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New Thermostat for 3-wire System

An_FoAn_Fo Member Posts: 2
I'm trying to update my thermostats around the house. They currently are old mercury-powered White-Rodgers, and I'm just looking to step up to anything newer.

The problem I am having is that the new Honeywell I put on doesn't turn the boiler off.

I have three White-Rodgers zone valves, and from what I can tell, they need a longer signal to start closing than just the thermostat stopping the heat call.

The old thermostat ran off of three wires: red, white, and green.

Touching the red and white together calls for heat, and the valve opens.

Touching the green to red for more than 5 seconds closes the valve. Any amount of time shorter than that, and I can hear the valve start to close, but if I release the wires, it doesn't continue closing.

With the new thermostat hooked up ( red to R, White to W, Green to G), when I stop the heat call the valve does not close, and the boiler just runs continuously. I've tried moving the wires to various other positions to no avail.

Am I missing something obvious? Are there other thermostats that might work? Other positions that I should try for the wires?


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