Well most DNO's wont allow the exportation of a TN-C-S system to a swimming pool installation due to the risks that are present should the neutral conductor go "open circuit".
I've always TT'd any sort of pool install, much safer IMO.
Found this a while back.....has a lot of garb on swimming pools.......the reg numbers refer to the 16th ed though.
(i) Swimming pools employ a zonal concept which influences the methods available for protection against electric shock. Thus the methods employed in the dwelling may be unacceptable for the pool areas.
Careful consideration of the extent of the zones would be required before stipulating the type and location of electrical equipment.
SELV is recognised in the common Part 4 of BS7671 as providing protection against both direct and indirect contact, however, 602 requires the additional precaution of barriers and enclosures or insulation.
SELV with an open circuit voltage not exceeding 12v is the only recognised method in zones A and B. Exceptions to this requirement are extended to floodlights providing they are individually served by a dedicated transformer with an open circuit secondary voltage not exceeding 18v and to rcd-protected socket outlets with certain provisos.
Supplementary bonding is required to connect extraneous conductive parts with the protective conductors of all exposed conductive parts in Zones A,B and C. Further, it would be recommended to consider the benefits of a metal floor grid connected to the local supplementary bonding, especially if the PME earthing system was being considered as being extended to the pool area.
Generally, DNOs would not provide a PME (TN-C-S) terminal for a swimming pool due to the possibility of diverted neutral currents or small potential differences due to the voltage drop along the supply neutral causing perceived shock problems. As with any extension to an electrical installation, the DNO should be notified, preferably in advance.
The recommendation here might be to treat the pool building as a separate TT installation and to install only suitably rated Class ii equipment.
(ii) Electrical equipment should be suitable for the external influences it might have to encounter. Particular IP requirements are made for equipment dependant upon the zone into which it is intended to be installed.
(iii) Surface wiring systems should be non-metallic in nature. Additionally, Zones A and B should not contain wiring systems for anything other than the electrical equipment in those zones. There is also a requirement that accessible metal junction boxes should not be used in zone A and B.
(iv) Switchgear, controlgear and accessories are not permitted in Zones A and B except for socket outlets complying with BSEN 60309-2 which may be installed in Zone B providing they are protected by a 30ma rcd or by electrical separation and are 0.3m above the floor and 1.25m from the boarder of Zone A.
Regulation 602-07-02 sets out similar requirements for sockets, switches and accessories in zone C.
(v) The electric underfloor heating should comprise a metallic sheath or otherwise be covered by an earthed metallic grid. In both circumstances the sheath or grid should be connected to the local supplementary bonding.
