Need help with PF100

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Amy in NH

New Member
Jan 21, 2012
8
Northern NH
This is our second year running the PF100 with oil backup. It ran great last year, but we've noticed it hasn't kept up on the coldest nights this winter. Aside from that it's been running fine. We only burn Okanagan.

My husband tops off the hopper each morning before he goes to work. He was puzzled this evening to see the low fuel light flashing in the hallway so he went down to check it out. For some unknown reason, the furnace dumped the whole hopper-full of pellets mostly unburned into the ash pan. He put in more pellets and restarted the furnace, but the auger won't kick on. It doesn't matter what setting it is on. Husband checked out the air intake, slide, and emptied the hopper to check the muffler, but they all checked out okay. He cleaned out the complete exhaust system in the fall before starting it up (after going through 10 tons last winter) and we've only burned 4-5 tons so far this winter, so he doesn't think it's the exhaust. He also replaced the ESP in the fall.

Is it the auger motor? And if so what would have caused it to dump a hopper-full of pellets?
 
I would check the low pressure switch... connected in line on the feed auger. page 36 in the manual. Shouldn't be an expensive part.

Let us know how you make out.
 
I don't have an answer yet for why the auger emptied all the pellets in the hopper into the ash pan so let me address the auger not running at startup. When the furnace is powered on, the combustion motor needs to start which will close the contacts on the low pressure switch, the auger will be powered, igniter will be powered. If the combustion blower runs and the auger and igniter are not powered, either the combustion motor needs to be removed and cleaned or one of the gaskets leak preventing the low pressure switch from closing. If the auger is being powered and doesn't run, remove the auger to determine if you have a jam which is stopping the auger or the auger motor needs to be replaced. When the ESP was replaced, what was the color wire of the original, the color of the replacement? I ask because dip switch #5 setting depends on which wire color of the ESP. The quanity of heat produced by the furnace is directly controlled by the feed rate, meaning that if the feed rate is set to the lower numbers not as much heat is produced at high demand. The feed rate must be adjusted when in high demand for heat so no unburned pellets are being pushed into the ashpan, this will give the maximum heat that the furnace can produce.
 

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Update: Husband called the Harmon dealer who installed the furnace and explained what I had originally posted. They were pretty stumped about the dumping and advised him to clean out the exhaust pipe and check the tube between the pressure switch and the muffler by pulling off the muffler end and sucking it until the relay clicked on. Husband cleaned the exhaust pipe and replaced the gasket on the hopper. It still wouldnThen he sucked the plastic tube over the pressure switch until it clicked. Amazingly it worked, however only while he had his finger placed over the end of the tube. He quickly popped the tube back onto the muffler attachment and now it is working normally and doesn't appear to be dumping.

The wires on the old & new ESP were both red, so no problem there.
 
About the furnace not keeping up on the -20 nights:

We had turned up the feed rate incrementally until it was at its highest setting and it still has not kept up on those super cold nights. I've resorted to shutting it down and using the oil backup on those nights, but I wonder if the level of ash in the ash pan somehow affects the amount of heat we are getting? Does anyone have any insight about that?
 
The level of ash should not affect the heat output. As long as the ashes aren't blocking exhaust air path.
 
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The feed rate setting is a "set it and forget it" adjustment if the same brand of pellets are used. I've already mentioned how to adjust this in order to get the maximum heat from the furnace. That being said, the harman pf100 is rated at 112000 BTU's, according to the Harman website, heats 2500-6500 sq. ft. How many sq. ft. are you heating? With the cold spell that we have had, how many bags of pellets per day are you burning?

http://www.harmanstoves.com/Products/PF100-Pellet-Furnace.aspx
 
What is the temp you have the fan come on? Sounds to me like that may be a little low. Also, how is the fines collection area? You keeping that clean?
 
We are heating just over 2400 sq ft. I figured out the # of BTUs we would need based on our oil consumption before we purchased the PF100 to make sure it would be sufficient. When it is very cold we burn through nearly a hopper full per 24-hour period. We have a 3-speed distribution blower set on medium, with the control box set from 70-140. I had it tweaked a bit higher last during last winter's heating season, but when we had our very cold snap in December it couldn't get hot enough to even kick on because the basement was so cold.

