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PLS – Miniature
Circuit Breakers
PKS – RCBOs
PFIM – RCDs
Moeller Consumer Units and the
17
th
Edition Wiring Regulations
2
3
The introduction of the 17
th
Edition of the IEE Wiring
Regulations on the 1
st
January 2008 has major
implications for all electrical contractors, designers
and consultants. From 1
st
July 2008 all new electrical
installations will have to be designed to comply with
the new regulations.
The biggest area of concern at present is the effect
on an individual’s home being wired or re-wired. The
examples used in this brochure will help the electrical
engineer to select the correct assembly. We use the term
assembly as there are no specific consumer units that
meet the 17
th
Edition – it is how the building is wired
that dictates the components required, which in turn are
assembled into a consumer unit.
Practically speaking, there are five aspects that
the 17
th
Edition identifies as requiring consideration
for installations that are not under the supervision of
skilled people (e.g. qualified electricians) or instructed
people (e.g. facilities managers) – i.e. most domestic
installations, but also some commercial installations.
These are:
●
Socket outlets for general use in domestic installations
must have the additional protection of an RCD not
exceeding 30mA (regulation 411.3.3)
●
All circuits in locations containing a bath or shower
must be protected by an RCD not exceeding 30mA
(regulation 701.411.3.3)
●
Cables buried in a wall or partition at a depth of
less than 50mm, and not mechanically protected by
appropriate earthed metal, must be protected by an
RCD not exceeding 30mA (regulations 522.6.6–8)
●
To prevent nuisance tripping, unnecessary hazards,
and minimise inconvenience, circuits should not be
connected to a single upstream RCD (regulation
314.1)
●
Separate circuits shall not be affected by the failure of
other circuits (regulation 314.2)
When designing the installation and selecting the correct
assembly, the electrician will need to consider the above
five aspects, in accordance with the regulations. It is not
solely the function of a particular consumer unit that has
one, two or three RCDs with an incomer isolator to solve
the problem of meeting the 17
th
Edition regulations.
The following pages will provide a practical guide to
help you to select the components for an assembly to
ensure that the installation complies with the 17
th
Edition
regulations.
Everything starts from the wiring scheme
When designing an installation in a new build project,
there are various options to consider, in order to satisfy
the requirements of the 17
th
Edition. For example,
consider burying the cables more than 50mm into the
walls, or protect the cable with earthed metal, to remove
the need for RCD protection.
Once the wiring scheme has been finalised, the
process of selecting how best to protect the circuits and
the people can begin.
The regulations are open to interpretation,
particularly regarding the division of installations, where
acceptable levels of inconvenience resulting from a fault
can be somewhat subjective. (See page 11 for regulations
314.1 and 314.2.)
To this end, the following pages outline various
consumer unit configurations that, dependent on the
installation design, will offer a Fully Compliant Assembly
(
FCA
) or Partially Compliant Assembly (
PCA
),
or illustrate possible pitfalls making an installation
potentially dangerous and so a Non-Compliant Assembly
(
NCA
).
Note that the above terms indicate Moeller’s
assessment of how a particular installation may comply
with the regulations: a Partially Compliant Assembly
has been judged by Moeller to satisfy all aspects where
an RCD has to be used for safety reasons but does not
comply with all parts of regulation 314; a Non-Compliant
Assembly is judged to satisfy neither safety aspects nor
regulation 314.
Customers are looking for a competitive offering,
balanced with potential safety aspects and avoiding the
hazards and nuisance that a short circuit trip, overload
condition or earth leakage may cause.
For example, a consumer unit with an isolator and
double RCD (see page 3 Example A) is often promoted
as a way of meeting the 17
th
Edition regulations on the
basis that every circuit is protected by an RCD, and the
circuits split evenly between two RCDs. However, in the
event of a fault on either set of MCBs, the RCD may
trip as well. This creates an unwanted disconnection
of the MCBs where no fault exists (contrary to section
314.1) and also causes unwanted disconnection of other
circuits (contrary to section 314.2). Many manufacturers
are promoting the dual RCD board as a fully compliant
solution; however compliance is dependent on the
design of the installation and at best this will only be a
Partially Compliant Assembly.
