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Anyone have a pellet boiler?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Damammel, Nov 30, 2007.

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  1. Damammel

    Damammel New Member

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    I am looking into a pellet boiler and was wondering if anyone has recently installed the Harman PB105 with a storage tank. I am wondering if the expense will be worth it in the long run. I was also looking at the Tarm but it looks like an additional 3000.00 to purchase the boiler. Also, are there any other vendors that make a good storage tank? Again the Tarm tank is about 4500.00. Any help or suggestions would be appreciated.

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  2. Alternate Heat

    Alternate Heat New Member

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    I have a PB105, this is the second heating season.
  3. Nofossil

    Nofossil Moderator Emeritus

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    $4500 for the tank? That's pretty impressive. Even out here in the sticks, I found a bunch of stainless tanks in various sizes for under $1000 at local scrap dealers - I paid $400 for and 880 gallon unit, which is actually half of a milk 'bulk tank' - a common thing in a farming area. You can but a lot of extra parts and plumbing for $3500. Of course, you can't fit one through most basement doors, but they're a good choice if you're going to locate it outside.

    Pictures on my web site - link below.
  4. pbvermont

    pbvermont Member

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    make your own tank, just like the TARM one using building supply-store materials for about $700. Its round, strong, tested, goes through a 28"-wide door and (when drained) breaks down and moves very easily.
  5. Damammel

    Damammel New Member

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    Thank you for the replies. The storage tank is for the extra heat storage. I have not been able to find many people using pellet boilers.
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    I've always wondered, pv, how do you get the foam board to bend around the inside of the tank? Is it hard to do?
  7. pbvermont

    pbvermont Member

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    this is one of the labor intensive aspects of the DIY tank: tools: 1.) 4 foot sheetrock T-square, 2.) utility knife.
    procedure: assuming you're using 1" thick foil board, use the T'square to make 4' long slits every 3" as you go along the 8' edge of the sheet. THe utility knife will slit one side of the foil and much of the way through the 1" foam. The foil on the UNSLIT side keeps the board intact and it will now curve in any degree radius you want. You will want to do a double layer of 1" board on the top bottom and sides of your tank. 6 sheets=96 slits. Done.
  8. stephenmoore

    stephenmoore Member

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    I have a Harman PB 105 in it's first season, in floor heat in 7 zones, 2500 sq feet, and one convector rad zone. Using a teckmar controller to operate the injection system. Outdoor temp sensor is also active. Min water temp is 140, max is 185. Am burning about 2 bags a day, east coast winter about -2- -6 Celsius per day temp. Sysytem works great except that I am about to install my third igniter on the PB 105. Has anyone else had troubles with this ? Am un clear as to how often the igniter chamber needs to be cleaned ( located under the burn pot ) It seems to fill up with fly ash too quickly. Hope this info is useful. I am also pre heating my hot water heater with the Harman Domestic Hot water coil. Using premium pellets from Nova Scotia at about $4.50 per bag.
  9. wdc1160

    wdc1160 New Member

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    PB, Do you try to keep any of the foil separated from touching other matierals. I keep running into problems that occur when foil touches other insulators. The foil apparently loses all of its radiation deflection abilities when it touches other things.
    Any comments?
  10. Sting

    Sting Feeling the Heat

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    I heat almost 5000 sq feet of money pit with a Traeger boiler - used to burn corn - this year, burning wood pellets
  11. Bob Rohr

    Bob Rohr Minister of Fire

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    Do some math regarding the cost of pellets for fuel. Figure 80% efficiency. Pellets took a big jump around here, not such a good option considering the cost of the boiler, tank, and related piping, maybe.

    LP actually dropped $.20 around here last week. At $1.89 per gallon and 94% efficiency on a mod con, it's not a bad choice.

    hr
  12. Sting

    Sting Feeling the Heat

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    I would be thrilled with 80

    as a master - you better figure more like 70% smoking an old Traeger
  13. webbie

    webbie Seasoned Moderator Staff Member

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    Agree that you would be real lucky to get 70% out of a Traeger.

    At $1.89 and 94%......LP would be.......about the same price as pellets at $230 a ton.
  14. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Have you ever put actual instruments on a Traeger boiler?

