Harman PF100 5 blink and 6 blink codes

[ex-oil slave]

I have been reading posts regarding this problem for 6 months now. I fired up my PF100 last October and it ran perfectly for the first 2 to 2-1/2 months. By the middle of December, I had run 2 to 3 tons thru it and I started experiencing the dreaded 5 and 6 blink codes intermittently. After trying every "fix" posted in these forums, I think I may have finally found the solution (at least for me) to these problems. At the very least, it's one more area for PF100 owners to check (and maybe other model owners as well) when you start having code problems.

Many posts made reference to "pellets bridging across the hopper feed opening" or pellet feed rates. This is accurate in a sense. The problem was pellet feed related and even hopper/auger related. Sticking my arm down in the pellet pile in the hopper and stirring things up would get the stove going again as others have mentioned. However, the problem (code) would soon return. Putting less than 4 bags (full hopper) did seem to help, and I ran with no more than 3 bags full for close to a month with fewer problems. The key word here is "fewer" problems. I was still getting codes more often than I wold like (like NEVER). Finally, I had enough and decided to really get serious. I was sure the problem was pellet feed related as I had ruled out most other causes such as air supply, exhaust (venting), interlocks, etc.

One evening, I emptied the hopper, pulled the feed motor (surprisingly easy - one bolt and two quick disconnect connectors), and flopped the pusher arm out of the way so that I could remove the slide plate assy. These items are shown in the PF100 manual on page 35. The bolt that releases the feed motor is item #3, the pusher arm that is flopped over to release the slide plate is item #4, and the slide plate is item #2. The feeder cover item #9 has to be off in order to get the slide plate out. Be sure and note the way the slide plate is installed in the mechanism before removing it as it can go back in upside down. Just make sure it goes back in as it is shown in the parts breakdown. I found that the slide plate and the area of the ultralight feeder item #6 where the pellets first feed into the auger were both coated with a mixture of pellet fines and "creosote" (for a lack of a better word). This mixture of pellet dust and tar made a very sticky coating on the slide plate and the hopper "throat" that prevented free movement of the pellets into the auger area. I cleaned the slide plate (top and bottom) and the hopper/auger area where the slide plate slides back in. I used a commercial product that is sold for cleaning soot buildup off of the stove glass as it seemed to dissolve the tar. Just be careful not to spray too much at a time as it will run down into the auger area and dissolve the tar there which may cause an even worse problem when the stove is put back into operation. I soaked a cloth with the glass cleaner solution and wiped as far back into the hopper/auger opening as I could reach to avoid this problem. I also had a metal scraper that I used to loosen/scrape off the heavy buildup. At the end of this heating season, I plan on pulling the auger and giving this area a really good going over. I just didn't have the time that evening to get that far into it. All in all, it took me about 45 minutes to pull the stove apart, clean it well and reassemble. It has now been running for 3 weeks without a code. Before I couldn't go 3 days code free.

To some, this may sound a bit daunting. It really isn't. At the very least, I suggest you empty your hopper and check this area for sticky buildup if you are experiencing 5 and 6 blink codes. If you have a sticky buildup and don't feel comfortable doing the cleaning, consider getting a "handy" friend to help or hire someone. It's worth it!

Feel free to PM me if you want any additional info, or open post so all can benefit from it. I hope this helps someone, somewhere.

 

[Lousyweather]

call your dealer, tell him about the "sticky" slide plate.......its gonna happen again.

 

[exoilburner]

Thanks for passing along your experience.

This is a long term observation so please provide some ongoing updates. If this truly does solve the pellet bridging problem it would be a great find for a lot of people.

I have been trying to figure it out for some time. My thinking is problem may be the symmetrical angles in the hopper that may not have sides that are steep enough. But if your fix works fantastic!

 

[ex-oil slave]

I'm not sure what my dealer could do to prevent this, Lousyweather. I know that smoke will travel back up the auger under certain conditions as I've had smoke in my hopper a few times when I let it run low. It's apparently this smoke and whatever tars and/or oils that are in it that mix with the fines and produce the sticky residue I found. Otherwise, the furnace is doing exactly what it is supposed to do. Yes, I fully expect it to happen again. I'm just adding it to my list of maintenance procedures. I think maybe twice a heating season for me may be sufficient. It will probably not be as often for most users as I go thru 5-6 tons a winter. Am I missing something. I get the impression that you think this is a problem that the dealer could resolve. Please explain your thinking to me. Thanks.

