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Harman P38+ Feed Rate Problem

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by nixonfamilyusa, Jan 6, 2008.

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  1. nixonfamilyusa

    nixonfamilyusa Member

    Joined:
    Jan 6, 2008
    Messages:
    6
    Loc:
    Maine
    Hi Gang,
    I have a Harman Pellet Pro P38+. This is our second season using our
    stove and we love it, we use it to heat our home in Maine.
    Last week i noticed a dirty orange flame and figured it was time for a
    good cleaning; and figured i would hold off till the weekend.

    To cut a long story short, I woke up one morning smelling smoke. The
    flame had died out and the smoldering smoke was seeping up through
    the pellets in the hopper. At first I suspected the combustion
    blower but decided I would clean out the stove and try it agian and
    see what happens. I cleaned the burn pot, combustion fan,
    distribution fan(according to Harmans maintenance guide) and vacuumed it all out.

    On turning the stove on I noticed that it works fine in Turbo Mode
    (it has a feed rate setting from 1-5 and Turbo) and since cleaning the flame is looking clean again.
    If I turn it down to five the augur feeds in pellets and it still has a nice clean flame; however, smaller than usual and the feed rate seems to be putting in less pellets than usual.
    If i turn it down to less than 5 (4,3,2, or 1) the flame is clean yet
    smaller than normal, the augur does not feed in pellets and
    eventually there are no pellets to burn in the burn pot and so the
    flame dies and the embers smolder. The only difference is now that
    stove is clean the combustion fan is blowing smoke out of vent pipe
    and so it is not causing house to smell of smoke.

    Any ideas?
    Could it be the circuit board?

    In my limited knowledge of stoves it seems like it cannot be anything
    mechanical as all the parts do work, it just seems like it is not
    feeding right.

    Thanks for you replies in advance
    Shaun

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  2. hearthtools

    hearthtools Moderator Emeritus

    Joined:
    Jan 6, 2006
    Messages:
    2,020
    Loc:
    Oakhurst, California, USA, Earth
    You stove might have just enough vacuum when it is cold to keep it going but when a stove heats up the Negitive pressure in the stove decreased and your vacuum switch might have tripped and killed the auger circuit.

    Clear the Vacuum switch tube
    Pull the tube off the vacuum switch and blower through the tube back to the stove
    or you may have to use a needle like object to Clear the port that the hole connect to at the stove.
    NOT AT THE SWITCH and NO NOT blow back into the switch.

    also check the tube for kinks in the line or cracks.

    Also let us know what you found was wrong.
    So many people ask a question we give them a possible solution and they never get back to us what they found.
  3. nixonfamilyusa

    nixonfamilyusa Member

    Joined:
    Jan 6, 2008
    Messages:
    6
    Loc:
    Maine
    Hi Rod,
    Excuse my ignorance I am still fairly new to all this. Are there any other names for the vaccum switch. I don't seem to see it in my stove manual. I do see a low pressure switch - could this be the same thing?
    It seems (according to wiring diagram) that it connects to the feeder motor and to the feeder part of the circuit board.
    If this is the same will there be a vacuum hose on here?
    will this be inside the stove somewhere?
  4. hearthtools

    hearthtools Moderator Emeritus

    Joined:
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    Messages:
    2,020
    Loc:
    Oakhurst, California, USA, Earth
    Sorry
    I made this page up today
    http://www.hearth.com/econtent/index.php/forums/viewthread/13499/
  5. nixonfamilyusa

    nixonfamilyusa Member

    Joined:
    Jan 6, 2008
    Messages:
    6
    Loc:
    Maine
    Thanks,
    I will take a look at this as soon as I can. It might be a little tough to get to.
  6. GVA

    GVA Minister of Fire

    Joined:
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    2,140
    Loc:
    Waxhaw, NC... Formerly North shore Mass
    You may have damaged the ESP while cleaning the stove.......
  7. nixonfamilyusa

    nixonfamilyusa Member

    Joined:
    Jan 6, 2008
    Messages:
    6
    Loc:
    Maine
    Thanks for all your input
    Here is my progress so far.
    Rod, I read through your page as recommended. Thanks it's very good. My vaccum switch (low pressure switch) is really tucked away. I am going to have to find the time to move the whole stove to get to it. For now I bypassed the switch as mentioned in your article. Theoretically the stove should operate as per normal. The good news is my stove (in bypassed mode) now feeds pellets at lower settings (other than Turbo and 5 like before).
    So I think i need to look at where the tube connects to the stove - at the back of the firebox. Any other ideas?
    The bad news is the flame is kind of puny. My father has the exact same stove and there is a difference in flame size on the exact same settings.
    My stove is a positive pressure system - what exactly does that mean?

    GVA, thanks for your input. You made a valid point. I try to be careful and follow the maintenance guide step by step; however, it is possible something happened to it. Is there any way to test the esp. Also what are common signs of a broken/messed up ESP.
  8. hearthtools

    hearthtools Moderator Emeritus

    Joined:
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    Loc:
    Oakhurst, California, USA, Earth
    Small fire (on high feed) could be from TO MUCH AIR OR DRAFT
    a Tall lazy flame is from not enough air.

    Not sure what you are asking about the positive pressure?
    A positive pressure stove is a stove that has a Combustion blower that pushes Air into the firebox and out the exhaust.
    Exhaust gases never go through the blower.

    A negative air stove is a stove that sucks air through the burn pot and fire box/heat exchange and out a exhast (combustion) blower and then out the venting.

    The difference of a Negative and Positive pressure Vacuum switches are where the vacuum hose Port is connected to the stove.

    A negative pressure Vacuum switch will have the hose port BEFORE or on the combustion blower on a negative air type stove.

    I think all stoves made today use negative pressure readings on the pressure switch.
  9. nixonfamilyusa

    nixonfamilyusa Member

    Joined:
    Jan 6, 2008
    Messages:
    6
    Loc:
    Maine
    Thanks Rod,
    It's good to speak to someone who is so knowledgeable about stoves.
    I myself am still trying to work out exactly how everything works. So if the flame is small does that mean that too much air is getting drawn in through the flap.
    Could a small flame still be the result of a dirty vaccuum tube?
  10. hearthtools

    hearthtools Moderator Emeritus

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    Loc:
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    I have not worked in a harmon myself
    so I dont know much about the air adjustment

    and NO the pressure switch has NOTHING to do with how the stove burns
    Just a safety feature if you flue or ash traps are full the pressure switch will shut the stove off. So you know it is time to clean.
  11. nixonfamilyusa

    nixonfamilyusa Member

    Joined:
    Jan 6, 2008
    Messages:
    6
    Loc:
    Maine
    Thanks to all who helped by giving ideas about my stove.
    The stove is now fixed and working properly.
    A stove tech came out and after looking around a bit and took a voltage reading of the ESP, he mentioned it was only putting out half the voltage it was supposed to and replaced the ESP.
    The stove is working great now.
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