60364-5-52/FDIS © IEC – 59 –

Table B.52.20 – Reduction factors for group of more than one multi-core cable
to be applied to reference current-carrying capacities for multi-core cables in free air –
Method of installation E in Tables B.52.8 to B.52.13

Number Number of cables per tray or ladder

of trays
Method of installation in Table A.52.3
or 1 2 3 4 6 9
ladders
Touching

1 1,00 0,88 0,82 0,79 0,76 0,73

2 1,00 0,87 0,80 0,77 0,73 0,68
3 1,00 0,86 0,79 0,76 0,71 0,66
Perforated 6 1,00 0,84 0,77 0,73 0,68 0,64
cable tray
systems 31 ≥ 20
20 mm
mm ≥ 300
300 mm
(note 3)
Spaced
Dee 1 1,00 1,00 0,98 0,95 0,91 –
2 1,00 0,99 0,96 0,92 0,87 –
3 1,00 0,98 0,95 0,91 0,85 –
≥ 20
20 mm
mm

Touching

1 1,00 0,88 0,82 0,78 0,73 0,72

≥
225 mm 2 1,00 0,88 0,81 0,76 0,71 0,70
225
Vertical mm
perforated
cable tray 31
systems Spaced
(note 4)
1 1,00 0,91 0,89 0,88 0,87 –

≥ 2 1,00 0,91 0,88 0,87 0,85 –

225 mm
Dee
225
mm

Touching

1 0,97 0,84 0,78 0,75 0,71 0,68

Unperforated 31 2 0,97 0,83 0,76 0,72 0,68 0,63
cable tray
systems 3 0,97 0,82 0,75 0,71 0,66 0,61
6 0,97 0,81 0,73 0,69 0,63 0,58
≥ 20
20 mm
mm ≥ 300
300 mm

Touching

1 1,00 0,87 0,82 0,80 0,79 0,78

Cable ladder 32
systems, 2 1,00 0,86 0,80 0,78 0,76 0,73
cleats, etc. 33
3 1,00 0,85 0,79 0,76 0,73 0,70
(note 3) 34
6 1,00 0,84 0,77 0,73 0,68 0,64
≥ 20
20 mm
mm
≥300
300 mm
mm
 – 60 – 60364-5-52/FDIS © IEC

Table B.52.20 (continued)

Number Number of cables per tray or ladder

of trays
Method of installation in Table A.52.3
or 1 2 3 4 6 9
ladders
Spaced
Dee
D 1 1,00 1,00 1,00 1,00 1,00 –
2 1,00 0,99 0,98 0,97 0,96 –
3 1,00 0,98 0,97 0,96 0,93 –
≥ 20
20mm
mm

NOTE 1 Values given are averages for the cable types and range of conductor sizes considered in Tables A.52.8
to A.52.13. The spread of values is generally less than 5 %.

NOTE 2 Factors apply to single layer groups of cables as shown above and do not apply when cables are installed in
more than one layer touching each other. Values for such installations may be significantly lower and has to be
determined by an appropriate method.

NOTE 3 Values are given for vertical spacing between cable trays of 300 mm and at least 20 mm between cable
trays and wall. For closer spacing the factors should be reduced.

NOTE 4 Values are given for horizontal spacing between cable trays of 225 mm with cable trays mounted back to
back. For closer spacing the factors should be reduced.
60364-5-52/FDIS © IEC – 61 –

Table B.52.21 – Reduction factors for groups of one or more circuits of single-core
cables to be applied to reference current-carrying capacity for one circuit of single-core
cables in free air – Method of installation F in Tables B.52.8 to B.52.13

Number of three-phase Use as a

Number of circuits per tray or ladder multiplier to
Method of installation in Table A.52.3 trays or current-
ladders 1 2 3 carrying
capacity for
Touching

Perforated 1 0,98 0,91 0,87

cable tray Three cables in
systems 31 2 0,96 0,87 0,81 horizontal
≥300
300 mm
mm formation
(note 3) 3 0,95 0,85 0,78

20 mm
≥ 20 mm

Touching
Vertical
perforated Three cables in
1 0,96 0,86 –
cable tray 31 ≥ vertical
systems 225 mm 2 0,95 0,84 –
225 formation
(note 4) mm

Touching

Cable ladder
32 1 1,00 0,97 0,96
systems, Three cables in
33 2 0,98 0,93 0,89 horizontal
cleats, etc. ≥300 mm
300 mm formation
34 3 0,97 0,90 0,86
(note 3)

20mm
≥ 20 mm

2D
≥2Dee
D
Dee
Perforated 1 1,00 0,98 0,96
cable tray
systems 31 2 0,97 0,93 0,89
≥300
300 mm
mm
(note 3) 3 0,96 0,92 0,86

20mm
≥ 20 mm

Spaced
Vertical
perforated
≥ 2D
2Dee 1 1,00 0,91 0,89 Three cables in
cable tray 31 ≥
systems 225 mm 2 1,00 0,90 0,86 trefoil formation
225
(note 4) mm
Dee

≥ 2D
2De
e D
Dee
Cable ladder 32 1 1,00 1,00 1,00
systems,
cleats, etc. 33 2 0,97 0,95 0,93
≥300
300 mm
mm
(note 3) 34 3 0,96 0,94 0,90

20mm
≥ 20 mm
 – 62 – 60364-5-52/FDIS © IEC

Table B.52.21 (continued)

NOTE 1 Values given are averages for the cable types and range of conductor sizes considered in Table B.52.8 to
B.52.13. The spread of values is generally less than 5 %.

NOTE 2 Factors are given for single layers of cables (or trefoil groups) as shown in the table and do not apply when
cables are installed in more than one layer touching each other. Values for such installations may be significantly
lower and should be determined by an appropriate method.

NOTE 3 Values are given for vertical spacing between cable trays of 300 mm and at least 20 mm between cable trays
and wall. For closer spacing the factors should be reduced.

NOTE 4 Values are given for horizontal spacing between cable trays of 225 mm with cable trays mounted back to
back. For closer spacing the factors should be reduced.

NOTE 5 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.

NOTE 6 If a circuit consists of m parallel conductors per phase, then for determining the reduction factor this circuit
should be considered as m circuits.