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Will DC voltage harm an AC thermostat

Actovon, I think any non-electronic stat should work. I know automag zone valve systems used DC to eliminate the 60 hertz hum from the solenoids. They use conventional stats. Some heat anticipators may have a very small amount of inductive reactance. I think it would be insignificant. bob


  • Actovon
    Actovon Member Posts: 2
    DC voltage with Thermostats

    I am going to redue my heating system, it is a coal, hot water system. I was able to get my hands on some 24 VDC relays and a DC power supply from my work. However, when I looked at the present zone control I noticed it was AC voltage. Will I be able to use the DC voltage to operate the thermostats?
    There are a total of 6 thermostats, 2 are the Honeywell round dial type, I believe T87. the other 4 are cheap rectangular type.
  • carol_3
    carol_3 Member Posts: 397

    I don't think the DC will work with AC stats. AC transformers are very inexpensive, so I'd recommend going that way.

  • Any mechanical thermostat, mercury switch or dry contact should work fine on DC. Keep in mind that the anticipator may not work correctly with a high coil resistance DC relay. The relay current draw may so low that it fails to heat the anticipator, even at the lowest current setting.
  • Ken_40
    Ken_40 Member Posts: 1,320

    They'll work. Done it more than once. It's all about the amp draw. If it's under 2 amps, your probably fine. If it's under one amp, you are absolutely fine.
  • Actovon
    Actovon Member Posts: 2

    Thank you all, I thought it should work, since it basicly is a switch, but wanted to get some opinions of people who know or may have done it. I was just about to go to the local Grainger store and purchase some AC relays. Thanks again for the info.
  • Mad Dog!!!!!!!!
    Mad Dog!!!!!!!! Member Posts: 157
    The only reason I could see to convert to a DC system

    is if you were going with PV (Photo-Voltaic) panels for your ENTIRE electrical generation. Are you sure you are not trying to "make" the things you got free from work, "work" in your house? My concern would be A) is it safe? b) The service nightmare this could be down the line...when you are not there or around to inform the person working on it. Curious to see how you make out. Mad Dog
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