2414

Starters, liquid, for electric motors, specification for ... ... ... ... ... ... ... ... ... 140—1923 Starters, multiple-switch, for electric motors, specification for ... ... ... ... ... ... ... ... ... 147—1923 Starters, switch (star-delta and series-parallel), for electric motors, specification for ... ... ... ... ... ... ... ... ... 141—1923 Switches, air-break knife and laminated brush, for voltages not exceeding 660 volts, specification for ... ... ... ... ... ... ... ... ... 109—1923 Switches, flame-proof air-break, for voltages not exceeding 660 volts, specification for ... ... ... ... ... ... ... ... ... 126—1923 Switches, oil-immersed, and circuit-breakers, specification for ... ... ... ... ... ... ... ... ... 116—1923 Switches, totally enclosed air-break, for voltages not exceeding 660 volts, specification for ... ... ... ... ... ... ... ... ... 124—1923

SECOND SCHEDULE.

Part I.—Minimum Switch-gear Equipment for Main Switch-boards.

A. THREE-PHASE FOUR-WIRE SYSTEMS.

1. To control the main supply a triple-pole circuit-breaker with an overload trip in each phase, or a triple-pole switch with a fuse on each phase shall be provided.

2. To control each outgoing submain or circuit from the switchboard in the case of a three-conductor circuit to which a supply is given from three phases, either a triple-pole circuit-breaker with an overload trip on each phase or a triple-pole switch with a fuse on each phase shall be provided.

3. (1) To control each outgoing submain or circuit from the switchboard in the case of a three-conductor circuit to which a supply is given from two phases and the neutral—

(a) When the neutral is multiple-earthed, either a double-pole overload circuit-breaker, controlling the phase conductors or a double-pole switch controlling the phase conductors with a fuse in each phase shall be provided.

(b) When the neutral conductor is not multiple-earthed, either a triple-pole circuit-breaker with overload trips on each phase or a triple-pole switch with a fuse on each phase shall be provided.

(2) A triple-pole switch controlling any circuit shall not connect the outer conductors to the supply before connecting the neutral, or open the neutral before the outer conductors have been opened.

4. To control each outgoing submain or circuit from the switchboard in the case of a two-conductor circuit to which a supply is given from one of three phases and the neutral—

(a) When the neutral is multiple-earthed, either a single-pole overload circuit-breaker on that pole which is connected to the phase or a single-pole switch and a single-pole fuse on that pole which is connected to the phase shall be provided.

(b) When the neutral is not multiple-earthed, either a double-pole overload circuit-breaker or a double-pole switch with a fuse on each pole shall be provided; but where the neutral is known to be earthed at the source of supply without a circuit-breaker or added resistance the fuse in the neutral may be omitted.

5. To control each outgoing submain or circuit from the switchboard in the case of a four-wire circuit, either a triple-pole circuit-breaker with an overload trip on each phase or a triple-pole switch with a fuse on each phase shall be provided.

6. A fuse or unlinked switch or unlinked circuit-breaker shall not in any case be included in the neutral conductor, but this requirement shall not prohibit the provision of an isolating-link for testing purposes.

B. THREE-PHASE THREE-WIRE SYSTEMS.

1. For each generator or for each service-main the supply for which is derived from an external source, either a triple-pole circuit-breaker with overload trips on each phase, or two overload and one earth-leakage trips, or a triple-pole switch with a fuse on each phase shall be provided.

2. For each outgoing three-conductor submain or circuit from the switchboard, either a triple-pole circuit-breaker with overload trips on each phase, or two overload and one earth-leakage trips, or a triple-pole switch with a fuse on each phase shall be provided.

3. For each outgoing two-wire submain or circuit from the switchboard to which a supply is given from any two of the three conductors, either a double-pole overload circuit-breaker or a double-pole switch with a fuse on each conductor shall be provided,

C. Two-wire Systems.

1. When the supply is from one generator, or when the supply is derived from a single two-wire service from an external source—

(a) To control the main supply there shall be provided—

(i) In the case of a two-conductor multiple-earthed system of wiring, either a single-pole overload circuit-breaker or a single-pole switch with a single-pole fuse on the insulated pole.

(ii) In the case of other two-wire systems of wiring (excepting concentric), either a double-pole overload circuit-breaker or a double-pole switch with a fuse on each pole; but where the system is known to be earthed at the point of supply without a circuit-breaker or added resistance the fuse in the conductor so earthed may be omitted.

(b) To control each outgoing submain or circuit from the switchboard, there shall be provided—

(i) In the case of a two-conductor multiple-earthed system of wiring, either a single-pole overload circuit-breaker or a single-pole switch with a single-pole fuse on the insulated pole.

(ii) In the case of other two-wire systems of wiring (excepting concentric), either a double-pole overload circuit-breaker or a double-pole switch with a fuse on each pole; but where the system is known to be earthed at the point of supply without a circuit-breaker or added resistance the fuse in the conductor so earthed may be omitted.

2. When the supply is from more than one generator, the generators being arranged to run in parallel, there shall be provided—

(a) To control each shunt-wound generator, a circuit-breaker with overload and reverse-current trips, the circuit-breaker being single pole in the case of a two-conductor multiple-earthed system of wiring, and double pole in the case of other two-wire systems of wiring.

(b) To control each compound-wound generator, a circuit-breaker with overload and reverse-current trips as aforesaid, and a single-pole equalizer switch.

(c) To control each outgoing submain or circuit from the switchboard—

(i) In the case of a two-conductor multiple-earthed system of wiring, either a single-pole overload circuit-breaker or a single-pole switch with a single-pole fuse on the insulated pole.

(ii) In the case of other two-wire systems of wiring (excepting concentric), either a double-pole overload circuit-breaker or a double-pole switch with a fuse on each pole; but where the system is known to be earthed at the point of supply without a circuit-breaker or added resistance, the fuse in the conductor so earthed may be omitted.

(iii) A fuse or unlinked switch or unlinked circuit-breaker shall not in any case be included in the earthed conductor, but this requirement shall not prohibit the provision of an isolating-link for testing purposes.

D. THREE-WIRE SYSTEMS (D.C. OR SINGLE-PHASE.)

1. To control the main supply there shall be provided—

(a) Where the neutral conductor is multiple-earthed, either a double-pole overload circuit-breaker controlling the outer conductors or a double-pole switch controlling the outer conductors, with a fuse in each outer.

(b) Where the neutral conductor is not multiple-earthed, either a triple-pole circuit-breaker with overload trips in the outer conductors only or a triple-pole switch with a fuse in each outer.

2. (1) To control each outgoing submain or circuit from the switchboard in the case of a three-conductor circuit there shall be provided—

(a) When the neutral is multiple-earthed, either a double-pole overload circuit-breaker controlling the outer conductors or a double-pole switch controlling the outer conductors with a fuse on each outer.

(b) When the neutral conductor is not multiple-earthed, either a triple-pole circuit-breaker with overload trips on the outers only or a triple-pole switch with a fuse on each outer.

(2) A triple-pole switch controlling any three-conductor circuit shall not connect the outer conductors to the supply before connecting the neutral, or open the neutral before the outer conductors have been opened.

3. (1) To control each outgoing submain or circuit from the switchboard in the case of a two-conductor circuit taken from a multiple-earthed neutral and one outer there shall be