PF 100 not heating well.... fix

[archie79]

I don't talk much on the forums. I do cruise them a lot when i have problems. I have been having the same ongoing problem with my stove since the end of last years heating season, to a few hours ago, and thought i might share.[
Ok, my furnace was working, but it wasn't heating well, and was going through way more pellets then it ever has before. I replaced the esp, i replaced the (insanely expensive) circuit board. I checked all the gaskets, and doors, I tried adjusting the exhaust fan to a lower setting. I even switched my fan limit switch to a known good switch just to be thorough. Sometimes on cold nights it wouldnt heat over 66 degrees.....The problem is that my exhaust blower is blowing to fast. there is to much airflow across the fire box, and it causes a pressure switch to not let the feeder turn. As the firebox changed temps it changed the suction in the firebox and wold cause the feeder to work sometimes, and not sometimes.

I finally figured that out, and a few days ago i was thinking about the air intake on the unit, and came to the conclusion that the smaller hose might create enough restriction in airflow to slow down the exhaust fan, thus fixing the problem, so i tested my theroy, and it seemed to help, but still not work exactly right. So i put aluminum tape over the air intake opening till the system seemed to work correctly (in my case it almost complety covered the air intake). That worked well for a few days so today i cut a cap out of metal that fit snugly over the air intake. Then i cut out almost half of the cap so it left half of the air intake hole open... Then i cut another circle the same size of the cap and cut a hole about half the size in it. Then i bolted both together so i could adjust the air intake as needed. The pf100 seems to be working better then it did when it was new.

There is a very easy way to see if this is your problem. Turn the breaker at the bottom of your machine off, then turn your feed rate to 6. Then makre sure your thermastat is calling for heat (atleast 4 degrees higher than the temp in your house or more). Turn the breaker back on and give it a few seconds. Then just put your hand over the air intake, and if your feeder starts turning, then that is your problem. note... it should only take a few seconds for your feeder to begin turning, and keept turning.

If anyone wants pics of what i did to fix mine, ill will send them some or post them here. I might be persuaded to make a few to send out, (for free) as long as i have the extra metal and the time to make them.

Anyways this particular problem has taken me a long time to figure out so i thought i would share it with anyone else with the same un-informative piece of junk owners manual, and absolutly no customer support from harman. And in my area there isn't a qualified service tech for 100's of miles. So to those of you who are considering one for the main heating source in your house, I would cation you to do your homework and make sure you have someone qualified is near. Even if you are pretty handy, there is always something that can happen that could take awhile to figure out, esp with there being no official information about how this system is supposed to operate. Thats just my 2 cents..

 

[Mt Bob]

If it ran ok before I think your modification may cause problems in the future,possibly dangerous.I hope one of the harmon repair guys checks in and helps out.

 

[wil lanfear]

Per Harman installation manual for the PF 100. IMHO, it is not possible for the combustion blower to draw excessive air from the firebox causing the draft pressure switch (vac switch) to open which results in the auger not feeding pellets. When you restrict the air entering the combustion area you are not only reducing the amount of air, actually you are increasing the velocity of this air.


FEEDER DOES NOT FEED
1. No pellets in hopper.
2. Firebox draft may be too low for low draft pressure switch
in feeder circuit to operate.
Check for closed doors,
loose or missing gasket on doors or hopper lid, or a faulty
pressure switch.
3. Feed motor will not run until ESP senses 165°F. Maybe
you did not put enough pellets in the burn pot before
lighting the fire manually.
4. Something is restricting flow in the hopper or causing the
slide plate to stick.
5. Feed motor has failed.

LOW HEAT OUTPUT
1. Feed rate too low
2. Draft too low because of gasket leak.
3. Poor quality or damp pellets
4. Combination of 1 and 2.