You can find examples of Fully Compliant Assemblies
on pages 5 and 6.
Introduction
2
3
Dual RCD split load board
A dual RCD split load board will meet the 17
th
Edition
requirements for the following:
●
Socket outlets for general use in domestic installations
must have the additional protection of an RCD not
exceeding 30mA.
●
All circuits in locations containing a bath or shower
must be protected by an RCD not exceeding 30mA.
●
Cables buried in a wall or partition at a depth of
less than 50mm, and not mechanically protected by
appropriate earthed metal, must be protected by an
RCD not exceeding 30mA.
However, depending on the installation design, it is
unlikely to satisfy the regulations on:
●
To prevent nuisance tripping, unnecessary hazards,
and minimise inconvenience, circuits should not be
connected to a single upstream RCD.
●
Separate circuits shall not be affected by the failure of
other circuits.
6A
MCB
6A
MCB
6A
MCB
32A
MCB
6A
MCB
32A
MCB
32A
MCB
40A
MCB
RCD
RCD
MAIN
ISOLATOR
smoke alarms
upstairs lights
outside lights
shower
downstairs and
bathr
oom lights
upstairs sockets
downstairs sockets
cooker
Example A
NCA
Example A
Dual RCD split load board
In the event of a fault on either set of MCBs, the RCD
may trip as well. This creates an unwanted disconnection
of the MCBs where no fault exists (contrary to section
314.1) and also causes unwanted disconnection of other
circuits (contrary to section 314.2).
Prior to the 17
th
Edition, lights have not been part of
the RCD circuit as they tend to trip the RCD whenever
an incandescent bulb fails, for example, causing
unacceptable nuisance. Having the lights in the same
circuit may cause nuisance disconnection to any other
circuit supplied on the RCD.
In addition there is a smoke alarm and a light circuit
on the same RCD, so every time the light circuit trips
(when a bulb fails) the house and the alarm circuit could
be disabled, putting the occupants at risk of a fire not
being detected.
The safety implications of this configuration by not
addressing the requirements of section 314 make this a
Non-Compliant Assembly.
4
5
Split load board with independent RCBOs
A split load board with independent RCBOs will meet the
17
th
Edition requirements for the following:
●
Socket outlets for general use in domestic installations
must have the additional protection of an RCD not
exceeding 30mA.
●
All circuits in locations containing a bath or shower
must be protected by an RCD not exceeding 30mA.
●
Cables buried in a wall or partition at a depth of
less than 50mm, and not mechanically protected by
appropriate earthed metal, must be protected by an
RCD not exceeding 30mA.
However, depending on the installation design, whilst
this layout takes into account the danger arising from the
failure of a single circuit (such as lighting) it does not fully
comply with:
●
To prevent nuisance tripping, unnecessary hazards,
and minimise inconvenience, circuits should not be
connected to a single upstream RCD.
●
Separate circuits shall not be affected by the failure of
other circuits.
Example B
32A
MCB
32A
MCB
32A
MCB
40A
MCB
6A
RCBO
6A
RCBO
6A
RCBO
6A
RCBO
RCD
MAIN
ISOLATOR
shower upstairs sockets
downstairs sockets
cooker
outside lights
upstairs lights
downstairs and
bathr
oom lights
smoke alarms
PCA
Example B
Split load board with independent RCBOs
It may be advisable to have a socket circuit on a
separate circuit. In larger residential properties it would
be advisable to separate the downstairs circuit or the
kitchen circuit from the other circuits supplied by a sole
RCD to ensure that in the event of a fault there would be
at least one power circuit available.
Prior to the 17
th
Edition, it was common to have all
socket power circuits supplied from one RCD with no
account of the implications for safety or significant
inconvenience being apparent. However, the increasing
number of electronic devices now found in a home
results in a greater amount of earth leakage current
that may lead to a tripping of the RCD and fall foul of
531.2.4.
