17th Edition explaination use of RCD's in Domestic Properties

The use of RCD's (Residual Current Devices) with a residual operating current not exceeding 30mA is the recognised means of providing this additional protection in the event of failure of the provision for basic protection and or the provision for fault protection or carelessness by users.



Under the new regulations an installation is required to incorporate one or more RCD's, depending upon the circumstances. Such instances include:-

All socket outlets not exceeding 20A, but with certain
exceptions. One such exception would be permitted for
a specific labelled or otherwise suitably identified socket
outlet for connection of a particular piece of equipment.
Mobile equipment with a current rating not exceeding
32A for use outdoors
All electrical circuits, including shower and lighting
circuits etc. in rooms with a fixed bath or shower e.g.
bathrooms and en-suite bedrooms.

The advent of the New 17th Edition of the Wiring regulations brings with it new challenges for installers and manufacturers alike, one such challenge involves the much greater use of RCD’s within the electrical installation. The new regulations BS7671:2008 published in January 2008 will come into force at the end of June 2008, when the previous 2001 version will be withdrawn.


Regulation 411.3.3.
States that additional protection by means of a 30mA RCD is to be provided for all socket outlets with a rated current not exceeding 20A for use by ordinary persons. The only exceptions allowed are for socket outlets for use under the supervision of “skilled” or “instructed persons” e.g. some commercial / industrial locations, or a specific labelled socket provided for connection of a particular item of equipment, e.g. a freezer circuit.


Regulation 701.411.3.3
In specific locations such as those containing a bath or shower there is a requirement now to provide RCD protection on all circuits, including the lighting and shower circuits.

Regulation 314.1 & 2
Requires that every installation shall be divided into circuits as necessary to avoid danger and minimise inconvenience, in the event of a fault. Also reducing the possibility of unwanted RCD tripping, due to excessive protective conductor currents but not due to an Earth fault.


Separate circuits may be required for parts of the installation, which need to be separately controlled in such a way that they are not affected by the failure of other circuits. The appropriate subdivision should take account of any danger arising from the failure of a single circuit e.g. An RCD trip on a socket outlet causing the unwanted failure of a lighting circuit and its associated hazards.


Regulation 522.6.7
Now requires a much greater use of RCD’s to protect the wiring concealed in walls or partitions even where installed in previously defined “Safe Zones”.




These regulations effectively mean that all concealed wiring at a depth of less than 50mm from the surface now requires protection by a 30mA RCD unless provided with earthed mechanical protection