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Heat the DHW while not there?

Brad White_9
Brad White_9 Member Posts: 2,440
a digital Intermatic timer on my MPI/Monitor DWH heater but set the temperature at 140 degrees for when it is on to kill any nasties. I encourage you to do that.

Tepid water is a dating bar for Legionella.

Viessmann Vitodens has a specific cycle to roast the little buggers and allows for setback so you are right, there is an application for this.


  • Gene Davis_2
    Gene Davis_2 Member Posts: 71
    Why do it?

    I didn't want to bury this question in the other one I just posted, so I thought I would start a thread all its own.

    A heating system is proposed, for a small house with total heat loss at its -30F design temp, of about 36K Btu/h. A combination of panel rads and infloor heat will run at max suppy temp of 120F.

    This question relates to the DHW side of the works. While the heating system will never call for the boiler to make water at a temp higher than 120F, the DHW loop will certainly make for higher temp demands.

    The projects being primarily vacation homes, with long periods of inoccupancy and therefore no DHW call, what might we do to make the system never produce water at a temp exceeding when the home is not in use?

    Or instead is this silly worrying? Might the system just undergo such small bursts of high temp water production, to keep the DHW cache in the SuperStor 45 at temp, that the efficiency loss and fuel usage is insignificant?
  • Couderay
    Couderay Member Posts: 314

    At my vacation house up north, I disable the indirect from the boiler electronically and drain the hot water from the tank.When I go north close the drain ,fill, plug the 2 wires back together and in a few minutes hot water.
  • adambuild
    adambuild Member Posts: 414

    I agree with Joe, install a switch that the homeowner can flip on when they get there. Even if someone doesn't want to drain the tank, why waste the fuel?
  • Lurkin' Murkin'
    Lurkin' Murkin' Member Posts: 136

    I have a Superstore - I think it's a good product, mine's almost 15 years old. I do an occasional drain and flush, to keep the coil clean - usually takes a few times to get the water clear again. If you drain this type of product when not in use, then try to refill it when you need the hot water - wouldn't you have a rusty water condition that would require alot of additional draining and flushing before you could utilize the water?
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