Note Also depending on the wiring scheme the smoke
detector may not need to be an RCBO.
4
5
Example C
Main switch with RCBOs on all circuits
A standard main switch disconnector controlled
consumer unit with RCBOs for every outgoing circuit
instead of the usual MCBs, will fully comply with the
17
th
Edition regulations. A fault on any circuit will
not impact on other circuits, and so all aspects of the
regulations are satisfied.
●
Socket outlets for general use in domestic installations
must have the additional protection of an RCD not
exceeding 30mA.
●
All circuits in locations containing a bath or shower
must be protected by an RCD not exceeding 30mA.
●
Cables buried in a wall or partition at a depth of
less than 50mm, and not mechanically protected by
appropriate earthed metal, must be protected by an
RCD not exceeding 30mA.
●
To prevent nuisance tripping, unnecessary hazards,
and minimise inconvenience, circuits should not be
connected to a single upstream RCD.
●
Separate circuits shall not be affected by the failure of
other circuits.
6A
RCBO
6A
RCBO
6A
RCBO
6A
RCBO
MAIN
ISOLATOR
shower
upstairs sockets
downstairs sockets
cooker
immersion heater
upstairs lights
downstairs and
bathr
oom lights
smoke alarms
16A
RCBO
32A
RCBO
32A
RCBO
40A
RCBO
40A
RCBO
burglar alarm
FCA
Example C
Main switch with RCBOs on all circuits
6
7
Example D
Main switch with RCBOs on critical circuits
By looking closely at the wiring scheme in an installation,
the assembly in Example C can be made more cost
effective by using MCBs to protect some circuits rather
than RCBOs, without compromising compliance with the
17
th
Edition.
For example, at the point of cable entry to the
consumer unit, incoming and outgoing cable runs are
all encased in suitable ‘metal trunking’ or buried deeper
than 50mm, so do not require RCD protection. As none
of the cables are in the walls, the smoke alarms similarly
do not require RCD protection.
The burglar alarm system may have its own trunking
or metal covering for the supply to the main control
6A
MCB
6A
MCB
6A
RCBO
6A
RCBO
MAIN
ISOLATOR
shower
upstairs sockets
downstairs sockets
cooker
immersion heater
upstairs lights
downstairs and
bathr
oom lights
smoke alarms
16A
MCB
32A
RCBO
32A
RCBO
40A
RCBO
40A
MCB
burglar alarm
FCA
Example D
Main switch with RCBOs on critical circuits
console. If it does, and all the other devices are low
voltage or cable runs in the ceiling, then this too could be
MCB protected. This will depend on the wiring scheme
employed for this ancillary piece of equipment.
You could also decide that the immersion heater cable
and cooker point (without socket) are in areas where
they can be surface mounted and shrouded inside a short
length of conduit, or buried deeper than 50mm in the
wall.
This example illustrates that by analysing the wiring
scheme, RCBOs can be replaced with MCBs, reducing the
costs whilst still providing a Fully Compliant Assembly
(FCA).
6
7
Example E
By reviewing the wiring scheme employed with the split
load assembly proposed in Example B, the cost of the
finished assembly can be reduced, and partial compliance
with the regulations achieved.
The split load board laid out here will meet the
17
th
Edition requirements for the following:
●
Socket outlets for general use in domestic installations
must have the additional protection of an RCD not
exceeding 30mA.
●
All circuits in locations containing a bath or shower
must be protected by an RCD not exceeding 30mA.
●
Cables buried in a wall or partition at a depth of
less than 50mm, and not mechanically protected by
appropriate earthed metal, must be protected by an
RCD not exceeding 30mA.
However, depending on the installation design, it is
unlikely to satisfy the regulations on:
●
To prevent nuisance tripping, unnecessary hazards,
and minimise inconvenience, circuits should not be
connected to a single upstream RCD.
