In article ,
"DerbyBoy" No-one writes:
A friend has a plumber fitting a Power Shower in place of an electric
shower.

The plumber is going to use the existing electric shower wiring (mostly) and
will down rate the MCB. The instructions for the Power Shower recommend a 3
amp fuse. For his Consumer Unit it appears that 6 amp is the lowest rating.
With motor surge in mind - does this seem correct anyway?

He can fit a Fused Connection Unit to terminate the shower cable, and
provide a flex outlet for the pump. If the pump is outside the bathroom,
another alternative is a standard 13A plug and socket. In either case,
a 3A fuse can be fitted. You should chose a make of socket or FCU which
has large conductor capacity terminals and can take the shower cable
(although if it's 10mm², you might struggle).

Then replace the MCB with a 16A or 20A or 32A one - it doesn't much
matter.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]