Harman p61A flutter flame/woofing issue

[Micmann]

Long time reader, first time poster.

I have owned and operated a Harman P61 for over 12 years. I have been dealing with the "flutter flame/ woofing" issue for about the past five years and have been in a long time search for an answer and have found none. (please note i understand the woofing of wood stoves is different from the woofing of pellet stoves, some forums point to wood stove woofing) The posts I find have people posting with the problem, but then trail off with no real solution. Has anyone ever specifically had and resolved this issue? I have read of various possible solutions, but nothing that has been a reason with a fix.

What perplexes me is that for about the first seven years it was not an issue and then i started to notice it. Something changed. Every year I dive into the stove for an ultra cleaning and looking for reasons for the flutter to no avail. I have replaced door gaskets, hopper gaskets, exhaust gaskets etc,. I have a fresh air intake that i have played with - removing, partially restricting etc,. I have also played with the exhaust (based on a forum suggestion that there is a natural draft conflicting with the mechanical fan draft) - nothing. I know cleaning is huge in keeping these stoves running properly and I get down and dirty with my cleanings and make it shine - ports, intakes,burn pot, ESP sensor, all of it. I have burned all types of pellets over the years, hard wood, soft wood, blends, the best and unfortunately some crap. Still nothing to resolve the issue. Only thing left is to completely remove the augur, feed unit and burn pot. Not sure what this would accomplish except for a couple fiberglass gaskets, but it may come to that.

After years of studying this issue with my stove here is what i have in a condensed form. If you could blink your eyes 10 times a second or shine a 10hz strobe light on the flame that is what the flame looks like in flutter. However it's not 100% of the time and sometimes it's much worse than others. I've narrowed down the flutter to certain auger positions. When i crack the hopper or the front door just a hair while the flame is fluttering the door will suck in and then release, suck in and then release in rapid succession - woofing. Some have got a noise from the stove during this succession with everything closed that can be very loud, I fortunately do not have any thing pronounced. When the augur turns the flame goes steady and may stay steady or return to a flutter depending on where the augur stops. If it stays steady, the door and hopper cover experiment does not happen, there is no rapid suction and release. Since it is not constant, but on only a certain augur positions that lead me to the sliding feed door (which over the years i have also removed, inspected, cleaned when necessary etc). It seems to be when the slide door is open i get the fluttering. When it is fully closed i don't. Which in itself is odd because the slide door does not have a seal, air can still pass by even closed. I have thought this means the hopper has a leak. I have replaced the gasket several times and even taped and sealed the hole hopper door and seams closed to inspect for leaks. I have checked all factory silicone seals. I starved the stove of fresh air to see if i could find a leak that would allow air - nothing. Even if there was a leak I would think it would be a constant air flow not a almost perfect flutter. If the flame is fluttering and i open the hopper fully the fluttering goes away, but then the flame is incorrect because the burn pot is also getting air from the augur chamber.

I have attached a link to a youtube video showing what i have. It stars in real time and finishes in slow motion so you can see the flutter up and down. This is with the pellet feed door open. At the end of the video the feed door closes and you can see the flame return to a solid flame. It's hard to see in the real time, be can easily be seen in the slow motion.

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In all my readings it seems Harman knows about this issue and many others have it, which leads me to believe there is a common issue that happens over time with these stoves aging and is not particular to my stove. it has also happened to other models of Harman. Question is what is it? I read Harman has stated this issue will not harm the stove. It may not harm it, but i feel it is impacting the efficiency and the cleanliness of the burn. It would only make sense since the burn is being starved of air several times a second. I also have read Harman has altered the newer stoves with some sort of draft port into the hopper and/or augur possibly to rectify this issue along with back burn/hopper smoke which I feel is related to the fluttering/woofing problem as i have had this as well at times

This issue may trail off as new stoves are purchased, but personally I purchased the "tank" of Harman stoves to last a good long time. I would love to get this resolved.

Any insights are appreciated. I will keep working on anything I can think of. If there is a real solution to this widespread issue i would love to hear it and maybe forward it on to others with the same issue and complete a thread with some effective solutions.