●
Separate circuits shall not be affected by the failure of
other circuits.
32A
MCB
32A
MCB
40A
MCB
RCD
MAIN
ISOLATOR
shower upstairs sockets
downstairs sockets
cooker
immersion heater
upstairs lights
downstairs and
bathr
oom lights
smoke alarms
6A
RCBO
6A
RCBO
6A
MCB
6A
MCB
16A
MCB
burglar alarm
40A
MCB
PCA
Example E
Split load board with RCBOs on critical circuits
With this example there is still the risk of one circuit
failure impacting on another (regulation 314.2); however
the level of inconvenience could be considered to be
acceptable (only the sockets and showers are affected),
and no hazard or safety issues are inherent. Again, the
installer will need to consider the amount of leakage in
the installation, due to electronic devices in the house,
and it may be a consideration to split the power sockets
and have one of them on an RCBO.
The end result is that no base consumer unit exists
that complies with the 17
th
Edition. The choice of
consumer unit and the configuration of devices within
it can only be made after the wiring scheme has been
finalised.
Split load board with RCBOs on critical circuits
8
9
2-Pole · 100A Main Switch Controlled
Outgoing Ways
Dimensions (mm)
Width Height Depth
Part Number
2
172
225
111
BC-P2
6
244
225
111
BC-P6
10
316
225
111
BC-P10
12
351
225
111
BC-P12
18
457
225
111
BC-P18
2-Pole · RCD Controlled
Type
Outgoing Ways
RCD Rated Current I
n
(A)
Dimensions (mm)
Width Height Depth
Part Number
30mA RCD-controlled
2
40
172
225
111
BC-P2R40
2
63
172
225
111
BC-P2R63
6
63
244
225
111
BC-P6R63
6
80
244
225
111
BC-P6R80
6
100
244
225
111
BC-P6R100
10
63
316
225
111
BC-P10R63
10
80
316
225
111
BC-P10R80
10
100
316
225
111
BC-P10R100
12
63
351
225
111
BC-P12R63
12
80
351
225
111
BC-P12R80
12
100
351
225
111
BC-P12R100
18
80
457
225
111
BC-P18R80
18
100
457
225
111
BC-P18R100
100mA time-delayed
RCD (Type G)
12
100
351
225
111
BC-P12R100G
18
100
457
225
111
BC-P18R100G
Split Load · 2-Pole · 100A Main Switch / 30mA RCD Controlled
Outgoing Ways
RCD Ways Available* RCD Rated Current I
n
(A)
Dimensions (mm)
Width Height Depth
Part Number
8
1–7
63
316
225
111
BC-P8SR63
8
1–7
80
316
225
111
BC-P8SR80
10
1–9
63
351
225
111
BC-P10SR63
10
1–9
80
351
225
111
BC-P10SR80
16
1–15
80
457
225
111
BC-P16SR80
Note
* number of freely configurable RCD protected ways.
Dual RCD · Split Load · 100A Main Switch / 30mA RCD Controlled
Outgoing Ways
RCD Ways Available* RCD Rated Current I
n
(A)
Dimensions (mm)
Width Height Depth
Part Number
14
1–14
63 + 63
457
225
111
BC-P14SR63R63
14
1–14
80 + 63
457
225
111
BC-P14SR80R63
14
1–14
80 + 80
457
225
111
BC-P14SR80R80
Note
* number of freely configurable RCD protected ways.
