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General Notes on Caravan Wiring. Dec.78.

12v wiring and "mains" wiring must be installed as separate systems.
Caravan Manufacturers who install "mains" wiring in their caravans, and Park Operators who offer "mains hook ups" for tourers should stipulate in their instructions to the user that the caravan should be uncoupled mechanically from the towing vehicle before connection to the "mains" is made.
The "mains" isolating switch and fuses should be installed as close as possible to the caravan " mains" inlet.
Caravan Manufacturers and others who install refrigerators capable of operation from the "mains" but in caravans without a "mains" wiring installation should issue clear instructions that, should the customer wish to use the "mains" facility of the refrigerator, he must have the "mains" wiring installed to I.E.E. regulations (which of course includes a "mains" inlet to B.S. 4343/CEE 17, on isolating switch, fuses, bonding etc.).
"Mains" battery chargers installed in caravans should comply with B.S. 3456 Part 2 section 2.36-1973:
Battery Chargers - and B.S. 3535: Safety Isolating Transformers - and should be so marked. If the battery charger does not have automatic regulation, it should be marked with the minimum size of the battery to be used. (It is essential that the maximum output of the charger in amperes should be no more than one tenth of the battery capacity in ampere hours at 20 hour rate).

Caravan Wiring (12v)

Wiring of caravan interior equipment should be fuse protected. When the supply is drawn from the towing vehicle, the fuse in the caravan should be as close to the source as possible.
The caravan body and/or chassis should not be used for the return circuit. The return circuit should be part of the cable system and connected to the white lead of the 7 core flexible cable to the towing vehicle.

Specifications of Accessories

Compatibility and performance requirements make it particularly important that accessory manufacturers provide detailed and accurate data of their products.

Trends outside Road Regulations
Because of the problems on interchangeability between cars and caravans, and the difficulty of designing control equipment for cars that will cope, it is strongly recommended that signalling devices (such as side repeaters ) outside the scope of the lighting regulations, are not fitted to caravans.

Car Wiring
With the introduction of combined flasher/hazard units, increasing use is being made of repeater relays to trigger the operation of the caravan indicator lamps. In these circumstances the caravan circuits can be deprived of fuse protection. Manufacturers of these devices should therefore include advice on the provision of fuses in their instructions.
Satisfactory operation of the 12v facility on a caravan refrigerator is likely to be achieved only when a suitable circuit solely for that purpose is provided direct from the charging circuit of the towing vehicle as provided for in the 12S concept). Accidental discharge of the battery should be avoided by the use of an ignition controlled relay, or a voltage sensitive cut out may be developed for this purpose,
Caravan Battery
The battery must be of the type which does not require removal of vent plugs or cover when charged by a "mains" charger. Battery terminals should preferably be of the flat lug type.
The battery must be firmly secured to prevent movement or upset of the battery when towing.
Leads to the battery should terminate in eyelets which should be clamped to the battery terminals with a nut arid bolt. Crocodile clips should never be used.
Unless the battery is mounted iii a carrying box with a clip down lid, the battery terminals must be shrouded If the battery is located in an external gas bottle locker, adequate ventilation must be provided above the battery in addition to floor ventilation.
If the battery is mounted inside the caravan it must be located in a separate compartment, The compartment must be fitted with a lid designed to give a reasonably air-tight seal arid also permit easy access to the battery for maintenance. The compartment should be vented to the exterior of the caravan at a polio above the top of the battery and at floor or base level. The interior of the compartment should have an acid resistant finish. Ventilators should be acid resistant and the sections of wall and floor apertures likely to come in contact with gas should also be protected from corrosion.
The battery feed should be taken as soon as possible to a multi fuse holder with as many fuses as appropriate. Normally at least two fuses will be needed, one for the interior lights and one for the electric water pump.
The Caravan Manufacturer should provide information regarding the installation and maintenance of batteries and give general safety precautions.
If charging of the caravan battery in the boot or rear of the towing vehicle is contemplated, the battery must be provided with a suitable carrying box with a clip-down lid and suitable vents. Connection must be via suitable connectors with shrouded terminals. A location device to prevent movement or upset of the battery when the vehicle is being driven must be provided.
Thomson Wiring Diagrams
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