My home is 3 zones (2 hot water, 1 steam) and heated with oil. I added a Nest Thermostat E to one of the zones and while it does work without the 'C' wire, I would like to wire it anyways so my relay stops buzzing when the Nest is powering itself. All of my thermostat wires have 3 conductors and since I have no air conditioning here, I believe I can use the unused 'Y' conductor.
I have 2 zone relay valves (Honeywell 8043F1036) and I'm not certain where the common wire is on this relay.
I believe it is either wires 1 or 2 labeled in the picture. The wiring diagrams on Honeywells website aren't clear which terminal is common, or if it is even one of these terminals.