    At $1.89 / gallon for LP, you're at $20.69 per million btu. At $230 per ton for pellets, you're at $14.02 per million btu.

    Factor in efficiency (94 and 80) and you're at $22.02 per million btu for LP and $17.53 per million btu for pellets. Even if your pellet boiler is running at 70% (get if fixed, if it is - that's not normal), you're at $20.03 per million btu.

    Close, but no cigar.

    Now figure that the actual system efficiency (not the meaningless AFUE) is 85% or less for the LP boiler, and 75% for the pellet boiler, and you're at $24.35 per million but for LP and $18.70 per million btu for pellets.

    Of course, last I checked, LP was running around $2.40 per gallon, here, so it would be over $30 per million btu...

    Joe
  15. webbie

    webbie Seasoned Moderator Staff Member

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    I don't know system efficiencies of Pellet boilers, but the unit efficiency is probably 80%.

    If I use Nofossils examples, they would probably be much less - that is, a wood boiler with a high efficiency ends up with 56% system. I assume the mileage will always vary, but as you said (Joe), only people using a tremendous amount of fuel end up seeing a big savings in most cases.

    Strangely enough, I created the first Traeger boiler! We contacted them back in 1990 or so (when I was Tarm) and sent them two of our 202 coal boilers which they modified for pellets....they then sent one back to us and we placed in the field.

    My take on the efficiency comes from the fact that Traeger (patented) mechanism was used in Earth Stove, which came in the lowest of all tested pellet stoves during an Omni field test - about 52%. I'm not saying the boiler or that a modern stove is that low, but the mechanism certainly has not changed much. So I'll guess at 70% rather than take the manufacturers or a sellers word for it. 70% (AFUE or equiv) is a very good efficiency, IHMO - for something subject to the ins and outs of pellets fuel, corn, etc.
  16. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    The burner mechanism has little to do with the efficiency, beyond a certain point.

    I can buy two brand-shiny-new oil boilers with identical burners on them, and get 87% AFUE from both. But actual system efficiency on one will be 55% and the other will be 85%, because of the design of the boiler and controls.

    As long as the burner is producing a clean burn at the right (high) temperature, that's really all you need from it. Extracting the heat from the hot gasses that the burner produces is the job of the rest of the system.

    Joe
  17. Sting

    Sting Feeling the Heat

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    Your the god I have searched for!!!! On corn I cannot run more than two of the three feed cups - I just cannot burn more than 8 lbs of corn per hour in any of my pots. It just will not burn more corn.
    [​IMG]

    At the GPM thru the vessel I get ALMOST 60,000 btu from an appliance rated at 130,000. Factor that I am only running on 2/3 feed potential the math says 70%

    I can run all three feed cups and smoke 12 pounds per hour of good wood pellets in ONE of my multi fuel pots. The others I cannot get enough air in - the fire is too rich and cooler than this pot. Factoring my GPM thru against Delta T it may be operating at 75%
    At my current cos to pellets by the truckload - I am heating for 15% less on pellets than on similar production with NG - too bad for me -last year on 70 a ton corn that was a far better ROI - but I got - so I burn it - as long as it doesn't cost me money.

    In mild weather pellets run flawlessly with one feed cup blocked and this pellet pot!
    [​IMG]

    When degree days rise above 50 I need to add more material into the pot -The factory pot has worked the best
    [​IMG]

    We are trying to figure a self cleaning pot - like the pellet pot above but that ill support a much larger pool of corn and also be self cleaning like the pellet pot. Close but yet no cigar. May we beg for suggestions?
    [​IMG]
    [​IMG]

    I have tried to stuff more air in - but more air simply dilutes my upper smoke chamber temp - so I can assume less gaas temp in the HX and thats not my goal either.
  18. webbie

    webbie Seasoned Moderator Staff Member

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    Well, as with all gods.....this one is gonna let you down hard. Promise you heaven, but give you earth.....

