P61 pulsing flame speed bump and pellets ?

[alternativeheat]

So I had this pulsating flame in my P61, even in low burn yesterday though high burn was worse. I could feel the vibration of that pulse when grabbing hold of my OAK tube. Thinking air starvation unhooked the oak from the stoves flange to find 0 change as a result. Yesterday was warm here and the stove shut down so i just shut it off to cool.. Now I have been scraping the burn pot, not to mention I cleaned the stove Sunday. Image my surprise when I scraped the pot last night with the stove shut off and scraped up a carbon chunk and inch wide and as long as the burn pot is wide ( commonly referred to as the Harman Speed Bump). It blocked about 3 rows of air holes in the lower most section of the pot where there are holes, below this point there are no air holes. I had to use a flashlight to see the carbon, the Harmon tool was just riding over it. I took a screw driver and the carbon lifted right out in one long chunk but thin. I believe this built since Sunday burning LG pellets also since Sunday. Anyway, relit the stove and it's running fine ..

Any of you Harman guys getting a bump so quickly ? I know some of you don't scrape for days. Well this was just two days of burning with a quick morning scrape each day. I had visions of blocked venting etc, never dreaming I had several air holes blocked in the burn pot.

 

[Phoenix Hatchling]

The vibration and pulsing is an anomaly native to Harman. Many on the site here have reported it, but a definitive cause has not been identified. A resonant frequency caused by intake air and exhaust air equalization has been hypothesized. As far as the bump goes, it seems to developed more quickly when the stove goes in to long low maintenance burns, as opposed to high heat pumping. I usually give a quick scrape down each day (5-10 seconds)while the stove is running, and then a thorough scraping every 3-4 days. It is very dependant on the pellets used as well, and I find deposits when burning Lacretes are removed very easily, while those formed from Cubex are much more resilient.

 

[mr47930]

I had to practically chisel the carbon build up off the side of the burn pot from 2 bags of O'Malleys pellets. I guess you get what you pay for, and since these 2 tons were free I expected them to be lower quality. I'll continue to burn them though, I have yet to get this "speed bump" just on the sides down by the auger.

 

[alternativeheat]

The vibration and pulsing is an anomaly native to Harman. Many on the site here have reported it, but a definitive cause has not been identified. A resonant frequency caused by intake air and exhaust air equalization has been hypothesized. As far as the bump goes, it seems to developed more quickly when the stove goes in to long low maintenance burns, as opposed to high heat pumping. I usually give a quick scrape down each day (5-10 seconds)while the stove is running, and then a thorough scraping every 3-4 days. It is very dependant on the pellets used as well, and I find deposits when burning Lacretes are removed very easily, while those formed from Cubex are much more resilient.

So Phoenix, have you experienced the pulsing flame ? Do you think it was not from the carbon build up then ? I had it the other day too, when the storm came through it lasted for a period of time. But we had 60 MPH gusts that morning.

mr47930, you eventually will experience the speed bump. Depends on pellets and burn rate.

 

[JDenyer236]

For the speed bump I spray the burn pot with anti-creosote. It doesn't prevent it but it does make it easier to remove and seems to slow it down some.

 

[ttdberg]

I get the pulsating flame from time to time as well. I don't know all of the possible causes of it, but for me it is most pronounced when I'm burning pellets with high MC, so it's just one of several signs (along with slow / difficult starting, poor heat output) that I'm burning pellets of questionable quality.

The speed bump is much more noticeable when I'm burning softwoods than hardwoods. Running the stove on a slow / low burn, especially for extended periods of time definitely exasperates the effect. My burn pot has 5 rows of holes, and I have never had a speed bump large enough to cover any of them, so your situation must have been extreme to say the least. Just curious, what were you burning over what time frame, how many bags, and how long had it been since the last good burn pot cleaning?

 

[alternativeheat]

I get the pulsating flame from time to time as well. I don't know all of the possible causes of it, but for me it is most pronounced when I'm burning pellets with high MC, so it's just one of several signs (along with slow / difficult starting, poor heat output) that I'm burning pellets of questionable quality.

The speed bump is much more noticeable when I'm burning softwoods than hardwoods. Running the stove on a slow / low burn, especially for extended periods of time definitely exasperates the effect. My burn pot has 5 rows of holes, and I have never had a speed bump large enough to cover any of them, so your situation must have been extreme to say the least. Just curious, what were you burning over what time frame, how many bags, and how long had it been since the last good burn pot cleaning?

Thanks TT, this bump was up the pot a bit but keep in mind the p61 pot is also a bit smaller than the p68 pot. LG are indeed softwood and that is what I was burning , I would say about three bags into them. I cleaned the stove Sunday but admit I did not use a flashlight to inspect the burn pot just scraped and vacuumed. Another warm day today so I shut the stove down again for today. In looking, yes there are about five rows of holes and I was incorrect before. The first two rows would have been covered with crud. I only burned overnight and crust is forming in the same location again, just dead center of the first row of holes though. And I gave it a quick scrape when I got up at 3:30 this morning ( don't ask, I don't know way I was up, this retirement stuff was supposed to work the other way around !!). The stove was burning ok though.

Oh, and I had the stove in room temp auto, so it was starting and stopping overnight. It used maybe 10-15 lb of pellets since I lit it up around 5 last night and shut it down while it was in an off cycle around 8 this morning..

 

[Phoenix Hatchling]

So Phoenix, have you experienced the pulsing flame ? Do you think it was not from the carbon build up then ? I had it the other day too, when the storm came through it lasted for a period of time. But we had 60 MPH gusts that morning.

mr47930, you eventually will experience the speed bump. Depends on pellets and burn rate.

No not from the build up. It's the pressure equalization or syncing of air intake and output, or so it's been troubleshooted to on this forum. It seems that the 60 mph winds putting back pressure on the airflow will cause this handily.

 

[alternativeheat]

No not from the build up. It's the pressure equalization or syncing of air intake and output, or so it's been troubleshooted to on this forum. It seems that the 60 mph winds putting back pressure on the airflow will cause this handily.

Hmm, it's pulsing a bit tonight and no wind. But the pellets are dancing in the pot, or some are so it's certainly not lack of air. There actually seems to be some separation between the flame and the pellets. Odd. Maybe it's these pellets. When it's most pronounced you can actually feel the vibration of the pulse if grabbing the OAK tube.

It's now not doing it. It seems to be as the fire cuts back after a full burn. The fire has an almost strobe looking effect when doing this. I never noticed it last year. Some kind of syncopation.