Toggle Colours
2 A
4 A
6 A
10 A 13 A
16 A
20 A 25 A 32 A
40 A
50 A 63 A
XBoard Consumer Units
Insulated
8
9
2-Pole · 100A Main Switch Controlled
Outgoing Ways
Dimensions (mm)
Width Height Depth
Part Number
2
180
223
113
BC-M2
6
252
223
113
BC-M6
10
324
223
113
BC-M10
12
359
223
113
BC-M12
18
465
223
113
BC-M18
2-Pole · RCD Controlled
Type
Outgoing Ways
RCD Rated Current I
n
(A)
Dimensions (mm)
Width Height Depth
Part Number
30mA RCD-controlled
2
40
180
223
113
BC-M2R40
2
63
180
223
113
BC-M2R63
6
63
252
223
113
BC-M6R63
6
80
252
223
113
BC-M6R80
6
100
252
223
113
BC-M6R100
10
63
324
223
113
BC-M10R63
10
80
324
223
113
BC-M10R80
10
100
324
223
113
BC-M10R100
12
63
359
223
113
BC-M12R63
12
80
359
223
113
BC-M12R80
12
100
359
223
113
BC-M12R100
18
80
465
223
113
BC-M18R80
18
100
465
223
113
BC-M18R100
100mA time-delayed
RCD (Type G)
12
100
359
223
113
BC-M12R100G
18
100
465
223
113
BC-M18R100G
Split Load · 2-Pole · 100A Main Switch / 30mA RCD Controlled
Outgoing Ways
RCD Ways Available* RCD Rated Current I
n
(A)
Dimensions (mm)
Width Height Depth
Part Number
8
1–7
63
324
223
113
BC-M8SR63
8
1–7
80
324
223
113
BC-M8SR80
10
1–9
63
359
223
113
BC-M10SR63
10
1–9
80
359
223
113
BC-M10SR80
16
1–15
80
465
223
113
BC-M16SR80
Note
* number of freely configurable RCD protected ways.
Dual RCD · Split Load · 100A Main Switch / 30mA RCD Controlled
Outgoing Ways
RCD Ways Available* RCD Rated Current I
n
(A)
Dimensions (mm)
Width Height Depth
Part Number
14
1–14
63 + 63
465
223
113
BC-M14SR63R63
14
1–14
80 + 63
465
223
113
BC-M14SR80R63
14
1–14
80 + 80
465
223
113
BC-M14SR80R80
Note
* number of freely configurable RCD protected ways.
Toggle Colours
2 A
4 A
6 A
10 A 13 A
16 A
20 A 25 A 32 A
40 A
50 A 63 A
XBoard Consumer Units
Metal
10
11
Miniature Circuit Breakers
· single-pole · 6kA
Rated Current I
n
(A)
B Curve
C Curve
2
PLS6-B2
PLS6-C2
6
PLS6-B6
PLS6-C6
10
PLS6-B10
PLS6-C10
13
PLS6-B13
PLS6-C13
16
PLS6-B16
PLS6-C16
20
PLS6-B20
PLS6-C20
25
PLS6-B25
PLS6-C25
32
PLS6-B32
PLS6-C32
40
PLS6-B40
PLS6-C40
50
PLS6-B50
PLS6-C50
63
PLS6-B63
PLS6-C63
Combined RCD/MCB (RCBO)
· single-pole + Neutral · conditionally surge current proof 250A · B & C curve · type AC
Rated Current I
n
(A)
Type / Tripping Current
B Curve · 30mA
B Curve · 100mA
C Curve · 30mA
C Curve · 100mA
6
PKS6-6/1N/B/003
PKS6-6/1N/B/01
PKS6-6/1N/C/003
PKS6-6/1N/C/01
10
PKS6-10/1N/B/003
PKS6-10/1N/B/01
PKS6-10/1N/C/003
PKS6-10/1N/C/01
13
PKS6-13/1N/B/003
PKS6-13/1N/B/01
PKS6-13/1N/C/003
PKS6-13/1N/C/01
16
PKS6-16/1N/B/003
PKS6-16/1N/B/01
PKS6-16/1N/C/003
PKS6-16/1N/C/01
20
PKS6-20/1N/B/003
PKS6-20/1N/B/01
PKS6-20/1N/C/003
PKS6-20/1N/C/01
25
PKS6-25/1N/B/003
PKS6-25/1N/B/01
PKS6-25/1N/C/003
PKS6-25/1N/C/01
32
PKS6-32/1N/B/003
PKS6-32/1N/B/01
PKS6-32/1N/C/003
PKS6-32/1N/C/01
40
PKS6-40/1N/B/003
PKS6-40/1N/B/01
PKS6-40/1N/C/003
PKS6-40/1N/C/01
Main Incoming Switch · 2-Pole · 10kA
Rated Current I
n
(A)
Part Number
63
IS-63/2
80
IS-80/2
100
IS-100/2
125
IS-125/2
Outgoing Devices
Incoming Devices
XBoard Consumer Units
Incoming and Outgoing Devices
Toggle Colours
2 A
4 A
6 A
10 A 13 A
16 A
20 A 25 A 32 A
40 A
50 A 63 A
Standard AC RCDs · 2-Pole
Rated Current I
