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wrote:
Matt Beard wrote:
The cooker may be rated at 5.5kW, but the principle is that every bit
of cable must be protected by a fuse or breaker that prevents it being
overloaded (and that protection must be on the supply end!) If the
cooker develops a fault that causes it to draw 44A the breaker on your
45A circuit will be perfectly happy - however the 2.5mm T&E will be no
more than a memory and a paragraph in the fire brigade's incident
report.

Not so really, a ring circuit is protected by a 32amp breaker but it's
quite alloweable (by IEE regulations) to have a spur wired in 2.5sq mm
cable. A fault on that spur could draw 32 amps which will overload
the cable but not trip the breaker.

The 2.5sqmm spur is protected by the fuse(s) in the socket or FCU at

Sorry, fuses are in the plugs of course

the end of it. The thinking is that a fault in the cable itself is
*very* unlikely to be the sort of fault that will draw more than the
cable can carry but less than will trip the upstream protection.

The cable must be sized such that the earth loop impedance is low enough
to trip the circuit protection (within 0.5 seconds?) if there's a short
to earth but not such that it can carry the current allowed by the MCB.

--
Chris Green

--
Chris Green