 

[archie79]

Thanks for the concern guys. There is a small flap in the air inlet. If you take your finger and push the flap open to much the machine will not work correctly, if you open it all the way the machine will not work at all. The flap is directly connected to the feeder assembly and is one of the 2 ways the firebox can get air from the outside. (the other being the igniter pump). IF i adjust to make the exhaust blower turn faster, you can see the flap opens more, makeing the feeder not work at all rather than just intermittently. Also if you restrict the flow of air on either side of the exhaust blower there is no way to increase the air in the fire box. In my understanding The esp senses the call for heat and regulates the feeder. One of the way it does this is by changing the amount of air flow in the fire box by changing the RPM's of the exhaust blower. (making it faster or slower) The flap on the air intake tells the circuit board how much air is going into the firebox, thus how hot the flames are. If That flap is open to much then the circuit board is thinking there is already a large enough flame for the heat demand, and wont allow the feeder to run, causeing the flame to be to small for heating demands

So yes there is a way for the fan to run to fast. Perhaps I have a bad ESP and its why my fan is putting to much airflow into the firebox? It is actually one of the few things that i haven't replaced. But for now my homemade fix would be tricking the incorrect esp to run correctly. I think I am going to make a youtube video and post the link here. Ill even order a new esp to test my theory (providing they don't cost as much as the POS circuit board (or ESP control board, as it is called in the schematics of the manual.

 

[wil lanfear]

I don't talk much on the forums. I do cruise them a lot when i have problems. I have been having the same ongoing problem with my stove since the end of last years heating season, to a few hours ago, and thought i might share.[
Ok, my furnace was working, but it wasn't heating well, and was going through way more pellets then it ever has before. I replaced the esp, i replaced the (insanely expensive) circuit board. I checked all the gaskets, and doors, I tried adjusting the exhaust fan to a lower setting. I even switched my fan limit switch to a known good switch just to be thorough. Sometimes on cold nights it wouldnt heat over 66 degrees.....The problem is that my exhaust blower is blowing to fast. there is to much airflow across the fire box, and it causes a pressure switch to not let the feeder turn. As the firebox changed temps it changed the suction in the firebox and wold cause the feeder to work sometimes, and not sometimes.

The "exhaust blower" (combustion blower) closes the contacts on the low pressure switch which then power the auger, the igniter, and the air pump for the igniter. If the combustion blower doesn't run or leaks in any gaskets, the low pressure switch (this switch has N.O .contacts) will not close to power the auger motor, quite the opposite of your way of thinking.

 

[archie79]

there are no contacts on the exhaust blower either... It all goes back into the circuit board, which does the regulation for most parts in the machine. The pressure switch is either off or on, and only regulates the hopper gaskets. There is a breather hole cut into the bottom of the fire door that the lower pressure switch would regaurd as a "hole" and completly shut the system down if everything worked like you say it does. The pressure switch is either opened or closed so it wont make your machine act intermittently.

You can very easily test your pressure switch by disconecting the muffler in your hopper, and see the machine instantly stop working all together. Actually the only thing that does run if pressure switch isn't working is the exhaust fan. (If you disconnect the muffler the vaccum line will fall, and you will need someone to help you put it back) This test clearly shows the pressure switchs purpose, which has very little to do with the firebox, or the exhaust fan. Its purpose is on or off.

When i get time to make the video I will show you what im talking about. Wil, you have a boiler, perhaps its set up differently then th pf100?? I don't know, the only harman products ive had any experience with are pellet stoves, Ive never even seen a pellet boiler. I can only speak about what I knoow..

The dealer i bought my stove from sent it too me with the muffler in the hopper disconnected to the suction line on the low pressure switch. It took me a day to figure out how to make my brand new pellet stove run. (Be very leary of PB Farms in VA, I had less than a good experience with them). Good luck to all, and I will try to make the video tonight.

 

[archie79]

P.S. there is a butterly valve in air inlet. the exhaust blower blows faster or slower and changes the position on the butterfly valve. The fire in the firebox also creates suction on this valve making it open more. This is how the furnace governs the fire from becomming to large. If the fire gets to big the valve will open more, and the circuit board will turn off the auger till the fire dies down a bit , (the exaust blower will slow down as well due to it being wired into the circuit board) So the butterfly valve in the air inlet is a very important piece.

