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Thermostat will not turn on

Installed a Hydro Smart HSPS1 120LT system with a floor sensor thermostat. System has been working fine. I rerouted the unit power cord and had to unplug the unit to do so. When I plugged the power plug back in the thermostat would not light up and give a reading. I checked all wire connections and could find nothing loose or disconnected. When unplugging and re-plugging the power cord could it have caused a problem with the Taco SR501 Switching Relay. Is thee some way to test the unit to see it the transformer from the unit is supplying power to the thermostat?

Thankd you.


  • neilc
    neilc Member Posts: 2,663
    did the power cord go back to the same receptacle ?
    and if to an other one, maybe that one is wired wrong, out of phase ?
    Is the ground lug in tack ?
    are there any lights lit on the Taco?
    battery dead in the thermostat? and coincidence ?

    do you have a meter? and know to use it?
    and the manual for the Taco and Thermostat?
    known to beat dead horses
  • mattmia2
    mattmia2 Member Posts: 9,390
    How old is this? it isn't uncommon for poor quality switching power supplies to work fine then not turn back on again when powered off when they fail.
  • HomerJSmith
    HomerJSmith Member Posts: 2,386
    edited December 2019
    Mattmia2, might have it correct. When you have two 120V systems that operate together plugged into different sources, you MUST make sure that both power sources are on the same buss in the sub-panel or meter panel. There are two busses in a panel each at 110V, but 180 deg out of phase. If they are not on the same buss, you get 220V across the circuit which fries everything.

    Buy a cheap meter at Harbor Freight and take some measurements. You could also turn off all the breaker on one side of the panel and see if you have power at both power inputs to you devices. If you have power to one and not the other than you are across both busses and the transformer and or thermostat may be shot.