Electrical Connection Autumn 2015

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3 8 E L E CT R I C AL CONNE CT I ON AUTUMN 2 01 5
installations” are to be installed, then you
may be breaking the law.
The harmonised WH&S legislation
requires appropriate RCDs for socket outlets
where electrical equipment:
> in normal use is exposed to conditions
likely to damage it or reduce its expected
life span, including moisture, heat,
vibration, mechanical damage, corrosive
chemicals or dust;
> is moved between locations, and damage
to the unit or flexible supply cord is
reasonably likely;
> is frequently moved during normal use;
> forms part of, or used in connection with,
an amusement device.
Check the legal requirements in your state
and industry, as not all states have adopted
the harmonised legislation. Some industry
sectors, such as mining, are likely to have
additional requirements.
MEDICAL PATIENT AREAS
You may be asked to perform electrical
installation work in patient areas of hospitals,
medical and dental practices, dialysis areas,
home care, and self-harm areas.
The Standard has special installation
requirements, including RCD protection,
above and beyond the Wiring Rules.
You will need a copy of AS/NZS3003
to ensure all additional requirements
are fulfilled. These requirements include
additional certification by experts, as noted
in the Standard, and regular inspections.
TESTING AND TAGGING
RCDs can and do fail, so testing is
extremely important.
The RCD push button allows twice the
rated residual current to flow, so this is
a reasonably good test. It is particularly
important for homes in which this may be
the only RCD test ever carried out.
You could add additional revenue to
your business by testing RCDs for residential
customers, and by doing so you help to ensure
safety. (It’s always good to retain customers –
especially by keeping themalive.)
AS/NZS3760 In-service safety inspection
and testing of electrical equipment specifies
that RCDs also be tested for trip time and
must be tagged for places of work, public
places, or equipment offered for sale.
This includes any residential areas such
as hotels, motels, boarding houses, halls,
hostels and accommodation houses. Again,
this may be an additional revenue stream
that you are not cashing in on.
OTHER ISSUES
It is important to select the right type of
RCD for the load.
Much of our equipment is electronic
in nature. It will probably need to include
DC sensitivity for an RCD or residual
current breaker with overcurrent (RCBO) to
effectively operate when required.
An RCD or RCBO categorised as Class
A will have sine wave and DC pulse
sensitivity. Check the manufacturer’s
information to ensure you are using the
right version for the situation.
Some makes and models of RCDs and
RCBOs have electronic circuitry, so their life
may be shortened by:
> overvoltage;
> transients such as those from lightning or
load switching;
> harmonics; and
> heat (particularly shortens the life of
capacitors).
With electronic circuitry, it will be more
important than ever to test RCDs and RCBOs
to ensure the electronics are operative.
With the drive to ensure safety, the
installation of RCDs and RCBOs is relatively
easy in small switchboards but can be
problematic in larger boards.
Some switchboard manufacturers do
supply a four-busbar carcass, making things
easier, but four-pole RCBOs don’t seem to be
the norm.
Some manufacturers supply an additional
pole and toroidal block to
a standard miniature circuit breaker
(MCB) to make a four-pole RCBO, and
some of these even take up five poles
on the switchboard.
Other makes of RCBO take up four poles
and insulate the fourth pole from the three
busbars, so only two poles are available for
the next circuit breaker. Those two poles can
then be used for single-phase circuits only,
or become spare slots.
To get around the problem of available
circuit breaker space on switchboards
and the cost of replacing boards, some
electricians are simply installing an MCB
on the switchboard and using RCD-
protected three-phase socket outlets (see
accompanying photo).
CONCLUSION
It seems that RCDs are now a must for
most situations, and you would be silly not
to install them.
For the residential sector, this will include
RCD protection on stoves, hot water systems
and air-conditioners, with an RCD as a main
switch. Some might say this will result in
nuisance tripping, but there is no such thing.
If an RCD is tripping, there’s a problem.
Requirements above and beyond the
Wiring Rules for RCDs include those detailed
in workplace health and safety legislation
and in specific Standards such as those for
patient areas.
Socket outlets above 20A amps in “other
installations”, such as commercial or industrial,
should be RCD protected to ensure safety
and compliance with legislation.
When testing and tagging, replace faulty
RCDs. Once identified, the circuit must be
isolated there and then, as RCDs are essential
safety equipment.
Read the Wiring Rules, other Standards
and the applicable legislation. Become
familiar with any additional requirements.
If in doubt, fit RCDs to all circuits, or seek
further advice.
> PowerLogic