Electrical
Installations and Appliances - Isolation Guidelines
Information Sheet 02/02
15 February 2002
Contents
In order for an electrical installation and associated
electrical appliances to be disconnected safely in the event
of an emergency, or to enable maintenance or repair to be
safely carried out, suitable means of isolation needs to be
provided in the Electrical installation wiring.
Fundamental Isolation Requirement
The fundamental requirement of the electrical safety
legislation (the Electricity Regulations 1997) is for suitable
isolation fittings to be provided to disconnect works and
electrical installations, or parts of them, from a power
supply where necessary, including in an emergency.
Isolation for Emergency
This is normally achieved by:
- A readily accessible switch located on or in the near
vicinity of the electrical equipment or appliance;
- A readily accessible and suitably marked switch at a
switchboard. This could be the main switch at the main
switchboard; or
- A circuit breaker (rated for isolation) located on the
switchboard from which the circuit is supplied;
- For plug in appliances, the withdrawal of the plug.
Isolation for Maintenance or Repair
This is normally achieved by:
- A readily accessible switch located on or in the near
vicinity of the electrical equipment or appliance;
- A switch or circuit breaker remote from the appliance
(e.g. on the switchboard) with a means of ensuring that
power will not inadvertently be restored;
- The withdrawal of a fuse on the switchboard from which
the electrical equipment or appliance is supplied. See
note 1;
- For plug in appliances (where the socket outlet is
readily accessible), by removal of the plug from the
socket outlet.
The use of the main switch on a switchboard is not normally
acceptable as a suitable means of isolation for the
maintenance or repair of fixed wired appliances because of the
need to have supply available for other purposes, such as
lighting or the operation of power tools.
Specific Isolation Requirements
The regulations contain specific requirements for some
electrical equipment and appliances:
Switchboards
Are required to "contain suitable isolation
switchgear."
Main switches are required to be suitably labelled.
Electric Ranges
"The installation wiring for supply to a low voltage
electric range that is not fixed in position must -
- Incorporate an isolating switch that is readily
accessible and located adjacent to the electric range ;
and
- Terminate at a socket outlet of appropriate current and
rating."
Socket Outlets with a Rating of 30
A or More
These socket outlets "must be fitted with an
associated switch for isolation."
Electric Motors
Must "have a means of isolation to disconnect all
voltage from the motors, and that means of isolation must:
- be located adjacent to the motor; or
- If not located adjacent to the motor, be capable of
being locked in the off position."
Isolation for Maintenance or Repair - Recommended Practice
Dishwashers
Either a switch on the wall above the dishwasher, or a
switch or socket outlet located in an accessible location in a
cupboard alongside, are considered the best alternatives. If a
socket outlet is used this need not have a switch as the
withdrawal of the plug can be considered as the means of
isolation.
A socket outlet located in the back of the dishwasher
enclosure, is not considered a suitable means
of isolation for maintenance or servicing purposes, because
this is often difficult to access, due to the presence of
plumbing connections and the need to withdraw the appliance
from the enclosure.
Ovens and Cooktops (Hobs)
Either a switch on the wall alongside the appliance or a
switch located in an accessible position in a cupboard (or
pantry) would be acceptable.
Note that these appliances are not
"electric ranges" and therefore do not require
connection via a plug and socket arrangement.
Security Alarms or Security
Lighting
Either a suitably located switch or a circuit breaker
(rated for isolation), or withdrawal of a fuse on the relevant
subcircuit at the switchboard, could fulfil the isolation
requirement. Where a circuit breaker or fuse on a switchboard
is used it should be suitably marked and steps should be able
to be taken to ensure that supply cannot be accidentally
restored.
"Split" Air Conditioning
Systems
Either a switch at one point to isolate the whole system,
or a switch for each part of the system, needs to be provided.
Where the system is "plug in" the withdrawal of
the plug from the socket outlet can be regarded as a suitable
means of isolation, provided suitable steps are taken to
ensure the supply will not be reconnected accidentally.
A circuit breaker or withdrawal of a fuse at the relevant
switchboard can be regarded as the means of isolation provided
it is suitably labelled and steps can be taken to ensure that
supply cannot accidentally be restored.
Notes
- The withdrawal of a fuse carrier
at a switchboard to provide isolation should be achieved
by turning off a switch (e.g. the main switch) before
withdrawing the fuse carrier. The switch can be turned
back on with the fuse element removed. Live parts (e.g. of
the fuse base) should not be left exposed.
- Means of isolation other than those mentioned may also
comply with the regulatory requirements.
- The methods mentioned are for emergency and maintenance
isolation only. Electrical workers should liaise with
clients/customers in regards to control or functional
switches that they may require for operational purposes.
- The legislation requirements for isolation are contained
in the Electricity Regulations 1997 (regulations 65, 78,
79, 80) and in electrical code of practice NZECP 14.
- An isolation switch is usually regarded as a switch,
that when the contacts are open, has a gap between
contacts of at least 3mm.
- Requests for interpretation of the electrical safety
legislation should be referred to the Energy Safety
Service, Ministry of Consumer Affairs, Phone 04-472 0030,
freefax 0508-723 336.
- Health and safety legislation may specify additional
requirements for control or isolation of electrical
equipment and appliances. Enquiries in this regard should
be directed to Occupational Safety and Health (OSH).
An OSH publication which may be of assistance is
"Electrical Interlocking for Safety in Industrial
Processes - Guidance notes for."
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