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Harman Pellet Boiler Burn Rate Question

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by wpessin, Jan 1, 2008.

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  1. wpessin

    wpessin New Member

    Joined:
    Dec 21, 2007
    Messages:
    13
    Loc:
    Boston Metrowest
    I recently had a Harman PB105 Pellet Boiler installed (posted questions earlier on the install and received some terrific tips). I am looking to compare notes on whether my burn rate is too high or perhaps I just needed to re-calibrate my own estimates on how many pellets I would burn.

    I have a fairly large house (about 6,000 sq ft), and have the system running in series with my oil boiler. It powers 3 air-handler zones, 1 base-board zone, and an 80 gallon super store/water tank. Each heat zone has a programmable thermastat that varies between 70 deg and 64 deg depending on the time. Since installation, the oil boiler hasn’t kicked in and I haven’t burned a drop of oil. The max temp is set to 180, min 170, and “3” on the feeder.

    I started out using Premium Ultra brand pellets from Home Depot, but was getting odd behavior out of the auto ignition (flash-bang starts where the chamber would fill with smoke then “flash-bang” on ignition kicking a huge billow of smoke out the stack) . I cleaned the pot, found lots of fines in there, and mixed in a bag of Cubex with each bag of the Fireside. Since then, have been getting normal auto starts, however, I’m average about 5 1/3 bags/day...much more than what I thought I would need. Granted it’s a big house, but that seems excessive to me.

    Other notes...it’s a direct vent (through the foundation), and the installer hooked up outside air. I’ve noticed a small amount unburned pellets in the ash pan. I think the unburned pellets are from slow startups with the old brand. The installer will be back in to check the draft and other aspects.

    Thanks in advance for your thoughts on this.

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  2. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    49,690
    Loc:
    South Puget Sound, WA
    6000 sq ft is an exceptionally large house. Given that an average 2000 sf house would be using about 1.5 bags per day at this point with current Boston temps, the 5 bag consumption may not be out of line. What are the zone temps set to? Is the storage tank well insulated?
  3. wpessin

    wpessin New Member

    Joined:
    Dec 21, 2007
    Messages:
    13
    Loc:
    Boston Metrowest
    I have all the zones on programmable thermostats that are set between 64 and 70 degrees, depending on the time of day/night, which were the same settings I had on my oil boiler. When I compare the amount of BTUs I consumed with oil (roughly 8.5 gal/day @ 139,000 BTU/Gal =1181500 / day) to my pellet BTU's (213 pounds/day @ 8500 BTUs/pd = 1812200), a 65% increase in BTU consumption, that's when I scratch my head thinking I've got a problem.

    Is it possible that too much outside air is causing the pellets to burn faster and/or that the draft is set too high "sucking" the heat out the vent? The vent pipe is blistering hot, and I do seem to get a lot of white smoke out the stack. This is my first pellet appliance so I am unfamiliar with what is normal. Thanks for your insight.
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