Originally Posted by HVACTECH96
end switch on zone valve
You hit the nail right on the head. The zone valve is a White Rodgers 1361-104. I noticed that when there was a call for hot water, the other valve, White rodgers 1361-102 would begin to turn and stop at 90degrees of it's starting point. This opened the valve and allowed the boiler to start. However, when the thermostat called for heat, the valve would start to turn and NEVER stop, so the boiler had no time to fire up. I found the installation instructions for the valve and discovered that once the valve started to open, a circuit SHOULD be made to the "switch heater" and "holding contact". This was not happening. I ordered a new valve ($90.00) and will put it on this Wednesday. I'm doing a work around til then to get heat in the house. I removed the motor from the valve and open the valve manually and jump the TT til the house heats up. Also, when there is a call for hot water I can manually open the valve and this too will circulate water to the baseboards. So in short, the problem is with the WR valve and NOT the Vision Pro IAQ.