2402
THE NEW ZEALAND GAZETTE.
[No. 48

provided that such value does not exceed 200 per cent. of
the normal full load.

61. In every case in which single-pole switches are required
    by these regulations they shall be fitted on the same pole
    or phase throughout the installation.

62. No lamp, portable heater, or portable domestic ap-
    pliance shall be supplied at a nominal pressure in excess of
    230 volts, and where the nominal pressure between the outer
    conductors of the three-wire D.C. system exceeds 230 volts,
    and the three wires of the system are brought into the
    premises, the circuits connected between the negative and
    neutral or middle conductor shall be kept apart throughout
    from those connected between the positive and neutral or
    middle conductor.

INSTRUMENTS.

SERVICE-METERS AND INSTRUMENT TRANSFORMERS.

63. Where service-meters are not mounted on the main
    switchboard they shall be mounted on a substantial base.

64. Where instrument transformers are used, and are easily
    accessible, all live metal shall be efficiently insulated.

SWITCHBOARD INSTRUMENTS.

65. Every generator switchboard, when the supply is not
    derived from an external source, shall be provided, as a mini-
    mum, with the instruments required by Part II of the Second
    Schedule to these regulations with respect to the particular
    system of wiring used in the installation.

SWITCHES, CIRCUIT-BREAKERS, AND CUT-OUTS.

SWITCHES AND CIRCUIT-BREAKERS.

66. Every switch, fuse-switch, and other device for breaking
    circuit shall comply with the following requirements :—

(a) All parts shall be so proportioned that when the normal
working current for which they are designed flows
through them continuously their temperature shall
not rise above that of the surrounding air more than
36° F. in the case of switches rated below 100
amperes and 54° F. in the case of switches rated at
100 amperes or above.

(b) Each fuse-switch when opening the circuit as a switch,
and each switch, shall break the circuit without per-
mitting an arc to be maintained when a current 50
per cent. greater than that for which it is rated is
flowing under a pressure 50 per cent. in excess of the
pressure of supply. Each fuse-switch when opening
the circuit as a fuse, and each circuit-breaker, shall
comply with Regulations 68 and 69 hereof for cut-
outs.

(c) Every circuit-opening device shall be so constructed
and arranged that when placed in the off position
it cannot accidentally move sufficiently to close the
circuit.

(d) If the current to be interrupted is sufficiently large to
cause damage to the main contacts, suitable ar-
rangements shall be made for the easy renewal of
the parts on which the arc is formed.

(e) The handles and their attachments shall be mechanic-
ally strong, and where switches and circuit-breakers
are readily accessible to unskilled persons they shall
be so designed and arranged that the hand of the
operator cannot accidentally touch live metal, or be
injured through an arc from the switch or the blowing
of an adjacent fuse, and they shall not operate
through unprotected slots.

(f) The bases shall be of durable, non-ignitable, non-
absorbent insulating-material. Semi-hygroscopic ma-
terials such as slate or marble, if used, shall be free
from metallic veins, cracks, or other defects. The
slabs shall be planed all over, and, if of slate,
treated, after drying, with a damp-proof medium,
all holes being similarly treated.

(g) Switches of the all-insulated type shall have covers
made of strong incombustible material other than
porcelain.

(h) In positions in which they are liable to mechanical
injury the covers, unless of rigid metal, shall be
protected by suitable guards. Metal cases shall be
kept well clear of live parts.

(i) All switches fixed in positions exposed to the weather,
to drip, or to an excessively moist atmosphere shall
be contained in weather-proof cases, which shall be
provided with cable glands or bushings, or be adapted
to receive screwed conduit, according to the manner
in which the cables entering the fittings are run.

(j) In strong-rooms, and freezing-chambers and the like,
the switches shall be grouped outside and adjacent to
the door, and, except in the case of a multiple-earthed
neutral system, the switches shall be double pole.

(k) (i) Every electro-magnetic circuit-breaker shall be pro-
vided with suitable means of adjustment for deter-
mining the current at which it shall open, and shall
be so arranged that it cannot be held in against this
current.

(ii) The maximum setting of the circuit-breaker
shall not exceed the carrying-capacity of the smallest
cable which the circuit-breaker controls.

(iii) In the case of all apparatus, other than motors,
in which the current under normal operating-con-
ditions does not exceed the full load current, the
circuit-breaker shall be set to operate at not more
than 150 per cent. of full-load current.

(iv) No circuit-breaker need be set to operate at a
current less than 7 amperes.

(v) In the case of motors the circuit-breaker shall
be set to operate within one minute at 200 per cent.
of full-load current.

(l) Circuit-breakers shall be so arranged and placed that no
combustible materials is endangered by their opera-
tion, and any resulting arc shall not come into
contact with any live metal of opposite polarity or
phase, nor with instrument-cases or earthed metal.

(m) Flush-type switches shall in all cases be contained in
metal boxes suitable for screwed conduit.

67. No pendant switch other than of a type approved by
    the Chief Electrical Engineer shall be used in any installation.

CUT-OUTS.

Extra-low Pressure.

68. For extra low pressure every cut-out shall comply with
    the following requirements :—

(a) All parts other than the fusible metal shall be so pro-
portioned that their temperature shall not rise more
than 54° F. above that of the surrounding air when
the normal working current for which they are
designed flows through them continuously.

(b) (i) The fusing-current shall be not more than double the
current - carrying capacity of the smallest cable
which the fuse controls, provided that no fuse smaller
than one rated to blow at 8 amperes need be inserted
in any final subcircuit.

(ii) The fusing-current in free air shall be taken as
that specified in column 3 of Tables XIII and XIV
in the Third Schedule hereto.

(iii) For the purposes of this paragraph the carry-
ing-capacity of a flexible cable or cord shall be that
specified in Table XVI in the Third Schedule hereto.

(c) In the case of fuses controlling individual pieces of
apparatus they shall be set to blow within one minute
at 200 per cent. of full-load current.

(d) The base shall be of durable, non-ignitable, non-absorb-
ent insulating-material.

(e) The circuit contacts and their terminals shall be so
spaced or shielded that an arc cannot be maintained
when the fuse blows.

(f) The fuse shall be of such construction, or be so guarded
or placed, as to prevent danger from overheating,
arcing, and the scattering of hot metal or other
substances when it blows.

(g) Fuses shall not be placed in ceiling-roses, in wall plugs
or sockets, or in switches other than fuse-switches or
those of the metal-covered type which comply with
the other requirements of these regulations. A fuse
rated at not more than 5 amperes may, however,
be placed in an approved intermediate device
designed for insertion into a wall-socket and for
receiving the pins of a smaller plug connected to
a consuming-device taking 5 amperes or less, pro-
vided that in all cases the wall socket or sockets
shall be protected by subcircuit fuses mounted in
accordance with paragraph (h) of this regulation.
Where such a device is used it shall not be sunk
below the surface of the wall, and its base shall
comply with the requirements of paragraph (d) of
this regulation.

(h) When cut-outs are not fixed on a main switch-board
they shall be grouped on distribution-boards, or,
unless completely enclosed, shall be contained
within cases conforming in all respects to the re-
quirements specified in Regulations 44 to 52 hereof.

(i) Except as provided in paragraph (g) of this regulation
cut-outs in which the fuses are without removable
carriers may be used only on extra-low pressure.
subcircuits, and may then only if,—

(i) They are protected by close-fitting covers; and

(ii) They are ventilated in such a manner that
fused metal cannot be ejected; and

(iii) The maximum generating-plant capacity does
not exceed 5 kilowatts.