2400
THE NEW ZEALAND GAZETTE.
[No. 48

SECONDARY BATTERIES.

GENERAL REQUIREMENTS FOR SUPPLY FROM SECONDARY BATTERIES.

18. When apparatus is supplied from secondary batteries, the work of connecting such apparatus to such batteries shall be done in accordance with the provisions of these regulations which would govern the connecting of such apparatus with a generating plant developing the same difference of potential.

ARRANGEMENT OF SECONDARY BATTERIES.

19. Every battery shall be so arranged that a potential difference exceeding 50 volts does not exist between adjacent cells without adequate protection against electrical hazard, and that each cell shall be readily accessible from the top and from at least one side.

20. In a lead-sulphuric-acid battery having more than thirty-three cells, and in a nickel-iron alkaline battery having more than fifty-three cells, the cells shall be supported on glass or vitreous porcelain insulators. Where a battery comprises more than fifty-six lead-sulphuric-acid cells or eighty-eight nickel-iron alkaline cells the stands also shall be insulated.

21. When acid is used as an electrolyte for the cells, the battery connecting-bolts, unless of the non-corrosive type, shall be kept covered with petroleum-jelly.

22. Cells having containers not sealed or not provided with screw-down covers shall be fitted with spray-arresters.

23. Celluloid shall not be employed in the construction of non-portable batteries; and where it is used for portable batteries the charging arrangements shall be such that if the cases become ignited the risk of a fire spreading shall be minimized.

VENTILATION OF SECONDARY-BATTERY ROOM.

24. The room in which batteries are placed shall be thoroughly ventilated.

CONTROL OF SECONDARY BATTERIES.

25. Suitable means shall be provided for controlling the current with which a battery is being charged. Such means shall comprise, as a minimum, an automatic cut-in and cut-out switch and fusible cut-out, or, alternatively, a circuit-breaker with overload and reverse-current trips.

STATIC TRANSFORMER AND CHOKE-COILS.

26. (1) Transformers and choke-coils, unless cased, shall be carried on supports of incombustible material, and so protected and installed that accidental contact with any part of the windings or terminals is impossible.
    (2) Protecting cases or enclosures shall be of incombustible material, and the conductors shall be adequately insulated from the protecting cases, enclosures, and supports.
    (3) Transformers and choke-coils shall be either amply ventilated or else oil-immersed. But in situations where inflammable or explosive gases, dust or flyings are liable to be present the transformers shall be oil-immersed.
    (4) Transformers shall be in accordance with British Standard Specification No. 72.

27. All woodwork or other combustible material which is within 24 in. (measured vertically above), or 12 in. (measured vertically below), or 6 in. (measured in any other direction) from the frames or cases containing transformers or choke-coils, which are not oil-immersed, shall be protected with non-ignitable material.

28. Auto-transformers, resistances or reactances shall not be used to reduce the voltage to low or extra-low pressure—
    (a) To supply general wiring in buildings, or
    (b) For any other purpose where the low or extra-low pressure circuit or apparatus has exposed live metal with which it is possible for any person to make contact.

PART IV.—SWITCHGEAR.

SWITCHBOARDS.

SITUATION AND PLACING OF SWITCHBOARDS.

29. The following provisions shall be observed in connection with the erection of switchboards, namely:—
    (a) They shall be placed only in dry, well-ventilated situations where inflammable or explosive dust or gases cannot accumulate, and they shall be so arranged as to prevent access of acid-fumes from batteries to the boards.
    (b) They must be so erected as to permit of ready access to the face and to all leads and fixing-bolts at the back thereof.
    (c) They shall not be erected above gas-stoves, or in bathrooms or washhouses, or in any situation where they will be exposed to steam or weather.
    (d) The main switchboard shall not in any case be erected in any room where cinematograph-film is stored, handled, or used.

30. Where it is necessary to have access to the back of a switchboard for wiring purposes, the board shall be so placed that there shall be a space between any immovable structure and the back of the board, or if any exposed live metal is mounted on the back, then between such structure and such metal, and the minimum such space shall be as follows:—
    (a) 4 in. where neither the width nor height of the board exceeds 2 ft.
    (b) 6 in. where each such measurement exceeds 2 ft. but does not exceed 3 ft.
    (c) 8 in. where each such measurement exceeds 3 ft. but does not exceed 4 ft.
    (d) 12 in. where each such measurement exceeds 4 ft. but does not exceed 5 ft.
    (e) 30 in. where each such measurement exceeds 5 ft., and in the last-mentioned case all stays and conductors shall be so arranged as to allow a clearance above floor-level of not less than 6 ft. for stays and 6 ft. 6 in. for conductors where crossing over the space provided at the back of the board.

31. Switchboards mounted upon the wall shall be so arranged that the space between all sides and the wall is completely enclosed by a containing case. Where any opening is made in the wall behind for access for wiring, such opening shall be closed on completion of the wiring so as to preclude the possibility of a draught tending to spread any fire which may start on the switchboard.

32. Containing cases shall, except as provided in the next succeeding regulation, be secured by screws in such a manner as to be easily removable for the purposes of inspection.

33. Non-removable cases may be used, but they shall be of sufficiently ample dimensions to allow of easy access for the attachment of cables and for conduits and fixing nuts.

GENERAL CONSTRUCTION OF SWITCHBOARDS.

34. (1) Switchboards shall be constructed wholly of durable, non-ignitable, non-absorbant materials, and all insulation shall be of permanently high electric strength and insulation resistance.
    (2) No composition material shall be used in the construction of switchboards unless such material has been approved by the Chief Electrical Engineer, and to ensure mechanical strength in composition switchboards the minimum thickness of any such board shall be in accordance with such one of the following tables respecting current and area respectively as specifies the greater thickness:—

35. Ironclad switch-gear may be mounted directly on a wall or on the metal framework of the switchboard.

36. Where the frames of switchboards require to be earthed in accordance with the provisions of Part XI of these regulations suitable terminals shall be provided to which the earthing lead shall be attached.

37. (1) The various exposed live parts of switchboards shall be so arranged by suitable spacing or shielding with non-ignitable insulating-materials that an arc cannot be maintained between any such parts or between such parts and earth. For pressures not exceeding 250 volts the minimum clearance between live metal parts of fuses of opposite polarity or phase, or between any live metal and any earthed metal, shall be 2¼ in. For medium pressures the clearance shall not be less than 4 in. Fuses which on blowing expel the gas parallel to the axis of the fuse, and which are of opposite polarity or phase, may be mounted one above the other if an insulating-shield is fixed between them.
    (2) The arrangement of all parts shall be such that the connections to all instruments and apparatus can be readily traced.
    (3) All parts, including connections, shall be readily accessible; and no fuse, circuit-breaker, or switch other than an isolating switch shall be fixed on the back of the switchboard panel if it is necessary to operate the same from behind.