This is the number one use for 4mm TPS in residential builds. Most large reverse-cycle split systems draw between 15A and 20A. A 2.5mm cable is often borderline for these units, so 4mm is the preferred choice to handle the startup current and prevent voltage drop, ensuring the compressor doesn't stall.
When buying 4mm cable in Australia, check the sheath printing. You will usually see or V-75 . current carrying capacity of 4mm cable australia
In Australia, a 4mm² copper cable has a under ideal laboratory conditions. However, real-world installations—particularly those involving insulation, high ambient temperatures, or cable grouping—can reduce this capacity by 30-50%. Always consult AS/NZS 3008.1.1 and AS/NZS 3000 (Wiring Rules), and when in doubt, upsize to 6mm² for sustained loads above 25A in enclosed or insulated spaces. This is the number one use for 4mm TPS in residential builds
While it is tempting to "upsize" just in case (and this is generally good practice), understanding why a 4mm cable is chosen requires understanding the load, the length, the insulation type, and the installation method. When buying 4mm cable in Australia, check the
This is why "grouping" is such a critical consideration in commercial fit-outs. A 4mm cable in a packed conduit might legally only be allowed to carry 20 Amps.
Before we get to the numbers, let’s define what we are talking about. In Australia, when someone mentions "4mm cable," they are almost always referring to .