I have just installed a Biasi B10-4 oil fired boiler with a Hydrolevel control to an existing system that has 3 zones controlled by Taco zone valves and a Smart 50 indirect on a pump. Supply house suggested a Taco ZVC 404 because I can allegedly control a DHW pump off of it on the priority zone. By following the wiring diagram we (electrician and myself) tied in the DHW pump and the system pump as per the Taco instructions. When one of the heating zones calls, the valve opens and the system pump does its thing. When the DHW calls both pumps come on. How do I get the system pump to NOT operate? I am not tied into the hydrolevel control cuz I figured the Taco board will control everything.
I am assuming your DHW Circ is tied to the zone 4 N/O relay and the system circ is to the extra TT?
If the system circ takes it's power from the N/C side of the DHW relay that should do it.
Just jumper from N/C to TT were the power goes now. The system circ will lose power when the dhw energizes.