Harman Absolute 63 whomp, whoop, flicker, or flutter

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New Member
Feb 19, 2024
Upstate NY
Good day all, I just recently completed an install of an Absolute 63 manufactured in late 2023. I've ironed out the some venting issues and have been hunting down flame flutter.

Essentially when the stove is running 40%-60% you can visibly and audibly see/hear the flames flickering with a WHOMP WHOMP sound, kind of like when you're driving along with only 1 of the rear windows open. This behavior stops when any of the doors or hopper lid are opened but will return once closed again, to add the behavior is not consistently all the time, seems to be when the auger is in certain positions.

Venting is appliance adapter, cleanout tee, 6ft, 90 degree, 2ft through the wall, horizontal cap. All piping is 3" and there is an outside air kit installed. Screen in cap has been removed per dealer recommendation. A complete clean was done within the last 2 weeks and this issues is not new.

Anyone have any other ideas of what to try next?
It's obnoxious, it comes and goes. The dealer will be here today to take a look. I did take the combustion fan out and washed it, tried to come up with a way to check balance but failed.

There's another thread here that I've read through but it trails off and the user hasn't been back in 10 years.... so...

Okay, so the very start of the video it's still kind of building a bed of coals but you can start seeing where the flame starts to kind of strobe really fast and that's when the flicker is happening. I don't think it picked up the audio but it's a deep bass sound that is very fast, much quicker then say the intake flap could ever move.

The dealer just left and the tech is kind of stumped on this one, he changed the combustion blower with no change and also checked venting and intake with no change.

I might try to extend the venting to see if that makes any difference.
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Yeah that is odd, I put a magnet on my intake flapper to hold it open, not sure if this would help your situation though. It really looks like inconsistent air flow, possibly not laminar enough through the air intake.
Also maybe inconsistent vacuum as you mentioned that it disappears when the door or hopper lid is opened
do you have an outside air intake?
Yes he does, mentions it in his original post
So with the OAK I've disconnected it and it's still the same deal, if I put my hand over the intake and restrict airflow it stops but will start again as soon as I remove my hand.

Currently trying to separate some compatible 4" pipe to extend the vent a little to see what happens. Not having much luck getting sections apart just yet.
remove the outside air intake and open a frame near your stove to let outside air in because your house may be becoming negative
Just took a 3" to 4" clean-out tee with 4' of pipe and swapped out the jet cap. No change there either. Looks like I'm going to be at the mercy of the dealer gods to swoop in and save the day.
Here's a comprehensive list of things I've already tried;

  • Connect and disconnect OAK
  • Disconnect OAK and open window
  • Fiddle with flap pinned open
  • Tightened doors slightly
  • Removed, inspected and cleaned combustion blower fan
  • Full clean scraped and vacuumed from intake to exhaust
  • Checked and cleaned out fines under igniter
  • Dealer replaced combustion blower
  • Removed jet cap, installed 3"-4" clean-out and added 4' of 4" pipe to check for resonance
I'm to a point where the next step is to launch it into space and hope it performs better as a satellite.
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Sounds like you have solved your problem.

So with the OAK I've disconnected it and it's still the same deal, if I put my hand over the intake and restrict airflow it stops but will start again as soon as I remove my hand.

put something in the intake to cause a slight restriction. The stove should still function properly as it will only pull what air it can use. Now not sure what happens when you ramp the stove up to full burn, but even then it should pull enough air if the fan spins faster.
put something in the intake to cause a slight restriction.
I actually did that too, a baseball was a little too big but a tennis ball fit perfect and stopped it.

I can kludge a solution but for a stove that's only been installed for two months it would be addressed by the manufacturer or the dealer.
Well the good part is you figured out the cause of the issue, so you can point them to it.
I know you shouldn't have to fix it, but helping them with this information should get it fixed faster.
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I think we're using the term "figured out" pretty loosely here. 😆
Dealer was here yesterday and replaced the combustion motor and blower fan which changed nothing.
At this point we have a long list of what it isn't but I'm hopeful to get a resolution soon. I'm starting to wonder if this is the Pellet Stove of Theseus.
My thinking is you still have it figured out, to much air being drawn in, I am uncertain how that is possible but you have proved what is causing the noise. Did you show your stove tech that discovery?
The saga continues! So I went in to scrape the burn pot today and did a quick clean, I noticed ash along the top of the door where it shouldn't be. After taking a look at the door seal and where the ash was I decided it might be a good idea to adjust the door again, so I tightened it up so it's absurdly hard to latch. The flicker continues but the noise is very much reduced. Seems odd that the entire rest of the door appears to seal well.