Thanks for the help.
Mic

 

[rayttt]

what about the little hanging air intake cover...needing oil or something..it may be flapping or something.

 

[Micmann]

what about the little hanging air intake cover...needing oil or something..it may be flapping or something.

rayttt - thanks for the suggestion. I make sure that is free every year and in good working order though. Also it would have to move extremely fast to get that speed of a flutter.

 

[SmokeEater]

I see that you have made changes in the air inlet and exhaust. Still one thought that comes to mind is the natural resonance that may be set up in the exhaust vent air column. This could be in the form of what is known as a standing wave and can be reduced and/or eliminated by changing the length of the exhaust vent. An easier method, if this is indeed caused by wave phenomena, then changing the length of the air inlet column. The standing wave may be set up by the combustion fan's rpm's and the number of blades on the fan itself. This is unknown but a possibility. If you could change the fan's rotational speed, that may disrupt the natural resonance set up in the length of your air column. Who knows, this may have some promise in solving your mystery.

 

[Micmann]

I see that you have made changes in the air inlet and exhaust. Still one thought that comes to mind is the natural resonance that may be set up in the exhaust vent air column. This could be in the form of what is known as a standing wave and can be reduced and/or eliminated by changing the length of the exhaust vent. An easier method, if this is indeed caused by wave phenomena, then changing the length of the air inlet column. The standing wave may be set up by the combustion fan's rpm's and the number of blades on the fan itself. This is unknown but a possibility. If you could change the fan's rotational speed, that may disrupt the natural resonance set up in the length of your air column. Who knows, this may have some promise in solving your mystery.

SmokeEater - That's a good thought and is a reason i have tried playing in various forms with the air intake and exhaust. I have tried increasing and decreasing the voltage POT in attempt to change the air flow. I can increase and decrease the fan speed slightly but it does not seem to have an effect. One thing i did find when looking around is a double bladed exhaust fan mostly used in higher elevation installations. I've been thinking of giving it a try, but didn't know if i would be burning too hot moving that much air.

Your theory may have a connection in that something may be changing the pressure in the stove when the feed door opens. Kind of like when you open the back window(s) in a car while driving and you get that intense pressure collapse and release, it sounds like a helicopter and feels like slamming on your head and eardrums. Something is creating the rinse and fall in pressure and maybe it is in the vents. I'll keep trying.

Thanks

 

[SmokeEater]

SmokeEater - That's a good thought and is a reason i have tried playing in various forms with the air intake and exhaust. I have tried increasing and decreasing the voltage POT in attempt to change the air flow. I can increase and decrease the fan speed slightly but it does not seem to have an effect. One thing i did fi..................................... Something is creating the rinse and fall in pressure and maybe it is in the vents. I'll keep trying.

Thanks

Micmann, good luck on that. I'll be interested in your solution.

 

[Bioburner]

We had a lengthy discussion on this last week. A lot of talk of V1 rocket, Lennox pulse furnace and other.

 

[Delta-T]

when this occurs can you feel the same resonance on the hopper lid if you just rest your hand on the lid? Have you ever removed the auger from the auger tube?

 

[ScotL]

Have you tried disconnecting your OAK to see if the problem goes away? That looks just like my PB105 when I had too small and too long of an OAK attached.

 

[Micmann]

when this occurs can you feel the same resonance on the hopper lid if you just rest your hand on the lid? Have you ever removed the auger from the auger tube?

Good question. I want to say yes as i think i have checked this before, but can't say for certainty. It's been almost 70 the past couple days so the stove is shut down. Temps supposed to drop and when i fire it back up I'll check this. I'm pretty certain it does slightly.

No, i have never removed the augur.

 

[Micmann]

Have you tried disconnecting your OAK to see if the problem goes away? That looks just like my PB105 when I had too small and too long of an OAK attached.

Yes I have removed the outside air and I have done everything i can think of to it. I have run the stove without it, with it, partially restricted, 1/2" off the stove inlet port so it could pull house and outside air. Doesn't seem to change. I am not using the factory OAK. I made my own out of 3" PVC to allow good air flow. The fact i still get flutter no matter what i do the to outside air leads me to think it's something else.

