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Thread: Added water heater to the mix

  1. #1
    DIY Junior Member velcrobots's Avatar
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    Default Added water heater to the mix

    OK, so I have an oil-fired Weil McLain boiler for both baseboard heat and hot water. The coil was starting to go, and was very unpredictable, so we decided to add a gas hot water heater.

    We just cut the in/out to the coil and re-routed to the new water heater. My question is this - what about the control mounted on the coil? Do we need to disconnect it?

  2. #2
    Journeyman & Gas Fitter Doherty Plumbing's Avatar
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    Quote Originally Posted by velcrobots View Post
    OK, so I have an oil-fired Weil McLain boiler for both baseboard heat and hot water. The coil was starting to go, and was very unpredictable, so we decided to add a gas hot water heater.

    We just cut the in/out to the coil and re-routed to the new water heater. My question is this - what about the control mounted on the coil? Do we need to disconnect it?
    You need to disconnect every thing that ties the two systems togeather....
    Last edited by Doherty Plumbing; 12-09-2009 at 11:14 PM.

  3. #3
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    You no longer need to maintain boiler temperature so you should either turn the low limit all the way down or by-pass it.

  4. #4
    DIY Junior Member velcrobots's Avatar
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    I set the aquastat to HI 180 LO 160, diff set to 20. That should be good, no?
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    Last edited by velcrobots; 12-10-2009 at 03:54 AM.

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    when you have an in-boiler, domestic water heater coil, the boiler is always kepts between the set points so you have instant hot water capability. If you are no longer using that, unless you disable that portion, the boiler will stay hot all year thinking it is making your hot water. You don't want to pay for that. You might save money by making a new zone and using your boiler to heat an indirect WH rather than a totally separate gas WH. Essentially, you want your boiler to be able to shut itself off when it is not needed, rather than staying hot all year round. How easy that is to do will depend on what controls you have.
    Essentually, you want the boiler to come on when there is a call for heating, and not maintain itself at the ready all year long.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    DIY Junior Member velcrobots's Avatar
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    I have honeywell control, not sure of the model number but it's in the image above. Is it just a matter of disconnecting some wires?

  7. #7
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    Its a Honneywell L8124. Turn the low limit down as far as it will go, leave the diff at 10

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