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Thermostat / wiring problem

Osborn Member Posts: 31
edited April 2015 in Thermostats and Controls
I am a homeowner with a a 9 zone radiator system: thermostat, to taco relay, to zone valves.

I have a problem with one of the zones, in which the zone valve is on despite the thermostat being off. The relay box shows the thermostat to be on (orange indicator), and is passing that on to the valve. If I pull one of the wires going into the zone valve the valve shuts off. So, I'm pretty sure the issue is between the thermostat and the relay. I tried another thermostat and the relay still showed "on". I also removed the thermostat and disconnected the wires. Still "on". I haven't looked into the relay box.

This system has worked for three winters.

Does anyone have a suggestion?


  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    If you've disconnected both leads from the stat, at the Taco relay terminals, and the indicator light is still on despite no input....and you're seeing 24v to that zv....then yes, I would suspect the relay. Is this Taco's ZVC panel or the SR?
  • Empire_2
    Empire_2 Member Posts: 2,343
    edited April 2015
    Right Bob,... I'm thinking along the lines of something happened inside the walls resulting in a short from stat to Taco pump relay. Bob has a good idea,....Disconnect the stat connection at the Taco pump relay and see what happens. If the same scenario occurs, then it's your Taco pump relay, if not there is some kind of short, wire to wire inside the wall.

    Bob Bona_4