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Locked Consumer units
Isolation - Locked Consumer units
AlthoughWylex in the past have offered a lockable consumer unit
(access to the devices MCBs /RCBOs and Isolating Switch is covered by
a lockable door); this unit can only be specified and used in certain
mitigating circumstances for example power to fire alarm circuits is
locked in the ‘On’ position (via interlocks) to ensure the safety circuit is
never isolated unless authorised (via interlocking procedure).
Wylex’s view on “lockable consumer units” is inline with good safety
practice; in that you should object to locking power in an “On” position
without the means of local isolation, especially in the case of an
‘Emergency’ to achieve immediate electrical shut down.The Main Switch
/ Isolator provided in a consumer unit is deemed the main isolation
point for the installation and is automatically classed as the Emergency
Switching point for isolating the complete installation in an crisis
situation.
In the case of an emergency and the immediate need to isolate the
power; if the Main Switch of the consumer unit can only be actuated
(turned off) by obtaining a key (kept separate away from the unit) to
unlock the door, to gain access to the switch, this can be interpreted by
its numerous operations as against good safety practice.
Extracts from various regulations that support this view are as follows:-
BS 7671:2008 17th Edition wiring regulations:
Incorporating amendment No1:2011
CHAPTER 13 FUNDAMENTAL PRINCIPLES
132.15.1 Effective means, suitably placed ready for operation, shall be
provided so that all voltage may be cut off from every installation, from
every circuit thereof and from all equipment, as may be necessary to
prevent or remove danger.
537 ISOLATING AND SWITCHING
537.1.3 Each installation shall have the provision for disconnection from
supply.
537.1.4 A main linked switch or linked circuit-breaker shall be provided
as near as practicable to the origin of every of every installation as a
means of switching the supply on load and as a means of isolation. A
main switch intended for operation by ordinary persons, e.g. of a
household or similar installation, shall interrupt both live conductors of
a single-phase supply.
537.4 Emergency Switching
537.4.1.1 Means shall be provided for emergency switching of any part
of an installation where it may be necessary to control the supply to
remove an unexpected danger.
537.4.1.3 Means for emergency switching shall act as directly as possible
on the appropriate supply conductors. The arrangement shall be that
one single action only will interrupt the appropriate supply.
537.4.1.4 The arrangement of the emergency switching shall be such
that its operation does not introduce a further danger or interfere with
the complete operation necessary to remove the danger.
537.4.2.7 A device for emergency switching shall so be placed and
durably marked so as to be readily identifiable and convenient for the
intended use.
ELECTRICAL SAFETY COUNCIL:
(ADVICE TAKEN FROMTHEIRWEB SITE/ LITERATURE).
A consumer unit or fusebox is used to control and distribute electricity
around our homes.
They usually contain:
A) Mains switch, B) Fuses or Circuit Breakers, C) Residual Current
Device
Mains Switch
The mains switch allows you to turn off the electricity supply to your
electrical installation. Some electrical installations have more than one
mains switch, for example, if your home is heated by electric storage
heaters, you may have a separate consumer unit (fuse box) for them.
The consumer unit should be easy to get to, so find out where the
mains switch is to turn the electricity off in an emergency.
LOCKING A CONSUMER UNIT TO STOP UNAUTHORISED
ACCESS / ACTUATION OF THE PROTECTION DEVICES.
A request is sometimes made to lock the consumer unit because the
installer / user don’t want unauthorised access to switch devices ‘On’
and/or ‘Off’. In this case, the isolation point to switch ‘Off’ the
installation and Emergency Switching requirements still applies to the
consumer unit and may be achieved in several ways.Wylex offer 3 cost
effective options as follows:-
Option 1. Use a standard consumer unit with a MCB/ RCBO locking
device and padlock on the individual outgoing circuits to lock in the ‘On’
or ‘Off’ position’s. When locked in the ‘On’ position the MCB / RCBO
will still ‘trip’ due to a fault condition on the circuit. (Note: you will need
to open the padlock and remove the locking device to reset a tripped
unit). The Main Switch Isolator is still accessible on the consumer unit
to isolate the installation under emergency conditions.
Option 2. Have all the outgoing protection devices MCBs / RCBOs
under a separate lockable door / cover to stop unauthorized access /
operation of the individual circuits.The operation of the Main Switch
Isolator is ‘outside’ of this lockable door / cover; via a protruding toggle
switch or door interlocked rotary handle connected to the Main Switch
Isolator.The operation of the Main Switch Isolator is still accessible /
unhindered on the consumer unit to isolate the installation under
emergency conditions.
Option 3. Have a lockable door on the complete consumer unit
stopping unauthorised access to all the outgoing devices and Main
Switch Isolator fitted into the unit. In this case, the Consumer unit must
also be fed by a separate Isolation Point that is “still local” (near as
practicable) to the consumer unit.This separate Isolation Device is used
to isolate the installation under emergency conditions. This Isolation
Point /Device should have easy access and is marked as the Emergency /
Isolation Point for the particular consumer unit. The consumer unit
should also be marked in a way to indicate the emergency isolation
point is separate / next to the unit and not part of the consumer unit.
In this case, because it is not intuitive that the Isolation Point is not
within / accessible directly on this consumer unit; Instructions should be
given to each user of the installation on how to isolate in emergency
conditions using the separate Isolation Point device.
Meter
CUT
OUT
FUSE
100A
REC
ISOLATING
SWITCH
Typical arrangement with REC Isolating Switch
Locked Visor