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3/036 t and e on domestic ring final

hertzal123

On conducting a condition report the rf was found to be wired in 3/036 on a b16 mcb.

Have calculated the csa of the live conductors to be about 1.9mm2.Subject to circuit

length,could I convert to 2 radials and use the OSG table for 1.5mm cable on a 16A

mcb?The circuit serves a small lounge and bedroom.Otherwise,suspect this would attract

a C2 code.

Thanks for any advice,Hz

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    On conducting a condition report the rf was found to be wired in 3/036 on a b16 mcb.

    If it's wired as a ring on a 16A OPD, I'd be happy if the CCC if the cable was above 10.72A  (0.67x In) - so no problem with 3/.036 on that score in most situations (provided the ring wasn't ridiculously unbalanced).

    c.p.c. size for fault protection might be an issue in theory - but hardly any worse on paper than 1.0/1.0 T&E on a B6 MCB, which seems to be thought acceptable whatever the numbers in BS EN 60898 might say. With knowledge of the actual PEFC you might be able to show that the 40ms disconnection time for the RCCB would be sufficient to protect it anyway.

    I don't see any advantage in breaking the ring into radials if keeping the same OPD rating - just disadvantages in terms of v.d. and loss of duplicate earthing.

    You can't condemn something on an EICR just because it doesn't match something in the OSG - you need to dig a lot deeper than that.

       - Andy.

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  • 0

    On conducting a condition report the rf was found to be wired in 3/036 on a b16 mcb.

    If it's wired as a ring on a 16A OPD, I'd be happy if the CCC if the cable was above 10.72A  (0.67x In) - so no problem with 3/.036 on that score in most situations (provided the ring wasn't ridiculously unbalanced).

    c.p.c. size for fault protection might be an issue in theory - but hardly any worse on paper than 1.0/1.0 T&E on a B6 MCB, which seems to be thought acceptable whatever the numbers in BS EN 60898 might say. With knowledge of the actual PEFC you might be able to show that the 40ms disconnection time for the RCCB would be sufficient to protect it anyway.

    I don't see any advantage in breaking the ring into radials if keeping the same OPD rating - just disadvantages in terms of v.d. and loss of duplicate earthing.

    You can't condemn something on an EICR just because it doesn't match something in the OSG - you need to dig a lot deeper than that.

       - Andy.

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