New Zealand Gazette – 1927 – No. 48

Page 2423

✨ Electrical Wiring Regulations



JULY 12.] THE NEW ZEALAND GAZETTE. 2423

TABLE XII.—PERMISSIBLE NUMBER* OF CONDUCTORS IN CONDUITS, AND
CAPACITY OF CONDUITS (TYPE B, SCREWED, B.S.S. NO. 31) FOR THE
DRAWING-IN OF CONDUCTORS.

Size of Conduit ½ in. ¾ in. 1 in. 1¼ in. 1½ in. 2 in. 2½ in.
Internal Diameter (Approximate) 0·498 in. 0·606 in. 0·856 in. 1·106 in. 1·34 in. 1·816 in. 2·316 in.
Nominal Area of Conductor. Number and Diameter(In.) of Wires comprising Conductor. Approximate Over-all Diameter. Maximum Number of Conductors.
Sq. in. 1. 2. 3.
0·0015 1/·044 0·173 5
0·002 3/·029 0·195 4
0·003 3/·036 0·215 3
0·0045 7/·029 0·226 2
0·007 7/·036 0·259 —
0·01 7/·044 0·287 —
0·0145 7/·052 0·317 —
0·0225 7/·064 0·359 —
0·03 19/·044 0·393 —
0·04 19/·052 0·441 —
0·06 19/·064 0·513 —
0·075 19/·072 0·596 —
0·1 19/·083 0·663 —
0·12 37/·064 0·702 —
0·15 37/·072 0·768 —

*These numbers shall not be exceeded.

The table applies to 250-volt, vulcanized-rubber, braided cables in
accordance with British Standard Specification No. 7, and to conduits
type B screwed, which comply with British Standard Specification
No. 31.

The grouping in one tube of more than two of the larger cables
is not recommended, and where it is done the current rating given in
Tables IV, V, and VI should be reduced to ensure that the cables are
not overheated.

For 650-volt, vulcanized-rubber, braided cables take one size larger
up to and including 7/·052.

It shall be possible to withdraw any conductor and draw in another
of equal size in its place without injury (see Regulation 137 (2)).

TABLE XIII.—APPROXIMATE FUSING CURRENTS OF COPPER WIRES IN
FREE AIR.*

Diameter of Wire. Equivalent S.W.G. Size. Fusing Current. Maximum Safe-working Current.*
In. 1. 2. 3.
0·0092 34 8·6 4·3
0·010 33 9·8 4·9
0·0108 32 11·0 5·5
0·0120 — 12·8 6·4
0·0124 30 13·5 6·8
0·0148 28 17 8·6
0·018 26 22 11
0·022 24 30 15
0·028 22 41 21
0·029 — 43 22
0·036 20 62 31
0·040 19 73 37
0·044 — 86 43
0·048 18 98 49
0·052 — 111 56
0·056 17 125 63
0·064 16 156 78
0·072 15 191 96
0·080 14 229 115
  • See note under Table XIV.

I



Next Page →

PDF embedding disabled (Crown copyright)

View this page online at:


VUW Te Waharoa — PDF NZ Gazette 1927, No 48


NZLII — PDF NZ Gazette 1927, No 48




✨ LLM interpretation of page content

🏗️ Electrical Wiring Regulations, 1927 (continued from previous page)

🏗️ Infrastructure & Public Works
11 July 1927
Regulations, Electrical Wiring, Safety, Compliance, Conductors, Cables, Current-carrying Capacity, Insulation Resistance, Tables