Risk Management Guidelines
Residual Current Devices (RCDs)
The Purpose of RCD’s
Where to Use RCD’s
Residual Current Devices (RCD) or Earth
Leakage Circuit Breakers (ELCB) are
electro-mechanical devices designed to
switch off electric current in the event of an
electrical fault. They can detect very small
faults before they become dangerous and
are an excellent additional protection
against electric shock and from fires of an
electrical nature. RCD’s work by measuring,
indirectly, the leakage current from the live
conductors to earth. They are not designed
to detect overcurrent and are not
replacements
for
fuses
or
other
overcurrent-tripping devices.
General
Availability
Outdoor Equipment
RCD’s are available in many forms and
ratings. If the tripping current of an RCD is
30 milliamperes, (30 mA), (0.03 Amps) or
less then the RCD will give some protection
from fatal electric shock and protection from
fires generated from electrical faults. If set
at above 30 milliamperes they will still
provide a lesser degree of protection from
electric shock but will still give protection
from fires generated from electrical faults.
All electrical outlets likely to be used to
supply outdoor equipment must be RCD
protected in new and existing installations.
Any equipment likely to be used in damp
environments must be designed for the
purpose and be RCD protected in new and
existing installations. Examples are in
greenhouses,
garages,
supplies
for
lawnmowers etc.
RMG 38 v7 01/11
When considering electrical safety and fire
from electrical fault, all electrical circuits in
new installations should be RCD protected.
However, other aspects of safety have to
be considered, other than that of protection
against electrical issues.
All power circuits in new installations should
be RCD protected unless there is an
overriding consideration such as high
integrity supplies, freezer supplies, lighting
etc. (modern UK practice is not to use RCD
to protect lighting circuits).
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2011 Royal & Sun Alliance Insurance plc
Risk Management Guidelines
Special Cases
Every piece of electrical apparatus has a
small leakage to earth due to the laws of
nature. If too many loads are connected in
parallel then the combined earth leakage
current may be enough to trip an RCD even
though each of the loads individually has no
excessive earth leakage.
Special cases such as laboratory test
supplies, supplies in school laboratories
and work areas, must be RCD protected in
new and existing installations.
Agricultural & Horticultural Premises
For the purposes of protection against fire,
RCD’s with a rated residual operating
current not exceeding 0.5 Amps should be
installed for the supply of all equipment
other than that essential to the welfare of
livestock.
Testing
An RCD is essentially a mechanical device
and there is no way of knowing if it will work
if it develops a fault. For this reason an
RCD must be regularly tested using the test
button. A notice should be fixed in a
prominent position at or near the main
distribution board. The notice should be in
indelible characters not smaller than the
illustration in section 514-12-02 of the 17th
Edition of the IEE Wiring Regulations as
reproduced below:
All socket outlets should be protected by an
RCD with a rated residual operating current
not exceeding 0.03 Amps. In view of the
special nature of farms and horticultural
premises, this advice applies to both new
and existing premises.
Spurious Tripping
"This installation, or part of it, is protected
by a device which automatically switches
off the supply if an earth fault develops.
Test quarterly by pressing the button
marked “T” or “Test”. The device should
switch off the supply and should then be
switched on to restore the supply. If the
device does not switch off the supply when
the button is pressed, seek expert advice."
RCD’s have in some cases gained a
reputation for unreliability due to so called
spurious tripping. In most cases the tripping
is not spurious but due to an incipient fault
in the protected system or due to
inappropriate use of RCD’s. The most
common fault is to try to protect too many
circuits with one RCD to reduce costs. In an
ideal world all socket outlets would have
individual RCD protection, thus a fault on
any one protected load would not trip out
any other circuit.
RMG 38 v7 01/11
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2011 Royal & Sun Alliance Insurance plc
Risk Management Guidelines
These and other Risk Management Guidelines addressing a wide variety of risk control issues
are freely available from: www.rsabroker.com/risk-management
The information set out in this document constitutes a set of general guidelines and
should not be construed or relied upon as specialist advice. RSA does not guarantee
that all hazards and exposures relating to the subject matter of this document are
covered. Therefore RSA accepts no responsibility towards any person relying upon
these Risk Management Guidelines nor accepts any liability whatsoever for the accuracy
of data supplied by another party or the consequences of reliance upon it.
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