2560
THE NEW ZEALAND GAZETTE.
[No. 65

gulation 47-12 hereof, situated on a consumer's premises
and embody special requirements in addition to any other
requirements of these regulations.

53-02. Transformers shall be installed only in situations
approved by the Electrical Engineer of the electrical supply
authority or where there is no such authority then ap-
proved by the Chief Electrical Engineer.

53-03. The installation shall be carried out in accordance
with the appropriate Electrical Supply Regulations, 1935.

53-04. Motors shall be installed only in situations approved
by the Electrical Engineer of the electrical supply authority
or where there is no such authority then approved by the
Chief Electrical Engineer.

PART 54.—EARTHING.

SPECIFYING WHAT SHALL BE EARTHED.

54-01. Where the voltage exceeds extra-low pressure
the following shall be earthed to the satisfaction of the
Authorized Inspector:—

(a) Metallic sheathing of metal sheathed cables.

(b) Metallic sheathing of armoured cables.

(c) Metal conduits.

(d) Isolated lengths of metal sheathed cables, armoured
cables and/or conduct, in each case not exceeding
20 ft. in length, need not be earthed when used in
positions which are more than 7 ft. 6 in. from any
unguarded earthed material or from any earthed
metal sheathed cables, armoured cables and/or
conduct.

(e) One side of the secondary winding of double-wound
transformers stepping down to extra-low pressure,
except where such transformer is provided with an
earthed metallic screen between the primary and
secondary windings, or which will withstand a test
pressure of 1,000 volts (R.M.S.) alternating current,
or which is used for medical and dental appliances
as provided in Regulation 47-12 hereof.

(f) All metal cases for motor-driven switching or flashing
apparatus for signs, outline and decorative lighting.

(g) All metal liable to become alive when in a damp situation
or in a place where a person touching it would be
likely, under normal conditions, to be simultaneously
making contact with earth or earthed metal, save
that appliances when used in any situation other
than one which is damp or which has a conducting
floor need not be earthed if due to the design and/or
construction of the appliance and/or particular
conditions of use earthing would introduce rather
than obviate an electrical hazard.

(h) Portable appliances, fittings, and accessories where
necessary to comply with Regulation 47-31 hereof.

54-02. Where the pressure exceeds low pressure, the
metal cases, frames or enclosures of all accessories, appliances,
fitting, generators, motors, transformers, choke-coils, and
all other apparatus shall be earthed to the satisfaction of
the Authorized Inspector.

54-03. Where practicable accessories, appliances, and
fittings of the all-insulated type shall be used in those places
where exposed metal is required by these regulations to be
earthed. The guards of shrouded hand-lamps made in
accordance with clause (1) of Regulation 27-11 hereof shall
not be earthed.

STRUCTURAL METALWORK.

54-11. Where structural metalwork (such as steel-frame
construction) or the side of a building having exposed metal
(such as corrugated-iron) is not itself earthed all metal conduit
and any metal liable to become alive shall be protected from
electrical contact with such metalwork or exposed metal.

METHODS OF EARTHING.

54-21. When any metal conduit or metallic sheathing of
a cable is required to be earthed, or is itself used as an earthing
connection, every joint in such conduit or sheathing shall
be so made that the current-carrying capacity of the joint
will not be less than that of the conduit or sheathing itself.

54-22. Where bed-plates or slide-rails are used the earthing-
lead shall be connected to the bed-plate or slide-rail, as the
case may be.

54-23. Where the current per conductor exceeds 50
amperes the metal conduit shall not be considered as an
earthing-lead, but where the current does not exceed 50
amperes metal conduit (other than flexible conduit) may be
used as an earthing-lead.

54-24. (1) Where supply to a device is given by means of
flexible cable or flexible cord the earthing-lead shall form
part of the flexible cable or flexible cord and shall be connected
to a separate terminal of the plug. If this flexible cable or
flexible cord has a metallic covering such covering shall in
addition be effectively connected electrically and mechanically
to the metal frame of the device and to the earthed metal of
the plug and socket connection.

