TABLE - 65
(FOR INSTALLATION IN AIR ONLY) GROUP RATING FACTORS FOR GROUPS OF MORE THAN ONE CIRCUIT OF SINGLE CORE CABLES TO BE APPLIED TO THE CURRENT-CARRYING CAPACITY FOR ONE CIRCUIT OF SINGLE-CORE CABLES IN FREE AIR
Use as a multiplier to rating for
Number of three-phase circuits (Note 3)
Number of trays
Method of Installation
1
2
3
1
1.00
0.98
0.96
Perforated trays
2
0.97
0.93
0.89
3
0.96
0.92
0.86
(Note 1)
Spaced
Vertical perforated trays (Note 2)
1
1.00
0.91
0.89
Three cables in trefoil formation
2
1.00
0.90
0.86
Ladder supports, cleats, etc. (Note 1)
1
1.00
1.00
1.00
2
0.97
0.95
0.93
3
0.96
0.94
0.90
Note 1: Values are given for vertical spacings between trays of 300 mm. For closer spacing, the factors should be reduced. Note 2: Values are given for horizontal spacing between trays of 225 mm with trays mounted back to back. For closer spacing, the factors should be reduced. Note 3: For circuits having more than one cable in parallel per phase, each three phase set of conductors should be considered as a circuit for the purpose of this table.
51 MKK XXS002-02/01-12-2014
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