How to calculate cable size if installed in direct sunlight

Modified on Wed, 27 Oct, 2021 at 9:33 PM

Method 1 - Choose an Installation method which is Exposed to sun

The reduction in current rating of cables installed in direct sunlight can be significant.  Cable Pro Web has standard installation methods which account for direct sunlight (see below).

The cable size for cables Exposed to the sun will be significantly larger than for shaded cables.

Method 2 - Increase the ambient temperature by 20 degrees

Another method is to use the Derating Wizard inside the software to apply a derating factor for the temperature increase above ambient. 

Section of Standard AS/NZS 3000:2018 suggests applying a derating factor for a temperature 20 deg.C. higher than the ambient temperature.

For example, see below the ambient temperature was increased from 40 deg.C. to 60 deg.C. which creates a derating factor of 0.6 (or a 40 % reduction in the cable current rating only due to direct sunlight exposure).

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