Code of Practice for the Electricity (Wiring) Regulations - 2009 Edition

equipment should be suitable for the suspended load at the
expected working temperature.
25B Wiring Installation Using Trunkings
(1) General requirements for installation of steel or PVC or plastic trunking
(a) Individual pieces of trunking should be independently supported by
means of at least two fixed points per piece. On straight runs,
supports for trunking should be fixed at regular intervals with
maximum spacings as given in Table 25(2). For runs with bends,
supports should be fixed as near to the bend as practicable.
(b) Holes in trunking should be drilled, punched or cut by ring saw.
After cutting, burrs and sharp edges on the trunking should be
removed to prevent abrasion of cables.
(c) Cables penetrating through trunking should be protected by
conduits except PVC insulated and sheathed cables if such cables
form part of a surface wiring system. In such case, the holes in the
trunking, through which such cables penetrate, should be fitted with
suitable rubber grommets or insulated bushes.
(2) Wiring installation using steel trunking
Connection between trunking and equipment should be made by means
of a standard flange coupling or an adaptor neck, fabricated or cast. For
direct attachment of trunking to electrical equipment, the cable entries
should be provided with smooth bore bushes or grommets and the
return edge of the lid of the trunking should be left intact.
(3) Wiring installation using PVC or plastic trunking
(a) Trunking should have covers secured by purpose-made rivets. Covers
of the clip-on type is acceptable for trunking sizes up to 100 mm ×
100 mm.
(b) The trunking should be fixed and supported in the normal way by
screws, but the holes in the trunking should be made oversize to
allow for the movement of expansion. Washers should be used
under the head of the screw which should not be tightened to its
full extent.
25C Installation of Cables
(1) General requirements
(a) All cables should be run in a vertical or horizontal direction, where
practicable, and should be secured flat on the surface of walls,
columns, partitions or ceilings, etc. throughout the entire route.
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