On/Off option for the domestic water part of hydronic system ?

Discussion in 'Boiler Forum' started by GG_Mass, Jul 9, 2014.

  1. GG_Mass

    GG_Mass Member

    Messages:
    57
    Location:
    Massachusetts
    Hi,
    I have an ultimate, oil fired, cast iron, with two heating zones and one zone for domestic hot water.

    During the day, we, like many families, are out of the house, for some time . During this time, obviously, the domestic hot water is being kept at the temp set by the aquastat . I see it as a bit of a waste, if there are options to have it shut down.
    I placed a recording device near the Boiler area and came to understand that the domestic water uses the system for 35 minutes of run time, each day, during the hours that there's no one at home. . (This was during summer-time, no heating was needed).
    Which leads me to:
    Is there an option, to add a switch (or any on/off mechanism), into my system ? Which, will completely disable the domestic hot water system, and will enable it only when set to "on" ? I do not mind flipping such a switch twice a day, if it enables to to achieve my goal, of not having the domestic water being kept to high temp, while no one needs it.

    Thank you

    Attached Files:

  2. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,311
    Location:
    Maine
    Couple of options.

    Shut the emergency switch off...least expensive
    Install a timer after the aquastat
    Install an indirect water heater
  3. GG_Mass

    GG_Mass Member

    Messages:
    57
    Location:
    Massachusetts
    Okay, it is doable them. That's very good to know.
    I assume the emergency switch is the one to the left , correct ? (pretty sure it is, but, I don't want to be "smart" and then find that I'm very wrong, not in HVAC..)
    Are there any cons to just using the emergency switch ? besides the obvious one of going down to the basement each time, etc. ?
  4. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,311
    Location:
    Maine
    Nope. There should be one at the top of the stairs too.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,319
    Location:
    New England
    A good indirect can have as little as 1/4-degree/hour temperature loss in a standby situation. So, once you get that tank of water heated up, depending on the cut-in temp on the tank, you could easily go a couple of days before the boiler would need to turn back on with no use, at least if the area was somewhat warm and not drafty. Some boilers, not all, can be successfully cold started, which is great for summer and indirect WH heating. Some would require a minimum temp, that generally could be lower than that required with an internal tank or tankless system, and only go to full fire when there's a call for heat. Many of the newest boilers are designed for cold starts, at least those that run on gas.
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