One zone not working - valve issue?

tapritch

Hello,

New homeowner here. One of our zones is getting no heat. It was sometimes working last winter and now not at all. The HVAC professional who came suggested it might be the zone valve but also didn't seem that knowledgeable so I'm asking here.

I have limited understanding but here's what I know:

• We tried to switch the zone valve to manual and there is resistance. The thermostat is turned up and should be calling for heat.
• When we switched the value to manual, the valve opened, water flowed, and heat came out of the baseboard heaters.

Do we need to replace the valve? Or is this an issue of the communication between the thermostat and the valve? (The resistance is the part that's making me question if it's the valve)

Are there other things we can easily test to diagnose the problem?

Thank you!!

109A_5

Hello tapritch,

Sounds like the actual valve works. What needs to be determined is if is is an electrical problem or if the zone valve motor has failed or can't overcome the mechanical resistance. If you have a multimeter is there 24 VAC across the zone valve's motor terminals or wires during a call for heat ? How does the mechanical resistance compare to other zone valves, excessive resistance may be stalling the motor.

mattmia2

Picture of the valve? If it is the type with a manual lever, that moves the gear train that the motor moves so it has some resistance to manually open the valve.