I recently purchased three Honeywell RTH221 thermostats to replace my old ones. I purchased three thermostats, one for each zone. For each zone, I have a red, black and white wire coming out of the wall. The lowest zone did not have the white wire hooked up when I disconnected the original thermostat, but the two other zones did. I hooked the red wires to the RH label, black to the W label and did not hook up any of the white wires to anything. My heat is turning on, but when the thermostat on the lowest zone turns on, hot water is sent to all 3 zones instead of only the one. Is it because the white wire isn't hooked up on the other 2? If so, where should I hook it up to on the thermostat? Or do I have the entire wiring incorrect? Thanks,