TW10i
5
ELECTRICAL REQUIREMENTS
5.1 When installed in a bathroom, exposed
metallic parts must be bonded together using a
cable of at least 4mm
2
cross sectional area. These
parts include metal baths, radiators, water pipes,
taps and waste fittings.
6 For close circuit protection DO NOT use a
rewireable fuse. Instead use a suitably rated
miniature circuit breaker (MCB) or cartridge fuse
(see table A).
6.1 In the interest of electrical safety a 30mA
residual current device (RCD) should be installed
in the circuit. This may be part of the consumer
unit or a separate unit.
7 A 45 amp double pole isolating switch with
a minimum contact gap of 3mm in both poles
must be incorporated in the circuit.
7.1 It must have a mechanical indicator
showing when the switch is in the OFF position,
and the wiring must be connected to the switch
without the use of a plug or socket outlet.
7.2 If the heater is installed in a bathroom then
the switch must be accessible and clearly
identifiable, but out of reach of a person using
the heater, except for the cord of a cord operated
switch.
8 If located in any room other than a
bathroom, all socket outlets in the room must be
protected by a 30mA RCD.
9 The current carrying capacity of the cable
must be at least that of the heater circuit
protection (see table B).
9.1 To obtain full advantage of the power
provided by the heater, use the shortest cable
route possible from the consumer unit to the
heater.
9.2 It is also necessary to satisfy the
disconnection time and thermal constraints which
mean that for any given combination of current
demand, voltage drop and cable size, there is a
maximum permissible circuit length.
10 The heater circuit should be separated from
other circuits by at least twice the diameter of the
cable or conduit.
10.1 The current rating will be reduced if the
cabling is bunched with others, surrounded by
thermal loft or wall insulation or placed in areas
where the ambient temperature is above 30°C.
Under these conditions, de-rating factors apply
and it is necessary to select a larger cable size.
10.2 In the majority of installations, the cable
will unavoidably be placed in one or more of
the above conditions. This being so, it is
strongly recommended to use a minimum of
10mm cabling throughout the heater
installation.
10.3
In any event, it is essential that individual
site conditions are assessed by a competent
electrician in order to determine correct cable size
and permissible circuit length.
Twin and earth PVC insulated cable
CURRENT CARRYING CAPACITY
clipped direct or
installed in an in conduit buried in a non
insulated wall or trunking insulated wall
6mm
2
6mm
2
6mm
2
32A 38A 46A
10mm
2
10mm
2
10mm
2
43A 52A 63A
16mm
2
16mm
2
16mm
2
57A 69A 85A
Note: Cable selection is dependent
on de-rating factors
Table B
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