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Cables in fire rated enclosures

Frankie 223

Hi there,

Does anyone know what would be the appropriate derating factor for LV cables installed inside fire rated enclosures?

I understand that this can be a requirement if LV fire rated cables supplying life safety equipment do not achieve diverse routes.

BS 8519 appears to recommend 50% derating factor for MV cables installed in fire rated enclosures. I would assume that this would be similar for LV fire rated cables?

Asking the cable manufacturers and fire protective enclosures suppliers does not usually get any results.

Would appreciate if anyone could share his opinion on this which ideally could be backed by any BS or plain physics/maths.

cheers

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    BSRIA BG 70 2021 confirms the 50% de-rating for MV cables. The table at 2.6 in BS 7671 gives factors for cables within insulation, >= 500mm is 0.5. 

    Would it be possible to ventilate the duct via a fire damper? I've never heard of this being done before but maybe it's worth looking into.

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  • 0

    BSRIA BG 70 2021 confirms the 50% de-rating for MV cables. The table at 2.6 in BS 7671 gives factors for cables within insulation, >= 500mm is 0.5. 

    Would it be possible to ventilate the duct via a fire damper? I've never heard of this being done before but maybe it's worth looking into.

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