Chris,
There is no requirement for RCD's on sockets only used within the "equipotential zone" roughly translated inside the building...
IF...
Gets regs book out...
This is gonna be a long post...
Reg 413.3.3 Additional protection
In a.c. systems… by means of an RCD… shall be provided for:
(i) socket-outlets with a rated current not exceeding 20A that are for use by ordinary persons and intended for general use, and
(ii) …
An exception to (i) is permitted for:
(a) socket outlets for use under the supervision of skilled or instructed persons, e.g. in some commercial or industrial locations, or
(b) a specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular item of equipment.
Please remember RCD’s are not the Holy Grail of electrical safety and are in fact very unreliable in the manner they are used by the vast majority of end users in the UK.
The definitions of skilled and instructed persons follow.
Skilled Person – A person with technical knowledge or sufficient experience to enable him/her to avoid dangers electricity may create.
IMHO this should be any tradesman, technician, or engineer who is working on, in, with, or around electrical equipment or installations, relevant to the extent to which they are involved with the equipment or installation.
Other skills may also have had sufficient training or experience also.
e.g. a carpenter (a tradesman) should have been trained sufficiently to know when his electrical tools, leads etc. are unsafe to use, but should not be expected to deal with issues within distribution boards of an electrical installation without undergoing significant additional training.
Instructed Person – A person adequately advised or supervised by skilled persons to enable him/her to avoid the dangers electricity may create.
Now again IMHO, this should be anyone in a place of employment. As, they must be advised that “electricity is dangerous” that they can and can’t do x, y, z, that they must not do a, b, c, with electrical items or apparatus, tools, equipment or fixed wiring parts without having been otherwise trained/advised to comply with other statutory legislation.
Thus, as far as I am concerned anyone in a place of work, must be suitably instructed to comply with other legislation.
Thus, there is no requirement for RCD protection on socket outlets in any commercial or industrial premises where the sockets are not for the use of the general public.