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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 21978
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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I have a weil-mclean boiler and a Taco 404 zone valve controller.

Customer Question

I have a weil-mclean boiler and a Taco 404 zone valve controller. 3 heating zones plus a side-arm hot water heater is the 4th zone. The hot water zone is the Priority zone. about once a week the boiler goes cold. green light is on and red and yellow lights for the priority zone are on - calling for heat. but boiler doesn't fire up. if i switch off the power supply and turn it back on it fires up, sometimes immediately, sometimes with a buzzing sound coming from the transformer. I tried running it for a few days with the priority zone off. makes no difference. how do i trouble shoot? the system is 18 years old and everything looks like the day it was installed. no loose wires.
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Submitted: 1 year ago.
Category: HVAC
Expert:  Rick replied 1 year ago.
Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.Next time it happens check for continuity across the end switch terminals. Also check the connections between the boiler control and those end switch terminals. 18 gauge wire is notorious for (partially) breaking unnoticed. When there is a call for heat once the zone valve opens the red light goes on and that end switch should close calling in the boiler. If a red light is on (priority or another zone if priority is satisfied) and the end switch doesn't close then you need a new ZVC.