Derating factor for bunched circuits

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Table 22: DERATING FACTORS FOR BUNCHED CIRCUITS

SINGLE-CORE AND MULTICORE IN AIR OR IN WIRING ENCLOSURES

Arrangement of cables Derating Factors
Number of circuits or cables
1 2 3 4 5 6 7 8 9 10 12 14 16 18 20+
Bunched in air 1 0,87 0,75 0,72 0,7 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67 0,67
Bunched on a surface or enclosed 1 0,8 0,7 0,65 0,6 0,57 0,54 0,52 0,5 0,48 0,45 0,43 0,41 0,39 0,38
Single layer on wall or floor touching 1 0,85 0,79 0,75 0,73 0,72 0,72 0,71 0,7 0,7 0,7 0,7 0,7 0,7 0,7
Single layer on wall or floor spaced 1 0,94 0,9 0,9 0,9 0,9 0,9 0,9 0,9 0,9 0,9 0,9 0,9 0,9 0,9
Single layer under ceiling touching 0,95 0,81 0,72 0,68 0,66 0,64 0,63 0,62 0,61 0,61 0,61 0,61 0,61 0,61 0,61
Single layer under ceiling spaced 0,95 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85 0,85

Table 23: DERATING FACTORS FOR CIRCUITS

SINGLE-CORE IN TRAYS, RACKS, CLEATS OR OTHER SUPPORTS IN AIR

Installation No. of layers No. of circuits per layer
1 2 3
Horizontal perforated cable tray system Touching
1 0.97 0.89 0.87
2 0.94 0.85 0.81
3 0.93 0.84 0.79
Spaced
1 1.0 0.98 0.96
2 0.97 0.93 0.89
3 0.96 0.92 0.86
Vertical perforated cable tray systems Touching
1 0.94 0.85 0.85
2 0.92 0.83 0.83
Spaced
1 1.0 0.91 0.89
2 1.0 0.90 0.86
Horizontal unperforated cable tray systems Touching
1 0.95 0.85 0.84
2 0.92 0.83 0.79
3 0.91 0.82 0.76
Spaced
1 0.98 0.96 0.94
2 0.95 0.91 0.87
3 0.94 0.90 0.85
Cable ladder systems, cleats, etc. Touching
1 1.0 0.95 0.94
2 0.95 0.90 0.88
3 0.95 0.89 0.85
Spaced
1 1.0 1.0 1.0
2 0.97 0.95 0.93
3 0.97 0.94 0.90

Table 24: DERATING FACTORS FOR CIRCUITS

MULTICORE IN TRAYS, RACKS, CLEATS OR OTHER SUPPORTS IN AIR

Installation No. of layers No. of cables per layer
1 2 3 4 6 9
Horizontal unperforated cable tray system Touching
1 0.97 0.85 0.78 0.75 0.71 0.68
2 0.97 0.84 0.76 0.73 0.68 0.63
3 0.97 0.83 0.75 0.72 0.66 0.61
Spaced
1 0.97 0.96 0.94 0.93 0.90 0.90
2 0.97 0.95 0.92 0.90 0.86 0.86
3 0.97 0.94 0.91 0.89 0.84 0.84
Vertical perforated cable tray systems Touching
1 1.0 0.88 0.82 0.77 0.73 0.72
2 1.0 0.88 0.81 0.76 0.72 0.70
Spaced
1 1.0 0.91 0.89 0.88 0.87 0.87
2 1.0 0.91 0.88 0.87 0.86 0.86
Horizontal perforated cable tray systems Touching
1 1.0 0.88 0.82 0.78 0.76 0.73
2 1.0 0.87 0.80 0.76 0.73 0.68
3 1.0 0.86 0.79 0.75 0.71 0.66
Spaced
1 1.0 1 0.98 0.95 0.91 0.91
2 1.0 0.99 0.96 0.92 0.87 0.87
3 1.0 0.98 0.95 0.91 0.85 0.85
Cable ladder systems, cleats, etc. Touching
1 1.0 0.87 0.82 0.80 0.79 0.78
2 1.0 0.86 0.80 0.78 0.76 0.73
3 1.0 0.85 0.79 0.76 0.73 0.70
Spaced
1 1.0 1.0 1.0 1.0 1.0 1.0
2 1.0 0.99 0.98 0.97 0.96 0.95
3 1.0 0.98 0.97 0.96 0.93 0.93

