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Joined: Feb 2004
Posts: 494
M
Member
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

Greg

2017 / 2014 NEC & Related Books and Study Guides
Joined: Aug 2003
Posts: 1,374
R
Moderator
Yes, any non-linear(harmonic) load creates a current carrying nuetral.


Ryan Jackson,
Salt Lake City
Joined: Nov 2000
Posts: 2,148
R
Member
Only on 3 phase systems.
Don


Don(resqcapt19)
Joined: Oct 2000
Posts: 2,749
Member
... 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
Joined: Jul 2004
Posts: 9,645
G
Member
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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