There is an increased risk of injury or death from electric shock at marinas due to the decreased body resistance from water or that a person can be connected to the general mass of ground by body immersion.
Additional factors with electrical equipment and apparatus at marinas that increase the risk include corrosion, movement of structures, mechanical damage, salt laden air, water spray and exposure to ultra-violet radiation.
Various methods of supplying electricity to or at marinas are prohibited including the use of:
- Aerial conductors or catenary wiring
- Aluminium or aluminium conductors clad with other metals
- Metallic pipes or conduits as the protective earthing conductor
- The marina as an outbuilding or detached portion(s) of an installation i.e. a separate MEN installation is NOT ALLOWED.
Various methods of electricity supply to boats are allowed including the use of RCDs with a maximum residual rating of 30mA, except for shore power outlets rated at 63 amps or over which may be protected by an RCD that operates at 100mA, and the use of isolation transformers (refer AS/NZS 3004.1).
Electric shock or electrocution issues can come about on boats from lack of compliance with wiring requirements from AS/NZS 3004.2 and lack of maintenance. Boats operate in harsh environments with salt laden air, water spray and at times, parts will be inundated with water. Galvanic corrosion prevention is particularly important as is ongoing maintenance. Faulty leads, appliances, and wiring can lead to electric shock or electrocution incidents.
Dangerous neutral to earth voltages can be transferred to the marina and boats from the shore power supply. Shore mounted isolation transformers will prevent the transfer of such voltages to the boat.
But what are neutral to earth voltages? The neutral conductor in an MEN system is connected to the general mass of ground via earth electrodes. These connections to the ground have resistance and so there can be a difference in voltage from the neutral to the general mass of ground caused by voltage drop across neutral conductors. If these connections were perfect, then the neutral and the general mass of ground would be at the same potential and this wouldn’t be an issue.
The transfer of neutral to earth voltage to marinas and boats comes about from the voltage on the neutral at the MEN connection of the power supply, transferring via the earthing conductor to anything connected at the marina and boat end. Even as little as 5 to 10mA can caused strong muscular contraction and this can occur at as little as 2 to 3 volts a.c. 50 Hz in saltwater where a large proportion of a person’s body is emersed in the water. Most people die from drowning if they receive an electric shock as their muscles contract and they can no longer swim. Their brain (if the head is immersed) and lung function may also be affected. For these reasons, PowerLogic supports the use of 10mA RCD protection for marinas, boats and swimming pools.
Need to know more, then undertake our electric shock investigation course: https://www.powerlogic.com.au/electrical-training-courses/