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480 v hps lighting circuit #205541
03/02/12 05:12 PM
03/02/12 05:12 PM
Cinner  Offline OP
Joined: Dec 2004
Posts: 78
Kelowna, B.C., Canada
I was working on a 480v hps lighting circuit and went to turn the circuit off to change the fixture but still measured 66 volts to ground on each leg. Does. Any one know why this would be?

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Re: 480 v hps lighting circuit [Re: Cinner] #205542
03/02/12 06:15 PM
03/02/12 06:15 PM
LarryC  Offline
Joined: Jul 2004
Posts: 783
Winchester, NH, US
What type of meter did you measure the voltage with? If it is an electronic meter with the high input impeadence, it will measure "ghost" voltages. These "ghost" voltages are due to the wires traveling next to energized wires. Both set of wires are acting as a transformer.

Measure the voltage with a Wiggy or equivalent and the voltage will PROBABLY disappear. If they do not disappear, you have a problem. If the voltage does disappear then you are measuring ghost voltages.

Re: 480 v hps lighting circuit [Re: Cinner] #205543
03/02/12 06:22 PM
03/02/12 06:22 PM
Cinner  Offline OP
Joined: Dec 2004
Posts: 78
Kelowna, B.C., Canada
Measured it with a fluke multimeter.

Re: 480 v hps lighting circuit [Re: Cinner] #205545
03/02/12 09:37 PM
03/02/12 09:37 PM
Tesla  Offline
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
Fluke multimeters ARE high impedance testers.

You need to use an old-style analog meter to load down these induced voltages. Since there is no current flow, it's really a capacitive effect.

Re: 480 v hps lighting circuit [Re: Cinner] #205547
03/02/12 11:21 PM
03/02/12 11:21 PM
HotLine1  Offline

Joined: Apr 2002
Posts: 6,934
Brick, NJ USA

You need a 'Wiggy', or any other brand solenoid type tester, or an analog multi-meter.

Re: 480 v hps lighting circuit [Re: HotLine1] #205550
03/03/12 04:26 AM
03/03/12 04:26 AM
sparkyinak  Offline
Joined: Jul 2007
Posts: 1,329
WIGGGGGGGY!!! I carry one in my pouch just for that

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Re: 480 v hps lighting circuit [Re: Cinner] #205556
03/03/12 06:36 PM
03/03/12 06:36 PM
Lostazhell  Offline
Joined: Feb 2004
Posts: 1,431
Bakersfield, CA (Originally Or...
This happens in a cogen I work in alot.. 480V wiring from VFD loads seem to induce voltage on other conductors more than anything.. HID loaded circuits have the same tendency


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