10. Electrical Systems

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10.1 General

10.1.1 Electrical arrangements should be such as to minimise risk of fire and electric shock. Particular attention should be paid to the provision of overload and short circuit protection of all circuits, except engine starting circuits, which are battery powered.

10.1.2 Where general lighting within the ship is provided by a centralised electrical system, an alternative source of lighting ( e.g. battery operated escape lights sufficient to enable persons to make their way up to the open deck) should be provided.

10.1.3 Electrical components and cables and wires of systems of dissimilar electrical characteristics should be kept separate to the maximum extent practical, and voltage characteristics should be identified at origination or the destination of the circuit.

10.1.4 All cables, connectors and terminations should be sized paying due regard to their current carrying capacities; all cables carrying less than 55 volts should have stranded copper conductors, flame retardant insulation and be of a suitable commercial grade rated for at least 75 °C service. For cables carrying over 55 volts, TC approved marine cable should be employed.

10.1.5 All electrical circuits should be provided with individual protection from the effects of overcurrent by suitable rated fuses or circuit breakers; both AC and DC circuit breakers should be of manual re-setting "trip free" type.

10.1.6 All electrical components and cabling exposed to the weather should be waterproof and of non-corrosive material. Any cable penetrations of ship structure on the weather deck should be by way of watertight connections.

10.1.7 Any electrical power supplies to navigation lights, steering systems or battery charging should include indication visible to the control point in the event that supply has failed.

10.1.8 The function of all switches, fuses and circuit breakers should be identified.

10.1.9 The cabinets or enclosures of all radios and electronic devices, fuel tanks and fuel filling connections should be bonded to a bonding system which is connected to the negative side of the electrical system. All bonding conductors should be copper or bronze.

10.1.10 Electrical wiring routing should, to the maximum possible extent, avoid any compass or compass system component. Where such a routing is unavoidable, D.C. wiring should be run in twisted pairs and be installed following compass manufacturers’ recommendations.

10.1.11 Lightning conductors should be fitted to each mast of non-metallic ships and to each mast of steel or aluminium ships having wooden masts or topmasts except where the height of any antenna exceeds that of the masts and the antenna is equipped with lightning arrestors or other effective devices.

10.1.12 Lightning conductors should be composed of continuous copper tape or cable having a cross sectional area of not less than 25 mm² (#4 AWG ) and should be continuous from a point 150 mm above the mast truck to a copper plate of not less than 0.2 in area fixed to the keel below the waterline in a manner that it remains immersed under all conditions of heel and trim; the lightning conductor plate should only be used for lightning conductor purposes.

10.2 D.C. Systems

10.2.1 D.C. systems should be of a two-wire type with insulated feed and return; systems of more than 55 Volts should be in accordance with TP 127.

10.2.2 Provided that engines installed in metallic-hulled ships are electrically isolated from the hull, all engine blocks may be used as a common ground return for engine-mounted electrical equipment.

10.2.3 Non-conducting exposed metal parts of electrical equipment should be grounded to the hull; in ships of wooden or reinforced plastic hull construction, this grounding should be by way of a continuous conductor terminating on the main engine or a copper ground plate of area not less than 0.2 fixed to the keel below the light waterline so as to be fully immersed under all conditions of heel.

10.2.4 All grounding connections should be of copper, readily accessible and securely fastened and protected as necessary against damage and electrolytic corrosion.

10.2.5 In grounded distribution systems, the grounded side should be of negative polarity.

10.2.6 Distribution panels and switchboards should be located in well-ventilated areas protected from rain or spray which may enter through scuttles, vents or deck openings.

10.2.7 The D.C. switchboard or distribution panel should include a voltmetre, an ammetre as well as an indicator of battery charging.

10.2.8 The D.C. switchboard or distribution panel should also provide indication of ship circuits to which power is connected. This may be by way of switches incorporating indicating lights.

10.3 Battery Storage

10.3.1 Battery storage facilities are to be well labelled and indicate the hazard contained within.

10.3.2 Every battery as installed should not move more than 25 mm when a pulling force of 40 kg or twice the battery weight, whichever is less, is applied through the centre of gravity, in each of the following five directions for one minute:

  1. vertically;
  2. horizontally, fore and aft; and
  3. horizontally, to port and starboard.

10.3.3 No battery should be installed directly above or below a fuel tank, fuel filter or fuel line fitting.

10.3.4 Batteries should not be installed in accommodation spaces, or spaces containing flammable stores. It is recommended that batteries not be installed in machinery spaces unless adequate arrangements are made for the dispersion of exhaust gases generated by charging; it is also recommended that batteries provided for engine starting purposes be installed adjacent to the engine, to reduce the length of conductors.

10.3.5 Every metallic fuel line and fuel system component above the level of the top of an installed battery should be shielded with dielectric material.

10.3.6 No battery should be installed such that metallic objects can come in contact with the ungrounded battery terminals.

10.3.7 Batteries of different types of construction, or using different electrolytes, should be secured in separate stowages.

10.3.8 The positive terminal of a battery should be identified on the terminal or on the battery case near the terminal with one of the following symbols:

  1. ‘POS’;
  2. ‘P’; or
  3. ‘+’ .

