Just a bit of info from the regs.
411.3.3 Additional protection
In a.c. systems, additional protection by means of an RCD in accordance with Regulation 415.1 shall be provided for:
(i) socket-outlets with a rated current not exceeding 20 A, and |
(ii) mobile equipment with a current rating not exceeding 32 A for use outdoors.
An exception to (i) is permitted: |
(a) where, other than for an installation in a dwelling, a documented risk assessment determines that the RCD
protection is not necessary, or
(b) for a specific labelled or otherwise suitably identified socket-outlet provided for connection of a particular |
item of equipment.
NOTE 1: See also Regulations 314.1(iv) and 531.2.4 concerning the avoidance of unwanted tripping.
NOTE 2: The requirements of Regulation 411.3.3 do not apply to FELV systems according to Regulation 411.7 or reduced low
voltage systems according to Regulation 411.8.
NOTE 3: See Appendix 2, item 10 in respect of risk assessment.
415.1 Additional protection: Residual current devices (RCDs)
415.1.1 The use of RCDs with a rated residual operating current (lAn) not exceeding 30 mA and an operating
time not exceeding 40 ms at a residual current of 5 lAn is recognized in a.c. systems as additional protection in the
event of failure of the provision for basic protection and/or the provision for fault protection or carelessness by users.
415.1.2 The use of RCDs is not recognized as a sole means of protection and does not obviate the need to
apply one of the protective measures specified in Sections 411 to 414.