sunny winter days, but it's the long winter nights that exercise our heating systems.
 
My current price for off peak is 6cents, half of regular rate. Our utility just increased the monthly hookup fee to $25 a month, up from $17. With our setup now will not have to pay for the basement infloor or domestic hot H20 in the winter which last season was 8 months:(
 
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