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Zone Valve Voltage issue

I had an HVAC tech come out to replace a Taco Zone Valve Head (second floor) due to no heat. Two weeks later no heat again, the Taco Zone Valve Head on the first floor needed to be replaced. The HVAC technician showed me on a voltage reader that 56 volts (not 24 volts) were being sent to zone valve head, and blew it out. He diagnosed that I needed to install a low voltage connector to fix the wiring problem. Can you explain what a low voltage connector is? Before he left, I saw him remove an Aligator Clip jumper wire from the Valve Control Module, and re-check the voltage. After being suspicious, I had another company come out to fix the voltage issue. The new technician confirmed there were only 24 volts, not 56 volts sent to the Zone Valve. Can someone explain how he rigged it to 56 volts to the zone valve head? Could this blow out the zone valve? Apparently, I have 120 volts from external power source and 24 volt transformer within the Valve Control Module. Could he have used the Aligator Clip jumper wires to double the voltage?


  • ratio
    ratio Member Posts: 3,702
    I don't know if he "rigged anything", but if there are two or more low voltage transformers present it is quite possible to end up with 56 volts. One side of the low voltage is usually grounded. If "opposite" sides of the two transformers are grounded, you'll see 24V + 24V ~= 56 volts between the other two transformer terminals. After that, a simple wiring fault or error is all that needed to have 56 volts present.
  • unclejohn
    unclejohn Member Posts: 1,833
    I keep two Taco power heads on my truck during the winter. Having to replace one power head and then the other, too me is not terribly suspicious. However needing a “ low voltage connector “ ONLY and not a knibbler pin with reverse threads along with it is very suspicious. What I would seriously do though is call the company and ask for the owner and have him explain what his tech. meant by the term “ low voltage connector “ as Ratio said you would need to have two transformers to get that hi of voltage and the power heads won’t last long at all with that kind of voltage.
  • Zman
    Zman Member Posts: 7,607
    It sounds like there is a problem with the way your low voltage is wired.
    You likely have 2 transformers that are wired to 2 different circuits. When they are separate you have 28 volts, when something switches they are combined and you get 56 volts. For the same reason your electric range has 240 volts while each leg only has 120.
    A picture or drawing would help.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein