TACO more problems

Jim Pompetti

ZVC404-EXP we installed 20 ,3 have failed.xx does not make to turn on the boiler. Is it a problem with HW V8043F1051 zone valves or all .

Plumdog_2

Most likely cause of problem

Check the end switch(s) in the zone valves. I would disconnect the red leads from the zone valves at the 3&4 terminals in the Taco control, connect your continuity tester to them, then one by one operate the zone valves (or touch the end switch button) to determine if contact is made. Then jump 3&4 at each station, and the xx should make at all of them. Sometimes if the valve stem has become hard to turn, the rubber ball has swollen for some reason, or just because of too many on/off cycles. Usually the most used zone valves go out first. 

Joe Mattiello

ZVC controls

Good morning Jim

I was reading your tread on the ZVC404 main end switch not closing on a demand for heat.  The ZVC control main and extra end switch close when the thermostat terminals at the top of control close providing 3, and 4 terminals at the bottom of the control close. The 3 and 4 terminals are communication input medium validating the zone valve is open before firing the boiler.  If 3, and 4 do not close the main end switch will not close.  That’s why we show a jumper installed at 3 and 4 terminals on the priority zone when using a circulator and no zone valve. 

For diagnostic purposes try placing a jumper across the thermostat terminals and a jumper across the corresponding 3 and 4 terminals on one of the four zones; then measure continuity at the main end switch.  If the end does not close, please call me to discuss the possibility of a faulty control.  I’m never quick to condemn one of these controls because of their robustness, and excellent track record.