Thanks for the suggestions! - Keep'm coming!

 

[turbosporsche]

You have a small leak somewhere . Just picture a bad head gasket on your cars engine. It's proboly a bad or cracked weld somewhere . As the stove heats up the gap grows causing the flutter

 

[Bioburner]

Its a known Harman stove issue. I can replicate it on demand by feeding the stove a lot of fuel. The stove design apperantly the right mix of chambers, fuel air mix and venting.

 

[Micmann]

You have a small leak somewhere . Just picture a bad head gasket on your cars engine. It's proboly a bad or cracked weld somewhere . As the stove heats up the gap grows causing the flutter

Thanks, I have thought this as well. That's why i have starved the stove for air to see if i can hear anything or watch the flame to see it's response. I have even smoke tested areas i can think of to see of i get air movement again nothing. Also if i have a leak wouldn't it be a constant flutter and not just on certain feed door positions? The last second of the slow motion video shows a good solid clean flame and that is right when the feed door closed.

 

[Micmann]

Its a known Harman stove issue. I can replicate it on demand by feeding the stove a lot of fuel. The stove design apperantly the right mix of chambers, fuel air mix and venting.

Over the years that's usually where a thread ends unfortunately, that "it's a known issue". There was an extensive thread here https://www.hearth.com/talk/threads...ng-their-burnpot-heres-the-information.81220/

It listed some with issues, what they tried, including Harman issuing PJPellet a newly designed burn pot. In the end it PJPellet didn't like the new burn pot - although it did stop his flutter - and was going to put his old one back on. Then it just trailed off with no solution. Perhaps there is no real solution, but I wanted to start this discussion again in case there has been more developments. Since the new prototype burn pot stopped the flutter there must be something causing it and can stop it. Does anyone know if Harman has a new burn pot on the market? Not a prototype.

Bioburner - You can replicate it, when you do, does the flutter happen all the time or only at certain augur positions?

 

[Bioburner]

It will last for minutes. So the auger would be operational. Usually pretty well buried as needs a fair amount of fuel burning. If its a pot issue, why the problem on the PC45 with a completely different burn tray assembly?

 

[Micmann]

It will last for minutes. So the auger would be operational. Usually pretty well buried as needs a fair amount of fuel burning. If its a pot issue, why the problem on the PC45 with a completely different burn tray assembly?

Good question.

 

[turbosporsche]

So I've been looking at my stove . Burned about 20 bags of hamers so far and while looking at the flame I also had that flutter. As soon as I began to loosen the door or hopper lid it stopped and the flame became more intense. I'm thinking it has something to do with intake blower . Because at the beginning of the season I completly cleaned her and there was def no flutter

 

[turbosporsche]

So I tool off the flame guide cleaned it scrapped all around where it mounts too . Put it back together and presto. No flutter. Not sure if it's luck or what but I'm happy

 

[Micmann]

This morning I came down to the stove after it running last night to this. Some of the worst flutter and something i haven't had for a while, smoke in the hopper. I must adjust my thesis. This is early season for me so the stove has been running only a total of about 5 days. My statement about it happening only when the feeder door opens needs to be adjusted. It was that way the past few running days, however this morning it was constant no matter what the feeder door position. The flutter on this occasion was happening constant and not just when the feeder door was open.

Still hunting for answers.

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[P38X2]

I gotta say, I'd shut her down til you figure out why there's smoke in there!

 

[Delta-T]

pull out the auger, I bet you gots material building up on it. could be "gummy stove" (cue scary movie music). also cue beginning of 6 million dollar man...we can fix it, make it better..blah blah, ect.

 

[Micmann]

After 12 years me and this stove got closer than we ever have. I saw all it's parts. I'll report back to what i did.

 

[Bioburner]

Didn't someone say that Harman changed the intake to three inch? May not be to make it easier to to hookup the OAK.

 

[P38X2]

Didn't someone say that Harman changed the intake to three inch? May not be to make it easier to to hookup the OAK.

My 2 month old P68 still has the 2 3/8 or 2 1/2...or whatever they've always used.