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POCKET GUIDE 28
Application of residual current
devices (RCDs)
This Guide gives information on typical applications of RCDs, according to
their rated residual operating current (I⌬n). See NICEIC and ELECSA Pocket
Guide 29 for information on the classification of RCDs according to whether
or not they incorporate a time delay and according to their ability to give
protection where current includes a d.c. component. See NICEIC and
ELECSA Pocket Guide 25 for information on the operating times of RCDs.
The ‘preferred’ values of I⌬n given in product standards for RCDs used in
electrical installations are 10 mA, 30 mA, 100 mA, 300 mA and 500 mA. For
most of these values of I⌬n, Table 1 summarises some typical applications
for RCDs, and the main requirements of BS 7671.
Table 1 – Application and use of RCDs
I⌬n
30 mA (Note 2)
Typical application(Note 1)
Socket-outlets rated at up to 20 A (Notes 4
and mobile equipment up to 32 A for
use outdoors
Cables concealed in walls and partitions
in certain circumstances (Note 6)
Lighting in places such as telephone
kiosks, bus shelters, advertising panels
and town plans
All low voltage circuits (e.g. 230 V) of a
location containing a bath or shower
either serving the location or passing
through zones 1 and/or 2 but not serving
the location
All low voltage circuits of a sauna
location, except sauna heater unless
recommended by manufacturer
Final circuits supplying socket-outlets
rated at up to 32 A in agricultural and
horticultural premises
Caravan pitch socket-outlets. Each
socket-outlet to be individually protected
by an RCD(Note 7)
Circuits supplying floor and ceiling
heating systems
BS 7671
Regulation
Additional protection
& 5)
411.3.3
522.6.202
522.6.203
714.411.3.3
701.411.3.3
703.411.3.3
705.411.1
708.533.1.13
753.415.1
Continued overleaf
Amd 3: 2015
Based on information as at January 2015
© Certsure LLP Pocket Guide 28 rev 1 01/15
PG28 17.3:pocketguide 8 new 24/03/2015 14:04 Page 2
POCKET GUIDE 28
Application of residual current devices (RCDs)
Table 1 – Application and use of RCDs (continued)
I⌬n
Typical application(Note 1)
BS 7671
Regulation
Certain circuits of a location containing a
swimming or paddling pool
Socket-outlets for boats, and circuits to
supply houseboats, at marinas and
similar. Each to be individually protected
by an RCD(Note 7)
The installation of a caravan or motor
caravan(Note 7)
Charging points for electric vehicles (Note 7)
Circuits supplying floor and ceiling
heating systems
See regulations Installations generally (if a sufficiently low
listed opposite earth fault loop impedance (Zs) for
(Note 3)
overcurrent device cannot be achieved)
Fault
protection
30 mA (Note 2)
702.410.3.4.1
702.410.3.4.2
709.531.2
721.411.1
722.531.2.101
753.411.3.2
411.4.5
(TN system),
411.5.3
Fault
protection
Protection
against fire
(TT system)
Not exceeding Final circuits supplying socket-outlets
rated at more than 32 A in agricultural
100 mA
705.411.1
and horticultural premises
Not exceeding Wiring systems except mineral insulated
300 mA (Note 8) cable, busbar trunking and Powertrack, in
locations with risk of fire due to
422.3.9
processed or stored materials.
Agricultural and horticultural premises
(Note 7)
705.422.7
Circuits in agricultural and horticultural
premises, except socket-outlet circuits
705.411.1
(covered earlier)
Not exceeding Final circuits supplying socket-outlets
500 mA
rated at more than 32 A on construction
and demolition sites, where the protective
measure is automatic disconnection of
704.411.3.2.1
supply
Notes.
1 The applications in Table 1 are not exhaustive. For example, RCDs required by Part 7 of
BS 7671 in Sections 710 (Medical locations), 711 (Exhibitions, shows and stands),
717 (Mobile or transportable units) and 740 (Temporary installations for fairgrounds etc)
are not included.
2 RCD must be of general (non-delay) type.
3 Except for a special installation or location for which Part 7 of BS 7671 gives a different
requirement.
4 Where, other than for an installation in a dwelling, a documented risk assessment
determines that the RCD protection is not necessary.
5 Except a labelled or otherwise identified socket-outlet for a particular item of equipment.
6 Cables without earthed metallic covering or earthed metallic enclosure or forming part of a
SELV or PELV circuit, at a depth of less than 50 mm from surface of wall or partition, or
irrespective of depth if the wall or partition has internal metal parts (except screws or
nails etc).
7 RCD must disconnect all live (line and neutral) conductors.
8 I⌬n must be not more than 30 mA where a resistive fault may cause a fire
(see Regulation 422.3.9 for details).
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© Certsure LLP Pocket Guide 28 rev 1 01/15