The effect of UV radiation on cables

26 November 2020

Beware of sunlight, particularly when considering the installation of fire-resistant cables outside.

Sunlight emits ultra-violet (UV) radiation, which can prematurely degrade the materials in a cable's sheath.

While all polymers eventually degrade with time, exposure to UV radiation will contribute to this degradation. Cables without a UV-stable sheath should not be installed outside without shielding as sunlight will break down the properties of the sheath, causing cracking and eventually deterioration. Cables with a UV-resistant sheath are manufactured to retain their mechanical properties for a far longer period of time.

Prysmian's fire-resistant cables FP200 Gold and FP PLUS each have a daylight UV stable outer sheath. This enables them to be used outside in the UK climate.

Exposure to Sunlight

Even if a cable has the benefit of a UV-stable sheath, it’s always good practice to limit its exposure to sunlight to maximise its lifespan.

A Prysmian FP PLUS cable clipped directly to a roof or wall, for example, may be exposed to direct sunlight for part of the day in winter. However, that same cable in the summer is likely to be exposed to more intense sunlight for a much longer period. Prysmian recommends shielding the cable, perhaps by clipping it to the underside of a cable tray. This will help limit its exposure to UV radiation.

If you are unsure about the amount of UV radiation a cable is likely to be exposed to over time, then it’s good practice to shield that cable from any direct sunlight.

Colour Fade

It's also worth mentioning that UV stability refers to a cable sheath’s mechanical properties and not to its appearance. The colour of a UV-stable sheath will fade over time in sunlight, but this is purely a cosmetic effect and doesn’t indicate deterioration of the sheath's properties.

Red sheaths are more susceptible to colour-fade while white or black sheaths are inherently more UV resistant. So, if you use Prysmian's FP400 or FP600s armoured cables, you are not only investing in a top-quality cable, but as their sheaths have a high carbon-black content they are also highly UV stable.

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