In 2020 a person died after touching the metalwork of a rangehood appliance while upgrading a kitchen, after an electrical worker had undertaken electrical work.
This tragedy deeply affected all involved and was 100% avoidable.
Sequence of Events
An electrician was engaged to remove an existing hardwired fan-and-light unit (refer Figure 1) and install a new socket outlet in its place (refer Figure 2) for a new rangehood appliance.
Figure 1: Hardwired Fan-&-Light Unit (was)
Figure 2: Rangehood Socket Outlet Installed (became)
The electrician cut the cable off the old fan-&-light unit, complete with the non-visible sleeved earth conductor inside, before fitting the new socket outlet in its place. The double-gang switch plate was not removed as part of the work, nor for testing. The new rangehood was then mounted and plugged-in.
A CoC with test results was issued for this work.
After being in use for approximately two weeks, a non-electrical contractor was engaged to carry out further work in the vicinity of the new rangehood. He received a fatal electric shock, with an entry wound consistent with contacting the live metalwork of the rangehood.
Investigations
WorkSafe Energy Safety undertook the investigation which identified the information summarised within Figure 1 and Figure 2. They also analysed the paperwork, training history, and other related factors.
Prosecution
The electrician who undertook the work was charged under section 163(c) of the Electricity Act 1992, and found guilty. Sentencing is pending at time of writing, with significant penalties available:
a maximum sentence of two years prison and/or $100,000 fine.
The completed documentation (ESC, CoC) contained a declaration that the work had been adequately tested and included a set of test results. Despite this, the Judge accepted the prosecution’s allegation of a failure to adequately test.
Opinion: What Went Wrong
The simplest explanation (Occam’s Razor) is: the green conductor was assumed to be earthed, and was terminated into the earth terminal of a three-pin socket, without adequate testing.
The situation in Figure 2 would have failed the first and most important measurement: earth continuity and resistance.
This fatality clearly shows that the required testing was either not done properly or was not done at all.
Preventing This Happening Again
Electricians are trained, registered, licenced and have ongoing (2-yearly) refresher/competence training. This training includes electrical safety testing specifically intended to prevent errors such as this.
The tragedy would not have happened if the required safety testing had occurred.
It also demonstrates that conductor colours cannot be trusted, whether due to sleeving, previous bad work, faults, or other causes.
Please note:
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The presence or absence of an RCD did not feature in the prosecution, which focused on the failure to adequately safety test. RCDs are only usable as additional protection; they must not be used as the primary ‘line of defence’.
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Maintenance work on fittings does not trigger installation of an RCD. New sockets on existing residential circuits generally does trigger a new RCD (NZS3000:2007 2.6.3.4).
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Sleeving of a green or green/yellow conductor for other purposes is no longer a compliant practice. However, such sleeving is legally present in a significant number of existing installations.
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While cheap and common, the ‘three–light–test–plug’ is not a recognised tool for safety testing of prescribed electrical work (PEW) and is insufficient to prove safety. In this circumstance (Figure 2), it is possible that leakage current through the rangehood’s exposed metalwork to the body of earth could have falsely indicated the presence of an earth connection if such a device was used.
END.
This note was compiled by Mark Harris from multiple sources on behalf of NZEIA. It was released for publication by NZEIA on 11/1/2024.
Mark is an Electrical Inspector and Chartered Professional Electrical Engineer based in Wellington.
Post expires at 2:02pm on Friday August 2nd, 2024