 

[Lousyweather]

Most likely the "tarry residue" is not only depositing itself on the slide plate, but also inside the auger cavity in the feeder mechanism as well. It might be eeasy to change out the slie plate and clean it, but another matter when the whole feeder cavity gets "tarry". Most likely what youre getting is early stages of pyrolysis prior to the pellets getting to the end fo the auger, and the tars evident are depositing themselves on the surfaces therein. When the residue gets heavy enough, it can stop, or greatly hinder, the slide plate from moving, therefore, interrupting the flow of pellets, which would also seem like a "pellet bridge". Your wouldnt be the first unit to do this, although it is somewhat rare. Unless you manage to clean out the feeder body as well, the tar is going to accumulate, causing a complete shutdown that you wont be able to rectify by cleaning the slide plate....Ive seen slide plates so bad, they couldnt be pulled out. Youre pretty lucky in that you seem to be a handy type of person, who takes great care in cleaning (if you pulled the slide plate, you already clean better than about 99% or more of the folks who have pellet stoves). Its possible to rectify the issue as well. Im sure your dealer knows this. The sticky stove syndrome is readily diagnosed by a smell upon entering the home, by a brown-yellow residue on the slide plate and the bottom of the bin.

 

[Delta-T]

there is a mod that can be done to the air intake to direct some of the combustion air directly into the auger tube. this helps to clear fines and whatnot out of the tube but also helps defeat the massive negative pressure in the hopper itself that sort of sucks the heat back into the auger tube. i have seen this mod done and have never seen the "sticky" slide plate occur on a machine that has had this done. your dealer should be aware of the whole thing. let us not also forget that junk pellets and frequent power losses can also contribute to this event. good luck

 

[Lousyweather]

there is a mod that can be done to the air intake to direct some of the combustion air directly into the auger tube. this helps to clear fines and whatnot out of the tube but also helps defeat the massive negative pressure in the hopper itself that sort of sucks the heat back into the auger tube. i have seen this mod done and have never seen the "sticky" slide plate occur on a machine that has had this done. your dealer should be aware of the whole thing. let us not also forget that junk pellets and frequent power losses can also contribute to this event. good luck

absolutely correct, Delta-T. Actually, the negative pressure is created by the combustion fan (which CAN and DOES create negative pressure via the auger tube to the hopper).......dont forget, the firebox here is negative pressure. Another part of this same problem, and this is a theory, is that the auger, in direct contact with the fire, necessarily conducts heat to the pellets prior to the pellets actually reaching the flames, beginning the process of pyrolysis, but in the absence of much oxygen, therefore, creating the "tarry" residue, which mixes with the fines, creating the stuff you saw. As for the mod, again correct. Any of the systems we have modified has seemed to solve the problem, but only time will tell. I must say though, that stoves that were sticky 2 years ago, after being mdified and run for a few months, have been running for 2 years with no more problems. I dont feel comforatble describing the mod, as some folks could damage their unit in doing so, and therefore void the warrantee.

 

[ex-oil slave]

Thanks to all the above posters for the info regarding "sticky stove syndrome". Let me see if I grasped the concepts posted so far... The combustion blower sucks air out of the firebox and pushes it out the vent, therefore creating negative pressure in the firebox and positive pressure in the vent. This negative pressure in the firebox pulls as much air as it can from the hopper creating a static, negative pressure in the hopper as long as the combustion blower is running, the remainder of the negative pressure pulls in air thru the flapper on the firebox door and the combustion air inlet tube where the backdraft damper and low pressure switch is located. At this point, there should be no air flow up the auger to the hopper as the hopper pressure cannot be more negative than the firebox pressure. If there is a power outage causing the combustion blower to stop, the positive vent pressure will "back flow" thru the firebox, up the auger, and into the hopper. Otherwise, there should never be an air flow up the auger while the fire is going since the combustion blower continues to run for some time after pellet feeding stops. The other part of the problem is heat conduction along the auger from the firebox back towards the hopper causing pyrolysis to occur before the pellets reach the burn area. This is where your mod comes into play by allowing a small air flow from the hopper end of the auger towards the firebox to carry these pyrolysis residues towards the firebox as well as keeping the auger cooled to minimize the residue creation.

This leads to the following question - If the firebox is negatively pressured due to the combustion fan pulling air out, why not crack the hopper cover slightly or drill a small hole in the upper part of the hopper to allow a small air flow thru the hopper and into the auger tube and ultimately into the firebox. This would keep any products of pyrolysis moving towards the firebox as well as minimizing the pyrolysis products by keeping the auger cool. Of course, in the event of a power outage, there will be a slight discharge of smoke since the hopper seal is no longer intact. However, the smoke getting into the hopper in the first place was caused by the negative pressure pulling it in thru the auger. If the hopper has another path (outside air) to neutralize this negative pressure other than the auger, firebox, vent route then perhaps it won't pull as much smoke from the firebox up the auger as it does now.

