"Dave Liquorice" wrote in message
. 1...

And if the overload is pre the plug?

That can't happen - the branch is feeding one socket only. (Unless you
connect three 3 kW fires through an ancient unfused 3-way adaptor...)

True enough, just doesn't "feel" right.

Consider the fact that for all sizes of T&E cable except 1.0 mm^2, the earth
conductor can be 'undersized' relative to the fuse rating. This is OK and
it is known, by design, that in the event of an earth fault the fuse will
blow before the earth wire in the cable overheats. The situation is the
same with an 'undersized cable' where overload protection is either not
required, or is provided downstream.

It's important to distinguish between 'faults' - i.e short-circuits caused
by someone cutting through a cable, or whatever - and 'overloads' where the
design load is exceeded - too much equipment connected, relative to the
design expectations.

Fault and earth fault protection is always required. Overload protection is
required in general, but can be omitted where the characteristics of the
load are such that overloading just can't happen. For example, a circuit
feeding a single heating appliance is designed for the maximum loading of
the appliance and doesn't need overload protection. Overload protection can
also be separate from the fault protection and can be downstream, as in this
case. The industrial motor circuit is another common example. The fuses in
the dis-board only provide fault protection for the wiring; overload
protection comes from an 'overload relay' in the motor starter.

--
Andy