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#92345 - 03/14/05 11:58 AM Neutral Counted As Current Carrying
mustangelectric Offline

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
If a circuit supplies a fluorescent, mercury or metal halide do the neutrals still have to be counted as current carrying? This neutral will carry a third harmonic.

Thanks for any replies

Electricity has no respect for ignorance!

2014 / 2011 NEC & Related Books and Study Guides
#92346 - 03/14/05 12:29 PM Re: Neutral Counted As Current Carrying
Ryan_J Offline

Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
Yes, any non-linear(harmonic) load creates a current carrying nuetral.
Ryan Jackson,
Salt Lake City

#92347 - 03/14/05 12:35 PM Re: Neutral Counted As Current Carrying
resqcapt19 Offline

Registered: 11/10/00
Posts: 2209
Loc: IL
Only on 3 phase systems.

#92348 - 03/14/05 02:09 PM Re: Neutral Counted As Current Carrying
Joe Tedesco Offline

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
... and only when that nonlinear load is the major portion (over 50%) ....

See the 2005 NEC .....

Nonlinear Load. A load where the wave shape of the steady-state current does not follow the wave shape of the applied voltage.

Article 310

(c) On a 4-wire, 3-phase wye circuit where the major portion of the load consists of nonlinear loads, harmonic currents are present in the neutral conductor; the neutral shall therefore be considered a current-carrying conductor.
FPN: Electronic equipment, electronic/electric-discharge lighting, adjustable-speed drive systems, and similar equipment may be nonlinear loads.
Joe Tedesco, NEC Consultant

#92349 - 03/14/05 07:58 PM Re: Neutral Counted As Current Carrying
gfretwell Offline


Registered: 07/20/04
Posts: 9026
Loc: Estero,Fl,usa
You can still induce out of phase currents in a single phase neutral (multiwire circuit) but you won't get the overload effect you get in 3 phase. It can still make measurememnts not balance if your meter isn't true RMS.
Greg Fretwell


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