We just finished a remodel job on my home, putting on an extra room. We have hot water heat with a zone for the basement and one for the upstairs and added a third zone for the extra room. 1st question: How many hook-ups can go on one transformer? Two are on it now. If I can put this third zone on, how would the wiring be connected? Does anybody have a diagram? I studied the present wiring, which looks just like any electrical wiring match up and connections, with a tail from the main zone to the one for the basement and then white wires being tied together etc. I need help to finish the job and to be able to get heat to the room with it's own thermostat setting. Thank you, Rick Smith

What you need to do is look at the power everything draws, the gas valve, pump relay coil, and each zone valve. Watts equals amps time the 24 volts. Get everything in either amps or watts. Compare the total power needed to the rating of the transformer. And yes, just wire the third one in like the other 2. In most systems the white is hot to valves and relays. A blue or black usually works like the white neutral of house wiring.