3" to 4" vent pipe

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MtDew

Burning Hunk
Oct 4, 2013
228
Perkasie, PA
What kind of performance increase could I expect to see when I increase my vent pipe from 3" to 4"?

Backstory: I have a Harman P38+ in the basement of my 1500 sq ft Rancher. Originally we were using a cheapo pellet stove from Tractor Supply then we upgraded to a new P38+. When we upgraded I relocated the Harman to a more central basement location so we get more heat up the basement stairwell. Not using my head, I added addition 3" piping to the outside of the house to terminate the venting above the roofline to eliminate the smoke and soot that was collecting on my siding.(this was before I discovered this wonderful site).
I ran the stove 2 seasons this way. No real issues other than stove cleaning and vent cleanings.

Now searching this site and learning about calculating vent length with clean outs and elbows, I realized I should have used 4" vent pipe. My new 4" vent pipe has been ordered so my stove show operate better.

I was just curious if I will see any significant increased performance, cleaner stove, cleaner venting etc.?

My venting is as follows: out the back of the stove1 ft horizontal to a "T" then 5 ft vertical to a 90* elbow to 1 1/2 ft horizontal thru the concrete block wall to the outside "T" then 12 ft vertical to the cap.
 
I would expect that the stove will run hotter and cleaner. Maybe it will add some time between vent cleanings, maybe. There is a lot of bends in that config.
 
My venting is as follows: out the back of the stove1 ft horizontal to a "T" then 5 ft vertical to a 90* elbow to 1 1/2 ft horizontal thru the concrete block wall to the outside "T" then 12 ft vertical to the cap
WOW....your EVL based on those numbers is around 26. Anything over 15 requires 4".
 
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He figured that out after searching for threads on EVL calculations.
How did you calculate 28.25? I get 26.0, not that it matters. It's still waaaay over 15.
 
He figured that out after searching for threads on EVL calculations.
How did you calculate 28.25? I get 26.0, not that it matters. It's still waaaay over 15.
Yep re-calculated and got 26. Must have put a wrong numbers in my evl spreadsheet calculator.
 
I'm hoping the stove runs cleaner and any extra heat she generates will be a bonus. Glad the 4" vent pipe was only a $600 mistake. I guess it could have been worse if I ruined my stove and needed to replace it.
 
I would have tried to check the draw with a manometer. With that much hot vertical pipe it may be surpisingly close to what the stove man. Wants for draw. Just may have a bit more problems with smoke on starting and more cleaning of lower pipes.
 
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