Have you heard of the butterfly effect? Wikipedia describes it as a popular hypothetical situation that illustrates how small initial differences may lead to large unforeseen consequences over time. You may be thinking of several movies involving time travel at this point.
When a significant event occurs, good or bad, it’s easy to think of some small detail in the past that, if changed, would have prevented the outcome. And when electricity is involved, a seemingly minor incident can have an effect of the greatest severity some time in the future.
The following case comes from an article entitled “dead but still alive” from September 2020 Australian Police Journal written by New South Wales Police Detective superintendent Paul Devaney. It was a detailed and very well written account of how seemingly unrelated minor flaws can have a devastating consequence far greater than could reasonably be expected.
The Incident
Detective inspector Devaney was asked to check in on an elderly lady. She failed to attend a function which was out of character for her. When Devaney got to her unit she was found deceased in her shower, still holding a flexible shower hose.
On attempting to move her body it was discovered that she was electrically live. An electrical contractor was called in to assess the situation and make it safe. He confirmed their suspicion that the bathroom was electrically live. Coincidentally, while the police were waiting outside they became aware of loud music from an adjoining unit. They thought it was unusual since it was late at night.
So the electrician was asked to also conduct some testing on the area surrounding the adjoining parts of that unit. It was also found to be live, and since that resident, another lady had not responded to earlier contact attempts her adjoining unit was also investigated. When the police gained entry the resident lady was found similarly deceased in her bathroom. Both were first floor units on a common floor slab.
The Findings
From a detailed and in-depth investigation the following was found.
A nail (then rusty) and possibly fired from a powder actuated tool into the floor slab unknowingly penetrated a plastic conduit and it’s wiring, this likely happened during construction. The nail contacted a conductor that was live, but only when a 2 way switch was in a certain position. The live conductor was powering lights on the floor below.
A leaking inlet water hose connection at the back of a washing machine in one of the units was continually wetting the floor. This made the floor highly conductive under the two adjacent bathrooms, but only when a particular light on the ground floor was switched on.
The above combination caused both deaths from electrocution by standing on their respective live shower floors. In conclusion it was deemed as an extremely unlucky set of circumstances. The deputy state coroner determined both were accidentally electrocuted with a number of recommendations, one of which included the installation of safety switches on light circuits.
It should be clearly understood that in this case there is no suggestion the installation was in any way at fault. But this case illustrates that where, and how wiring is installed can have a major impact on the potential of lethal shock incidents at any time.
Butterfly effect
Several actions in the past, if changed, could have prevented this tragedy. The nail could have been fired into the concrete just a few centimetres away in either direction. The washing machine water leak could have been repaired. The conduit could have been set deeper in the concrete, or steel conduit used. Unfortunately this electrical fault could not have been detected when the electrical installation was completed and tested.
In this case the last line of defence would have been an RCD, also known as a safety switch. If there had been an RCD installed on the lighting circuit it’s almost certain this tragic outcome would have been averted.
It is now mandatory for RCDs to be fitted to lighting circuits in new and modified installations. However there are still millions of houses and other residential as well as commercial and industrial installations built before 1991 that may still not have any RCDs whatsoever, or only on a limited number of circuits. This leaves a huge number of installations with zero or only partial RCD protection. Consequently there are countless situations where responsible owners or occupiers of homes, offices and factories are not meeting their lawful or present day expected duty of care for their families, employees and the public at large.
I cannot emphasise strongly enough the recommendation to upgrade power circuits from CB protection, which only protects the cable, to RCD protection which protects people.
