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PB 105 burnpot bubble issue update

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by wil lanfear, Oct 6, 2012.

  1. wil lanfear

    wil lanfear Feeling the Heat

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    Three month update: Last friday while cleaning my boiler I noticed hair-line cracks, no bubble, on the surface of the newly designed burnpot so this burnpot was not the answer to the burnpot issues. Today, I called Harman, asking what the plan was now. The person I talked to confirmed that the engineers at Harman are still working on a solution to the burnpot issue, explaining to me how important it is to keep the holes in the burnpot surface clean, basicly trying to pass the buck to me not keeping the holes clean. I mentioned to him this wasn't the case because I clean the burnpot weekly including the holes. When I asked as to what material the burnpot was made he told me stainless steel, I asked what grade, he didn't know. I did mention to him that to my knowledge, no grade of stainless steel has a heat resistant value high enough to withstand the heat created in the combustion area of these boilers, mentioning maybe to try using alloy 600 for the burning surface of the burnpot. His response was that it might be cost prohibited to do so to which I responded, if the metal alloy that is used for the burning surface of these burnpots doesn't have a heat resistant value higher than the temps created in the combustion area, the burnpots are going to continue to fail.
    SmokeyTheBear and exoilburner like this.

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  2. Former Farmer

    Former Farmer Feeling the Heat

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    Thanks for the update Wil.

    I was hoping that they came up with a solution. I will be replacing my burn pot for the second time this heating season. Still under warranty, but not for much longer.

    Cost prohibited - and replacing 5 burn pots on my unit is making them any money?
  3. iceguy4

    iceguy4 Minister of Fire

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    I have been following you and your problem even before I purchased my boiler. is there anything that is common to your problem? IE same pellets... R U running it hard...what is your boiler (existing before you installed your PB 105) rated at in BTU's...what is your chimney? is it tall making excessive draft?. I have read of others having issues but this HAS to be some what an isolated issue or we would be hearing more about it...IMHO.... I also have my fingers crossed as next year I will be pounding the crap out of my boiler with the addition of another building added to my system...:confused:
  4. wil lanfear

    wil lanfear Feeling the Heat

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    I don't feel that I'm overfiring it, I burn around 8.3 ton of fuel heating 2100 sq. ft., about 2 ton of that for DHW in the off heating season. My chimney is 26 ft high, in fact when the three Harman reps inspected my boiler over 4 months ago now, one of them adjusted the draft so it runs at full speed as long as a fire is in the burnpot so my guess is that this rep thought it is a good thing if my chimney is creating a good draft drawing more air through the burnpot. Check this poll out, I'm not alone with this issue.

    http://www.hearth.com/talk/threads/...pot-hump-and-crack-failure.48014/#post-627683
  5. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    Wil, sorry to hear that you are now getting cracks forming
  6. iceguy4

    iceguy4 Minister of Fire

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    me too will...and I'm starting to worry_g
  7. wil lanfear

    wil lanfear Feeling the Heat

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    I find it hard to believe that a company that employs engineer(s) that haven't been able to resolve this issue yet, as implied per the phone call to Harman yesterday. I do know if these same engineer(s) were working at my place of employment, if they hadn't come up with a solution for an issue after 6 years, they would be looking for a paycheck elsewhere.IMHO, I believe the engineers know what the solution is, the reason Harman has tried to come up with a less costly fix, that this solution, whatever it may be is costly to Harman.

    I now see on the Harman web site that the warranty on the pb105 boiler no longer includes the burnpot weldment. I wonder why!!


    Warranty Exclusions: This warranty does not cover the following: (1) consumable and normal wear items, including,
    without limitation, flame guides, grates, coal bars, afterburner hoods, fire brick, gaskets, paint, glass discoloration, burnpot housing weldments
  8. stephenmoore

    stephenmoore Member

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    I feel your pain on the burn pot , I'm on my second one and I think it too has started to bubble a bit. It would be great if someone at Harman could figure this out. Having said that do any of you 105 ers have a better method for manually lighting the boiler? The method they spec in the manual just doesn't seem to fly. I thought I had it figured out but after my monthly clean last weekend I couldn't seem to get her lit. Any suggestions?
  9. Former Farmer

    Former Farmer Feeling the Heat

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    Put in another burn pot today. Seventh one in 5 years.

    I talked with the dealer and they said that after your warranty is expired, you are all on your own. They also said that Harman told them that you should scrape your burn pot at least once a day if not twice. I told them that in the owners manual that came with the boiler, lists that you need to scrape the burn pot at least once a week, not daily. Harman is blaming the burn pot failures on the accumulation of ash on the burn pot that then only allows air to be pushed through the bottom holes and this is where the bubbles, cracks appear.

    So I get the impression that Harman is saying "Yeah we have a problem with the design of the burn pot, but we really don't care."

