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20 Output Circuit Grounding
- N! G9 w7 U. H4 h20.1 The requirements for circuit grounding specified in 20.2 – 20.12 apply to the output circuit of fixed6 F* ]: g7 R8 s
units and of units having standard configuration grounding type receptacles for the output ac power2 y3 T/ C' ^; D7 {; b {
connections.9 {. x. C/ Z- L' l. D, v5 d
20.2 An output ac power circuit shall be grounded when:
0 d7 e' {& i- y9 p* G3 p. c4 F3 Ka) The circuit has no electrical connection, including a solidly connected grounded circuit
* } J8 u1 X: G, [: v1 mconductor, to supply conductors originating in another wiring system;0 k* h: L. [, P/ \; B
b) The circuit is rated 50 – 600 volts; and
) h. l3 ]3 x" s5 B1 N3 y. _2 nc) The circuit is as described in (1) – (3). See requirements for Alternating-Current Circuits and2 I' n X1 B4 W
Systems to Be Grounded in the National Electrical Code, ANSI/NFPA 70, for other circuits:
: P& {8 i, Y' ^- Q# m1 N R1) A circuit that is grounded so that the maximum voltage to ground on the
: k# b% T2 M! [6 e4 Aungrounded conductors does not exceed 150 volts. This requires that one conductor of
- l5 ]" Y' C, J! u3 Feach of the following circuits be grounded:
" f- P" ?& m" f. {i) 120 volts, 2-wire;6 A" l$ f* c1 l' M8 M
ii) 240/120 volts, single-phase, 3-wire;3 Z8 S' Z% S( H: k- c3 o! U
iii) 208/120 volts, two-phase, 3-wire;
. Q2 G* N' ~! div) 208/120 volts, three-phase, 4-wire.
; r: A$ | A4 `; c6 V: ]6 {- u2) A circuit nominally rated 480 wye/277 volts, 3-phase, 4-wire in which the neutral is
- I, q; f5 n5 m9 D& c/ u( J. lused as a circuit conductor.
5 g* k0 y2 B. W! R: D7 {( s3) A circuit-nominally rated 240/120 volts, 3-phase, 4-wire in which the midpoint of one
# q. X0 ?: G& u. s8 f. Gphase is used as a circuit conductor.
b; W! R' U/ b% j3 hFor other units, an output ac power circuit complying with (a) is able to be grounded when the construction
# J: d/ A& f+ ]6 Wcomplies with the requirements described in 20.3 and 20.11." @- y/ o. n# q7 q a7 H
20.3 With reference to 20.2, the conductor to be grounded shall be as follows:2 k! i1 ?8 r8 O+ C. E
a) Single-phase ac system, 2-wire – one conductor.4 e! v& o4 j: r" S# v5 H
b) Single-phase ac system, 3-wire – the neutral conductor.
5 f2 y2 m, y1 F9 P2 D$ I# c5 K; G5 Zc) Multiphase ac system having one wire common to all phases – the common conductor.
- ^1 W# \( M! z; F& I- l4 Md) Multiphase ac system where one phase is used as in (b) above – the neutral conductor./ f5 j( H+ ^2 `; l" L
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