Low cension (LT) cores of these cables are insulated with PVC and are suitable for operation up to 440 V rms at frequencies up to 1.6 kHz. High tension (HT) cores are insulated with polyethylene and are suitable for operation up to 2000 V rms at frequencies up to 1.6 kHz.

Current carrying capacities for multi-core cables are not given owing to the varied conditions of loading and construction. However, for guidance, where a single core of a multi-core cable is loaded, the current in a 16/0.2 mm conductor should not exceed 2.5 amp, and in a 37/0.315 mm conductor the current should not exceed 13 amp.

The recommended maximum (conductor) operating temperature for the cables in, Table I ( A ) is 70°C but they may be operated at slightly higher temperatures for short periods. No definite limit can be given for low temperature because conditions of use are varied and include, for example, the rate of bending, the radius of bending, and the length of time the cable is exposed to the low temperature. PVC compounds become increasingly stiff and brittle as their temperature decreases, with the result that if the cable is bent too sharply or is struck sharply at temperatures lower than about 0°C there is a risk of shattering the PVC.

Although the insulation and sheath of the cables are tested in a specified manner a t temperatures down to -15° and -30°C respectively, and although in storage and when once installed , (but not subjected to flexing or severe vibration) the cables can withstand temperatures as low as -55°C, it is recommended that they should not be bent in handling unless cable and ambient temperatures are above 0°C and have been so for the previous 24 h or unless special precautions have been taken to maintain the cable above this temperature.

The recommended maximum (conductor) operating temperature for the cables in Table I ( B ) is 85°C and the lower test temperatures for insulation and sheath are -15° and -20°C respectively. In other respects clauses 1.3 and 1.4 above apply.