10.3.9 No battery terminal connector should depend upon spring tension for its connection to the terminal.

10.3.10 Vented batteries connected to a charging device with a power output of more than 2 KW are to be housed in an adequately ventilated compartment assigned to batteries only, or may be installed in a suitable box on deck.

10.3.11 Vented batteries connected to a charging device with a power output within a range of 0.2 KW to 2 KW are to be installed in accordance with 10.3.10, or may be installed in a box within a well vented machinery or similar space.

10.3.12 The interiors of all compartments for vented batteries, including crates, trays, boxes, shelves and other structural parts therein are to be of a corrosion resistant material and if necessary covered with a suitable paint or lining material.

10.3.13 Battery compartments and boxes should be provided with ventilation in accordance with subsection 10.3.14 to prevent accumulation of dangerous flammable gasses which may occur during the charging and discharging processes and due consideration should be given to the protection of the battery (batteries) from environmental conditions.

10.3.14 Natural ventilation may be provided for batteries if ducts can be run directly from the top of the compartment or box to the open air above, with no part of the duct inclined more than 45° from the vertical; if natural ventilation is impractical, mechanical exhaust ventilation for vented batteries should be provided where the quantity of air expelled is at least equal to:

Q = 110×I×N

Where :

N = number of cells in series

I = maximum current delivered to the charging equipment during gas formation, but not less than 25% of the maximum obtainable current in amperes

Q = quantity of air expelled in litres/hr

10.3.15 All batteries permanently connected to the ship's electrical systems should be provided with a charging circuit, which should include arrangements to prevent reversed polarity of the charging circuit and to prevent battery discharge through the charging circuit.

10.3.16 Any permanently installed batteries which may experience thermal runaway should be equipped with a temperature warning device which activates a distinctive audible warning. The charging circuits should be provided with isolating switches or circuit breakers.

10.3.17 Battery isolator switches should be provided to disconnect all permanently installed batteries from the ship's distribution system.

10.4 A.C. Systems

10.4.1 Preferred system characteristics, to which this standard refers, are 120 V , 60 Hz , single phase 2-wire insulated system, 120/240 V , 60 hz , single phase 3-wire with grounded neutral or 3 phase, 3-wire ungrounded system.

10.4.2 The system should be polarized and conductors should be uniformly identified:

  • insulated ground conductors = green;
  • ungrounded conductors = black and/or red
  • neutral = white.

10.4.3 Grounding conductors should be connected to the ground at only one point, the main distribution switchboard (panel).

10.4.4 Circuit design should ensure that no circuit may be fed simultaneously by more than one power source.

10.4.5 Any connector for the supply of shore power should be of weathertight design.

10.4.6 The power feed cable from a shore connection to the switchboard or distribution panel should have a circuit breaker or fused disconnected switch located not more than 3 m inboard of the shore connection. A polarity indicator for DC or single phase AC systems or a three phase sequence indicator should be fitted at the shore receptacle or on the switchboard.

10.4.7 All power feed conductors, from on-board generators or shore connection should be provided with over-current protection by common trip circuit breakers as follows:

120 V single phase - both ungrounded conductors.

120/240 V and 240 V single phase - both ungrounded conductors;

120/240 or 120/208 V three-phase - all ungrounded conductors.

10.4.8 Each branch circuit operating at voltages of 55 volts or over should be provided with a switch or circuit breaker with a pole for each conductor; any switch or circuit breaker fitted should operate simultaneously in the grounded conductor and the insulated conductor.

10.4.9 All fuses or circuit breakers should be rated so as not to exceed the current rating of the smallest connected conductor; motors should be protected by devices which are responsive to motor current.

10.4.10 On a grounded neutral distribution system ground fault circuit interrupters may be used on single-phase circuits to protect personnel and equipment; ground fault protectors may be used to protect equipment.

10.4.11 Transformers should be protected from short circuit on the primary side, and protected from overload by devices either installed on the primary or secondary side set or rated less than 125% of their respective currents.

10.4.12 The two wire branch circuit should not supply points which exceed 80% of the set value of the branch circuit protection device.

10.4.13 The AC switchboard or distribution panel should be provided with instrumentation indicating generator voltage and current to indicate the state of insulation to ground.

10.4.14 All systems of 120 V and above should have cable insulation resistance tests carried out upon completion of installation.

10.5 Emergency Power Supply

10.5.1 In every ship, battery capacity should be sufficient to power the following equipment simultaneously for 12 hours;

  1. Emergency lighting on the weather deck at survival craft deployment and embarkation points;
  2. Emergency lighting at each exit used as a primary means of escape to the weather deck;
  3. Compass illumination;
  4. One radio transceiver, assuming a total accumulation of 30 minutes transmission;
  5. Any fire detection or extinguishing system which relies on electrical power for its effectiveness.
  6. Where required by the collision regulations, the electrical supply to the navigation light panel.

In the case of a ship engaged regularly on voyages of short duration, a lesser period than 12 hours specified above may be allowed.

10.5.2 Any of the requirements of 10.5.1 may be satisfied by local batteries subject to suitable arrangements to ensure their condition.

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