Table 25(1): DERATING FACTORS FOR GROUPS OF CIRCUITS

SINGLE-CORE BURIED DIRECT IN GROUND

No. of circuits Below Ground Grouping (Buried direct) Derating Factor
Touching (zero distance) Distance (in m)
Trefoil Laid flat 0.15 0.30 0.45 0.60
2 0.78 0.81 0.83 0.88 0.91 0.93
3 0.66 0.70 0.73 0.79 0.84 0.87
4 0.61 0.64 0.68 0.74 0.81 0.85
5 0.56 0.60 0.64 0.73 0.79 0.83
6 0.53 0.57 0.61 0.71 0.78 0.82
7 0.50 0.54 0.59 0.69 0.76 0.81
8 0.49 0.53 0.57 0.68 0.76 0.81
9 0.47 0.51 0.56 0.67 0.75 0.81
10 0.46 0.50 0.55 0.67 0.75 0.80
11 0.44 0.49 0.54 0.66 0.74 0.80
12 0.43 0.48 0.53 0.66 0.74 0.80

Table 25(2): DERATING FACTORS FOR GROUPS OF CIRCUITS

MULTI-CORE BURIED DIRECT IN GROUND

No. of cables Below Ground Grouping (Buried direct) Derating Factor
Touching (zero distance) Distance (in m)
0.15 0.30 0.45 0.60
2 0.81 0.87 0.91 0.93 0.95
3 0.70 0.78 0.84 0.88 0.90
4 0.63 0.74 0.81 0.86 0.89
5 0.59 0.70 0.78 0.84 0.87
6 0.55 0.68 0.77 0.83 0.87
7 0.52 0.66 0.75 0.82 0.86
8 0.50 0.64 0.75 0.81 0.86
9 0.48 0.63 0.74 0.81 0.85
10 0.47 0.62 0.73 0.80 0.85
11 0.45 0.61 0.73 0.80 0.85
12 0.44 0.60 0.72 0.80 0.84

Table 26(1): DERATING FACTORS FOR GROUPS OF CIRCUITS

SINGLE-CORE IN UNDERGROUND WIRING ENCLOSURES—ENCLOSED SEPARATELY

No. of circuits Below Ground Grouping (Buried direct) Derating Factor
Touching (zero distance) Distance (in m)
0.45 0.60
2 0.87 0.91 0.93
3 0.78 0.84 0.87
4 0.74 0.81 0.85
5 0.70 0.79 0.83
6 0.69 0.78 0.82
7 0.67 0.76 0.82
8 0.66 0.76 0.81
9 0.65 0.75 0.81
10 0.64 0.75 0.80
11 0.63 0.74 0.80
12 0.63 0.74 0.80

Table 26(2): DERATING FACTORS FOR GROUPS OF CIRCUITS

SINGLE-CORE OR MULTICORE IN UNDERGROUND WIRING ENCLOSURES—MULTICORE CABLES ENCLOSED SEPARATELY OR MORE THAN ONE SINGLE-CORE CABLE PER WIRING ENCLOSURE

No. of cables Below Ground Grouping (Buried direct) Derating Factor
Touching (zero distance) Distance (in m)
0.30 0.45 0.60
2 0.90 0.93 0.95 0.96
3 0.83 0.88 0.91 0.93
4 0.79 0.85 0.89 0.92
5 0.75 0.83 0.88 0.91
6 0.73 0.82 0.87 0.90
7 0.71 0.81 0.86 0.89
8 0.70 0.80 0.85 0.89
9 0.68 0.79 0.85 0.89
10 0.67 0.79 0.85 0.89
11 0.66 0.78 0.84 0.88
12 0.66 0.78 0.84 0.88


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