Harman PF100 - Not Reaching Max Burn Rate / BTUh

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farmermaker

New Member
Mar 17, 2022
6
Canada
Hi everyone,

We have a Harman PF100 set up to heat a greenhouse but it is not reaching the max burn rate of 13 pounds an hour in automatic or service mode.

When we time the feeding and not feeding with a stopwatch we get roughly 32 seconds of pause between feeding and 33 seconds of feeding on the max feed setting of 6. My understanding is we should be getting 60 seconds of feeding on the max setting.

Do you know what might be tripping up the furnace and preventing it from feeding more pellets to achieve the max burn rate?

Things we've done in the last week to improve the situation:
  1. Worked with our local dealer but they are out of practice - not many furnaces still in use
  2. Replaced the control board
  3. Replaced the slide plate (the old one was split and getting jammed up)
  4. Cleaned the combustion chamber and ESP thoroughly
  5. Bypassed the vacuum switch to rule that out
This is a second-hand unit that we purchased based on our BTU needs. It's rated for 112,000 BTU/h.

Did we miss something? Thanks!
 

gfreek

Minister of Fire
Nov 5, 2010
1,561
WNYS
Just a thought, could the auger motor have been replaced at one time with the wrong RPM motor ?? Parts list shows 4 or 6 rpm depending on age..
 
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Former Farmer

Minister of Fire
Apr 12, 2008
632
NE Wisconsin
Not familiar with the PF100, but have a PB105 boiler.

Maybe the ESP is telling the system that is all the hotter it is suppose to be. DIP switches 7 & 8 set the max ESP temperature.

How many pounds of pellets are you burning in an hour? 112,000 btu is around 14 pounds of pellets per hour. Let the hopper run near empty, then dump in a 40# bag. Come back in 3 hours and see if hopper is just about empty again. This will tell you if your burning the right amount of pellets, not the auger turn times. Turn times can vary with different length and different quality pellets.
 

farmermaker

New Member
Mar 17, 2022
6
Canada
Not familiar with the PF100, but have a PB105 boiler.

Maybe the ESP is telling the system that is all the hotter it is suppose to be. DIP switches 7 & 8 set the max ESP temperature.

How many pounds of pellets are you burning in an hour? 112,000 btu is around 14 pounds of pellets per hour. Let the hopper run near empty, then dump in a 40# bag. Come back in 3 hours and see if hopper is just about empty again. This will tell you if your burning the right amount of pellets, not the auger turn times. Turn times can vary with different length and different quality pellets.
I noticed the Max ESP setting on the dip switch but the Harman guide that comes with the control board says it is only for certain models. The image of the settings for the PF100 dipswitch show this setting being "off" and doesn't say if it can safely be turned "on". Do you think Should I try to run it with the Max ESP setting turned on? Is there a combo to it or just push both pins to "on"?

We are definitely not burning 14 lbs an hour. I ran the unit for 11 hours last night on service mode at the max feed of 6 and about 40 lbs remained in the hopper. It should have been completely empty as the hopper takes a full 3 bags or 120 lbs.

Something funky is going on. I may look to replace the ESP sensor and give it another go.
 

Former Farmer

Minister of Fire
Apr 12, 2008
632
NE Wisconsin
Has the unit ever worked properly or or you just trying to get it to work? I see in your other post that you bought it used but you never say if it has ever worked right.

What is your venting setup? What amount of draft are you seeing? Do you have an outside air kit connected to it? Has the entire unit and venting been totally cleaned? Was the combustion motor ever replaced?

I would recommend not to change the DIP switch settings on the control board unless you know what they are going to change.
 

farmermaker

New Member
Mar 17, 2022
6
Canada
Has the unit ever worked properly or or you just trying to get it to work? I see in your other post that you bought it used but you never say if it has ever worked right.

What is your venting setup? What amount of draft are you seeing? Do you have an outside air kit connected to it? Has the entire unit and venting been totally cleaned? Was the combustion motor ever replaced?

I would recommend not to change the DIP switch settings on the control board unless you know what they are going to change.
Your guidance is much appreciated.

We were told it was working well when we bought it. And it does work just not optimally (i.e. doesn't reach max burn rate). We can tell that some parts have been replaced over time. Your suggestion of ensuring the right parts are installed is spot on. I will double-check the combustion fan tomorrow. We also just replaced the ESP probe but that hasn't helped us reach the max burn rate.

Our venting setup is basic: from the furnace, we use 4" pipe - it goes up 12" and straight out horizontally over 4 or 5 feet. Would a rise help to create more draft and make the flame burn hotter? What does a good draft look like? Flame behaviour?

There is no outside air kit installed - it's just pulling air from our drafty greenhouse.
 
Last edited:

Former Farmer

Minister of Fire
Apr 12, 2008
632
NE Wisconsin
I can't answer what the flame should look like in the PF100. The PB105 will have a nice blue color at the bottom of the flame and will shoot out of the burn pot, at about the same angle as the bottom of the burnpot. Definitely nothing lazy about the flame.

Is it possible that you have a problem with wind affecting the termination cap on your venting? Not allowing the combustion blower to move as much air as is needed?