Marinas and similar locations are considered in BS 7671 to be locations with an increased risk of electric shock. This is because of the presence of water, a reduction in body resistance, and contact of the body with Earth potential.
In this article we give an overview of the requirements of Section 709 of BS 7671 for circuits intended to supply houseboats and pleasure craft in marinas and similar locations. The requirements of Section 709 add to and modify the general requirements in Parts 1 to 6 of BS 7671. Throughout this article, the term ‘marina’ means ‘marina or similar location’.
External influences
Some external infuences particularly likely to affect electrical installations of marinas are:
- the presence of water
- the movement of structures (such as pontoons)
- the presence of solid foreign bodies, and in many cases
- Impact.
Equipment installed on or above a jetty, wharf, pier or pontoon is required by Regulation 709.512.2.1.1 to have ingress protection of at least:
- IPX4 where likely to be splashed with water
- IPX5 where likely to be subjected to water jets (e.g. hosing), or
- IPX6 where likely to be subjected to waves.
The equipment in these locations is also required, by Regulation 709.512.2.1.2, to have protection of at least IP3X against the ingress of small objects. Also, the equipment is required by Regulation 709.512.2.1.3 to be suitable for use in the presence of whatever polluting substance or corrosive atmosphere is likely to be present, such as a salt laden marine environment, and is to be protected against mechanical damage caused by impacts of medium severity.
Protection against impact may be achieved by installing robust equipment having a degree of protection against external mechanical impact of at least IK08 (5 joule impact energy) according to BS EN 62262, or by providing local or general mechanical protection, or by locating the equipment so that damage by any reasonably foreseeable impact may be avoided. (Regulation 709.512.2.1.4)
Supplies
The nominal voltage of the supply to a houseboat or pleasure craft is required to be 230 V single-phase AC, or 400 V three-phase AC (Regulation 709.313.1.2 refers). Regulation 709.411.4 highlights the prohibition against the connection of a PME earthing facility to any metalwork in a boat, in The Electricity Safety, Quality and Continuity Regulations 2002 as amended (ESQCR). Therefore, where the supply provided by the electricity distributor is PME, the electrical installation of a boat should use an installation earth electrode as its means of earthing (see the next item of this article) and be arranged to meet the requirements of BS 7671 for an installation forming part of a TT system. Where permanent buildings exist, Regulation 709.411.4 does not preclude the use of a PME earthing facility as the means of earthing for the installations of these buildings.
Plugs and socket-outlets for supplies to pleasure craft or houseboats
Socket-outlets for the connection of the hook-up cables to supply pleasure craft or houseboats from the shore are required by Regulation Group 709.553.1 to be provided on the basis of one socket outlet per pleasure craft or houseboat. Each socket-outlet is to be located as close as practicable to the berth to be supplied and is either to be provided in an enclosure or form part of a distribution board. No more than four socket-outlets are to be grouped together in any one enclosure, so that hazards due to long hook-up cables from moored craft are avoided.
The socket-outlets are to comply with BS EN 60309-2 if the rated current is 63 A or less, or BS EN 60309-1 if the rated current exceeds 63 A. In general, 16 A single-phase socket-outlets are required, as stated in Regulation 709.553.1.12. However, where a higher demand is envisaged, socket-outlets with a higher rated current, or 400 V three-phase socket-outlets, will need to be provided. The socket-outlets are generally to be installed at least 1 m above the highest water level. However, an exception is allowed for socket-outlets installed on floating pontoons or walkways, in which case the height may be reduced to 300 mm above the highest water level if additional measures are taken to protect the socket-outlets against the effects of splashing. A degree of protection of at least IP44 is to be provided for socket outlets.
Where the supply is PME, the earthing terminals of the socket-outlets must be connected to an installation earth electrode and not to the PME earthing facility (PEN conductor of the supply), due to the requirements of the ESQCR, mentioned under the heading ‘Supplies’, earlier.
The socket-outlets may be isolated individually or in groups (Regulation 709.537.2.1.1 refers). There must be at least one means of isolation for every four socket-outlets and at least one for each distribution cabinet. The means of isolation must disconnect all live (line and neutral) conductors.
Overcurrent protection
Each fixed final circuit for the supply to a houseboat, and each socket-outlet for the supply to a pleasure craft or houseboat, is to be protected by an individual overcurrent protective device (Regulation 709.533 refers).
Additional Protection by means of an RCD Each fixed final circuit for the supply to a houseboat, and each socket-outlet for the supply to a pleasure craft or houseboat, is to be protected individually by an RCD having the characteristics given in Regulation 415.1.1 (see Fig 1). This means the RCD must have a rated residual operating current (I∆n) not exceeding 30 mA and an operating time not exceeding 40 ms at a residual current of 5 I∆n. The RCD is to disconnect all live (line and neutral) conductors. (Regulation 709.531.2 refers.)
Types of wiring system
Regulation Group 709.521 points out that wiring systems suitable for distribution circuits include:
- underground cables
- sheathed or non-sheathed overhead cables
- mineral insulated cables with a thermoplastic covering
- thermoplastic or elastomeric insulated armoured cables with extruded non hygroscopic fillers
- cables that are at least equivalent to the above
However, wiring systems on or above a jetty, wharf, pier or pontoon must not use:
- cables suspended in free air or incorporating a support wire
- non-sheathed cables in cable management systems (this is to prevent chafing of the cables)
- cables with aluminium conductors
- mineral insulated cables
Cables are to be selected and installed so that mechanical damage due to the movement of floating structures, caused by waves or tide for example, is prevented. Where there is such movement, consideration should be given to the use of equipment such as flexible cable and flexible conduit. Special consideration is needed for wiring systems passing from one pontoon to another, due to the relative movement of the pontoons.
Where cable management systems such as conduit or trunking are used, they should be installed to allow for the drainage of water by having a slight fall and/or suitably located drainage points. All overhead conductors are to be insulated and must be installed at least 6 m above the ground in areas where there is likely to be vehicle movement. In other areas, a height of at least 3.5 m above the ground is required. The poles and other supports for overhead wiring are to be located so that they are unlikely to be damaged by any foreseeable vehicle movement, or protected against such damage. Where cables are to be installed underground, they are to be buried at a sufficient depth (typically at least 0.5 m) to avoid damage, such as may be caused by heavy vehicle movement. Additional mechanical protection should be provided where required.
Protective measures against electric shock that are not to be used (709.41)
Not surprisingly, Regulation Group 709.41 states that obstacles, placing out of reach, non-conducting location and earth-free local equipotential bonding are not permitted for protection against electric shock in marina installations.
Instruction notice
It is recommended in Section 709 that the marina operator provides an instruction notice for people intending to connect pleasure craft to the shore electrical supply, prior to them making such a connection. To achieve this, BS 7671 recommends that a notice is placed adjacent to each socket-outlet or group of socket-outlets. The recommended content of the notice is given in Fig. 709.3.