Our home is ~100 years old, so the insulation is spotty in some areas, which we are working to rectify. Husband replaced the back sill last summer including replacing an old crumbling brick sill footer with a poured concrete wall between the stone foundation and the sill. I thought that might be the limiting factor, so we put up 2" rigid foam on the concrete and fiberglass in the sill plate.
 
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Seems a bit low for the fan controller. Should be on about 120 for a low and 155 for a high. That 75 for a low isn't doing anything for you.
 
Ejectr said:
Seems a bit low for the fan controller. Should be on about 120 for a low and 155 for a high. That 75 for a low isn't doing anything for you.
Click to expand...

A 35-degree span isn't very wide. My fan blower would just keep cycling on and off instead of delivering the heat. And I'd be losing all the heat it has built up between my thermometer setting and 120. I figured the factory setting was a 60 degree span, so I would stick with that, and it seemed to work well last year when I had the whole span bumped up. I also thought that if the house was down around 65 (brr), which it was when it wasn't keeping up, even if the furnace is blowing 70 it would still be adding heat. Perhaps I should rethink this?
 
Amy in NH said:
A 35-degree span isn't very wide. My fan blower would just keep cycling on and off instead of delivering the heat. And I'd be losing all the heat it has built up between my thermometer setting and 120. I figured the factory setting was a 60 degree span, so I would stick with that, and it seemed to work well last year when I had the whole span bumped up. I also thought that if the house was down around 65 (brr), which it was when it wasn't keeping up, even if the furnace is blowing 70 it would still be adding heat. Perhaps I should rethink this?
Click to expand...
I'd definitely rethink that. The stove is having a heck of a time staying on in this bad cold we're having. I looked at mine and I'm set at 120 for a low and 150 for a high. I have no trouble keeping the house at 70 when it gets cold. Built in 1986 and there are plenty of areas that suffer from little to no insulation...but I'm working on it. Stove would easily hit the high 70's if I adjusted it to do so. maybe change your pellet to one that gives a higher btu, like Okanagan. I use those exclusively through the whole winter.
 
70 is too low. at the very least you want the fan to shut off/turn on somewhere nearer to the temps the ESP is looking for to know its running correctly...mid 90s. We never set them below 100 for the off, and generally leave the factory set on point of 150ish. Works pretty well for several dozen people I know with the unit. The blower wont cycle on/off that much with a 35 deg span...as the ESP temp drops along with the fan sensor temp drop, the unit will ramp up until the thermostat is satisfied. The only thing that would cause short cycleing is if the unit is unable to increase pellet consumption (obstruction/low feed rate setting/longish pellets).
 
Do you have a oil furnace in parallel with your PF100? If you do, does your ductwork have isolation dampers installed in them?

I had a fan control switch go bad in the fan control/hi limit box and had to replace the box in my PF100. You might try sliding the cover off yours and watching it operate and see if the distribution blower is switching correctly when the switch roller rolls on and off the cam. If the distribution blower is not being switched on correctly you may be losing heat out the vent pipe instead of into your house.
.

Fancontlswbox_zps3c7ff37c.jpg
 
exoilburner said:
Do you have a oil furnace in parallel with your PF100? If you do, does your ductwork have isolation dampers installed in them?

I had a fan control switch go bad in the fan control/hi limit box and had to replace the box in my PF100. You might try sliding the cover off yours and watching it operate and see if the distribution blower is switching correctly when the switch roller rolls on and off the cam. If the distribution blower is not being switched on correctly you may be losing heat out the vent pipe instead of into your house.
.

Fancontlswbox_zps3c7ff37c.jpg
Click to expand...

Thank you. I do have the cover off because I was wondering if that was a possibility. At the beginning of the heating season it seemed like it wasn't switching on properly, but now it seems to be working okay. I think I just had the "on" setting up too high and air temperature in the plenum was not getting high enough for it to turn on because it was dissipating into the cold room.

Yes, the PF100 is in parallel with the oil furnace, and there is a mechanical damper in the plenum.
 
Amy in NH said:
Thank you. I do have the cover off because I was wondering if that was a possibility. At the beginning of the heating season it seemed like it wasn't switching on properly, but now it seems to be working okay. I think I just had the "on" setting up too high and air temperature in the plenum was not getting high enough for it to turn on because it was dissipating into the cold room.

