Rating Factors

The current rating mentioned in above tables based on ambient temperature 30°C in accordance with IET Wiring regulations for Electrical Installations, BS 7671.

Rating Factor for variation in Ambient Air Temperature.

Air Temperature (°C)

25

30

35

40

45

50

55

60

Rating Factor

1.02

1.00

0.96

0.91

0.87

0.82

0.76

0.71


Rating Factor for one circuit or one multicore cable or for group of circuits or a group of multicore cables.

Arrangement

 

 

 

Number of Circuits or Multicore Cables

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(cable Touching)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

2

3

4

5

6

7

8

9

12

16

20

 

Bunched in Air,

 

 

 

 

 

 

 

 

 

 

 

 

 

on a surface,

1.00

0.80

0.70

0.65

0.60

0.57

0.54

0.52

0.50

0.45

0.41

0.38

 

embedded or

 

 

 

 

 

 

 

 

 

 

 

 

 

enclosed

 

 

 

 

 

 

 

 

 

 

 

 

 

Single layer on

1.00

0.85

0.79

0.75

0.73

0.72

0.72

0.71

0.70

0.70

0.70

0.70

 

 

Single layer

 

 

 

 

 

 

 

 

 

 

 

 

 

multicore on

 

 

 

 

 

 

 

 

 

 

 

 

 

a perforated

1.00

0.88

0.82

0.77

0.75

0.73

0.73

0.72

0.72

0.72

0.72

0.72

 

horizontal or

 

 

 

 

 

 

 

 

 

 

 

 

 

vertical cable tray

 

 

 

 

 

 

 

 

 

 

 

 

 

system

 

 

 

 

 

 

 

 

 

 

 

 

 

Single layer

 

 

 

 

 

 

 

 

 

 

 

 

 

multicore on cable

1.00

0.87

0.82

0.80

0.80

0.79

0.79

0.78

0.78

0.78

0.78

0.78

 

ladder system or

 

 

 

 

 

 

 

 

 

 

 

 

 

cleats etc.

 

 

 

 

 

 

 

 

 

 

 

 

 


Minimum Bending Radius:

 

Single core                                                                Multi Core Cable

Armoured        -8 x OD                                                Armoured    -8 x OD

Un Armoured - 6 x OD                                                 Un Armoured - 8 x OD

 Where ‘OD’ is overall diameter of cable                         Where ‘OD’ is overall diameter of cable