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Wood boiler interface with home oil boiler.

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Betz
Betz Member Posts: 58
They do seem to overcome the laws of physics, as they did in my case. I am surprised how well my system works with a direct hookup to an outdoor boiler. I realize that the oxygen is a problem with my piping but I keep feeding the unit an oxygen eating treatment and until I am able to afford the heat exchanger/additional pumps to put in a nice primary/secondary loop I'll be pretty happy...I do use a lot of wood but compared to the $500 to $700 monthly gas bills I'll take the work. I'm still not buying any wood and I don't plan on having to in the way off future.

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  • Steven Eisenhauer
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    Wood boiler interface with home oil boiler.

    I am putting together an interface between a 250,000 BTUs Wood Gun- high efficiency wood boiler and a 250,000 BTUs Buderus oil fired boiler. The wood boiler will live out in the barn in a boiler room where it will heat the adjoining shop spaces, and the Buderus lives in the basement of my house. I have a 120" 1" supply and return line going to the house. Question- would a flat plate heat exchanger capable of 100,000 BTUs driven by a Grundfps UP 2699 F circulator with 25 GPM take care of moving what the line will handle, and how best to take that heat and put it to work in the house. I want the Buderus to be up to temp at all times for domestic HW.
  • Steven Eisenhauer
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    Wood boiler interface with home oil boiler.

    I am putting together an interface between a 250,000 BTUs Wood Gun- high efficiency wood boiler and a 250,000 BTUs Buderus oil fired boiler. The wood boiler will live out in the barn in a boiler room where it will heat the adjoining shop spaces, and the Buderus lives in the basement of my house. I have a 120" 1" supply and return line going to the house. Question- would a flat plate heat exchanger capable of 100,000 BTUs driven by a Grundfps UP 2699 F circulator with 25 GPM take care of moving what the line will handle, and how best to take that heat and put it to work in the house. I want the Buderus to be up to temp at all times for domestic HW.
  • Al Corelli
    Al Corelli Member Posts: 454
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    Wouldn't you need piping sized to carry 250,000btu?

    Why undersize it?
  • hr
    hr Member Posts: 6,106
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    I agree

    those 1" lines will limit how much heat you can move. At a 20° delta T, plan on about 80,000 BTU/hr.

    If you can design around a 40° delta T you can move 135,000 BTU/hr.

    I can't see how you will ever move 250,000 through that 1" line??

    The interface between the two boilers is best done with a primary secondary loop.

    No need to use a heat exchanger unless the Wood Gun is an open unpressurized system, or you want to glycol antifreeze only that boiler.

    hot rod

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  • Steven Eisenhauer
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    The reason for a 1" line was advice from a heating contractor who no longer shows interest in the job. Unfortunately the $1,200.00 line is in place ready for service. I am running anti freeze in the boiler loop so that when I am out of town and can't feed the wood eating monster, it can go to sleep. Any great ideas on where to find good info on this sort of project?
  • hr
    hr Member Posts: 6,106
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    It's going to take

    some number crunching to get a plan. you will need to figure the volume of the boiler, piping and misc. Then a glycol percentage. With this you can size the pump, expansion tank, and heat exchanger for the wood burner side.

    Then I would create a primary secondary loop to tie the current boiler into, as well as the B side of the flat plate HX.

    This gives you freeze protection for the outdoor system, and allows the inside piping and boilers to get along hydronically speaking.

    You will take a bigger heat on heat transfer through the 1" lines with the glycol mix, but at this point you have what you have.

    You might hire an engineer or designer fromhere to do some calcs and a piping layout.

    Here is a quick, and crude, sketch on some of the components and methods to put this type of system together.

    Be mindful of pressure relief safety valves sized to those BTU appliances!

    hot rod

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  • Glen
    Glen Member Posts: 855
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    I have noticed -

    that most outdoor wood boiler mfgr's recommend one inch Kitec piping - regardless of size of boiler.
    http://wooddoctorfurnace.com/hookup1.html
    Seems they can overcome the laws of physics with large pumps .....
  • [Deleted User]
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    They can comfortably recommend 1\" Kitec

    because they never intend for the total boiler capacity to be transported to the house. The heat loss that occurs when you run this tubing through a DIY "insulated" trench makes 1" the perfect size. ;0)
  • ALH_4
    ALH_4 Member Posts: 1,790
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    Piping

    These are a few methods we have come up with. I like the Vitodens method best because it's possible to pull the alternative source storage to a lower temp using just the 155. For the Vitodens and HK1 methods, the Tekmar 155 controls the diverting valve. Unfortunately the HK1 method is somewhat limited by how low you can run the oil fired boiler.

    -Andrew
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