:confused: I have 2 zone steam boiler with honeywell mechinal zone valves controlled by a three wire thermostat zone valves need power to open on call from thermostat as well as power to close from thermostat... valve is definitely working but I can't figur how to wire 3 wire t stat properly... help

This type of control system uses a special thermostat with a reostat in it, the thermostat either sends voltage through one wire to open or the other wire to close, usually you will have a red, a white and a blue wire, try touching the red wire to the white wire and the valve should open allowing steam to go through the coil, if this does not work try another combination. The thermostat will have letters on the terminals that will (or should) match the wire colors. Good luck, Mike