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BS 8436 Cable

Jonesy
Hi all I am new to the Forum.


I have a question regarding BS 8436 Compliant Cables. I am aware iof the requirement to protect circuits wired in BS 8436 Cables with "B" Type devices etc due to the requirement to limit fault current in the event of the cable being penetrated by a nail or a screw. However, what if you install the cable clipped direct to the surface and on Cable Tray or basket where the risk of accidental penetration is very low, would it them be acceptable to protect the circuit with "C" Type devices?


I have hunted high and low on the internet for an solution but have failed to find a definitive answer.
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    I guess it boils down to why BS 8436 cable was specified? If it's because it's a bit of a rough environment and otherwise something like SWA would be used then you'd probably want ADS to operate in the case of cable damage even if it's not from nails/screws being driving unseen though a wall.


    If it's the type of environment where a simple soft-sheathed cable like T&E (or flex) would be acceptable, then ADS not working on the foil sheath isn't so much of an issue.

     

    due to the requirement to limit fault current in the event of the cable being penetrated



    Just to be clear - MCBs can't limit fault currents (that's a direct result of the source voltage and the loop impedance) - they can only limit the energy let-though (the product of the fault current and disconnection time).  As it happens, C-types rated 16A and below have the same (or lower) energy let-though as B-types rated over 16A but not over 32A (and might be lower again by manufacturer's data) - so "B-type only" might be a rather over-zealous simplification.


      - Andy.
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  • 0
    I guess it boils down to why BS 8436 cable was specified? If it's because it's a bit of a rough environment and otherwise something like SWA would be used then you'd probably want ADS to operate in the case of cable damage even if it's not from nails/screws being driving unseen though a wall.


    If it's the type of environment where a simple soft-sheathed cable like T&E (or flex) would be acceptable, then ADS not working on the foil sheath isn't so much of an issue.

     

    due to the requirement to limit fault current in the event of the cable being penetrated



    Just to be clear - MCBs can't limit fault currents (that's a direct result of the source voltage and the loop impedance) - they can only limit the energy let-though (the product of the fault current and disconnection time).  As it happens, C-types rated 16A and below have the same (or lower) energy let-though as B-types rated over 16A but not over 32A (and might be lower again by manufacturer's data) - so "B-type only" might be a rather over-zealous simplification.


      - Andy.
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