    Would a "lemon law" apply here? I don't need to be spending over $200 for a burn pot each year.



    The Magnuson-Moss Act provides another option for any Wisconsin buyer saddled with a lemon appliance. This regulation covers appliances that cost $25 or more, and had undergone multiple unsuccessful attempts at repairs under the manufacturer's warranty. This lemon law entitles consumers to a refund, cash, or replacement
    Complaints

    • Keep records and document everything pertaining to your appliance, including sales receipts, repair orders, and written guarantees. Write down the date, time, and name of everyone you talk to, including customer services representatives. State in your correspondence that you will take the matter to the Wisconsin Department of Agriculture Trade[​IMG] and Consumer Protection and Better Business Bureau.
  10. 343amc

    343amc Feeling the Heat

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    Scrape once or twice a day? That's something I'd expect to hear from US Stove, not Harman.

    I have zero personal experience with Harman stoves but I'd be pretty upset if I paid a premium for a stove and that was the answer I got.

    To Wil and all who are having the problem, best of luck with your issues.
  11. iceguy4

    iceguy4 Minister of Fire

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    well guess I will be fixen my burnpot myself when it fails. I also will badmouth Harman at every turn if they refuse to help me,,,also scrape my burnpot twice a day???you got to be phuque-ing kidding me! I'll be talkin to my dealer over the weekend::-)
  12. iceguy4

    iceguy4 Minister of Fire

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    [QUOTEMy dealer told me that this will be the burnpot used in both new central heating units manufactured from now on][/QUOTE]

    As far as I can see this is NOT true.. My boiler DOB 11/12 doesent have it and I just installed a newer one last week( I did the plumbing) with the same burnpot as mine. I'm gonna clean mine this weekend and inspect and post pictures. the holes stop about 3 of 4 rows sooner (more then likely there are no holes where it has been failing) and there are no holes on the side. Like I said before... I will fix mine myself. although I'm not a welder by trade ...I believe I have the skillset to repair it and if I didn't I would have a welding shop fix it. next problem...where do I get the hi-temp steel?
  13. wil lanfear

    wil lanfear Feeling the Heat

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    As far as I can see this is NOT true.. My boiler DOB 11/12 doesent have it and I just installed a newer one last week( I did the plumbing) with the same burnpot as mine. I'm gonna clean mine this weekend and inspect and post pictures. the holes stop about 3 of 4 rows sooner (more then likely there are no holes where it has been failing) and there are no holes on the side. Like I said before... I will fix mine myself. although I'm not a welder by trade ...I believe I have the skillset to repair it and if I didn't I would have a welding shop fix it. next problem...where do I get the hi-temp steel?[/quote]

    Here are couple places that I would think that you could purchase alloy 600. I'm thinking that it may be best to contact them first to see if they would accept a burnpot, to refab the burnpot using alloy 600 for the burning surface. The failing of these burnpots is between the holes, either cracking or a bubble forming, always where the holes are located.

    http://www.sandmeyersteel.com/A600.html
    http://www.onlinemetals.com/merchant.cfm?id=880&step=2&top_cat=131
  14. Centurion

    Centurion Member

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    Interesting build up in area of bubble formation. This is a pic that I took after vacuuming but before scraping. Typical slag formation on either side of burnpot. If the slag is building up on the sides because it is cooler there maybe those holes next to the sides should be plugged up to force more air thru the center of the BP? The center formation is not a slag but a powdery crust. This BP is about 4 weeks old, no bubble yet with the new ignition system installed but I assume that will occur at some point just like Wil's. Assuming that, I am going to block the first two rows of holes with small screws and nuts just in from either side just to see the results at next weeks cleaning. Before I do that, any comments would be appreciated?

    Burnpot appearance after 1 week.jpg
  15. wil lanfear

    wil lanfear Feeling the Heat

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    Last week I got a call from my dealer telling me he received another burnpot from Harman, they want the burnpot with the cracks returned for inspection. This burnpot appears to be the same as the one that will be sent back, the only difference I can see is the sides of this burnpot are a thicker metal. I did ask if the alloy used for the burning surface was different, my dealer said he didn't know but he is supposed to find out for me.
    iceguy4 likes this.
  16. exoilburner

    exoilburner Feeling the Heat

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    Sounds like they are at least still working on it. Thanks once again for pushing this issue and keeping all of the rest of us informed.
    iceguy4 likes this.
  17. iceguy4

    iceguy4 Minister of Fire

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    I have been remiss in not posting picgtures of my burnpot but I have been rather busy with the bulk hopper(I freckin love it:cool:) but it seems to me it has way less holes ...like only 5 or 6 rows max from edge. the last row has like three on the right side (looking at it) and none closer to augar..mine still looks good after 6 tons.
  18. SmokeEater

