I have a baseboard hot water system with a gas boiler. Boiler is 6-7 years old. It has three zones with 3 separate pumps and thermostats. I checked the thermostat wires and they are 110 volts. Folks at the local hardware store I talked to were surprised with the 110 volts but suggested I could use a thermostat used for electric baseboard heaters. I would think this would work since the new and old thermostats have only 2 wires. The instructions for the Honeywell RLV430 caution that this thermostat can not be used with systems that have a contactor of relay. How can I confirm that the Honeywell is compatible with my system?

But it clearly states it is for 120 V applications. And your termostat wires are 110 V? Do you know what gauge wire it is? Do these termostats turn on the pumps directly?

The wires are 14 AWG. I checked the wire with a voltmeter and read 116 volts. I have included 3 pictures. The 3 thermostat wires run into a single electrical box and then into 3 individual Culter Hammer boxes and back. From there 4 armored cables exit the electrical box. Three of these run into the 3 pumps, one per pump. The other runs into another Cutler Hammer box attached to the side of the boiler. Hope this helps.