3 Zone Boiler Electrical Help

marckcl52

Hello - I have a boiler with 3 zones with Taco zone valves. One of the zones is not working. I opened the Taco valve manually and the water flowed when another zone was running so I know it doesn’t need to be bled of air. Thermostat seems to be working. Just red and white wire. I twisted them together and still nothing at the zone valve. I do get 24v at the thermostat.

Looking at the Taco valve with the thermostat calling for heat, there is no voltage between 1 and 2. I swapped 2 of the power heads and the problem zone still does not work while the power head works on another zone.

So I seem to have eliminated the thermostat and power head. Not sure where else to turn. The wiring looks good. It worked in the spring. I was thinking that it could be a broken thermostat wire but I’m getting 24v at the thermostat. Any recommendations on that else to test?

fentonc

If you can short the wires together at the thermostat, but the thermostat wire that makes it back to the zone valve still doesn't have any voltage on it, that sounds like the return thermostat wire is broken. With a multimeter that can do a continuity test (or just measure the resistance), you should be able to disconnect the thermostat wires near the boiler and tie them together at the thermostat end and measure the end-to-end resistance across them.

109A_5

During a call for heat you should have 0 (zero) Volts across the thermostat (a closed switch) and 24 Volts between terminal 1 and 2 of the zone valve (the load). By your description it would seem like the wiring is compromised somewhere (high resistance) and can't support the load of the zone valve.

Joe Mattiello

jumping 2, and 3 terminals validates a demand to enable boiler. If boiler fires, it could be a bad ZV head

Call Taco tech support for assistance at 401-942-8000