Section 20 Cargo craft, patrol and pilot craft, workboats and other similar craft of less than 500 tons gross tonnage for operation in Service Groups 1 to 3, and yachts less than 500 gt

20.1.1 The requirements of this Section are applicable to electrical installations where the voltage of supply does not exceed 440 V a.c. or d.c.

20.1.2 The electrical installations for propulsion and auxiliary service where the voltage of supply exceeds 440 volts are to be constructed and installed in accordance with Pt 16, Ch 2, 1 General requirements.

20.1.3 Cargo craft of 300 tons gross tonnage and above are also to comply with Pt 16, Ch 2, 3.7 Radio installation.

20.1.4 Alternative arrangements, including those in accordance with IEC 60092-507:Electrical installations in ships – Part 507: Small vessels, or a relevant International or National Standard acceptable to LR may be considered.

20.2.1 At least three copies of the plans and particulars in Pt 16, Ch 2, 20.2 Plans 20.2.2 are to be submitted for consideration. Single copies only are required of plans in Pt 16, Ch 2, 20.2 Plans 20.2.7.

20.2.2 Single line diagram of main power and lighting systems which is to include:

1. rating of machines; transformers; batteries and semi-conductor converters;

2. all feeders connected to the main switchboard;

3. section boards and distribution boards;

4. insulation type, size and current loadings of cables;

5. make, type and rating of circuit breakers and fuses.

20.2.3 Simplified diagrams of generator circuits and feeder circuits showing:

1. protective devices;

2. instrumentation and control devices;

3. preference tripping;

4. earth fault indication/protection.

20.2.4 Calculations of short circuit currents at main switchboard and distribution boards, details of circuit breaker and fuse operating times and discrimination curves.

20.2.5 For battery installation, arrangement plans and calculations are to show compliance with Pt 16, Ch 2, 20.12 Batteries.

20.2.6 Details of electrically operated personnel safety systems which are to include single line diagrams and a general arrangement plan of the vessel showing location and cable routes of:

1. fire detection, alarm and extinction systems;

2. internal communication and alarm systems.

20.2.7 Schedule of normal operating loads on the system.

20.3.1 The installation is to be inspected and tested by the Surveyors, in accordance with the requirements of Pt 16, Ch 2, 21 Testing and trials, as appropriate, and is to be to their satisfaction.

20.4.1 No addition, temporary or permanent is to be made to an approved installation until it has been ascertained that the current carrying capacity and the condition of the existing equipment, including cables and switchgear, are adequate for the increased load.

20.4.2 Plans are to be submitted for consideration, and the alterations or additions are to be carried out under the survey and to the satisfaction of the Surveyors.

20.5.1 Electrical equipment is to be accessibly placed, clear of flammable material in well ventilated, adequately lighted spaces, in which flammable gases cannot accumulate and where it is not exposed to risk of mechanical damage or damage from water, steam or oil. Where necessarily exposed to such risks, the equipment is to be suitably constructed or enclosed. Equipment is to be accessible for maintenance.

20.5.2 Insulating materials and insulated windings are to be flame retardant, and resistant to tracking, moisture, sea air and oil vapour unless special precautions are taken to protect them.

20.5.3 Securing arrangements used in connection with current carrying parts are to be effectively locked.

20.5.4 The operation of all electrical equipment is to be satisfactory under such conditions of vibrations, movements and shock as may arise in normal practice.

20.5.5 The design and installation of electrical equipment is to be such that the risk of fire due to its failure is minimised. It is, as a minimum, to comply with a National or International Standard revised where necessary for ambient conditions. Equipment is to be tested at the manufacturer's works and a certificate of tests issued by the manufacturer.

20.6.1 The following systems of generation and distribution are acceptable:

1. two wire insulated;

2. two wire with one pole earthed;

3. three phase three wire insulated neutral;

4. three phase, four wire with neutral earthed but without hull return.

20.6.2 A device(s) is to be installed for every insulated distribution system, whether primary or secondary, for power, heating and lighting circuits to continuously monitor the insulation level to earth.

20.7.1 Except where exempted by Pt 16, Ch 2, 20.7 Earthing 20.7.2 all non-current carrying exposed metal parts of electrical equipment and cables are to be earthed.

20.7.2 The following parts may be exempted from the requirements of Pt 16, Ch 2, 20.7 Earthing 20.7.1:

1. lamp-caps, where suitably shrouded;

2. shades, reflectors and guards supported in lampholders or light fittings constructed of, or shrouded in, non-conducting material;

3. metal parts on, or screws in or through, non-conducting materials, which are separated by such material from current-carrying parts and from earthed non-current carrying parts in such a way that in normal use they cannot become live or come into contact with earthed parts;

4. apparatus which is constructed in accordance with the principle of double insulation;

5. bearing housings which are insulated in order to prevent circulation of current in the bearings;

6. clips for fluorescent lamps;

7. cable clips and short lengths of pipes for cable protection;

8. apparatus supplied at a voltage not exceeding 55V direct current or 55V root mean square, between conductors, or between any conductor and earth in a circuit isolated from the supply. Autotransformers are not to be used for the purpose of achieving the alternating current voltage;

9. apparatus or parts of apparatus which although not shrouded in insulating material is nevertheless otherwise so guarded that it cannot be touched and cannot come in contact with exposed metal.

20.7.3 With wood and other non-metallic hull constructions earthing connections are to be made to the generator frame, engine bedplate and earthing plate. Earthing connections are not to be made to hull sheathing, skin fittings or plumbing.

20.8.1 Installations are to be protected against overcurrents including short circuits. The tripping/fault clearance times of protective devices are to provide complete and co-ordinated protection to ensure:

1. availability of services not affected by the faulty circuit;

2. elimination of the fault to reduce damage to the system and hazard of fire.