I would be interested in discussing in private the mod you described. I purchased this furnace from a dealer in Minnesota who's is over 100 miles away and on the other side of an international border. Getting a house call is out of the question. I purchased this furnace knowing full well I'd be on my own and I'm comfortable with that. I installed it myself which involved electrical, duct work, venting, etc. Modifying it should not present any problems. I've already got a few options in mind if you can't share. However, I would rather talk to you (Lousyweather and/or Delta-T) as you both seem rather knowledgeable.

One thing I did learn from the posts is that pulling the auger and finishing the cleaning I started is now more imperative than ever. So, thanks for the heads up.

 

[ex-oil slave]

Just one more thought after posting my previous long dissertation. With the slide plate closed as it is most of the time except when cycling to feed pellets, there may not be enough air flow from the hopper side to the auger. Therefore it is probably necessary to cross connect the air inlet (after the back draft damper) across to the feeder assy just below the slide plate to achieve proper flow along the auger to the firebox. I can see where that could require drilling holes in steel and probably tapping them to install fittings to connect a metal line from one point to another.

 

[exoilburner]

This leads to the following question - If the firebox is negatively pressured due to the combustion fan pulling air out, why not crack the hopper cover slightly or drill a small hole in the upper part of the hopper to allow a small air flow thru the hopper and into the auger tube and ultimately into the firebox. This would keep any products of pyrolysis moving towards the firebox as well as minimizing the pyrolysis products by keeping the auger cool. Of course, in the event of a power outage, there will be a slight discharge of smoke since the hopper seal is no longer intact. However, the smoke getting into the hopper in the first place was caused by the negative pressure pulling it in thru the auger. If the hopper has another path (outside air) to neutralize this negative pressure other than the auger, firebox, vent route then perhaps it won't pull as much smoke from the firebox up the auger as it does now.

I'm not an expert but it seems to me that if Harmon made sure the hopper was sealed (cover gasket and seams sealed) there must be a reason.

I have seen a few posts about fires in the hopper that were pretty messy. If the negative air pressure in the hopper was relieved, being so close the intense heat of the burnpot would the fire be more likely to creep up the auger tube and into the hopper? Especially if the power went out and the combustion blower shut off with a blazing burn pot?

 

[Lousyweather]

This leads to the following question - If the firebox is negatively pressured due to the combustion fan pulling air out, why not crack the hopper cover slightly or drill a small hole in the upper part of the hopper to allow a small air flow thru the hopper and into the auger tube and ultimately into the firebox. This would keep any products of pyrolysis moving towards the firebox as well as minimizing the pyrolysis products by keeping the auger cool. Of course, in the event of a power outage, there will be a slight discharge of smoke since the hopper seal is no longer intact. However, the smoke getting into the hopper in the first place was caused by the negative pressure pulling it in thru the auger. If the hopper has another path (outside air) to neutralize this negative pressure other than the auger, firebox, vent route then perhaps it won't pull as much smoke from the firebox up the auger as it does now.

I'm not an expert but it seems to me that if Harmon made sure the hopper was sealed (cover gasket and seams sealed) there must be a reason.

I have seen a few posts about fires in the hopper that were pretty messy. If the negative air pressure in the hopper was relieved, being so close the intense heat of the burnpot would the fire be more likely to creep up the auger tube and into the hopper? Especially if the power went out and the combustion blower shut off with a blazing burn pot?

yep...and in the newest pelelt stove models, the vac switch runs directly to the hopper...leave the lid open, and it wont feed.

 

[ex-oil slave]

[/quote]

I'm not an expert but it seems to me that if Harmon made sure the hopper was sealed (cover gasket and seams sealed) there must be a reason.

I have seen a few posts about fires in the hopper that were pretty messy. If the negative air pressure in the hopper was relieved, being so close the intense heat of the burnpot would the fire be more likely to creep up the auger tube and into the hopper? Especially if the power went out and the combustion blower shut off with a blazing burn pot?[/quote]

