2398
THE NEW ZEALAND GAZETTE
[No. 48

“Machine, flame-proof,” is one in which the enclosing case can withstand, without injury, any explosion of gas that may occur in practice within it under the conditions of operation, and will prevent the transmission of sparks or flames capable of igniting any inflammable gas or particles, such as coal-dust, or flour or textile flyings, which may be present in the surrounding atmosphere.

“Machine, flame-proof slip-ring enclosure” is one in which only the slip-rings and brushes are enclosed in a flame-proof case.

“Machine, forced draught,” is a pipe-ventilated machine in which the ventilating-air is supplied under pressure by means external to the machine itself.

“Machine, immersible,” is one that can work when submerged under a considerable head of water for an indefinitely long period without detriment to its operation.

“Machine, induced draught,” is a pipe-ventilated machine in which the ventilating-air is drawn through the machine by means external to the machine itself.

“Machine, open, end-bracket,” is one which has end-bracket bearings, the bearings forming an integral part of the machine, and in which there is no restriction to ventilation other than that necessitated by good mechanical construction.

“Machine, open, pedestal,” is one which has pedestal bearings, supported independently of the machine-frame, and in which there is no restriction to ventilation other than that necessitated by good mechanical construction.

“Machine, pipe-ventilated,” is an enclosed machine in which the frame is so arranged that the ventilating-air may be conveyed to or from the machine through pipes or ducts attached to the frame, the ventilation being maintained by the fanning action produced by the machine itself, assisted or not by a fan or fans directly attached to the rotating parts.

“Machine, protected,” is one in which the internal rotating parts and live parts are protected mechanically from accidental or careless contact, whilst ventilation is not materially obstructed.

“Machine, totally enclosed,” is one so enclosed as to prevent circulation of air between the inside and outside of the case, but not to such an extent as to make the machine airtight.

“Multiple-earthed neutral” (m.e.n.): The neutral conductor of any low or medium-pressure alternating-current system is said to be multiple-earthed when it is earthed at the point of supply (that is, generating-station, substation, or transformer) and at one or more other points along the distribution or service line, and at each consumer’s premises, the resistance between any point of the neutral conductor and earth not exceeding 10 ohms.

“Point” is the termination of the wiring for attachment to a fitting for one or more lamps or other consuming-devices of any nature whatever.

“Pressure, extra-low,” means a pressure between conductors (or between conductors and earth if the neutral is known to be earthed at the source of supply without a circuit-breaker or added resistance), normally not exceeding 30 volts in the case of alternating current and 100 volts in the case of direct current at the point at which the supply is delivered.

“Pressure, low,” means a pressure between conductors (or between conductors and earth if the neutral is known to be earthed at the source of supply without a circuit-breaker or added resistance), normally exceeding 30 volts in the case of alternating current and 100 volts in the case of direct current, but not exceeding 250 volts in either case at the point at which the supply is delivered.

“Pressure, medium,” means a pressure between conductors (or between conductors and earth if the neutral is known to be earthed at the source of supply without a circuit-breaker or added resistance), normally exceeding 250 volts, but not exceeding 650 volts at the point at which the supply is delivered.

“Service Fuse” is the device installed by the electrical supply authority for automatically disconnecting the installation on a consumer’s premises from a service line.

“Service Main” is that portion of the wiring between the main switchboard and the electric-service line from which supply is obtained.

“Subcircuit”: A subcircuit is that portion of the wiring system extending beyond the final set of fuses.

“Submain” is a branch main connecting a distribution board or fuse-board to a main switchboard.

“Switchboard”: The term “switchboard” denotes an assemblage of switch-gear with or without instruments, and includes “distribution-board.”

“Switch, double-pole,” is a switch suitable for making or breaking a circuit on two poles or phases simultaneously, or for making or breaking two separate circuits simultaneously.

“Switch-gear” means any apparatus for controlling the distribution of electrical energy, or for controlling or protecting electrical circuits, machines, transformers, or other apparatus.

“Switches, linked,” are switches linked together mechanically so as to operate simultaneously or in definite sequence.

“Switch, single-pole,” is a switch suitable for making or breaking a circuit on one pole or phase only.

“Switch, triple-pole,” is a switch suitable for making or breaking a circuit on three poles or phases simultaneously, or for making or breaking three separate circuits simultaneously.

“System of wiring”:

Two-wire.—A two-wire system of wiring is one comprising two conductors between which the load may be connected, the wiring being effected by either of the following methods:

(a) Two-conductor, insulated: Conductors insulated throughout are provided for all connections to both poles of the supply, the conductors being separate, twin, or concentric.

(b) Two-conductor, earthed: Conductors are provided throughout for all connections to both poles of the supply, those connected to the one pole being insulated throughout, and those connected to the other being uninsulated throughout and efficiently earthed. The uninsulated conductor, known as the “external” conductor, completely surrounds the whole length of the other, known as the internal conductor. (Earthed concentric wiring.)

Three wire.—A three-wire system of wiring is one comprising three conductors, one of which, known as the “neutral” or “middle,” is maintained at a potential midway between the potentials of the other two, referred to as the “outer” conductors. Part of the load may be connected directly between the outer conductors, and the remainder divided as evenly as possible into two parts connected respectively between the middle and each outer conductor.

Two-phase Three-wire. — A two-phase three-wire system of wiring is one comprising three conductors, between one of which, known as the “common return,” and the other two are maintained respectively alternating differences of potential displaced in phase by one-quarter of a period.

Two-phase Four-wire. — A two-phase four-wire system of wiring is one comprising four conductors, divided into two pairs, which have maintained between their conductors alternating differences of potential displaced in phase by one-quarter of a period.

Three-phase Three-wire.—A three-phase three-wire system of wiring is one comprising three conductors, between successive pairs of which are maintained alternating differences of potential successively displaced in phase by one-third of a period.

Three-phase Four-wire.—A three-phase four-wire system of wiring is one comprising four conductors, three of which are connected as in a three-phase three-wire system, the fourth being connected to the neutral point of the supply.

“Weatherproof”: Fittings, accessories, and consuming-devices are said to be weatherproof if they are so constructed that when installed rain, snow, and splashings are excluded.

(2.) The term “British Standard Specification” means a specification for wiring, or other materials, fittings, accessories, appliances or apparatus for electrical purposes, issued under that name by the British Engineering Standards Association, and where any such specification is prescribed in these regulations the latest revision thereof, or any specification issued in lieu thereof, by that association is implied. Particulars of the British Standard Specifications prescribed in these regulations are set out in the First Schedule hereto.