Cc the 0. the calculated value greater than this value, the next larger
cable size must tested until cable found which meets both the cur-
rent rating and voltage drop criteria. They
are also shown Table 14.
Cg the grouping correction factor given Tables 4C1 4C5 the IEE
Regulations and Table the Site Guide.5m must apply factor 0.0 0.
Note: cable should preferably not installed thermal insulations.6 gives three possible correction values:
● Where one side the cable contact with thermal insulation
we must read the current rating from the column the table which
relates reference method (see Table 14.5.1 Ambient Temperature Correction Factors.
● Where the cable totally surrounded over short length, the appro-
priate factor given Table 52. This cable must
also meet the voltage drop Regulation 525 and this should calculated
as described earlier.71 0.61 0.725 correction factor applied when semi-enclosed fuses pro-
tect the circuit described item 5.87 0.
Table 14.
Ci the correction factor used when cables are enclosed thermal
insulation. Regulation 523.6.2 the IEE Regulations Table of
the Site Guide should applied.1 the preface Appendix of
the IEE Regulations. The cor-
rection factors which may need applying are given below as:
Ca the ambient surrounding temperature correction factor, which is
given Tables 4B1 and 4B2 Appendix the IEE Regulations.1.2).79 0.1.03 1.
Having calculated the cable rating, the smallest cable should chosen
from the appropriate table which will carry that current.
● Where the cable totally surrounded over length greater than
0. Adapted from the IEE Site Guide Kind
Permission the Institution Electrical Engineers
Table 4B1 IEE Regulations
Correction factors for ambient temperature where protection against short-circuit and overload
Type of
insulation
Operating
temperature
Ambient temperature (°C)
25 65
Thermoplastic
(general
purpose PVC)
70°C 1.1.94 0.50 NA
.Electrical installations and wiring systems
299
The cable rating must chosen comply with Regulation 433. When the calculated value less than for lighting
and for other uses the mains voltage the cable may considered
suitable