n
(A)
Tripping Current
30mA
100mA
300mA
500mA
16 *
PFIM-16/2/001
–
–
–
25
PFIM-25/2/003
PFIM-25/2/01
PFIM-25/2/03
PFIM-25/2/05
40
PFIM-40/2/003
PFIM-40/2/01
PFIM-40/2/03
PFIM-40/2/05
63
PFIM-63/2/003
PFIM-63/2/01
PFIM-63/2/03
PFIM-63/2/05
80
PFIM-80/2/003
PFIM-80/2/01
PFIM-80/2/03
PFIM-80/2/05
100
PFIM-100/2/003
PFIM-100/2/01
PFIM-100/2/03
PFIM-100/2/05
Note
* 16 A RCD is rated for 10mA earth leakage.
10
11
Key Extracts
from 17
th
Edition Regulations
Note: There are exceptions when the socket
outlets are used by skilled or instructed
persons, but not relevant in residential
property. For example 411.3.3 relates to socket
outlets located anywhere in a home, including
the socket in the cooker outlet. However RCD
protection for the cooker outlet is required if
any of the cables are buried in the wall and
not deeper than 50mm, as indicated in 522.6.
Part 5 Requirements for protecting cable against impact
This will often result in the need for additional RCD protection. This
is covered in 522.6.6, 522.6.7 and 522.6.8 and can be summarised
as follows:
All circuits buried in a wall or partition at less than 50mm depth and
without mechanical protection require RCD protection.
Key extracts from 17
th
Edition of the
IEE Wiring Regulations BS 7671 : 2008
314 Division of Installation
314.1 Every installation shall be divided into circuits, as necessary, to
(i) avoid hazards and minimize inconvenience in the event of a fault
(iii) take account of danger that may arise from the failure of a
single circuit such as a lighting circuit.
314.2 Separate circuits shall be provided for parts of the installation
which need to be separately controlled, in such a way that those
circuits are not affected by the failure of other circuits, and due
account shall be taken of the consequences of the operation of any
single protective device.
411.3.3 Additional protection
In a.c. systems, additional protection by means of an RCD in
accordance with Regulation 415.1 shall be provided for:
(i) socket-outlets with a rated current not exceeding 20A that are
for use by ordinary persons and are intended for general use.
Section 701 Locations containing a bath or shower
701.411.3.3 Additional protection by RCDs
Additional protection shall be provided for all circuits of the
location, by the use of one or more RCDs having the characteristics
specified in Regulation 415.1.1 (30mA RCD)
531.2.4 An RCD shall be so selected and the electrical circuits so
sub divided that any protective conductor current which may be
expected to occur during normal operation of the connected load(s)
will be unlikely to cause unnecessary tripping of the device.
Note: see regulations 314.1 and 531.2.4.
“
”
“
”
“
”
“
”
Extracts printed with permission of The Institute of Engineering and Technology.
12
A
We keep power under control.
Moeller Electric Limited
PO Box 35, Gatehouse Close
Aylesbury
Buckinghamshire HP19 8DH
Direct sales ordering and technical support
tel 01296 397400
fax 01296 392413
email sales@moeller.co.uk
email support@moeller.co.uk
© Moeller Electric Limited 05/08
T0200-276GB
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