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the circuit. This removes the need to check
your earth loop impedance.
3.9
A double-pole isolating switch, with a
contact separation of at least 3mm in each
pole, must be incorporated in the circuit.
This must have a mechanical indicator
showing when the switch is in the OFF
position. A neon lamp alone is not sufficient.
3.9 for minimum switch rating.)
If it is fitted in the bathroom it must be of the
cord-operated type. It should be placed so
that it is:
(i)
Not possible to touch the switch body
when standing in the bath or shower
cubicle.
(ii)
Preferably outside the shower
enclosure.
(iii) Readily accessible (you should switch
off after using the shower).
3.10 Choosing cable and fuse sizes
Refer to
3.9 to determine the nominal
current of your shower.
The current rating of your cable must be at
least that of the shower itself. Then use
3.10 to choose a fuse or mcb with a
rating less than that of your chosen cable.
We advise against using rewirable fuses.
If the cable is to be:
(i)
bunched with others
(ii)
in an ambient of above 40°C
(iii) in an insulating wall or within thermal
insulation, e.g. loft insulation
(iv)
any other unusual situation
the current rating will be reduced.
IF IN DOUBT ALWAYS SEEK ADVICE
FROM A COMPETENT ELECTRICIAN.
Product
Nominal
Min Rating of
Max Cable Length (based on 9.6V drop)
Rating at
Current at 240V
Isolating
(metres)
240V(kW}
(amps)
Switch at 240V
(amps)
4mm
2
Cabie
6mm'Cable 10mm
2
Cabie
7.2
30
30
29
43
I
72
8
33.5
35
26
39
65
8.5
35.5
40
24
37
61
8.7
36
40
24
36
60
9
37.5
40
N/A
35
58
9.5
39.5
40
N/A
33
55
9.8
41
45
N/A
32
53
10.8
I
45
45
N/A
29
48
Figure 3.9
Rating of showers, switch and maximum cable runs.
Note: In certain installations the combination of low voltage and extended cable lengths may
result in lower flow rates.
PVC Twin and Earth Cable
4mm2
6mm'
10mm 2
Cable Installation Method
Current
Suitable:
Current
Suitable:
Current
Rating
Suitable:
Fuse MCB
Rating
Fuse MCB Rating
Fuse MCB
Direct in plaster or clipped to
vertical wall
In conduit or trunking, within or
on the surface of a brick wall
36
30
30,35
30
30,32
30
46
38
40,45
35
40,45
30,32
63
52
45
40, 45
45,50
40,45,
50
Figure 3.10
Cable rating, and suitable cartridge fuses/mcb's (rewirable fuses are not recommended
and are not covered by this table). NB Fuses with ratings above 45A are not generally available.
Values are in amps.
II
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