CABLE SELECTION

Cable selection is a very important part of being an electrician or cable installer. Correct cable selection can mean the difference between a good job and a bad job.

When is comes to cable selection, heat is our main enemy. Heat is a byproduct of current passing through the conductor in our installation. AS 3008.1.1 explains that within Australia we assume our soil ambient temperature to be 25 degrees and our air ambient temp to be 40 degrees. The cables that are used in Australia currently are mostly V90 insulated copper conductors. This gives us a maximum operating temperature of 90 degrees before the insulation starts to break down.

Why is the V90 important? Due to the chemical compounds that make V90 what it is, that compound also determines the ability of that cable to release its heat through the insulation. What you will find through out AS 3008.1.1 is that different insulation types attract different results.

*TAG THIS in AS3008* TABLE 2 is where you start your cable selection based on current carrying capacity.

To start your cable selection process, go to table 2

There are four table 2's.

• Table 2(1) details cables unenclosed in air - (cables that are in stud walls, ceilings, surface ran and many other common types)
• Table 2(2) details cables enclosed - (cables installed in ducts, conduits, trunking or in thermal insulation)
• Table 2(3) details cables buried direct in the ground - (cables installed with no enclosure in the ground directly)
• Table 2(4) details cables enclosed in the ground - ( cables installed in underground conduits, ducts or trunking.