Thermostat stuck calling heat

maxsimon03

Hi, I have a Lochinvar boiler with a Taco ZVC406 6 zone controller with a second SR501 that runs to a separate building.  The building has two Honeywell thermostats that lead to the one zone controller.  Both thermostats are shut off and set to 60, and do not say they are heating.  However, the controller light indicates they are calling for heat, resulting in the building temp being over 90.  I tried disconnecting the red wire on the controller which shut it off.  Any help is greatly appreciated, thanks!

bburd

Sounds like a short circuit in the wiring between the thermostat and the zone controller. You can check this with a test meter.

Jamie Hall

Short circuit -- or possibly a stuck relay in the controller (not the thermostat).

HVACNUT

The space can't be getting heat if the zone valves are closed. At least one is powered or stuck open. So it's not the wiring between the buildings.
2 Honeywell thermostats are connected to the SR501? Is R-W (TT) in the SR501 connected to end switches for zone valves in the other building and not connected to the ZVC board?
If so, then in the other building there's either a bad thermostat, shorted thermostat wiring powering a zone valve open, or a zone valve stuck open and closing the end switch. 

maxsimon03

Thanks for the help!  Both zone valves are stuck open, which I’ve tested by jumping the yellow wires.  I will replace both and update.

maxsimon03

In response to HVAC nut, the zone valve relays (red wires) are connected to the TT circuit, and the zone valve motors (yellow wires) are connected to the thermostats.