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#205541 - 03/02/12 01:12 PM 480 v hps lighting circuit
Cinner Offline
Member

Registered: 12/01/04
Posts: 77
Loc: 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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#205542 - 03/02/12 02:15 PM Re: 480 v hps lighting circuit [Re: Cinner]
Happy Birthday LarryC Offline
Member

Registered: 07/05/04
Posts: 776
Loc: 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.

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#205543 - 03/02/12 02:22 PM Re: 480 v hps lighting circuit [Re: Cinner]
Cinner Offline
Member

Registered: 12/01/04
Posts: 77
Loc: Kelowna, B.C., Canada
Measured it with a fluke multimeter.

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#205545 - 03/02/12 05:37 PM Re: 480 v hps lighting circuit [Re: Cinner]
Tesla Offline
Member

Registered: 06/16/04
Posts: 1280
Loc: 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.
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#205547 - 03/02/12 07:21 PM Re: 480 v hps lighting circuit [Re: Cinner]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
Cinner:

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

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#205550 - 03/03/12 12:26 AM Re: 480 v hps lighting circuit [Re: HotLine1]
sparkyinak Offline
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Registered: 07/08/07
Posts: 1295
Loc: Alaska
WIGGGGGGGY!!! I carry one in my pouch just for that
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#205556 - 03/03/12 02:36 PM Re: 480 v hps lighting circuit [Re: Cinner]
Lostazhell Offline
Member

Registered: 02/21/04
Posts: 1248
Loc: 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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