Current Ratings - Conversion Factors: for grouping on walls, on the floor, in insulation tubes or in conduit and under the ceiling

Number of Multi conductor cables or number of a.c. or 3-phase circuits of single conductors	1	2	3	4	5	6	7	8	9	10	12	14	16	18	20
Installation Methods	Conversion Factors
One layer under the ceiling with contact	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
One layer under the ceiling with a space equal to outer diameter (d)	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
One layer on the wall or floor with a space equal to outer diameter (d)	1.00	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
One layer on the wall or floor with contact	1.00	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
Bunched directly on the wall, on the floor, in insulating tubes or trunking or in the wall (see image below)	1.00	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

Notes:
These factors are to be applied for the calculation of power ratings, the same type of cables and with equal loaded conductors in the same installation method shall correspond.
At the same time the cross-section are permitted to differ maximum one grade of cross-section.

If the actual horizontal-space between the adjacent cables is more than double of the outer diameter, no reduction factor is necessary

The same reduction factors are to be applied for grouping of two or three-conductor or multi conductor cables. For a system consisting of two or as well as three-conductor cables, firstly the total number of cables will be assumed as the number of circuits. For that the applicable factor is to be used either in the tables for two-conductor loaded cables or the tables for three- conductors loaded cables.

If the grouping of single conductor cables consist of n loaded single conductor cables, the rating factor shall be determined for n/2 or n/3 circuits and applied to the current carrying capacity of two or three loaded conductors.