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20 Output Circuit Grounding; Z- T4 s p o* V+ q6 l5 p
20.1 The requirements for circuit grounding specified in 20.2 – 20.12 apply to the output circuit of fixed0 b0 [! i5 G# i
units and of units having standard configuration grounding type receptacles for the output ac power
* z4 P7 U3 z K0 C2 j) x) i* Qconnections.: b0 x- H! u6 |- G5 n5 y- w! @2 W
20.2 An output ac power circuit shall be grounded when:
: L7 m) Q w5 S7 G2 Pa) The circuit has no electrical connection, including a solidly connected grounded circuit. H/ f4 b# [0 t( d. a
conductor, to supply conductors originating in another wiring system;4 ^+ \3 e9 w' p6 F% J: j9 H4 w. E
b) The circuit is rated 50 – 600 volts; and' x4 ?" \. f/ g9 W& {
c) The circuit is as described in (1) – (3). See requirements for Alternating-Current Circuits and
/ q+ {% ] E% w$ rSystems to Be Grounded in the National Electrical Code, ANSI/NFPA 70, for other circuits:/ c5 U$ `, c `7 g- A
1) A circuit that is grounded so that the maximum voltage to ground on the2 ~ K9 I% N7 [ |/ [( z
ungrounded conductors does not exceed 150 volts. This requires that one conductor of* C1 L) G0 B; W$ w7 z
each of the following circuits be grounded:
' y& D9 `! ~! M8 ~i) 120 volts, 2-wire;
# U7 k i a# q( Vii) 240/120 volts, single-phase, 3-wire;
9 y1 s" Z2 \- R# K1 e9 D$ {iii) 208/120 volts, two-phase, 3-wire;
; \' Q8 \! u, Y7 B' Uiv) 208/120 volts, three-phase, 4-wire.
& g9 O& E1 a; y5 a: `2) A circuit nominally rated 480 wye/277 volts, 3-phase, 4-wire in which the neutral is+ L, n& Q/ h6 ?& o
used as a circuit conductor.( A) r9 v' M9 P$ ~1 D2 o) @* t
3) A circuit-nominally rated 240/120 volts, 3-phase, 4-wire in which the midpoint of one
: L# r# ^ f) `% `1 Cphase is used as a circuit conductor.
2 b7 S W: n7 eFor other units, an output ac power circuit complying with (a) is able to be grounded when the construction
% b1 z2 ]" g/ U6 i1 S- Y6 ]7 Ncomplies with the requirements described in 20.3 and 20.11.
7 ?8 M- L# N6 g5 `; ~- ^20.3 With reference to 20.2, the conductor to be grounded shall be as follows:
: D) y' G& p) e& Ba) Single-phase ac system, 2-wire – one conductor.! i6 b# ~* m, d, q
b) Single-phase ac system, 3-wire – the neutral conductor.
Z+ M& b: x! W5 X* X4 ?% Jc) Multiphase ac system having one wire common to all phases – the common conductor.
2 e4 r) s2 N3 A1 x3 i# s- k3 S5 {d) Multiphase ac system where one phase is used as in (b) above – the neutral conductor.. n" ^% H7 ^! K# w; }! [, j$ O
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