David King asks whether PME earthing should be used in a marina electrical installation, which he describes. His question is answered by SELECT (Theme – Regulations & Legislation):
Question: In a private boat club, the main supply is 230V single-phase and the supply earth is PME. From the incoming main, supplies are taken to distribution boards in various permanent buildings on site.
There are also a number of canalside linear moorings with access to shore-based electrical supplies via 'commando' type socket outlets. The socket outlets appear to be looped and fed from one of the distribution boards containing MCBs.
I understood that PME earthing should not be used for this type of installation - however, the premises have recently been subject to electrical inspection and the contractor has not commented on the earthing arrangements in his report. Is this correct?
Answer: The Electricity, Safety, Quality and Continuity Regulations 2002 (statutory regulations relating to supply distribution) prohibit the connection of a PME earthing system to any metalwork in a boat. This type of system earthing is, however, permitted for the supplies to permanent buildings on the site such as shops, toilets, laundries etc.
Where PME earthing is in use on such a site, some separation may be required from this earthing system for the supplies to the boats (note 30mA RCD protection will be required for such socket-outlets)
The IET Guidance Note 7 Special Locations, Chapter 8, is a good source of reference and guidance.
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