Harman P68 Never Shutting Down

[derek456]

Hello,

I have a Harman P68 pellet stove that is the main source of heat in my house. In December, the stove began to constantly burn pellets until the hopper empties, regardless of the room temperature. We woke up one morning to a 90 degree house! Here is what I know/have tried:
- The stove is being run in room temperature mode.
- After running out of pellets, the stove does not start until the temperature dips below the setting on the control panel.
- After the fire starts, the room temp/stove temp knob can be turned to OFF, and the stove will continue to burn indefinitely (overnight, if I put enough pellets into it).
- I have replaced the control board and the ESP probe that checks the temperature of the output air.
- The "status" error light is not blinking at any point.

I am tempted to replace the room temperature sensor, but since the stove starts correctly, it would seem that this part is working properly.

Any ideas on what the problem could be? I would appreciate any suggestions you may have!

 

[DAKSY]

How does it run on STOVE temp?

 

[derek456]

How does it run on STOVE temp?

I haven't tried it on STOVE temp mode. The user manual said that makes it run indefinitely for a nice viewing flame while not blowing excess heat into the house. That didn't seem like a step in the right direction to me.

 

[DAKSY]

Well, until you figure it out, you can run it that way, set to low & be able to manage your fuel consumption.
Meantime take your room sensor to a hearth shop & see if it works on a floor model...

 

[Harmanizer]

I haven't tried it on STOVE temp mode. The user manual said that makes it run indefinitely for a nice viewing flame while not blowing excess heat into the house. That didn't seem like a step in the right direction to me.

You are incorrect on stove temp.Reread the manual.I use my unit in stove temp almost all the time.How old is the stove?Did you replace with a black wire esp or red wire?Dip settings may be wrong.

 

[derek456]

You are incorrect on stove temp.Reread the manual.I use my unit in stove temp almost all the time.How old is the stove?Did you replace with a black wire esp or red wire?Dip settings may be wrong.

Looks like you're right, I misunderstood it - I will try it in stove temp mode.

I replaced it with a red esp, same as it had before. Dip settings are matched to the control board I replaced.

 

[The Grintch]

Sounds like an ESP issue.

 

[derek456]

Sounds like an ESP issue.

As per the post, it has been replaced already.

 

[Nitro-Fish]

Just because it was replaced doesn't mean it's good; you may have purchased a bad probe. I would run it in stove temp to see how it acts, if it still acts up I would say ESP. The ESP being bad will let the stove act like you are describing. Double check the board settings as well, set to the instructions that came with the board.

 

[The Grintch]

So what was the issue/fix?

 

[derek456]

So what was the issue/fix?

The dip settings were somehow incorrect. The full fix was a new control board and setting the dip switches on it properly

 

[derek456]

Doing the same thing again now, 5 years later. Time for a new control board again I guess.

 

[derek456]

Ok so a new board and new esp didn't fix the issue this time. Talking to a stove shop, they think the stove just needs cleaned...

The thought is there's too much insulating ash coating the inside, keeping too much heat in, causing odd behavior.

Would mean I've bought 2 control boards for nothing, but makes sense since the issue happened about 2.5ton into the year both times. Will update again after I try a thorough mid-season clean out.

 

[Whitenuckler]

Hi. I am a bit late jumping in here, but I thought I'd ask what position the Igniter switch is/was on when operating in Room mode. If the switch is set for off/manual the stove will keep running, but is supposed to throttle down. In auto it is supposed to stop the feed motor and possibly go out. I have noticed that if you don't have enough combustion air the ESP probe won't heat up properly. Maybe try turning the POT up to full to get more speed along with the cleaning. I have run in Stove mode for weeks now and if you set the temp to minimum and the feed to say 1, you should have a nice lower heat. Do you use OAK? I noticed when I hooked my OAK to -15C air the stove acted differently as well. I stopped doing that and now suck combustion air from a vented old oil furnace room.
Found this post: Read toward the end,

M

Thread 'HARMAN NOT SENSING TEMPERATURE'

Dec 29, 2021

I have a Harman ACC52i pellet stove with dial controls on the side for control the temp. The dial is no longer working. It moves and all but does not turn on or off the stove. The manual 'on' dial works fine so I'm assuming its a thermostat or sensor. CAn't find a single thing online about it...any ideas??? I like to do things on my own when I can

• mpoland33
• Replies: 17
• Forum: The Pellet Mill - Pellet and Multifuel Stoves

Also, have you tried running it in Room mode, Auto and warming up the room thermostat by moving it next to the stove and turning the temp setting down? Then watch the feed motor and count how many seconds it stays running. It should stop running.

 

[Washed-Up]

Post in thread 'Leaf Blower Trick'

Feb 28, 2025

https://www.supplyhouse.com/Bluefin-FRC400-300-4-x-3-Rubber-Coupling-Cast-Iron-or-PVC-to-Cast-Iron-or-PVC?utm_source=google_ad&utm_medium=Shopping_Plumbing&utm_campaign=Shopping_X_Plumbing_X_SSC_ClassA&utm_campaignid=21633352515&utm_adgroupid=172230901128&utm_targetid=pla-2348139003970&utm_product_id=FRC400-300&utm_matchtype=&utm_keyword=&utm_adtype=pla&utm_category=Plumbing&gad_source=1&gclid=Cj0KCQiA2oW-BhC2ARIsADSIAWrVU_-7R9eSvnAHp_nPXCKE5obSCDMraHJDvZ1CZeHYx83kj8wY8ksaAigLEALw_wcB

• Ssyko

• 

 

[Whitenuckler]

Post in thread 'Leaf Blower Trick'

Feb 28, 2025

https://www.supplyhouse.com/Bluefin-FRC400-300-4-x-3-Rubber-Coupling-Cast-Iron-or-PVC-to-Cast-Iron-or-PVC?utm_source=google_ad&utm_medium=Shopping_Plumbing&utm_campaign=Shopping_X_Plumbing_X_SSC_ClassA&utm_campaignid=21633352515&utm_adgroupid=172230901128&utm_targetid=pla-2348139003970&utm_product_id=FRC400-300&utm_matchtype=&utm_keyword=&utm_adtype=pla&utm_category=Plumbing&gad_source=1&gclid=Cj0KCQiA2oW-BhC2ARIsADSIAWrVU_-7R9eSvnAHp_nPXCKE5obSCDMraHJDvZ1CZeHYx83kj8wY8ksaAigLEALw_wcB

• Ssyko

• 

Is that to hook up the leaf blower? Good idea

 

[Washed-Up]

Yessir

 

[derek456]

I'm embarrassed. A simple thorough clean fixed my issue, and probably was my issue 5 years ago to. Everything is back to normal after cleaning it well. At least now I know what to do

 

[Whitenuckler]

I'm embarrassed. A simple thorough clean fixed my issue, and probably was my issue 5 years ago to. Everything is back to normal after cleaning it well. At least now I know what to do

Get all those old parts back in, and get some proven spares. I'm glad you got it working, and the members could help. I know that is why I'm here. To help and learn. My dealer is just a regular guy like you and me. He learned how to install stoves and went for WETT. He is not an expert on pellet stoves, and I would not want to have to depend on him.