2412
THE NEW ZEALAND GAZETTE.
[No. 48

(o) All metal liable to become alive from any cause when such metal is so situated that there is risk of accidental contact with earthed metal (other than earthed metal mounted on a switchboard).

(p) The exposed metal of any switch operating at any pressure other than extra-low, if such switch is so situated that any person operating it is liable to make contact with earth.

(q) All exposed metal in bathrooms which is liable to become alive and which is within reach of a person standing in or on or otherwise in contact with the bath.

SPECIAL AS TO STEEL CONSTRUCTION AND MACHINERY.

253. (1) In buildings containing steel construction, earthed metal forming part of the electric installation shall be earthed independently of the structural steelwork, but may be secured to it, provided that such steelwork is itself earthed.

(2) Where the structural steelwork is not earthed, metal which is not earthed and which is liable to become alive should the insulation become defective shall be protected from contact with the structure.

254. Where electrical apparatus is mounted on machinery—e.g., cranes and lifts—the metal covers and frames of such apparatus, and the metal conduits or sheathings of the conductors, shall be connected to the machinery, which shall itself be earthed.

METHODS OF EARTHING.

255. All Class T metal conduits shall be earthed as near as practicable to the point of entry of the supply.

256. When the metallic conduits or sheathings of cables have to be earthed, or are themselves used as earthing connections, every joint in such conduit or sheathing shall be so made that the current-carrying capacity of the joint shall not be less than that of the conduit or sheathing itself.

257. 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.

258. Every fixed heating and cooking appliance shall, for the purpose of earthing, be provided with a suitable terminal to which the earthing-lead shall be connected.

259. In the case of fixed heating and cooking appliances, and of motors of over 5 horse-power, an earthing-lead other than the conduit shall be taken direct from the appliance or motor to the nearest earth.

260. (1) In all cases where portable metal fittings or appliances have to be earthed in accordance with paragraph (n) or paragraph (o) of Regulation 252 hereof, all metal parts shall be connected to earth by means of an additional conductor contained within the flexible cord, and connected to a separate terminal on the plug. If this flexible cord has a metal armouring, it shall, in addition to such additional conductor, be efficiently connected electrically at one end to the metal frame of the fitting, and at the other end to the earthed metal of the plug-and-socket connection.

(2) Such fittings shall have strong metal guards in metallic contact with the exposed metal of these fittings.

(3) The connection to earth shall be made automatically when the plug on the flexible conductor is connected to the supply circuit.

261. (1) Where the multiple earthed neutral system is used, the earthing-lead shall be taken from the neutral bar or stud, and the conduit shall (in addition to being itself earthed) be connected to this earthing-lead.

(2) Save as provided in the last preceding subclause the neutral wire of any system shall not be used as an earthing-lead.

PRECAUTIONS IN EARTHING.

262. Great care shall be taken to secure as far as possible that the earthing systems used shall be such that the combined resistance of the earthing-lead and of the earthing system itself is low enough to permit the passage of the current necessary to operate the fuse, circuit-breaker, or the earth leakage trip of the circuit-breaker protecting the circuit, and the earthing-lead shall be as short as possible.

263. (1) Where an efficiently earthed water-supply with metal-to-metal joints is available, the earthing-lead shall be connected to the pipes of such water-supply as near as practicable to the point of entry of such pipes to the consumer’s building.

(2) Where an efficiently earthed water-supply system is not available, 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. The minimum length of the driven pipe shall be 4 ft. Alternatively, an earth plate or plates approved by the Authorized Inspector may be used. The earth-wire shall be placed in such a position and in such a manner that it cannot be accidentally damaged or cut.

264. Pipes conveying gas, hot water, or an inflammable liquid shall not be used as an earthing system.

265. Where the metal cases of switches, distribution-boards, or other apparatus have to be earthed, special precautions shall be taken to guard against the risk of shock or burning to any one when working on live conductors in or adjacent to such apparatus.

EARTHING-LEADS.

266. Every conductor used as an earthing-lead shall be of high-conductivity copper, protected by tinning or otherwise against corrosion and against mechanical injury.

267. All connections of the earthing-lead to the installation and to the earthing system itself shall be readily accessible.

268. If more than one plate or tubular earth is employed for one earthing system they shall be efficiently and permanently connected together.

269. (1) Whenever an earthing-lead is connected to a pipe, conduit, cable-sheath, armour, or other cylindrical earth a substantial tinned-metal clip of not less than No. 18 gauge, 1 in. wide, of incorrodible metal, or any other earthing-device approved by the Chief Electrical Engineer, shall be used.

(2) For armoured cables such clips shall be so designed as to grip firmly the whole of the wires of the armouring without damage to the insulation.

(3) For lead-sheathed armoured cables the principal contact shall be with the lead, but the clip shall be so designed as to grip the armouring firmly without damage to the lead.

270. The ends of all earthing-leads, unless of flat strip not less than ¾ in. wide, shall be provided with a soldering-socket of such a size that all the strands of the conductor can enter the socket simultaneously, or, alternatively, the earthing-leads shall be taken into a binding-post or terminal fitting of a type approved by the Chief Electrical Engineer.

271. In the case of a multiple earthed neutral system the earthing-lead and the neutral main shall be sweated together into a cable-socket, which shall be efficiently connected to the neutral bus-bar. The area of this earthing-lead shall not be less than one-half the area of the neutral main.

PART XII.—ADDITIONS TO AND ALTERATIONS OF INSTALLATIONS.

272. Before an addition is made to any installation care shall be taken to ascertain whether the existing conductors and accessories affected by the proposed addition are of sufficient capacity for the augmented current which they may have to carry.

273. Where alternative plug positions are provided for electric heating appliances, it shall be ascertained whether the existing conductors are of sufficient size to allow of the simultaneous use of apparatus connected to more than one plug.

274. All dead or disused wires, fittings, accessories, and apparatus which do not conform to these regulations shall either be removed from the building or be rendered useless for electrical purposes to the satisfaction of the Authorized Inspector.

275. Every addition to or alteration of an existing installation shall be deemed to be a new installation, and all the provisions of these regulations shall apply to such alteration or addition.

DIVISION III.—INSPECTION AND TESTING.

PART XIII.—INSPECTION AND TESTING.

GENERAL.

276. (1) On the completion of any installation the registered electrical wireman in charge of the work shall sign in ink a label to be provided by the contractor carrying out the work.

(2) Such label shall bear the name and registration number of the said wireman and the date of completion of the work, and shall be securely tied by him to the main switchboard.

(3) Such label may be removed from the switchboard only by the Authorized Inspector.