    I was certainly hands-on to some extent at Tarm (we had two employees including me!), but not to the point of Joe and the nofossil and the "real" boiler people here. We pretty much relied on Traeger to put the mechanism on, and since the boiler was only rated at 80,000 maximum....and less in this case because there is no way we could use all the heat exchange as well as coal would have in the same boiler (which was designed for hard coal).

    Chances are that you are ahead of the curve as far as modifications and guesses - but hopefully some others will have some guesses.

    Only comment I would offer might relate to the corn output and output in general. It might be that the boiler ratings are the BOILER ratings, in other words what the heat exchanger and boiler are capable of in the best of all possible worlds. It would also, sadly, be an exaggeration or marketing tactic....meaning that pellet boilers are probably not IBR rated and any solid fuel is likely to perform worse in the field than claimed in the lab or by the sales people. We regularly have folks here that cannot get their freestanding pellet stove up to near the rated input or output - they tend to get about what you get - 70-75%. The reason that no one usually complains is that they are operating at 40% most of the time anyway...in other words, very few folks run up against those limits.

    So my thinking is that you are unlikely to ever get the corn up above about 75% of rating. With the right pellets, it might be possible to get higher, but I still doubt you will reach the rated input or output. Hopefully that will not mess you up too bad, as most of the time you may not need that much heat. At the same time, this should serve notice to pellet stove/boiler/furnace buyers not to expect the full rated input/output...or at minimum do a lot of homework and get it in writing as to the lbs per hour that they promise!

    Sorry I had to let you down from heaven, but I have worked more with words (and computer code) in the past 10+ years than with boilers!
  19. Sting

    Sting Feeling the Heat

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    [​IMG]

    I once tried some scrap baffles to do just that. Try and direct some heat back into the corn pool
    Drive off the moisture or make some secondary combustion on the escaping vapor.

    It didn't do any good. I actually lost a few degrees of temp in the upper smoke chamber.

    But thanks for the idea. I have been thinking about this for two seasons. A fresh evaluation is very welcome!

    Thanks for letting me down ez Craig. I had hoped you had the silver bullet. Yes I know now this baby boiler is over rated. When I picked it up as a used orphan I expected more - never burnt corn but I thought I knew a little about wet systems so "What could be so hard - Right???" Daaaa -->corn is an art
    I stock in a 6 ton bin out doors - some call it the space shuttle. Replace from that the daily pounds used into a conditioner/preheater/dryer. Then auger that product as needed into the appliance bin for best result of burn. Well maybe corn will stay out of reach and Ill just keep burning pellets, and I won't need to anguish about a self cleaning corn pot!
  20. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    What's the GPM and delta T on the water side?

    Making any ROI on NG is very good. NG is one of the cheaper fuels, and 15% is about where I would put you, based upon the published efficiency numbers, so I think you may be running closer to the published efficiency than you think, or your NG system is extremely inefficient.

    Peak efficiency tends to coincide with minimal excess air, as you've noted.

    What's your combustion temp?

    Joe
  21. Sting

    Sting Feeling the Heat

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    What's the GPM and delta T on the water side?

    --Did the calc last season - lost the data - recall the result


    Making any ROI on NG is very good. NG is one of the cheaper fuels, and 15% is about where I would put you, based upon the published efficiency numbers, so I think you may be running closer to the published efficiency than you think, or your NG system is extremely inefficient.

    --- sure - I think?


    Peak efficiency tends to coincide with minimal excess air, as you've noted.

    What's your combustion temp?

    Joe
    --- I do not possess equipment to measure the actual combustion temp in the burn pot - I can measure the surface temp of the upper smoke chamber and I do 24/7 with analog temp registration - BUT I know that is corrupted data by the condition of the HX at any time other than hours after cleaning and the variable vessel temp by ODR. It does give me another reference to glance when feeding the beast.

