Harman XXV - smoke in hopper?

[Pellet_Pete]

Got home just now and went to check hopper levels - when I opened the hopper llid, a puff of smoke came up at me. It was almost empty. Did I just suck up some smoke through the auger from the negative pressure of opening the hopper (which admittedly I do with gusto)? Never had it happen before, but I did adjust my draft down this year and it's the first time I've run that low before refilling. Anything to worry about?

 

[F4jock]

Got home just now and went to check hopper levels - when I opened the hopper llid, a puff of smoke came up at me. It was almost empty. Did I just suck up some smoke through the auger from the negative pressure of opening the hopper (which admittedly I do with gusto)? Never had it happen before, but I did adjust my draft down this year and it's the first time I've run that low before refilling. Anything to worry about?

I'd worry some about the possibility of a hopper fire but I'm sure that there are others here with more experience than my five years with Harman who'll comment. I've sucked my hopper down pretty dry and never had that happen. If I saw that I'put my draft back where it was and monitor things closely.

 

[Doug Doty]

I am tuning in for this thread, seems concerning since hopper fires seem to be the biggest concern

 

[Pellet_Pete]

Well, I retried a forum search using "hopper smoke" and searching titles only. I found this thread helpful:
https://www.hearth.com/talk/threads/p68-smoke-from-hopper.126621/
I know I need to change my ash pan & door gaskets. I noticed the ash pan gasket was especially matted when I cleaned it out yesterday.

Lots of other threads pop up discussing the "dreaded gummy stove" problem, but I just cleaned the stove yesterday and it was spic & span except for ash in the burn pot cleanout.

 

[Delta-T]

the negative pressure in the hopper is generally greater than the combustion system. If these's excess restriction on the intake, like a kink or foreign object in the OAK, that negative pressure environment increases and when there are shifts in the pressure, smoke can get pulled back into the hopper. I'd take a look at the intake assembly from the flapper on the intake flange all the way to the end of the OAK. The only way to check for "gummy stove" is to inspect the slide plate, but it's very uncommon on units less than a few years old. Usually see it on some of the older feeder body styles.

 

[MCPO]

Got home just now and went to check hopper levels - when I opened the hopper llid, a puff of smoke came up at me. It was almost empty. Did I just suck up some smoke through the auger from the negative pressure of opening the hopper (which admittedly I do with gusto)? Never had it happen before, but I did adjust my draft down this year and it's the first time I've run that low before refilling. Anything to worry about?

Every couple years I remove the auger on my Harman and check the slide plate and the auger tube for evidence of the gummy burn back .
Two years ago I replaced the auger when the tip burned off / disintegrated. At that time I cleaned the auger tube which had some gummy stuff in the tube and was starting to build up on the slide plate.
Haven`t noticed any since but over the years it can happen.

 

[Pellet_Pete]

Well, I replaced both door & ash pan gaskets 2 weeks ago, but that didn't change the smoke-in-hopper problem. Still only notice it when pellets are low, which is consistent with what folks described in old posts I've read. Stove is otherwise burning like a champ. I guess I'll have to figure out how to get at the slide plate to assess "gummy stove" potential - this isn't a new stove, was bought by previous homeowner in March 2007. Getting at the auger assembly doesn't look like it's going to be terribly fun . Better save it for one of those warm winter days .

 

[Pellet_Pete]

One last thought...I didn't try replacing hopper door gasket. Should that be put to the dollar bill test too?

 

[SmokeyTheBear]

One last thought...I didn't try replacing hopper door gasket. Should that be put to the dollar bill test too?

Yes.

 

[SidecarFlip]

What exactly is a 'gummy stove?

 

[MSmith66]

Does your stove have a cross over tube? It would be located in the back on the feeder housing and is a large Poly tube, white in color. If not, i recommend you have one installed. I would contact the dealer if you do not have one in stalled. I have installed them on XXV's and Accentra's. The gaskets should be fine unless they are chewed up.

 

[Pellet_Pete]

Does your stove have a cross over tube? It would be located in the back on the feeder housing and is a large Poly tube, white in color. If not, i recommend you have one installed. I would contact the dealer if you do not have one in stalled. I have installed them on XXV's and Accentra's. The gaskets should be fine unless they are chewed up.

As far as I could tell at last cleaning, no. I did find a very thorough old post about installing the crossover tube to solve smoke-in-hopper (https://www.hearth.com/talk/threads/harman-accentra-gummy-stove-syndrome-solution.45548). It's looking like that's what needs to be done. Hopefully its early enough that the buildup isn't a serious issue.

What exactly is a 'gummy stove?

Apparently it's an air-feedback issue in Harmans of a certain vintage that sometimes causes smoke to leak up the auger, ultimately depositing a gummy buildup of smoke residues in the auger and the underside of the slide plate. Lots of posts on this from 4-5 years ago - Harman has since remedied the issue.

 

[MarkF48]

Is your house pretty tight and was there any other appliance in the house that may have caused a negative pressure within the house such as a running clothes dyer or bathroom fan that exhausts to the outside?

 

[Pellet_Pete]

Is your house pretty tight and was there any other appliance in the house that may have caused a negative pressure within the house such as a running clothes dyer or bathroom fan that exhausts to the outside?

Not that tight & negative on dryer or bathroom fan running. I have an OAK installed, so not sure those would affect the stove in that way regardless?

Coming full circle to my first clouded thoughts, the big changes this year were adding OAK & lowering draft setting...Guess I could recheck my draft now that the gaskets are new & see if that changes things. Would be a heck of a lot easier to turn that little draft dial than to take my feeder apart!

Thanks for the advice, suggestions, and for just letting me "think out loud" here. If I get a resolution, it will be posted.