Furse Total Solution to Earthing & Lightning Protection

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Furse, Wilford Road, Nottingham, NG2 1EB • Tel: +44 (0)115 964 3700 • Email: • Web:
Conductors
Copper conductor ratings
For below ground earthing applications we produce a large range of bare copper, tape and stranded conductors thus
offering the designer of the system the correctly rated conductor without the need to oversize.
The following conductor ratings are based upon the recommendations of BS 7430 with an initial conductor
temperature of 30 °C and a maximum temperature of 250 °C.
Conductor
size
C.S.A.
(mm 2)
kA for
1 sec
kA for
3 sec
Conductor
size
C.S.A.
(mm2)
kA for
1 sec
kA for
3 sec
12.5 x 1.5 mm 18.75 3.3 1.9 31 x 6 mm 186 32.7 18.9
12.5 x 3 mm 37.5 6.6 3.8 38 x 3 mm 114 20.1 11.6
20 x 1.5 mm 30 5.3 3.0 38 x 5 mm 190 33.4 19.3
20 x 3 mm 60 10.6 6.1 38 x 6 mm 228 40.1 23.2
25 x 1.5 mm 37.5 6.6 3.8 40 x 3 mm 120 21.1 12.2
25 x 3 mm 75 13.2 7.6 40 x 4 mm 160 28.2 16.3
25 x 2 mm 50 8.8 5.1 40 x 5 mm 200 35.2 20.3
25 x 4 mm 100 17.6 10.2 40 x 6 mm 240 42.2 24.4
25 x 6 mm 150 26.4 15.2 40 x 6.3 mm 252 44.4 25.6
30 x 2 mm 60 10.6 6.1 50 x 3 mm 150 26.4 15.2
30 x 3 mm 90 15.8 9.1 50 x 4 mm 200 35.2 20.3
30 x 4 mm 120 21.1 12.2 50 x 5 mm 250 44.0 25.4
30 x 5 mm 150 26.4 15.2 50 x 6 mm 300 52.8 30.5
31 x 3 mm 93 16.4 9.5 50 x 6.3 mm 315 55.4 32.0
31.5 x 4 mm 126 22.2 12.8 50 x 7 mm 350 61.6 35.5
Conductors for earthing systems
Furse earthing conductors form an integral part of the single earthing arrangement for a structure, whether they
provide the means of connection to the final earth electrode (earth rod or plate), or whether they comprise the earth
electrode itself (through an earth grid or ring earth arrangement).
An earth conductor must be capable of carrying the maximum expected earth fault current and
leakage current likely to occur at a structure.
The size or minimum cross-sectional area of the conductor must
therefore be gauged in accordance with these criteria.
A good earth conductor must also:
be able to withstand mechanical damage
be compatible with the material of the earth electrode, and
resist the corrosive effect of local soil conditions
Furse conductors effectively meet these requirements
and are available in a range of sizes to meet differing
current ratings (see table below).
Copper conductor is recommended as, following
BS 7430, aluminium should not be installed in contact
with soil, nor in damp areas, and it should not be used
to make the final connection to an earth electrode.