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E L E CT R I C AL CONNE CT I ON
W I NT E R 2 01 5
THE BUZZ
Current concerns
T
here are residual current
devices (RCDs) here, there and
everywhere; at least, that’s what
I’d like to think. But, sometimes I still feel
that more can be done.
The RCD provides a lifeline against
inadvertent mistakes, but we should not
rely entirely on them.
It is important to remember that
RCDs are considered to be additional
protection under the definitions in the
Wiring Rules. There are many more
mechanical ways of protecting a wiring
system so that no one gets to touch live
or single insulated cables and equipment
in that system.
Earthing of equipment is of utmost
importance for safety. Double insulation is
a perfectly acceptable way of preventing
inadvertent touch.
It is also important to consider that a
direct active to neutral fault is not likely
to be picked up by an RCD, as it requires a
fault to earth from the active or neutral.
Hence, mechanical protection is
necessary.
The Wiring Rules require all final sub-
circuits (20A and below) to be protected
by an RCD. But this is not retrospective – it
applies to new installations.
Certainly all new homes over the past
20 or 30 years do have RCD protection
on their final sub-circuits. However, it was
only recent changes to the Wiring Rules
that added the need to RCD-protect
lighting circuits as well.
The result is that quite a number of
homes built before the changes have
protection only on the power circuits.
Also, there were exceptions to RCD
protection, such as cooker circuits, for
which mechanical protection is valid.
Many homes still have ceramic fuses at
their switchboards and, even now, I hear
stories about old places with rubber-
sheathed cable.
We have a legacy of installations that
were ‘electrically safe’ when built, but over
the years the definition of that phrase has
changed greatly.
It is important to remember that
the committee has been charged with
ensuring that an installation is electrically
safe when amending or revising the AS/
NZS 3000 Wiring Rules.
So lots of issues are continually laid on
our table, affecting the way we think and
act. The most terrible of these are the
findings of a coronial inquest when the
worst happens – death or massive loss
of property. These findings cannot be
disregarded or given lip service, because
they provide legal precedents that can be
used in other court proceedings.
Death especially has a very big effect
on how the committee reacts and that’s
why the meaning of ‘electrically safe’
changes from what was previously
accepted.
And what of the recent cable scandals
with Infinity and E-cables? They make one
feel that a terrible tragedy is impending.
The breakdown of insulation due to
natural load and subsequent heating is
scary indeed. Only a small percentage of
new installations have been appropriately
reviewed and upgraded, which means we
can expect some real nuisance tripping of
RCDs at some stage.
We hope all the installations have RCDs.
If they haven’t, there is a better than even
chance of exposure to electrical shock.
Findings handed down by the Royal
Commission into the Home Insulation
Program were sent to the Wiring Rules
committee for action. Here is a case in
which people died because of poor risk
review and management.
The findings asked “why weren’t RCDs in
place in all installations?”; and the big one,
“why wasn’t the power switched off at the
switchboard before worked commenced
in the ceiling?”
This project was not electrical work as
such, but RCDs or turning off the power
before working could have saved lives.
Very simple!
And we all know when doing electrical
work that the power should be off,
don’t we?
Older houses were wired
according to the safety
standards of their time.
Gary Busbridge
calls for
more RCDs to bring things
up to date.