Taco ZVC problem

Slimpickins

I just had an old customer that lives out of town call saying he had no heat. He said the boiler was working because he had hot water but no heat and the Taco ZVC 406 had no lights showing.  I told him to shut off the power and check the fuse on the control and he said it was blown. He replaced it with a 4 amp and it blew immediately. Fortunately he has space heaters to get him through the night.



I'm not sure what is causing this. I'm controlling the system pump with one of the end switches and wondering if the pump could have caused it or could I have a short on the 24 volt side? I just installed the system a few months ago so I'm puzzled, never had a problem with a Taco control before. Thanks for any advice before I make the 3 hour drive tomorrow.

EricAune

How many zone valves?

How many and what type?



Is it possible one of the zones has not fired until today? Maybe some wires were routed/connected incorrectly and the problem wasn't caught because of the tendancy to manually operate on start-up?



I have only ever blown a fuse when I start getting "fancy" with my end of the "need the control to do". 

Slimpickins

return visit

I went back to the job with extra fuses. Then I disconnected all the thermostats from the thermostat connections on top and disconnected  the system pump wiring from the end switch, I'm operating 5 zone valves on the ZVC406 BTW. I connected the thermostats one by one and they each opened the zone valve and fired the boiler, A Prestige Solo 110. I next connected 120v which I ran a leg from where I tied in the transformers on the box to the end switch and it immediately blew the 7 amp fuse. I checked and tested the wiring from my service/emergency shut off switch and it looked good. 



I took the box back my to supplier and swapped it out and it's working perfectly. Still not sure what happened, I've installed dozens of these with nary a problem. So I guess thats a pretty good success rate.