The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
230 or 345 kV transmission lines?
by Vlado
Yesterday at 09:33 AM
breaker meltdown
by crselectric
Yesterday at 12:42 AM
Electrical mast flashing product
by ThomasWinfrey
09/22/16 12:14 AM
What estimating software do you recommend?
by sparky
09/21/16 07:20 PM
"Dry Run" Inspection goes awry
by HotLine1
09/20/16 07:39 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
HotLine1 17
gfretwell 9
sparky 9
sparky66wv 8
Vlado 6
Who's Online
1 registered (Webmaster), 63 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#170916 - 11/14/07 07:09 PM 480v lighting
etech Offline
Member

Registered: 06/16/07
Posts: 17
Loc: 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.

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#170923 - 11/14/07 11:01 PM Re: 480v lighting [Re: etech]
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: 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
Just Say NO To Green Eggs And Ham!

Top
#170930 - 11/15/07 07:57 AM Re: 480v lighting [Re: Scott35]
Zapped Offline
Member

Registered: 10/01/02
Posts: 481
Loc: 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!

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals