electrical services minimum requirement - NSW Public Works

Part 1 - Installation
110 CABLE TRAY, LADDER AND TROUGHING
110.1 Generally
110.2 Cable Tray
Cable tray, cable ladder and all accessories shall be proprietary items from a single
manufacturer whose range includes splice connections, expansion splices, covers, risers,
crossovers, reducers, bends and all other accessories used. Supply covers
manufactured from the same material as the tray or ladder up to 2000 above finished
floor level.
Cable tray shall be manufactured from steel, hot dip galvanised after fabrication or from
aluminium or stainless steel.
Minimum thickness for cable tray shall be:
1mm up to 150 wide 1.6 for aluminium
1.2 mm from 150 up to 300 wide 2 for aluminium
1.6 mm above 300 wide 2.6 for aluminium
All cable trays shall be slotted similar to "Admiralty" pattern and shall have folded or rolled
edges. The "standard" tray shall be formed with the perforations punched from outside
the folded edge to avoid any sharp edges or burrs existing on the outside face. The
"reverse" tray shall be perforated from the inside and shall be used in positions where
cables are laid horizontally in the tray or alternatively, trays shall have the metal
reinforced by folding to provide equivalent stiffness.
Cable trays installed externally must be aluminium or stainless steel.
110.3 Cable Ladder
110.4 Installation
Cable ladder shall consist of two folded steel or extruded structural grade aluminium side
rails with cable support rungs between the two rails. The rungs shall be either welded or
fitted to the side rails.
Unless otherwise indicated rung spacing shall not exceed 300. Cables smaller than 13
OD installed on cable ladder shall be run on perforated tray or ducts installed on the
ladder. This requirement does not apply where the rungs of the ladder form a continuous
base.
Cable tray and ladder shall be installed by either:
(a) surface fixing to ceilings or walls; or
(b) suspending by hangers from ceilings, or by angle brackets out from walls.
Fixings, hangers and angle brackets are to be spaced at a maximum distance of 1000.
Joints shall be adequately supported.
Where possible, cable tray and ladder shall not be mounted less than 2300 above floor
level. Adequate access shall be provided to cable tray and ladder. Where supported by
hangers or angle brackets, a minimum distance of 150 shall be allowed above and 600
on one side of the tray or ladder.
Alternative systems and supports with greater spacing may be accepted if they give equal
rigidity and strength.
Where cable tray or ladder span open areas they shall be capable of supporting an
additional load of 70kg at mid span without permanent deformation.
Cables or groups of cables shall be securely strapped to the tray or ladder using
proprietary nylon cable ties or straps: for vertical runs at 1000 maximum; for horizontal
runs at 2000 maximum.
Cables shall leave the cable tray or ladder in such a manner that no cable shall be in
contact with the side rails. In general, cable shall leave the tray or ladder in conduit,
Page 20 MEW E101