    SmokeEater Feeling the Heat

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    My 105 had first fire in late Feb 2012 and almost to the day have burned 11 T of pellets. I have a 6 inch stainless liner in a 29 foot chimney in a windy area. In order to control the draft a little better I installed a 6" damper just on the 6" side of the 4" x 6" reducer. The damper was adjusted once at the start of the season and using a magnahelic with a range of 0 to 1" on pos or neg draft, set the fan voltage (white plastic screw) to the Harman recommended draft of 0.85" wc. Knock on wood, the burn pot has no deformation of the holes, no cracks nor bubbles. The stack temperature seven feet from the combustion fan never goes over 180* F. Ash has always been gray to white. I have since burned another ton to date. Heating the basement and two floors of a 3000 sq. foot cape in northern NY. Even the coldest days of -20*F and 30 mph winds didn't require more than 4 bags. Cleaning took place on weekends after burning as much as 28 bags. Scraping a little slag off the lower portion of the burn pot and a quick vacuum made the 105 ready for another week of heating. The basement was at 80* while the first floor was set at 74*. I don't know if the high draft chimney plays a part in this or not.
    Centurion and iceguy4 like this.
  19. iceguy4

    iceguy4 Minister of Fire

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    Will ,
    who is your dealer?
  20. mrheene

    mrheene New Member

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    I burn about 8 tons of a variety of hardwood pellets per season in my 2008 PB-105. I'm on my third burn pot and 3 ignitors (coincidental number of *3* failures, they were not coupled). My burn pot failures are first manifested by the classic bump formation at hole rows 4 thru 6 (from the open end), followed by a crack forming perpendicular to the hole rows as the season proceeds. The steel in the bump region is badly spalled probably due to heat of the burning gases which are given off during chemical decomposition of the wood. Interestingly wood does not burn, it gives off gas which if heated sufficiently will ignite. The gas released from the heated pellets is comprised mostly of hydrogen sourced from cellulose (C6H10O5) and lignins (C9H10O2, C10H12O3, C11H14O4) in the wood, mostly in the form of sinapyl alcohol and coniferyl alcohol. If you carefully observe the ignition process through the window in the fire box door of the PB-105, you will eventually see smoke pouring out of the burn pot (I have the finned ignitor), it helps to use a flashlight to observe the smoke. The smoke is the visual indicator that gasses are being liberated from the pellet fuel. At a sufficiently hot temperature ignition happens all at once (sometimes you can hear an audible *pop*) and the burn pot lights and flames start shooting upwards towards the internal boiler cross pipes. The pellets in back of the flame front from the auger output to the first row of holes are unburned. If you empty a lit burn pot you can observe these pellets that are effectively cued up to be exposed to the heat and air required to release their combustion gases. Also, if you have a entire burn pot full of pellets during the ignition process you can appreciate that what will happen is that a great deal more gas will be liberated due to the increased quantity of pellets and when ignition occurs, there is significant overpressure created by the sudden increase in temperature from the recently combusted expanding gas P=nRT/V which causes the spring loaded backfire plate to compress the retention springs to their minimum height, allowing the overpressure gas to safely be discharged along with an unhealthy gulp of smoke, into the boiler room. Backfires can be prevented by setting the dip switches 1,2, and 3 to minimize the pellets in the burn pot during ignition, as mentioned in several previous threads. Minimizing the pellets during ignition is key to long term reliable operation especially as the outside temperature begins warming up and the cycle times extend, often using up all the fuel in the burn pot which required a re-ignition cycle to commence as often as several times per day.

    Steel is definitely not fire proof, it degrades significantly in the presence of high heat. I found a graph of structural steel (I couldn't find one for boiler steel which probably has a higher temperature performance) strength vs temperature which clearly shows how rapid steel strength drops off as a function of temperature, note temperature is in °C. By 600 °C steel only has 1/2 its strength and loses most of its strength altogether at about 1200 °C.
    In the presence of high air flow (air has 21% oxygen which reacts with CO liberated during combustion of HxCyOz molecules creating CO2), wood pellets can achieve burn temperatures of 1000 to 1200 °C and it shouldn't be a surprise why the steel in the burn pot degrades. Steel has a thermal coefficient of expansion of about 13 ppm/°C. If the outer edges of the burn pot are at a much colder temperature, say 300 °C, the difference of 700 °C x 13 ppm/°C causes an expansion of approximately 0.05 inches across the area of the burn pot where the burning gases are most intense and since the temperature of the steel is at or above the plasticity limit for the steel, the steel expands and as we know if has a propensity to expand upwards into the flame because that side of the steel is warmer than the steel in the plenum side. As the steel rises into the burning gases, it gets even hotter and since the steel has exceeded the plasticity temperature it expands and permanently deforms until finally the expansion has reached equilibrium. At this point the steel is subjected to repeated flame fronts that beat against the surface of the steel like a blow torch (remember those things?) causing the surface to spall and exhibit macroscopic degradation until finally a crack is formed and I suspect in the limit a hole will form as the material at the bump site is completely compromised and falls away. Normal high temperature steel will likely always exhibit this failure mode so it will take a very high temperature specialty steel to accommodate the high temperatures that exist in the burn pot. I would like to take in situ measurements of side walls and the bump burn pot temperature to confirm these calculations and will write back with that information as well as anything I can find on very high temperature steel. It is plausible that the good folks at Harmon don't yet fully understand the root cause of this failure and therefore are shooting somewhat in the dark for a solution which is why Harmon has not simply *fixed* the burn pot problem.

