# Problems with Harman PB105



## uredo (Jan 12, 2012)

Been happily using the Harman PB105 for the last year without any problems. Unfortunately, we developed a strange problem that the dealer or Harman hasn't been very helpful in resolving. The unit loads pellets, ignites, and feeds pellets for a few minutes, but then quickly decides to quit loading pellets and the fire eventually burns out despite not reaching max temp. The unit will not start loading pellets again until I reset it and the process starts all over again. There doesn't seem to be any obvious problems with the burnpot, feeder motor, or blower fan. Any ideas? Thanks!


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## AndrewChurchill (Jan 13, 2012)

Does the feed motor light stay lit but it stops feeding?

If that's the case then one of two things is wrong.  Either you have a air leak and the vacuum sensor is shutting the stove off or the vacuum sensor is bad.

I had the same problem and I spent several hours watching the stove trying to get it to light and the problem was the ash pan door wasn't closing tight enough.  I had to hammer the latch until I got a snug fit.  Once I did that the problem went away.


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## uredo (Jan 13, 2012)

Thanks for the quick reply. The feed motor light does not stay lit. However, I'll check for an air leak as well as the vacuum sensor. Again, thanks for the suggestions.

I think it must have been the ash pan door. I emptied it a few days ago and it hasn't worked well since then. Took a hammer to get it shut. Still find it a bit hard to believe that was the source of the problem. Good to know I am not the only one who has spent hours staring at the boiler wondering why it wasn't working right. Thanks again.


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## AndrewChurchill (Jan 13, 2012)

Did checking the ash pan drawer resolve the problem?


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## SmokeEater (Jan 13, 2012)

What and where is the vacuum sensor on the 105?


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## AndrewChurchill (Jan 13, 2012)

Harman is calling it the differential switch now.  It's part number 5 on page 36 in the PB105 User Manual found here 

http://www.hearthnhome.com/downloads/installManuals/PB105.pdf

It's a vacuum switch and it's purpose is to determine if there is enough of a draft being produced by the combustion motor.  



			
				SmokeEater said:
			
		

> What and where is the vacuum sensor on the 105?


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## uredo (Jan 13, 2012)

Unfortunately, it doesn't look the ash pan was the culprit. I banged on the unit after getting the ash pan door closed and it completed a full cycle to max temp. However, it then went back to its old ways and wouldn't feed after initial ignition. The only way I can get it to feed more pellet is to either restart the unit or tap on the feed motor. I also couldn't find the vacuum senor on the wiring diagram. Thanks again!


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## AndrewChurchill (Jan 13, 2012)

Aaron, look at post #5 and click on the link to see where the differential switch is.  It's located just about the air intake under the hopper.  Remove both wires from the sensor and then stick one piece of wire into both contacts.  This will tell the boiler that you have the proper amount of vacuum.

If the boiler starts to run normally you know you have an air leak someplace.  If it doesn't then you have another issue.


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## uredo (Jan 13, 2012)

Thanks Andrew. Found the differential switch and it seems to be the culprit. Not sure why the troubleshooting guide in the manual doesn't mention? The temporary solution for now is a sock over the air intake until the tech can come and fix the real issue. I really appreciate your help as I and the dealer were stumped on it. I sure enjoy the boiler, but do hate being an early adapter sometimes.


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## AndrewChurchill (Jan 13, 2012)

What does the sock do?  I would think if the differential switch is bad you would just keep the wire in the two contacts to trick the boiler into thinking there was a good vacuum.




			
				AaronW said:
			
		

> Thanks Andrew. Found the differential switch and it seems to be the culprit. Not sure why the troubleshooting guide in the manual doesn't mention? The temporary solution for now is a sock over the air intake until the tech can come and fix the real issue. I really appreciate your help as I and the dealer were stumped on it. I sure enjoy the boiler, but do hate being an early adapter sometimes.


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## SmokeEater (Jan 14, 2012)

Andrew Churchill said:
			
		

> Harman is calling it the differential switch now.  It's part number 5 on page 36 in the PB105 User Manual found here
> 
> http://www.hearthnhome.com/downloads/installManuals/PB105.pdf
> 
> ...



