03-31-2008, 09:22 PM
I have a boiler with 3 (taco) zones (air handlers on two floors and an indirect water heater) and a single circulator (taco). For some reason one of the zones provides no heat. I noticed when the thermostat calls for heat the air handler kicks on, the zone valve opens and the boiler fires up, however no circulation of hot water occurs. It was working fine, then intermittently started this behavior which is now constant. I can get the zone to produce heat by shutting off all thermostats, then turning on the one zone in question. If the circulator works for the other zones what could be the problem?