Stray Voltage Troubleshooting

[jerjwillelec]

Picture this...A 10 year old Family Aquatic Center has 5 light poles with 4 Medal Hallide lights on each pole. One of the 4 lights on each pole is on a (208 volt) night light (NL) circuit and 3 other (208 volt) circuits feed the rest of the lights. 2 conduit runs from the source (lighting contactors) with 2 poles and 1 circuit (plus NL circuit) in one conduit run and 3 poles with 2 circuits (plus NL circuit) in the other run...this run also has an outlet circuit with GFCI protected receptacles on each of the 3 poles. When only one of any of the 4 circuits is on, I am reading anywhere from 18 to 28 of stray "backfed" voltage (on the other circuit's conductors) at the contactor. Turning the receptacle circuit on and off seems to make a difference as well. When all are on, everything seems to work fine. Any ideas???

Please ask questions...This origional post is just the basics...and I will add another (maybe related) issue as we go on...

 

[LarryFine]

If you're using a typical high-input-impedance voltmeter, that's normal. Energized conductors can induce voltages in parallel wires.

If you don't have a low-impedance meter, try reading the voltage (line to neutral only) with a 120v bulb in parallel with your meter.

 

[brian john]

Picture this...A 10 year old Family Aquatic Center has 5 light poles with 4 Medal Hallide lights on each pole. One of the 4 lights on each pole is on a (208 volt) night light (NL) circuit and 3 other (208 volt) circuits feed the rest of the lights. 2 conduit runs from the source (lighting contactors) with 2 poles and 1 circuit (plus NL circuit) in one conduit run and 3 poles with 2 circuits (plus NL circuit) in the other run...this run also has an outlet circuit with GFCI protected receptacles on each of the 3 poles. When only one of any of the 4 circuits is on, I am reading anywhere from 18 to 28 of stray "backfed" voltage (on the other circuit's conductors) at the contactor. Turning the receptacle circuit on and off seems to make a difference as well. When all are on, everything seems to work fine. Any ideas???

Please ask questions...This origional post is just the basics...and I will add another (maybe related) issue as we go on...

Larry hit it on the head.

http://us.fluke.com/fluke/usen/community/fluke plus/articlecategories/dmms/dual impedance.htm

http://support.fluke.com/find-sales/download/asset/2105317_a_w.pdf

An inexpensive option.

http://us.fluke.com/fluke/usen/accessories/test-leads-probes-and-clips/tl225.htm?PID=56740

 

[jerjwillelec]

Thank you very much!!! I know I can always count on this forum when I'm stumped. Thanks again.