1

I have the same circuit shown here in my house minus any ground wires. I was doing renovations and had the ceiling fixture removed. When I was going to reinstall the ceiling fixture I made sure the switch was off and used a multimeter to test for voltage across the black and white wire coming out of the ceiling where the fixture goes. It reads 65 volts with the switch off. Is this correct? Why is there voltage? Is it dangerous to have this circuit without any ground wires?

enter image description here

2
  • 1
    In the US it would be 120V. But understand that "phantom voltage" is commonly encountered in household circuits.
    – Hot Licks
    Commented Jan 15, 2023 at 17:53
  • How are you measuring? It's probably a measurement error e.g. due to a too-high-impedance meter e.g. any cheap DVM. Not a big deal, you just have to know that DVMs do that lol and take wobbly readings with a grain of salt. Commented Jan 15, 2023 at 18:17

1 Answer 1

-1

You see those wires "from source"? They still have power in them with the switch off.

You never trust a switch when working with electricity, always use the breaker and double check.

Your meter is probably picking up phantom voltage from the live wires.

If you have metal conduit instead of just cable, then the metal conduit can act as your ground wire. One test is to use a voltage meter between the hot(black) and the metal junction/light box. If ground is good you will get a reading of 120v.

7
  • 2
    We really should work out a setup to confirm that induced/"phantom" voltage is just that, with no amperage behind it. Simplest approach I can think of might be to hook an incandescent bulb as a load between the suspect point and ground, then (assuming the bulb doesn't light up) check voltage across the bulb; it ought to drop to negligible, right? (BTW, "phantom power" means something different to a sound tech: common-mode voltage from a balanced input pair to ground, used to cheat 48VDC out to power electret mics and similar devices.)
    – keshlam
    Commented Jan 15, 2023 at 17:11
  • 1
    @keshlam -- a solenoid tester, or a DMM with a "LoZ" function, can be used to distinguish between phantom voltage and something with "oomph" behind it Commented Jan 15, 2023 at 20:19
  • 1
    True. I'm thinking of the folks who have only a basic meter -- just enough to confuse themselves with, as in this case -- and how we might give them something better at minimal cost (and without undue safety issues).
    – keshlam
    Commented Jan 15, 2023 at 21:17
  • There can be other reasons for a reading of 65v and should be ruled out, but in most cases of being close to known live wires and no problems reported with the circuit, phantom voltage is near/at the top of reasons.
    – crip659
    Commented Jan 15, 2023 at 21:33
  • 1
    DON'T TRY THIS: That's the same real world in which an technician my grandfather worked with tested voltage by making sure he wasn't grounded, wetting two fingers on the same hand (to avoid through-the-heart current) and swiping those fingers quickly across the wire pair. If he couldn't feel it, it was low voltage or off. If it tingled, it was 110V. If it hurt, it was 220. If his whole arm spasmed, it was 440. Reportedly pretty reliable until it kills you ...
    – keshlam
    Commented Feb 14, 2023 at 21:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.