(2) The connection to earth shall be made automatically
when the plug is inserted in the socket.

54-25. The neutral conductor of any system shall not be
used as an earthing-lead, except that in the case of a multiple-
earthed neutral system—

(a) An earthing-lead shall be taken direct to earth from the
neutral bus-bar (or stud) on the main switchboard
and the metal conduct or metallic sheathing of
cables shall be connected to this earthing-lead at
the neutral bus-bar (or stud); and

(b) Such neutral may be used for earthing metal (other than
structural metalwork or the side of a building having
exposed metal) in any building which is detached
from the building containing the main switchboard,
provided—

(i) That no earthed water-supply system as
prescribed by clause (1) of Regulation 54-31 hereof is
available at such building, or that it is not practicable
to provide at such building an earth-connection as
prescribed by clause (2) of Regulation 54-31 hereof
with a resistance to earth not exceeding that pre-
scribed by Regulation 62-55 hereof; and

(ii) That such neutral is of a cross-sectional area
not less than that prescribed by Regulations 43-16,
44-31, or 44-33 hereof (as the case may be); and

(iii) That where an earth-connection as prescribed
by clause (2) of Regulation 54-31 hereof has a resist-
ance to earth in excess of that prescribed by Regula-
tion 62-55 hereof such earth-connection shall be
interconnected with the neutral only in such cases
where the person touching metal liable to become
alive will be simultaneously standing on an earthed
conducting floor (such as earth or earthed metal),
and such floor shall, where practicable, be connected
to the earth-connection.

(c) Such neutral may be used for earthing stays, outdoor
lamp-brackets, earthing-guards, and other line hard-
ware provided that it is of a cross-sectional area not
less than that prescribed by Regulations 43-16,
44-31, or 44-33 hereof (as the case may be).

PRECAUTIONS IN EARTHING.

54-31. (1) Where an earthed water-supply system with
metal-to-metal joints is available the main earthing-lead shall
be connected to the pipes of such water-supply system, and
the earthing-lead shall be as short as possible.

(2) Where an earthed water-supply system is not avail-
able a galvanized-iron water-pipe (or pipes), of not less
than ¾ in. (internal diameter) shall be driven vertically
into the ground to such a depth as to ensure adequate contact
with the moist subsoil with a minimum depth in the ground
of 4 ft., and the main earthing-lead shall be connected to such
pipe (or pipes). Alternatively an earth-plate, or rod, approved
by the Authorized Inspector may be used. In either case
the resistance to earth shall not exceed that prescribed by
Regulation 62-55 hereof.

54-32. Pipes conveying gas or an inflammable liquid or
other inflammable material shall not be used as part of an
tearthing system.

EARTHING-LEADS.

54-41. Every conductor (other than metal conduit or the
metallic sheathing of cables) used as an earthing-lead shall
be of high conductivity copper, protected by tinning or other-
wise against corrosion.

54-42. Where an earthing-lead is run across an open space
it shall be adequately supported. All earthing-leads shall be
run, as far as possible, to avoid risk of interference and shall
be protected against mechanical injury. Where the earthing-
lead is fixed to the outside of a building the mechanical
protection shall extend to a distance of not less than 6 ft.
above ground. A bare earthing-lead shall not be enclosed
in conduit or pipe containing insulated conductors if such
conduit or pipe is more than 6 ft. in length or if it contains
any elbows, tees, or bends.

54-43. All connections of the earthing-lead to the installa-
tion and to the earthing system itself shall be accessible.

54-44. If more than one plate, pipe, or rod is employed for
one earthing system they shall be effectively and permanently
connected together.

54-45. In the case of a multiple-earthed neutral system
the earthing-lead and the neutral service-main shall be sweated
together into a cable socket which shall be effectively con-
nected to the neutral bus-bar (or stud). The carrying-
capacity of the earthing-lead shall not be less than one-half
the carrying-capacity of the neutral service-main and shall
comply with Regulation 43-16 hereof.