Taco Zone Valve box noise

Peter2

I have a Taco ZVC403 zone valve control box. I have 3 zones each having their own thermostat. When a zone calls for heat there is a “LOUD” buzzing noise and I believe it is coming from the zone valve box. What would cause this? The strange thing is it doesn’t happen all the time. I’ve been shutting the power switch (electric) off to the boiler when it does happen. Any help would be greatly appreciated. Thank you in advance. Peter

STEVEusaPA

It's a relay vibrating, or causing vibration.
If I were there I'd first do the non-technical, but aware of electricity, 'pushing on stuff' while it's buzzing to see if it stops. I've seen them buzz if the cover isn't screwed on tight.
If that hail mary doesn't work, it's time to open it up, get a meter and see whats doing.
Do you have any power stealing thermostats (brand/make/model)?

Peter2

Thank you Steve. 

Two of the thermostats are Lux 1500 and the other is Honeywell Home RTH7560E1001. 

My system is HEAT only. 

Alan (California Radiant) Forbes

I believe the old Taco ZVC's had replaceable relays. Don't know it that's still the case. If not, you will probably have to buy a new control to make the noise go away.

Peter2

Thank you Alan.