Single circulation pump not activating for one zone.

bezerk1

Oil furnace, hydronic heat. System has 3 zones, three thermostats, three Honeywell valves, and one circulation pump. I have confirmed that all three valves work properly when activated via thermostat. When my number 2 zone thermostat calls for heat, the valve opens but, the circulation pump does not start. If the circulation pump is already running because of another zone, zone 2 will heat.

How does the circulation pump circuit work? Is the circulation pump activated by the auxiliary contact wires in the Honeywell zone valves?

Thanks in advance.

STEVEusaPA

What type of zone valve?
How did you confirm the zone valve was opening.
Assuming the usual control set up, all your zone valves are wired so when a thermostat calls it opens the zone valve. When the zone valve is opened, the end switch closes, making a complete circuit with T-T on the aquastat, turning on the circulator (and maybe firing the burner).
So it's either the zone valve head is bad, or the wiring is bad.
Easy enough to swap out to check. Just make sure the power is off to the transformer controlling the zone valves. Many times they are on a separate circuit, or wired constantly hot and turning off the service switch to the boiler does not de-energize the transformer.
Even though it's low voltage, if you cross wires replacing the zone valve head, you'll probably smoke it.

bezerk1

Thank you for your information. It is very helpful and makes perfect sense now. I believe the valves are Honeywell 8043. I confirmed the valves are working by placing my finger and the manual actuation lever. When the thermostat activated I could feel the valve moved to the open position. When the thermostat stops calling for heat, the valve closes. Is the end switch located in the valve head? Can just the valve head be replaced? Once again that you very much.

HVACNUT

Yes you can replace the head only.