    With this in mind - do you have any suggestions to improved burn with the factory multi fuel pot or the contraptions we display above? I have even considered building a shaker grate burn pot and trying rice coal - but after some quick ciphering and the influence of alcohol - in Wisconsin the freight cost kills the possibility! IF I could burn more ponds per hour of corn I could get to appliance rated potential - Do you have users who burn fuel other than wood pellets with all three feed cups in play? Does you buddy? Hope you can suggest option to improve the rather sad performance of this appliance - yet I understand it a very simple single pass vertical fire tube boiler and hi performance is a lofty goal. Is it in reach? This all may be mute with corn as I expect the acquisition cost will remain higher than pellets - but even improvements on pellets will lower the daily operational cost of heating my little abode. And isn't that why we lurk here?
  22. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Well, if you don't know the temperature difference between the flame and the flue, you aren't really measuring the efficiency...

    I think you have a heat extraction issue, not a burn issue. The feed system meters a given amount of fuel per rotation, and if we're talking pellets, that's a given amount of btus going into the burn pot.

    If the thing isn't smoking like a beast, and you aren't running massive amounts of excess air, then you are converting the fuel into hot gas pretty effectively. If that's all happening, then the burner is doing its job.

    Extracting the heat from the hot gas is the responsibility of the heat exchanger. Assuming a proper burn (ie, not too much excess air), and relatively-clean heat exchange surface, that becomes primarily a function of the flow rate and delta-T of water through the heat exchanger. Those things can also cause dirty burning, and excess air to compensate, if the flow rate is too low and the system is short-cycling.

    Running the system with all three feed cups, I'd want to see a minimum flow of 10 gpm.
    Running on two cups, you could get by with 7 gpm. I'd never design for that, though, in case someone wanted to run all three in the future.

    What sort of duty cycle is the burner making? Only if it's sitting in "burn" mode all the time and still can't keep up, would the system not be producing enough btus. If that's not the case, and it is cycling between the limits (hits high limit, switches to pilot, hits low limit, switches back to burn), then you definitely have a water flow problem.

    Joe
  23. Sting

    Sting Feeling the Heat

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    Thanks for the quick reply

    I circulate at about 6GPM (that jogs my old head as to how we rated - that and delta T) when burning corn like you say thats what the pump performance specs are and the loop is sized correctly so head pressure issues do not play- I pump at higher GPM when on full feed and pellets - what ever it takes to keep the Delta T in parameter. Sort of like NOFO is pumping his plant. I don't have a pump or design problem - the Traeger is a heat extraction problem by its simple design - that cannot be changed - I have not incorporated flow monitor capability in the loop - too expensive - I accept the pump it working correctly - lets move on.

    Duty cycle - Baby boiler is far outmatched by the load I place on it. Only lucid pumping - boiler protection - and an occasional assist from its strong NG brother on the primary loop keeps the little place warm when degree day load exceeds 60. Again its under sized a bit - but it works better under load than at idle. It is producing all it can now - I am looking for suggestions to increase its potential by the only part that can reasonably be varied - the fuel input and combustion of that fuel. Is that direction wrong?

    If I had deep pockets I would have an HS TARM pellet appliance in my boiler room and there would be no issues in performance or economy of operation!
  24. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    What's the actual delta between the supply and return at the pellet boiler?

    Does it ever hit high limit? Or is it in "burn" mode non-stop?

    Joe
  25. Sting

    Sting Feeling the Heat

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    0 to 40 degrees differential usually 10 to 12 % and or +- 2 degrees - dependent on load - pumping - heat soak - degree day I don't pump thru when SUPPLY cannot be 145 or more - pumping is greatly curtailed or stopped till appliance recovers to 160 supply water.

    Never hi limits except on the occasion that the sun comes out and heat soak carries the appliance away - heat dump protection launches at 205 - Hi limit protection aqustat samples by probe directly in place of the old Triple honeywell troublesome control - IT stops ALL operation at 195 - even idle fire timing. I don't run my stuff hotter, don't need to Radiation and load is sized for cooler water. ( I can heat on the worst day of the year with the energy of 170 degree water if I can produce enough of it!) Normal vessel temperature modulation is controlled by an Teckmar (older generation) single boiler control in relation to outdoor temp - boiler sensor is taped inches above the supply port in the same size loop pipe.

    AS I say its undersized for the load - on higher degree days It can burn all day and heat soak - the more it burns the better it works.

    Have I passed the interview yet? :>) Can you help me with ideas to make more heat? I have control - I understand your misgivings of such when we bench race like this!
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