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air on domestic side?

ScottEScottE Member Posts: 8

I have a Versa Hydro (HTP) on a new install it is the only source of heat in the home.  The homeowner goes on vacation 3 weeks in the cold of winter. During this time he is in the habit of shutting the water off to the home. My question is if i have no draw from the domestic side for that period of time will air come out of solution and allow air to cavitate my hot side of the heat exchanger? and follow that question with how do i stop it? Thank-you in advance,  Scott


  • ZmanZman Member Posts: 3,517
    Water off

    The concerns I see with turning the water off are 2 part.

    The first is that the tank could lose water and overheat. This could be caused by a leaky faucet or someone checking on the house inadvertently turning on a faucet.

    The second is that once the house depressurizes, most boiler backflow preventers will "vent" and cause the boiler side to lose pressure as well.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • icesailoricesailor Member Posts: 7,265
    Decompressing Backflows:

    Maybe you have seen that but I haven't. First of all, a Watts 1156F  PRV has a check valve in it. So, if the valve works, it is a check valve. Then the 9D has TWO checks. To protect against the check failing in the 1156F. 

    There was a discussion recently that said that the manufacturers don't want water boiler feed valves "ON". because of the potential for flooding. I have quite a few houses that have hydronic heat that is left on for the winter. I drain the water but leave the boiler running. This winter, with the water drained, the heat went off at the end of December and the heat circulator ran until the end of February with no breakage of pipes and no leakage from the 9D. The caretaker was in Florida.

    I was told by a boiler inspector that I should take off a backflow from a boiler because it could syphon all the water out of the (steam) boiler. The valve was installed 12" OVER the top of the boiler.

    Perhaps this subject is approaching a Urban Legend.
  • heatpro02920heatpro02920 Member Posts: 991
    I wouldnt shut off

    the water unless I was winterizing the house, 3 weeks what is the sense of that, more trouble than its worth, does the house freeze often? I would sell him either a winterizing connection {which is a wall mounted compressor and the draining pressurising station, or a floodmaster {whole house model, I have a 1" in my house with a sensor in the first floor ceiling under the bathroom/laundry room {installed in a light fixture on the first floor} and one in the basement under the boiler area, plus one on the third floor air handler but that just shuts the air handler down and the water coil so even if its an a/c leak it wont do a lot of damage...
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