I am trying to solve a perplexing problem I think is with the thermostats and controller of my boiler system (hot water baseboard).
I have a Peerless Purefire PF-80 with a Taco ZVC403-4 controller and two Hunter model 44110 programmable thermostats. We have two heating zones – upstairs and downstairs. The problem is, in the early morning when the first floor thermostat calls for heat, the furnace won’t come on. The yellow light on the controller turns on, indicating that the thermostat is communicating with the controller. In about thirty seconds, the red light on the controller comes on and the water valve opens. However, it is supposed to get the board’s main relay to close which activates the circulating pump and the furnace, but I don't think that happens (I don't think I heard the relay snap closed). Whenever the second floor thermostat calls for heat, it works perfectly. In addition, the furnace will stay on if the first floor thermostat is calling for heat after the second floor thermostat shuts off, but it seems that the second floor thermostat has to get things going.
At this point we have replaced all batteries in the thermostats, we replaced the first floor thermostat and replaced the controller. When I rewire the thermostats at the controller so that they are operating the opposite zone, the upstairs thermostat continues to work properly with the system and the first floor thermostat continues to fail. (It does not seem that the circuitry of the controller is malfunctioning for the zone that was used for the first floor.) Thinking that there must be something wrong with the thermostat wire, I began tracing it out. I did find that they spliced it at one point and capped it with wire caps. They did not twist the wires together and they used too large a wire nut – only the tips were touching. I twisted the wires together and the first floor system worked – that one time. I think that there was some sparking while I was doing that and that may have jagged the system enough to get the controller main relay to close. It hasn’t really worked since, though.
Has anyone else come across this sort of problem? Are these thermostats supposed to provide a certain amount of amperage to get the controller to do what it is supposed to do? The only thing I haven’t done yet is move the upstairs thermostat to the first floor to see if there’s something with the wiring I can’t see. It just seems that if it is communicating with the controller – turning on the yellow light and getting the water valve to open, it should be able to get the main relay to close. Thanks for any help with this! - Mike