7
These conductor ratings are based upon the recommendations 7430 with initial
conductor temperature 30°C and maximum temperature 250°C.5 37.5 5.1 23.6 35.5 126 22.4 9.9
38 114 20.1
25 100 17.3
38 228 40.2 12.4 15.1 12.2
31 16.2
40 120 21.7 18.6
38 190 33.2
50 200 35.3
40 200 35.8
31 186 32.
(mm2
)
kA for
1 Sec
kA for
3 Sec
20 1.6 6.1 11.6 10.
Copper conductor recommended following
BS 7430, aluminium should not installed in
contact with soil, nor damp areas, and should
not used make the final connection to
an earth electrode.
Conductors for earthing systems
For below ground earthing applications offer
a large range bare copper tape, solid circular
and stranded conductors thus offering the
designer the system the correctly rated
conductor without the need oversize.2
30 15.
The size minimum cross-sectional area of
the conductor must therefore gauged in
accordance with these criteria.8 30.8 5.4
50 300 52.5
50 350 61.1
30 120 21.
19
—
Earth conductors
.8 9.2 24.
A good earth conductor must also:
• able withstand mechanical damage
• compatible with the material the
earth electrode
• Resist the corrosive effect local soil
conditions
Furse conductors effectively meet these
requirements and are available range sizes
to meet differing current ratings (see table left).5 6.2
40 160 28.2 7.
These conductors provide either the connection
to final earth electrode (earth rod plate), or
the earth electrode itself (earth grid ring
earth arrangement).0
20 10.2
25 150 26.CONDUCTORS
Conductor Size
(mm)
C.2 20.4 19.
An earth conductor must capable carrying
the maximum expected earth fault current and
leakage current likely occur structure.3
40 240 42.2 45.8
25 13.0 25.3
50 250 44.3 3.4
50 150 26.2 20.6 3.S.1
25 1.5
50 400 70.1 12.2 16.2
30 150 26.6
25 8.4 15.A.4 40.6
75 450 79.5
31.4 15
