PLEASE HELP!!! When the 2nd floor heat is on, I have heat coming into the other 3 zones. Sometimes it will only affect one additional zone, sometimes two additional zones, sometimes three additional zones. There does not seem to be a pattern. I don;t know if the problem exists when one of the other zones is on and not the second floor. My mother lives on the 2nd floor, is 78 years old and always has the heat on (thermostat set to about 78), the rest of the house is way to hot. I have a Burnham gas baseboard heating system which was installed in 1994. At that time three zones were installed with zone valves from Bell & Gossett. In 1998 a 4th zone was added using a TAGO zone valve. The problem has been occurring for at least three heating seasons. I called a plumber who wants to replace all the zone valves. He says the wiring is OK. I feel there is some underlying problem. How could all these relatively new zone valves go bad at the same time?
The problem has been since you had the TACO zone valve installed. The B&G valves fail into the open position. It is probable that the TACO overloaded the transformer. Changing to a 75 VA transformer to power the zone valves might solve the problem.