17th edition
From January 1st to December 31st 2008 the 17th edition of the wiring regulations is being phased in throughout England and Wales. During this time it is at the discretion of the installing electrician whether the installation complies with the 16th or 17th edition. From January 1st 2009 all new installation work will have to comply with the 17th edition.
For simplicity, we have listed below the major additional requirements for protection against shock in domestic premises listed in the new regulations. Our comments in italics.
Principally:
All socket outlets should be protected by a 30mA RCD (Residual Current Device). Previously, only certain socket outlets that could resonably be used to supply equipment intended for outdoor use needed RCD protection. Now ALL socket outlets require an RCD.
All circuits in a room with a fixed bath or shower should be protected by ONE or MORE 30mA RCDs. Practically, this means any lights, extractor fans, shavers points, electric wall or underfloor heating and electric showers must be RCD protected.
All cables burried beneath the plaster surface of a wall or partition at less than 50mm and without earthed mechanical protection should be protected by a 30mA RCD. For all practical purposes, this means any cable that is currently in use in a domestic premises in England and Wales now needs to be protected by an RCD.
All cables concealed with metal stud partitions without earthed mechanical protection should be protected by a 30mA RCD. This pertains to the increased use of stud metal partitions in refurbishments and new build.
Moreover;
Installations should be divided up into circuits so as to avoid danger and inconvenience caused by a single fault - e.g. a single lighting fault should not disconnect all lighting and power circuits. E.g. the bathroom lights cannot be on the same RCD as the electric shower. Therefore two separate RCD will be required at the consumer unit.
Installations should be designed and arranged so as to avoid unwanted (or nuisance) tripping of RCDs. Again this means circuits should be separated across two or more RCDs at the consumer unit.
For a fuller description of these regulations please consult the 17th edition at the IEE.
In summary, these additional requirements mean that for any electrical work to be carried out in almost every domestic premises in England and Wales there will be an increased requirement for the use of multiple RCDs. In most circumstances this will require the installation a new consumer unit.