26 / 164
26
WIRING ACCESSORIES AND SINGLE PHASE DISTRIBUTION
PG00400018U – March 2012
17th Edition regulations and consumer units
The advent of the 17th Edition of the Wiring regulations
brought with it new challenges for installers and manufacturers
alike, one such challenge involves the much greater use of
RCDs within the electrical installation. The regulations BS
7671:2008 now incorporate amendment No.1 2011.
Regulation 411.3.3.
States that additional protection by means of a 30mA RCD is
to be provided for all socket outlets with a rated current not
exceeding 20A for use by ordinary persons. The only exceptions
allowed are for socket outlets for use under the supervision
of “skilled” or “instructed persons” e.g. some commercial /
industrial locations, or a specific labelled socket provided for
connection of a particular item of equipment, e.g. a freezer circuit.
Regulation 701.411.3.3
In specific locations such as those containing a bath or shower
there is a requirement now to provide RCD protection on
all circuits, including the lighting and shower circuits.
Regulation 314.1 & 2
Requires that every installation shall be divided into circuits
as necessary to avoid danger and minimise inconvenience, in
the event of a fault. Also reducing the possibility of unwanted
RCD tripping, due to excessive protective conductor currents
but not due to an Earth fault. Separate circuits may be required
for parts of the installation, which need to be separately
controlled in such a way that they are not affected by the
failure of other circuits. The appropriate subdivision should
take account of any danger arising from the failure of a single
circuit eg. an RCD trip on a socket outlet causing the unwanted
failure of a lighting circuit and its associated hazards.
Regulation 522.6.102
Now requires a much greater use of RCDs to protect the
wiring concealed in walls or partitions even where installed in
previously defined “Safe Zones”. These regulations effectively
mean that all concealed wiring at a depth of less than 50mm
from the surface now requires protection by a 30mA RCD
unless provided with earthed mechanical protection.
Application of RCDs
The 17th Edition of the IEE wiring regulations ( BS7671 ),
detail a number of regulations relating to protection against
electric shock, including the need for additional protection.
The use of RCDs (Residual Current Devices) with a residual
operating current not exceeding 30mA is the recognised
means of providing this additional protection in the event
of failure of the provision for basic protection and or the
provision for fault protection or carelessness by users.
Such RCDs should not be used to provide the sole means of
protection and do not obviate the need to apply one or more of
the recognised protective measure as detailed in the regulations.
Under the new regulations an installation is required
to incorporate one or more RCDs, depending upon
the circumstances. Such instances include:-
• All socket outlets not exceeding 20A, but with certain
exceptions. One such exception would be permitted for a
specific labelled or otherwise suitably identified socket outlet
for connection of a particular piece of equipment.
• Mobile equipment with a current rating not exceeding 32A
for use outdoors
• Electrical circuits installed under “Special installations and
locations” as defined in Part 7 of the regulations e.g.
Swimming Pools / Saunas.
• All electrical circuits, including shower and lighting circuits
etc. in rooms with a fixed bath or shower e.g. bedrooms
and en-suite bathrooms.
In addition to the protection requirements of the
outgoing circuits / loads, the requirements of the
installed cabling also must be taken into account.
Where a cable is concealed in a wall or partition at a depth
of less than 50mm from the surface, even if installed in
the “safe zone”, if not provided with earthed mechanical
protection e.g. Metal trunking or conduit, it must be provided
with additional protection by means of a 30mA RCD.
Whilst it may be desirable to have one or two circuits fed via
an unprotected circuit e.g. an identified / dedicated freezer
circuit, the installation of the wiring may still dictate that the
circuit must be RCD protected. The protection of a circuit
by means of a 30mA RCD is also required where cables are
concealed in walls constructed with metal stud partitions
which are common in modern buildings, irrespective of the
depth from the surface, unless provided with protection
in the form of earthed metallic covering, trunking, conduit
or other mechanical protection so as to avoid damage to
the cable during installation or construction of the wall.
IEE Regulations and British Standards are subject to
amendments. This Eaton guide to consumer unit solutions is
not a substitute for the regulations which should always be
used for all types of electrical installations and design work.
Product overview
Memera consumer units and devices
1.4