Again you can test this theory by turning up the thermastat and makeing sure it is calling for heat, then push the butterfly valve in (making it open all the way) and watch your machine almost instantly change the rate of the auger pushing pellets into the firebox.

 

[archie79]

P.S.S. the pressure switch im reffering to in the statment highlighted by Wil is written into the programing on the circuit board and really isn't a pressure switch at all., (sorry Wi,l i should have clarified that in that post) There is only 1 mechanical pressure switch on the machine and its function is to make sure the hopper lid is closed and sealed.

 

[wil lanfear]

P.S.S. the pressure switch im reffering to in the statment highlighted by Wil is written into the programing on the circuit board and really isn't a pressure switch at all., (sorry Wi,l i should have clarified that in that post) There is only 1 mechanical pressure switch on the machine and its function is to make sure the hopper lid is closed and sealed.

Please look at the wiring diagram for the PF 100 on page #36 of the owners manual. This low pressure switch as Harman refers this to has 2 wires going to the contacts within which should close when the combustion blower runs. When these contacts close the auger motor, igniter and the igniter air supply is powered.

 

[archie79]

Ok, I looked and what do i see... i see that the white wire goes into the main junction box, where it gets its power, and the red wire goes into the circuit board!! So I think you probably need to check the prescription on your glasses.

Everything that I have said in this thread I have backed up with simple test to prove my idea. All you can do is tell me im wrong, but you offer no reason as to why Im wrong. So no offense, but if you don't understand the system, or cant back up what you are saying with facts or test that prove your statements you probably shouldn't post. People come here with real problems and they just want help to try to heat their homes, if someone keeps giving them incorrect information on how the system runs, then the concequences could be very bad.

We are all here to learn and help, and i appreciate the information I get from people on here, and i really like the site. Im just saying that maybe we should use the site to learn, before we try to help, cause if we try to help, and we dont' really know, bad things could happen. That being said there are some I hope i have helped someone who might have this same issue.

 

[wil lanfear]

Ok, I looked and what do i see... i see that the white wire goes into the main junction box, where it gets its power, and the red wire goes into the circuit board!! So I think you probably need to check the prescription on your glasses.

Everything that I have said in this thread I have backed up with simple test to prove my idea. All you can do is tell me im wrong, but you offer no reason as to why Im wrong. So no offense, but if you don't understand the system, or cant back up what you are saying with facts or test that prove your statements you probably shouldn't post. People come here with real problems and they just want help to try to heat their homes, if someone keeps giving them incorrect information on how the system runs, then the concequences could be very bad.

We are all here to learn and help, and i appreciate the information I get from people on here, and i really like the site. Im just saying that maybe we should use the site to learn, before we try to help, cause if we try to help, and we dont' really know, bad things could happen. That being said there are some I hope i have helped someone who might have this same issue.

WHOA, WAIT A MINUTE, all I'm trying to do is to explain to you the sequence of things that happen prior to the ignition of your furnace which is supported by the Harman wiring diagram. The white wire that you mention actually comes from the white 11 pin plug connected to the controller. It then, in the main juction box, is connected to another white wire that goes to the high limit N.C. switch, if it's closed like it should be, it now becomes a sky blue wire that connects to one side of the N.O. low pressure switch. When the combustion blower is powered, the low pressure switch is suppose to close, which will power the auger, igniter, and the igniter pump. As you can see (maybe not) that I don't need my script changed for my glasses, instead you should learn how to follow a wiring diagram such as this one, know the function of each component, prior to telling me or anyone else what to do. So..., the theory of restricting air flow, so more pellets will be fed in by the auger for more heat doesn't hold water, if you want more heat, larger fire in the burnpot, this is accomplished by adjusting the feed rate to a higher number.

EDIT: Forgot to mention, rotate the wiring diagram so it's easier to read.