Harman XXV creosote buildup

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lbdavis

New Member
Dec 5, 2021
3
Maine
I have an ~ 8 year old Harman XXV with a top vent (vents vertically about 15' straight up through roof) that is building creosote and I don't understand why.

The top vent adapter (that comes out the back and bends around the top of the stove) gets filled with ash so I clean it. Which I did again the past off season.

Years past - I could tell if it needed a mid-season cleaning because I would start to get a creosote buildup.

This year - only a month into burning, we started to get creosote buildup. I thought this was odd as I usually often make it a whole year with out having to clean the top vent adapter. I ignored it for a week and we had a chimney fire last week at 2am.

I cleaned adapter and entire chimney (which was pretty clean), put it all back together and guess what: I'm getting creosote buildup again.

The exhaust fan which I replaced in 2018 is pulling very well (strong suction in fire box). No apparent air leaks around door or around adapter.

I do burn cheap hardwood pellets from Tractor Supply. Harman suggests softwood, but I've been burning hardwood for years... Could this be bad pellets? Or is there something else that I'm missing?

I guess I should stop running the stove until I can get it to burn clean.

EDIT: adding that holes in burn pot are clear. I run in stove mode. Feed rate set around 3.5. Never run it wide open (maybe I should).
 
Last edited:

Washed-Up

Minister of Fire
Nov 5, 2011
987
Kananaskis,Alberta, Canada
Could you post see t a photo of your setup? And yes running it on stove temp at4 and 4 on your dials will help, I do that to my stove weekly
 

lbdavis

New Member
Dec 5, 2021
3
Maine
PXL_20211205_172827643.jpg


Sure! Here's the top vent adapter. The rectangular box running up the back starts with a 90, then has two 45s at the top of the stove. This is the piece that on occasion chokes down flue and causes creosote. But now I'm building creosote with that thing clear.

Is 4 and 4 full for you? My "stove temp" goes to 7 and feed rate goes to 6. Should I do 7/6, or are you suggesting 4/4? Also - how long do you do this for? :30?
 
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Washed-Up

Minister of Fire
Nov 5, 2011
987
Kananaskis,Alberta, Canada
Yeah 4 feed and 4 on stove temp should do it, I’ve never run my P61 on max settings, in the photo, the stove tem should be all the way down to the right

759E99DF-9B97-4E1F-A86F-1D02B55FC59D.jpeg
 

lbdavis

New Member
Dec 5, 2021
3
Maine
Cool. My knobs are same, but in different places on my XXV. I'll do some 4/4 burns once a week going forward.

Do you think that will fix the creosote buildup that's happening right now?
 

Washed-Up

Minister of Fire
Nov 5, 2011
987
Kananaskis,Alberta, Canada
It would be best to clean/brush it out, as long as it’s not too thick it should just heat up and turn to a brown dust
 

Washed-Up

Minister of Fire
Nov 5, 2011
987
Kananaskis,Alberta, Canada
On that note, make sure that it’s not a gooey mess of creosote or you could cause a chimney fire. Here’s a thread that may help.
 
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Oregun

Burning Hunk
Jan 12, 2017
143
Oregon
I have an XXV with the same top vent about the same number of years old. I burn softwood pellets. (Bear Mountain or Golden Fire)
There is zero creosote in our pipes, just loose powder ash.
Our stove does not have outside air intake.
 

rickwai

Minister of Fire
Nov 1, 2011
1,313
ohio
I would try a few bags of a different pellet to rule the fuel out. Also check the back side and be sure the air inlet flapper is not sticking closed. If it sticks it will cause this same issue.
 
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