OP
Engineer54
That's what I would have thought, however the notes on Fig 708 in BS7671 say that for a caravan supply at 16A the flex must have a minimum CSA of 2.5mm, that would mean that a 20A overcurrent device would be protecting both the installation cables and a flex with a ccc of 25A, so that's fine. But if the flex is 4mm it has a ccc of 32A so why is the radial limited to 20A?
I should probably get on with revising rather than obsessing over one question that I now know the answer to!
Because the circuit conductors are still 2.5mm!!
Why would you wire the plug top with a flex of 4mm, if the supply is limited to a 16A?? Which is the norm, on a site caravan supply point??
Were going round in circles here, flex sizes are related to the load of the machine/equipment being taken from the socket, nothing to stop you using an over sized flex mind. It's always prudent to use a flex size that's going to be protected by the OCD, but not always necessary?? If you need a 32A supply to a machine or whatever, your not going to use a 16A socket are you, you'll be using a 32A socket, which will in turn have suitably sized circuit conductors and over current device....
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