Specifications

Design Guidelines & Procedures Version 18 ©
Electrical Services Section 20.00 / Page 17
All cable trays, ladders and ducts shall have 50% spare carrying capacity. All cable ladders or
ducts leaving switchboards or load centres shall have 100% spare capacity up to the ceiling
space.
20.10.04 Cabling in Ceiling Spaces & Risers
Main sub-board feeders and sub circuit wiring, shall generally be run on cable ladders in risers
and on trays to major routes in ceiling voids.
Where not run on ladders or trays, cables shall be supported clear of the ceiling structure by an
approved cable support system such as ‘Unicon’ or ‘Ezi-Fix’ at a maximum interval of 1.2m or
tied to catenary wires.
Care must be taken to have enough slack in the cable runs to eliminate stretching of the cable
and strain on the supports.
The practice of laying the cable on ceiling tile, tying cable to ceiling supports or outside of a
‘Unicon’ with a cable tie will be rejected.
If more than six (6) cables run in ceiling space in parallel, a cable tray must be used.
Where connections are made between fixed and flexible conduits it is to be done using the
appropriate adaptor and not be glued.
Where cables are made redundant they must be removed in their entirety, and the legend card
amended.
20.10.05 Cable Ducts & Poles
Distribution of power and communication wiring may be by means of three channel perimeter
grey aluminium duct equal to ‘Moduline T50150’ or ‘Skirtec CA15035’ complete with factory
manufactured corners, fittings and duct covers. Sheet metal cable duct will not be acceptable.
Where conduits cannot be cast in floor slabs, use service poles similar to ‘Moduline Space Pole’.
All conduits cast in slabs shall be surveyed and clearly shown on the ‘As Constructed’’ drawings.
Where island rooms exist, these shall be conduited to allow for the installation of power from the
relevant distribution board where these are not installed in the first instance. All ducts shall have
a minimum of 2 x 32mm feeds from the distribution board to each section of the duct.
In computer laboratories, a three (3) channel duct shall be run on the wall above the benches
and along fascias of computer benches.
In other areas, ducting to service desks and benches shall be run at approximately 1000mm
above f.f.l. This shall be discussed with the Superintendent before final resolution.
20.10.06 Cables in Partitions & Wall Cavities
Power circuits within partitions or wall cavities shall be installed vertically from the ceiling space
to the outlet or connection position. Outlets within 1m of each other may be connected
horizontally, providing the total horizontal route between successive outlets shall not exceed 1m.
Cables shall not be installed diagonally.
Where cables are installed within concealed areas or horizontally within partitions they shall be
installed within conduit so that they can be withdrawn and so that sufficient segregation can be
afforded if a new telecommunication cable is installed across its path. Services mounted beneath
windows or viewing panels shall be duct mounted.
20.10.07 Installation of Mains & Submains
Mains and submain cables run on cable ladders/trays shall be installed in trefoil. All submains
for distribution boards are to be installed within electrical risers or down corridors. No submains
are to be installed through occupied rooms or offices.