Swimming pools, paddling pools and their surroundings are locations of increased electric shock risk. This is due to the reduction in body resistance and the increased contact between the body and Earth potential due to wet, bare skin.
For such locations, the general requirements of BS 7671 are supplemented and modified by the requirements of Section 602 of BS 7671 (Swimming Pools). One of the additional safety measures identified by that section is local supplementary bonding, for additional protection against indirect contact.
Conditions that make local supplementary bonding a requirement
Local supplementary bonding is required if there are any exposed-conductive-parts in zones A, B or C of the location, except exposed-conductive-parts of equipment supplied by a SELV circuit (Regulation 602-03-02 refers). Where there are no exposed-conductive-parts, local supplementary bonding is not required.
The dimensions of zones A, B and C are illustrated in Figures 602A and 602B of BS 7671, which are reproduced below for ease of reference.
Examples of exposed-conductive-parts that may be present in zones A, B or C, and which may make local supplementary bonding a requirement, include metallic enclosures of:
i) socket-outlets in zone B (socket-outlets are permitted in zone B only where it is not possible to install them outside that zone, and where the other conditions stated in Regulation 602-07-01 are met)
ii) Class I switchgear, controlgear or accessories in zone C, where such equipment is permitted in that zone by Regulation 602-07-02
iii) other Class I electrical equipment in zone C (such as surface wiring systems employing metallic conduit, metallic trunking or exposed metallic cable sheaths), where such equipment is permitted in that zone by Regulation Group 602-08.
There should be no exposed-conductive-parts in zones A or B that would make supplementary bonding a requirement, except possibly for exposed-conductive-parts of any socket-outlets permitted in zone B (see (i) above). This is because, except for such socket-outlets, only SELV may be used for protection against electric shock (Regulation 602-04-01 refers), and it is not permitted to install surface-mounted wiring systems employing metallic conduit or metallic trunking or metallic cable sheaths, or accessible metal junction boxes (Regulation Group 602-06 refers).
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