Rating factor for variation in Ambient temperature /Correction Factor for groups of Cables


Rating factor for variation in Ambient temperature
Ambient temperature (°C) 25 30 35 40 45 50 55 60 65
PVC Insulated Cable (85°C) 1.02 1 0.95 0.90 0.85 0.80 0.74 0.67 0.6
PVC Insulated Cable (70°C) 1.03 1 0.94 0.87 0.79 0.71 0.61 0.5 0.35

Correction Factor for groups of Cables
Arrangement( Cables touching)  Number of circuits or multicore Cables
2 3 4 5 6 7 8 9 10 12 14 16 18 20
Bunched in Air, on a surface,
embedded or enclosed(Methods A to F)
0.80 0.70 0.65 0.60 0.57 0.54 0.52 0.50 0.48 0.45 0.43 0.41 0.39 0.38
Single layer on wall or Floor (Method C) 0.85 0.79 0.75 0.73 0.72 0.72 0.71 0.70 0.70 0.70 0.70 0.70 0.70 0.70
Single layer multicore on a perforated horizontal or
vertical cable tray system (Methods E&F)
0.88 0.82 0.77 0.75 0.73 0.73 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72
Single layer multicore on cable ladder
system or cleats etc. (Methods E & F)
0.87 0.82 0.80 0.80 0.79 0.78 0.78 0.78 0.78 0.78 0.78 0.78 0.78 0.78

(Ref. IEEE wiring regulation Seventeenth edition)