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modifying older tarm multifuel boiler

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by mikeyny, Feb 29, 2008.

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  1. mikeyny

    mikeyny Feeling the Heat

    Joined:
    Nov 16, 2007
    Messages:
    294
    Loc:
    upstate ny
    I have been burning in a early 80's tarm multifuel boiler for about 4 yrs now in my detached garage. I got it for free. The problem is that my house is too big for that boiler. A new bigger better boiler is not in the budget in the near future, ( 3 kids in college), so I may modify it this summer.to get more out of it. Here are my thoughts:

    The boiler has 2 separate chambers, 1 for wood, 1 for oil. I hardly ever use the oil side.
    The btu rating of the wood side is 110,000. Combined oil and wood is around 230,000, under ideal conditions of course.
    I need somewhere around 175,000 btu.
    Pull out the oil burner, Install a draft inducer in place of the oil burner, drawing the exhaust gas (via piping) from the exit of the
    wood burning side.
    Since the boiler has 2 sets of tubes I was thinking I could get the exhaust gas to travel up through the tubes on the wood
    side and then down through piping to the draft inducer where the oil burner was and then up through the back section of
    tubes where the exhaust from the oil would go. Thereby getting 2 passes through the entire boiler and getting more out of
    it. The way it is set up I could let it draft naturally using only the first set of tubes while not running the draft inducer, when
    the heat load is smaller, and then use the draft inducer when the heat load is bigger. I have most of the parts to do it,
    including the draft inducer and several different controls. I could even use an outside temp sensor to help automate things
    a bit. I have insulated most of the house and replaced 27 of the 36 windows in the house so far. I do a few each yr. if its in
    the budget.
    I am hoping this will increase my heating output by 25 to 30%. I will probably add storage also. I presently have a 110 gal
    tank as storage but don't use it much on the cold days when heat demand is high.

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  2. Sting

    Sting Feeling the Heat

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    477
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    The products of combustion that you move into that second burn chamber ---???? will they have enough 02 to support a second combustion chamber???

    I think - and what do I know - you would be better served to fire each side ad you do the wood side now - as long as you size your smoke pipe and chimney to accommodate both sides. Maybe you will need two stacks but look at the bright side - in mild weather you could burn one or the other side and under heavy load burn both. Make sure you have enough circulation to evacuate the added energy!
  3. mikeyny

    mikeyny Feeling the Heat

    Joined:
    Nov 16, 2007
    Messages:
    294
    Loc:
    upstate ny
    I don't think I will get any secondary combustion in the second chamber. I just though that if I pulled that hot exhaust through a longer path of the heat exchanger i might extract more heat out of it. If My stack temps are around 4 to 600 degrees during full burn that means 4 to 600 degrees going up the stack. The water temp rarely gets over 190. If I could pull that smoke through the rear heat exchanger which is typically idle I would hope to get more out of it.
    mike
  4. Sting

    Sting Feeling the Heat

    Joined:
    Jan 8, 2008
    Messages:
    477
    Loc:
    Wisconsin
    Certainly added HX will benefit but don't expect too much! What the heck - your not using the oil side anyway - it couldn't cost much to make the modification and try it - just watch so your not condensing on the second side!
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