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Adding C Adapter to 2 Wire Thermostat in a 3 Zone Configuration

I have 3 2-wire thermostats for my baseboard boiler heating. On one of the zones I want to add a Honeywell T9, so I can put a remote sensor in a different room (i.e. a den that is on the same heating zone as my basement). The thermostat has 2 wires (R and W). It attaches to my TACO 3 zone ZVC403 controller. Where it goes in, the screw terminal has 3 wire connections for each zone, of which only 2 connections are used. There is a C connection that is not used. Is the connection of the c-wire adapter as simple as connecting the adapter to R,W,C board terminals and the R,W wires from the thermostat to the adapter? If not, how do I install the adapter?

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,269
    edited December 2022
    NO

    Is there an unused wire in the thermostat wire from the thermostat location to the ZVC-403?


    Take a picture of the thermostat wire connection inside the ZVC-403 control from about 3 ft back with the cover off, so I can see the wires outside the box for about 1 ft in all directions.

    The C wire adaptor assumes that there are at least 4 wires to the thermostat because it assumes that you have air conditioning and heat form your old thermostat.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?