Yes, the PF100 is in parallel with the oil furnace, and there is a mechanical damper in the plenum.
Click to expand...

These micro-switches in the fan control are known for being intermittent when they fail. If seems inconsistent or fails one time replace the whole box. I got my new fan control/hi limit box on amazon.com it was much cheaper than thru the Harman dealer and was exactly the same. Get the mfr. & model number off the box and check Amazon's price if you need a new one.
 
Amy in NH said:
Thank you. I do have the cover off because I was wondering if that was a possibility. At the beginning of the heating season it seemed like it wasn't switching on properly, but now it seems to be working okay. I think I just had the "on" setting up too high and air temperature in the plenum was not getting high enough for it to turn on because it was dissipating into the cold room.
Click to expand...

Is your fan control/hi limit box located in the correct location in the plenum. Eleven inches above the top of the PF100? Not sure what effect it has but they do specify 11 inches.

How cold is the room? The cabinet & pellet vent pipe of the PF100 puts out a lot of heat. The cabinet of mine heats my whole basement. Is your room closed in from the outside air?

How often to you use your shaker chains to clean the heat exchanger and scoop the fly ash out from under the heat exchanger behind the lower baffle plate?

FanHilimitcontrol.jpg
 
Yes, the control box is in the correct place.

We shake the chains at least a couples of times per week, and clean out everything except the exhaust pipe every ton.

The room is an open basement. It is closed to the outside, but still chilly - probably around 55F. When it was super cold out (-20s) it was probably colder than that, especially before we got the insulation put up on the new back foundation wall.
 
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Your not going to believe this but after looking at my fan controller to tell you the settings, it won't work right. Turns the fan on OK, but doesn't shut it off. Once the minimum temp set on it is reached, it keeps running and running. Even after it's reached its shut off temp it keeps running. If I hit the box with a screw driver, it shuts off.

I've sent Harman an email for a new one. Got 7 months more to go on the warrantee.
 
Did you accidentally bump the switch at the top from auto to manual? That happened to my husband this fall and it took me a while to figure out what he had done when the distribution blower wouldn't shut off.
 
No.... I wish it was. The temp reaches the bottom and it won't shut off unless I hit it with the screw driver.

I did notice that if I go to manual it starts and if I then go back to auto, it remains running unless I hit it with the screw driver and it stops.
 
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Ejectr said:
No.... I wish it was. The temp reaches the bottom and it won't shut off unless I hit it with the screw driver.

I did notice that if I go to manual it starts and if I then go back to auto, it remains running unless I hit it with the screw driver and it stops.
Click to expand...

I believe it because that is exactly what mine was doing when I caught it failing with the box cover off.
 
Amy in NH said:
Yes, the control box is in the correct place.
We shake the chains at least a couples of times per week, and clean out everything except the exhaust pipe every ton.
The room is an open basement. It is closed to the outside, but still chilly - probably around 55F. When it was super cold out (-20s) it was probably colder than that, especially before we got the insulation put up on the new back foundation wall.
Click to expand...
How is the air flow out of the heat registers in your living area. Can you feel good warm air flow out of all of them? If not check the cold air return filter on the PF100 and see if it is dirty or installed with the air flow arrow in the wrong direction. Maybe your the distribution blower is not moving enough air thru the hot & cold air plenums.
If there is a way to check the isolation damper in your plenum check it to be sure it is closing off the air flow to the oil furnace but not the PF100. If it is open to both the PF100 and the oil furnace, a portion of the hot air from the PF100 may be bypassing your living space and circulating around the oil furnace and the PF100.
 
Ended up buying a brand new controller from eBay for $58. Took 2 days. The dealer wanted...are you ready for this...$189 plus $19.95 shipping! Told him that stove was under warrantee and it would probably be free. Said it would take 2 weeks,

Fixed the problem and I'm all done with Harman. The next stove/furnace will NOT be from Harman.
 
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I am having an issue where the distribution blower won't stay on. Will run for a minute than shut off....New circuit board installed two weeks ago to fix an ignitor issue (always) on. Appreciate any thoughts and/or questions.
 
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