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#170916 - 11/14/07 11:09 PM 480v lighting  
etech  Offline
Member
Joined: Jun 2007
Posts: 17
Oregon
14 pole lights draw 14 amps at 480v single phase.
Clamp on meter reads 14 amps on one leg, 12 amps on the other leg. The other group of 12 pole lights draw 12 amps on both legs. Am I wrong to think that both legs should read the same. All comments are welcome
Thanks.


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#170923 - 11/15/07 03:01 AM Re: 480v lighting [Re: etech]  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
Good question!

Is the CT of the Ammeter too close to the Ballast's Core, resulting in an incorrect reading?

Additionally, could the Branch Circuitry be Multiwire with a common Grounded Conductor?

Additionally, could the unbalanced fixture's ballast be leaking some current to the equipment grounding conductor? (like a grounded segment at the Reactor Coil, or an uncapped AutoTransformer Multivoltage Tap lead connecting to grounded metal equipment)

Maybe someone has tapped into that 14 amp line, and made an L-G connection somewhere - causing the unusual imbalance.

Scott


Scott " 35 " Thompson
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#170930 - 11/15/07 11:57 AM Re: 480v lighting [Re: Scott35]  
Zapped  Offline
Member
Joined: Oct 2002
Posts: 482
Huntington Beach, CA, USA
Yes, ballasted loads do strange things when hooked up to meters (take a look at a spectrum analyser and a sine wave graph on a multi ballasted circuit some time - ugly business). Double check your readings, then ask yourself a few questions...

Is there a problem with the lighting performance? (i.e. a slow starting ballast, cycling or super bright lamp, etc.)

Which reading (12A or 14A) matches the expected draw of the lighting?

If you take a few fixtures off the circuit, do the legs level out?

My guess is that you'll find one or more of the fixtures to be your culprit(s). Once narrowed down, a ballast change out (or two) may be in order. Either that, or the wiring to/from a particular fixture is the answer.

Good Luck!



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