It is EXACTLY THIS NEGATIVE PRESSURE that causes smoke to be pulled up the auger tube into the hopper. The pressure gradient as it exists now is highest negative pressure in the firebox and lower negative pressure in the hopper. This in and of itself would cause air flow from the hopper to the firebox until the hopper negative pressure equals the firebox negative pressure (ignoring any losses along the hopper/auger path due to imperfect seals or leaks). Opening the hopper or breaking the seal in any way causes air flow from the now lower negative pressure towards the firebox. This will PREVENT the fire from creeping up the auger to the hopper rather than assist it. This all assumes normal operation i.e., combustion fan running, combustion air inlet normal, venting normal, etc. Now if the power goes out in the present configuration the negative pressure in the firebox is immediately neutralized by the air flow from the positively pressured vent pipe backwards thru the combustion fan into the firebox (nature hates a vacuum - or a low pressure area). Now the firebox has a higher pressure than the hopper which has been negatively charged. The only way for the pressure to equalize (since we DON'T want any air leaks in the hopper) is for air to flow up the auger into the hopper from the firebox. So it seems to me that creating a negative pressure in the hopper is causing exactly what we are trying to avoid. I certainly DON'T want hot gases, smoke, or fire flowing up the auger tube to the hopper where there are 160 lbs of pellets waiting to burn. I just fail to see how relieving the negative pressure in the hopper will contribute to this. It seems that it will do just the opposite. What am I missing?

Anyway, as I indicated in my followup post, I don't think breaking the seal of the hopper is the answer. By introducing combustion air after the slide plate, negative pressure in the hopper and all its attendant problems go away and it is not necessary to break the hopper seal. The combustion blower CANNOT negatively pressure the hopper now because air flow thru the auger tube won't allow it. The air flow carries any gases with it out to the fire and keeps the auger cool at the same time reducing premature pyrolysis. A Win Win solution. Yes? If the power goes out, there will be no pressure gradient pushing hot gases and smoke up the auger towards the hopper. That's not to say that some smoke won't find its way to the hopper since heat rises and the hopper is higher than the burn pot. However, it should be minimal.

 

[exoilburner]

Ex oil slave,
Again I’m no expert. Your points are engineering issues that I’m not qualified or experienced enough to debate from more than an owners perspective, especially where safety is concerned. Although it is tempting. I was a test engineer for Philips Medical Systems. From my experience when an engineering team had designed a piece of equipment from a prototype, and developed and tested it through all of the unforeseen failures, they probably have highly experienced, and qualified, reasons for the final design. Also getting it thru certification by international regulating agencies is no small feat. They also benefit by getting problem feedback from their customers and dealers world wide. I have read some scary owner modifications on the forums and am kind of a skeptic when it comes to changing designs where safety may be degraded.

Your posts are well written and raise some really interesting and thought provoking ideas. Wish Harmon had a presence here. The Harmon dealers that take the time to post the good info have been so helpful. Thanks to them!

 

[ex-oil slave]

Thank you for the kind words Exoilburner,

I understand your concerns and agree that manufacturers try to get it right before releasing a product. However, all you have to do is look at the number of recalls the auto industry puts out each year to see that it is an imperfect process. I was happy using my furnace just the way it came from the factory until I began having problems. I would LOVE to talk to Harman directly or get one of their "factory trained dealers" over for a chat. Unfortunately, neither is an option. I'm left to resolve my issues on my own. I know that I have been having smoke backup into the hopper when the stove is running. A few times I let it run low on pellets (not out but down to 1/2 a bag or so) and when I opened the hopper to add pellets, the hopper was full of smoke even though the combustion blower was running and there should not have been any smoke in the hopper. This is with a completely unmodified, factory designed, 4 month old stove. Obviously something is not right. If smoke can get up the auger then heat (and fire?) can as well. I'm not interested in "pushing the envelope" or "living on the edge". I just want a stove that will heat my house for a reasonable price, safely. I'm committed to using this furnace now for at least the next 5 years to recover my costs. Therefore, I see no alternative but to fix the problem myself. I would appreciate all input from any posters out there that have an opinion or better yet, factory contacts or info. If no-one cares to contribute, then I guess that I'm on my own. If you read Lousyweather's and Delta-T's posts, it seems that the factory has recognized this as enough of a problem to issue a mod on it. I know there are poster's on this site that have knowledge that would be useful to me, whether they will chime in or not remains to be seen.

Anyway, thanks for your input and your interest. Stay warm.

 

[exoilburner]

ex-oil slave,
The Harmon dealer tech was at my place today. I asked him about your issue. He is aware of the modification that Delta-T and Lousyweather mentioned but did not feel comfortable with passing the information along. Suggested the best course of action would be to set up an appointment with your dealer to get the mod done. That way there would be no warranty or safety issues. You have probaly already though about that.

He also mentioned a bearing on the motor end of the auger shaft (not the cam bearing) that is installed with silicone around it to seal it. He said Harmon told them, when removing the auger do not replace the silicone around the bearing, and remove the old silicone around it to allow air to be pulled into the auger tube. Have not seen this myself but just passing the info on. The pic is a PF100 dwg but an old one.