Current set up is a hot water boiler running 3 zones for heat and one zone for domestic hot water that fills a 100 gallon tank (4 total). the current thermostats are : mercury dial for first and second floor controlled with 2 wire (red/white). third floor is a go well digital that controls the hot water baseboards for the third floor and A/C as well. I have run a secondary set of wires to the second floor thermostat to the boiler zone valve control unit for the purpose of the “C” wire. In the zone valve control unit there is a common and 24v supply. I attempted to hook this up and it ended up just turning the zone valve solenoids off and on and the thermostat would power up and shut off in the process. Do I have the correct thermostat? If not what do I need? Which thermostat should I use for the first floor that is only two wire and the third floor which will also run the A/C ? RTH6580 Wf is the thermostat I am trying to use. Honeywell is the brand.
This one has no common wire. Some older HVAC systems may not have one. You need to rely on a battery if you have no c wire. https://www.amazon.com/Honeywell-Ly...-Systems/dp/B01M064ULB/ref=asc_df_B01M064ULB/
