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Thread: Disconnecting domestic hot water coil

  1. #1

    Default Disconnecting domestic hot water coil

    I have decided to abandon my oil fired boiler domestic hot water coil for my hot water usage but could use some clarification. I will be installing a 50 gal electric water heater. i am a diy'er and need advise on how to handle the coil. i have read on some internet sites not to leave the coil in the boiler. i really do not want to try to remove it. is this process as simple as cutting the inlet and outlet of the coil, making sure there is no water in the coil and then capping them, reroute the lines to the electric water heater, or am i overlooking something?? what are the cons of leaving the coil in the boiler?? i do know i will have to do something with the aquastat- which i will research further the closer i get to the project. any advise is appreciated. Thanks.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    This is discussed more than once, so a little search should answer your questions. Today, the boiler keeps the water hot enough to allow the system to heat your domestic hot water supply. You don't need it to stay that hot any longer once you reroute the water to the WH. But, depending on the design of the boiler, there may be a minimum temp it needs to run during the heating season (and you could probably shut it down until then) to prevent damage to the burner. If the water is allowed to get too cool, if the boiler isn't designed for it, you'll get condensation, and that can eat it up quickly.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Junior Member gettingitdone's Avatar
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    Cool Bypassing tankless to hot water heater in the summer

    I'm getting the basic understanding on the conversion but to be sure, is there any place to get a sketch up on how to add an electric hot water heater to my oil boiler to bypass the boiler during the warm months of the year and then switch back to the boiler in the fall? I know I can do the work myself but just need to be sure where to cut and sweat in the new lines to the electric heater. Would there be any youtube videos for this? I can't seem to find one just yet. Thanks.





    QUOTE=jadnashua;259616]This is discussed more than once, so a little search should answer your questions. Today, the boiler keeps the water hot enough to allow the system to heat your domestic hot water supply. You don't need it to stay that hot any longer once you reroute the water to the WH. But, depending on the design of the boiler, there may be a minimum temp it needs to run during the heating season (and you could probably shut it down until then) to prevent damage to the burner. If the water is allowed to get too cool, if the boiler isn't designed for it, you'll get condensation, and that can eat it up quickly.[/QUOTE]

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    There is more than one way to make this happen. Assuming you want to shut the internal coil functionality down in the summer, but still want to take advantage of it in the winter, you could do it one way. If you never want to use that coil ever again, there's others.

    In the first, you'd just take the outlet , run it into the inlet of the WH, and then take the outlet of the WH and connect to where you cut it in the first place. With the boiler off, it would still get to the electric tank, and the tank would heat it.

    If you ever wanted to still use the boiler for heating that water, you could still leave things the same way, and the electric WH may never have to come on except to rewarm the water cooled off during storage. Since an electric WH is reasonably well insulated, you would not have much storage loss, and feeding it with at least warm water, it wouldn't need to run much, if at all, and would just be a storage tank. If you did that, you could change the controls on the boiler to allow it to cool off more and not maintain a high temp 24/7, as the electric WH would give you the hot, and when the boiler was running, or even sitting at its standby point, it would at least preheat the water, and when it was heating the house, it may be hot enough so the electric never ran.

    Or, you could bypass the boiler entirely, and just run the water to the new WH, capping the inlet/outlet to the internal coil. You'd want to change the controls so it could cool off to a less expensive standby temp, though.

    There's a few other decisions to be made, but those outline the general choices.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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