BS EN ISO 10133:2017 ISO 10133:2012(E)


Annex A (normative)


Conductor requirements A.1 Table A.2 gives allowable maximum current ratings in amperes determined for 30 °C ambient temperature.


For conductors in engine rooms (60 °C ambient), the maximum current rating in Table A.2 shall be derated by the factors below.


Table A.1— Derating of conductors in engine rooms


Temperature rating of conductor insulation, °C


70


85 to 90 105 125 200


Multiply maximum current from Table A.2 by:


0,75 0,82 0,86 0,89 1


A.2 As a guideline: the voltage drop (E) at load, in volts, can be calculated using the following formula: E


=


where S l


0 0164, S


×× lL


is the conductor cross-sectional area, in square millimetres; is the load current, in amperes;


L is the length, in metres, of conductor from the positive power source to the electrical device and back to the negative source connection.


NOTE On a 12 V system an approximation of a 3 % drop can be obtained by the following:


S lL= × 20


10


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