Thanks,  I'd never heard of it.  Good reasons for me to belong to this forum   .   .   .learn something new every day.


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## bluepaso906 (Jan 20, 2012)

Unbelievable!  My PB105 just started exhibiting the same symptoms (fire starts OK and then stops feeding until it goes out).  On my owner's book, page 36 is entirely different, and there is no mention anywhere of a vacuum sensor.  However, I put my hand over the intake and the fire immediately came to life.  Since the boiler is in the basement, I didn't have a sock handy, but a roll of duck tape was right there on my bench, so I covered half the hole, and we are cozy once more.  The PB105 has been wonderful - heats the house just fine and domestic hot water as well, even in the summer.  One of the posts asked if the feel light remains lit, but the feed screw does not operate.  That was true of my stove also.  Any clue why the two symptoms?  I thought that the feed light indicated that the pellets were being fed to the fire, but apparently not.

-warm in NW Massachusetts.


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## uredo (Jan 20, 2012)

Unfortunately, my sock trick only lasted for a few hours and then I had to address the real problem. Turns out the problem was even simpler than the vacuum sensor as I just need to clean my flue lines. We had only been using the boiler for 6 months so I didn't expect there would be much buildup in the flue. Turns out there wasn't much buildup as I had expected, but I guess it was enough to cause the fire to burn itself out. Guess I'll add that to the monthly maintenance schedule.


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## bluepaso906 (Jan 20, 2012)

That may in fact by my problem.  I haven't cleaned the exhaust pipe at all for now, the second winter.  When the stove was installed, the flue pipe was siliconed together, so I have been in denial as far as cleaning the pipe because it looks like a hassle.  Years ago, when I heated with wood, all I could get was birch, which burned like tar paper and we had our first (and only ) chimney fire.  After that, I was religious about keeping the chimney clean - had a 4 X 4 with nails sticking out of it on a rope that I pulled up and down. Now, I'm spoiled.  Where in central Maine?  I have in-laws  on the coast just north of Ellsworth.  Oh - we have a super market that sells a ton of hardwood pellets for $197.  It takes a few trips in my Suzuki car, but it is worth it.  The local hardware store ( when they have them ) sells for around $250.  Even at that price, we saved several thousand over heating with oil.  Luckily, when the stove was acting up, I could switch back to the oil furnace by flipping two switches and throwing some valves.


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## AndrewChurchill (Jan 20, 2012)

What did the build up look like.  Was it light fluffy ash or more like creosote?




			
				AaronW said:
			
		

> Unfortunately, my sock trick only lasted for a few hours and then I had to address the real problem. Turns out the problem was even simpler than the vacuum sensor as I just need to clean my flue lines. We had only been using the boiler for 6 months so I didn't expect there would be much buildup in the flue. Turns out there wasn't much buildup as I had expected, but I guess it was enough to cause the fire to burn itself out. Guess I'll add that to the monthly maintenance schedule.


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## uredo (Jan 20, 2012)

Very light fluffy black ash. Made one heck of a mess, but came out very easy. I think our problem is that we don't have a straight flue, but one with multiple bends. I guess I should have expected some build-up. Regardless, I really appreciate all the help and I am sure I'll need to call upon your expertise the next time the boiler doesn't perform up to expectations. 

We're in Winterport and get our pellets from a local company for about $210/ton. We're just excited to be heating our house with a renewable and locally manufactured product. Before purchasing the unit, I read a ton of horror stories about it and Harman's lack of customer service. Fortunately, we haven't had a single problem yet.


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## dingees (Jan 23, 2012)

the vacuum switch is there for several reasons and one being that it will shut the auger off if #1 there is a lack of draft if the doors are left open or the hopper lid is not closed properly  #2 if there is not enough vacuum because the vent is restricted from too many elbows and pipe, or the venting is getting plugged from lack of proper owner maintence and cleaning. #3 if the heat exchanger is getting plugged up. 
one must get very familiar with these systems  as to their cleaning and proper maintence or they will continually have a problem and it will always come up oh I did not know I had to do that or clean that area or where is that part that will not let the  unit work . the first complaint will be against the unit,the manufactuer,the dealer  but not the home owner for his lack of knowlege.


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