    Upon further reflection I now believe the temperature gradient from the inside of the burn pot floor to the inside surface facing the plenum is worse than originally thought. The combustion air is near 20 °C and is percolating up through the holes in the burn pot floor creating a temperature gradient closer to 975 °C, thereby making the thermal expansion worse than the 700 °C temperature difference I used in earlier calculations to determine the expansion of the burn pot floor. The high thermal gradient is undesirable and can be mitigated by pre heating the combustion air. Just thinking about it overnight, it may be possible to construct the burn pot with a double floor between the fire bearing surface and the plenum. The space between the two floors creates a volume where the combustion air can pick up some heat before entering the burn pot surface. Clever routing/baffling of the incoming air between the double burn pot floor, may allow it enough time to pick up adequate heat to lessen the thermal gradient. I don't know for sure if this would work, but by constructing a SolidWorks model and with a few hours to tinker around, it should be possible to figure out exactly what is happening and then try different configurations to lessen the thermal gradient effects. I measured 923 °C at the surface of the burn pot using a K type thermocouple probe. I posted this to the Ectoteck thread before I realized it wasn't a PB 105 thread.
  21. Centurion

    Centurion Member

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    I just don't get it. Why do some PB105s have the burnpot issues and others don't. I stopped by my dealer today to drop off the 2nd bad burnpot of the season and he seems to think that I am doing something wrong because of all the units sold I am the only one with the issue. He asked me what my boiler temp range is and I told him 155* for a low and 180* for a high. I used to operate it at 140* - 180* but when the thermostat called for heat the domestic would cool down. At 155* I don't have that issue. The dealer thinks 180* is pushing it too hard. I said what does that have to do with the burnpot getting a bubble? The flame in the burnpot will stay on a little longer but its temp will be the same. Then he asked me how many tons I burned this winter I told him 6 tons and he said that was too much! I said how many should have I burned..I have house that is 2600 sq feet. I am really getting the SH*ts of this whole issue. I operate the boiler according the the manual so I shouldn't have to deal with this crap. Why would Harman give me a $1500 dollar ignition system if I was at fault? Has anyone ever said why some have the burnpot issue and others don't? How can I dispute my dealer when none of his other customers have had a problem? If I am operating my boiler incorrectly why doesn't he come to my house and show me what I am doing wrong? For me to be be the only one with this frigging issue I would think that the mistakes that I am making would standout like a sore thumb. I love burning pellets and my fuel bill is half of what oil used to cost me but this whole thing is bring me down. Thanks for reading my rant. Just a little frustrated.
  22. Ejectr

    Ejectr Minister of Fire

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    I don't blame you for ranting. That's like Ford saying the reason your spark plugs wear out in 10,000 miles is because you're driving 70 instead of 65.. If you cranked your feedrate settings up to max to get 100% of the BTU capability out of the furnace...what would be their excuse then! Harman....the dealer...all of them are full of BS.

    I have a PF100 and haven't had a problem with the burn pot....yet., but they've given me the run around for just a stinking bad igniter and it's soured my taste for anything Harman again. Their customer relations mantra SUCKS!
  23. Lousyweather

    Lousyweather Guest

    Harman requires the selling dealer to provide all service and warranty work. Its been said on here, ad nauseum, that one very important thing to consider is the dealer who you buy your unit from....what's their track record? Do they keep parts in stock? Do they have service folks? How long have they been selling the units? How long have they been in business?, etc.

    Bargains are rarely what they seem.....
  24. Ejectr

    Ejectr Minister of Fire

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    They SUCK. I also have an Enviro and have never been treated like Harman treats me. And the dealer I bought my Enviro from went out of business 1 year after I bought it. So there is no difference that I bought the Harman from a dealer out of business. As I said before, Harman acts like they're building Space Shuttles when all they really do is weld metal together and supply electronics made by others. This stuff is NOT rocket science. It's industrial controls at its simplest form.
  25. Lousyweather

    Lousyweather Guest

    as I said, the selling dealer is supposed to cover service work.....did you buy your stove locally near you by chance, or from a distance? Harman does put alot of faith in the dealer for customer support, I agree with that.....but most harman service issues lie with the dealer rather than the company itself....

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