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CSA on a Radial, what length would you reach with a 4mm?

Don246

So I have been down a rabbit hole for some time now and need a bit of clarification.

Possibly someone might be able to explain Fig 15B - Radial final circuit arrangement

it's suggested that 4.0/1.5mm cable could serve a 75 m2 on a 30A or 32A CB

what would the length be of that cable?

when I perform a voltage drop calculation the length of the cable is 32m which is no where near 75m.

The OSG mentions that the max length for a radial on a 32A CB is 43m with an assumed load of 26A.

Anyone able explain how 75 m2 in fig 15B has been worked out, surely there should be a not stating what length cable its equivalent to.

on a separate note what if the radial circuit was supplying 1 x 13A socket, is there an equation to work out the overload allowance of a circuit or is it simply Ib < In < Iz?

if so then what would the maximum load be expected on a 13A socket? there's nothing stopping someone plugging in an extension lead or adaptor to increase the load.

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  • Don246 said:
    on a separate note what if the radial circuit was supplying 1 x 13A socket, is there an equation to work out the overload allowance of a circuit or is it simply Ib < In < Iz?

    that would be 13 A if it were a single socket-outlet.


    Don246 said:
    there's nothing stopping someone plugging in an extension lead or adaptor to increase the load.

    The fuse in the plug, so as long as it's a single socket-outlet ...

    If there were only one socket-outlet, I guess you'd not run a 32 A radial, though, but a 16 A or 20 A one?

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  • Don246 said:
    on a separate note what if the radial circuit was supplying 1 x 13A socket, is there an equation to work out the overload allowance of a circuit or is it simply Ib < In < Iz?

    that would be 13 A if it were a single socket-outlet.


    Don246 said:
    there's nothing stopping someone plugging in an extension lead or adaptor to increase the load.

    The fuse in the plug, so as long as it's a single socket-outlet ...

    If there were only one socket-outlet, I guess you'd not run a 32 A radial, though, but a 16 A or 20 A one?

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  • in reply to gkenyon

    If there were only one socket-outlet, I guess you'd not run a 32 A radial, though, but a 16 A or 20 A one?

    Historically, a 30A+ fuse would be preferred for feeding 13A sockets - as that would give you discrimination with the 13A plug fuses - so a faulty appliance disconnects only itself, leaving the rest of the circuit in service. Of course the current fad for circuit breakers and RCDs at the CU/DB have undermined all that ... but that's "progress" I suppose.

       - Andy.

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