20.8.2 Short circuit protection and a means of complete isolation is to be provided for each source of power.

20.8.3 Protection for battery circuits is to be provided at a position external and adjacent to the battery compartments; batteries used solely for engine starting may be provided with only a means of isolation.

20.8.4 Short circuit and overload protection together with a means of isolation is to be provided in each non-earthed outgoing circuit of the main switchboard and each distribution board.

20.8.5 Each final sub-circuit is to be provided with short circuit protection and a means of isolation in each non-earthed line.

20.8.6 Lighting circuits are to be supplied by circuits separate from those for power.

20.8.7 Control circuits for engine monitoring and other services are to be provided with short circuit protection.

20.8.8 Protective devices are not to be fitted in any earthed line of a distribution system.

20.8.9 Circuit breakers and fuses are to have a certified fault rating adequate for the installation and are to comply with a National or International Standard.

20.8.10 In the absence of precise data the calculation methods given in Pt 16, Ch 2, 6.2 Protection against short-circuit 6.2.4 are to be used for evaluation of short circuit currents.

20.8.11 Generators for a.c. systems are to be provided, as a minimum, with the protective gear required by Pt 16, Ch 2, 6.8 Protection of generators 6.8.2 and Pt 16, Ch 2, 6.8 Protection of generators 6.8.3 and additionally provided with the instrumentation required by Pt 16, Ch 2, 7.11 Instruments for alternating current generators.

20.9.1 Unless specified otherwise electrical equipment, other than that supplied by battery systems, is to operate satisfactorily with the following simultaneous variations, from their nominal value, when measured at the consumer input terminals.

1. Voltage:

   • Permanent variations +6 per cent, -10 per cent
   • Transient recovery +20 per cent, -15 per cent
   • Recovery time 1,5 seconds.

2. Frequency:

   • Permanent variations ±5 per cent
   • Transient variations ±10 per cent
   • Recovery time five seconds

20.9.2 Generator voltage regulators and engine governors are to be such as to ensure that the above supply variations are not exceeded.

20.10.1 Under sea-going conditions where electrical power is required for services for the propulsion, navigation and safety of the craft and crew, it is to be provided by either a generator(s) having a rating sufficient to ensure the operation of these services or by an engine-driven charging system in conjunction with a battery(ies).

20.10.2 Under emergency conditions where electrical power is required for lighting to enable persons to evacuate the craft, for navigational lights, fire detection and alarm systems and internal communication and alarm systems, it is to be provided by alternative source(s) of electrical power located separately from the source(s) of power in Pt 16, Ch 2, 20.10 Sources of electrical power 20.10.1 and suitably located for use in an emergency. This source(s) of electrical power is to be adequate to permit evacuation and to supply the navigation lights, fire detection and alarm systems and internal communication and alarm systems, for a period of 5 hours duration.

20.10.3 Where electrical power is required for services for the propulsion, navigation and safety of the yacht or craft and for the safety of the crew it is to be provided by:

1. for non-passenger type yachts of scantling length between 24 m and 50 m, at least two generators having ratings sufficient to ensure the operation of these services when any one generator is out of action; or

2. for non-passenger type service craft for Service Groups 1 to 3, a generator(s) having a rating sufficient to ensure the operation of these services without being overloaded.

20.10.4 Additionally, for non-passenger type yachts of scantling length between 24 m and 50 m:

1. generators fitted to satisfy the requirements of Pt 16, Ch 2, 20.10 Sources of electrical power 20.10.3 may be driven by the main engine provided the requirements of Pt 16, Ch 2, 20.9 Quality of power supplies 20.9.1 are satisfied for all main engine speed and load conditions and that there is at least one of the remaining generators driven by a prime mover independent of the main engine; and

2. any batteries provided for the duty, referred to in Pt 16, Ch 2, 20.10 Sources of electrical power 20.10.2, are to be rated for at least 5 hours duration.

20.10.5 Additionally, for non-passenger type service craft for Service Groups 1 to 3, in a single generator installation, or where in a multiple generator installation with one generator out of action the remaining generator(s) is not capable of supplying the circuits serving any safety, essential lighting and communication equipment, an alternative source of electrical power of 5 hours duration is to be provided for these services.

20.11.1 Cables and cable installations are to be in accordance with the requirements of Pt 16, Ch 2, 11 Electric cables, optical fibre cables and busbar trunking systems (busways).

20.11.2 Where the emergency services referenced in Pt 16, Ch 2, 1.16 Operation under fire conditions are fitted, their cables are required to be in accordance with Pt 16, Ch 2, 1.16 Operation under fire conditions.

20.12.1 Batteries and battery installations are to be in accordance with the requirements of Pt 16, Ch 2, 12 Batteries.

20.13.1 Lightning conductors complying with IEC 60092-401: Electrical installations in ships – Part 401: Installation and test of completed installation are to be fitted to each mast of all wood, composite and steel craft having wooden masts or topmasts. They need not be fitted to steel craft having steel masts.

20.14.1 Where a fire detection and alarm system is fitted, it is to be in accordance with the requirements of Pt 16, Ch 2, 17.1 Fire detection and fire alarm systems.

20.15.1 Stops for ventilation fans for machinery spaces and enclosed galleys are to comply with the applicable paragraphs of Pt 16, Ch 2, 17.6 Fire safety stops.

20.16.1 Where internal communication and alarm systems are provided for use in an emergency, they are to comply with the requirements of Pt 16, Ch 2, 18.2 General emergency alarm system and Pt 16, Ch 2, 18.3 Public address system as appropriate.