Elderly couple, son in Jurong flat electrocuted to death after cables in plug for water heater fused together
SINGAPORE: Three people who died in a flat in Jurong Lakeside in December 2020 were electrocuted after the cables in the plug supplying power to their instant water heater fused together, an expert witness from the Energy Market Authority (EMA) testified on Wednesday (Mar 9).
Investigation officer Goh Chin Fong, a senior associate engineer with EMA, was the first of two witnesses called to the stand during a coroner’s inquiry into the deaths of an elderly couple and their son.
A police investigation officer also gave testimony. The findings of the inquiry are set to be released at the end of April.
The elderly couple, Mr Omar Manan and his wife Mdm Asmah Bujang, had lived in the three-room flat at Block 120, Ho Ching Road since the 1970s.
On Dec 10, 2020, their son, Mr Muhamad Ashikin Omar, and his daughter went to the flat to check on them after calls to the home went unanswered.
According to a statement the daughter gave to police, they saw the elderly couple slumped on the floor of the bathroom. Water was still flowing from the shower head.
When Mr Ashikin saw his parents on the floor, he cried out and ran to them, calling “mak”. He then collapsed and fell on his mother’s body.
Believing that he had fainted, Mr Ashikin's daughter tried to shake him awake. When she touched him over the material of his jeans, she felt a “tingling sensation” near her elbow.
Paramedics arrived shortly after and took Mr Ashikin to the hospital, where he was pronounced dead. Mr Oman and Mdm Asmah were pronounced dead that day as well.
An autopsy report found that the cause of death for all three individuals was electrocution. The police do not suspect foul play.
CABLES FUSED IN THREE-PIN PLUG
The water heater in the bathroom was manufactured in 2008 and installed sometime after that, according to Mr Goh. It was powered by a three-pin plug connected to an extension outlet, which was in turn connected to a power outlet in the kitchen.
A three-pin plug contains a live cable along which the electrical current enters the appliance, an earth cable that provides a path for the current to flow to the ground in case of a fault, and a neutral cable that completes the circuit.
Mr Goh testified that when the plug to the water heater was opened after the incident, the cables inside were “badly burnt” and the earth cable and neutral cable had fused together.
Ordinarily, the electrical current would flow through the live cable and heating element in the water tank, and return through the neutral cable.
However, as the earth and neutral cables were touching, the current flowed back through the copper housing of the water heater and “energised” the metallic water hose, he said.
In the wet environment of the bathroom, where Mr Oman was holding onto the hose and not wearing any shoes as he was taking a shower, this caused the elderly man to be electrocuted, said Mr Goh.
He said that the cables fused because they were overloaded. The plug had a 13-amp fuse but the maximum current when the water heater was operating was more than 14 amps.
Daily use of the heater over a prolonged period damaged the cables and their insulation, causing the wires to burn and fuse together, said Mr Goh, adding that even the live cable suffered some damage.
Mr Goh said the use of a 13-amp plug to power a water heater was the wrong practice, and that a double-pole switch should have been used instead.
In a double-pole switch, each cable has its own terminal positioned in such a way that the cables cannot cross or touch each other. Even if heat was generated through overloading, the cables would remain intact, he said.
He added that double-pole switches should be used for other appliances that draw large amounts of electricity, such as ovens and air conditioners.
NO CIRCUIT BREAKER
Mr Goh also testified that the household’s electrical circuit comprised two wiring systems: An older system installed in 1971, and a newer system installed when the flat underwent the Housing and Development Board’s (HDB) Main Upgrading Programme completed in 2003.
As part of the HDB upgrading, a residual current circuit breaker (RCCB) was installed for the newer wiring system. The RCCB would trip the system and cut off the current when an earth leakage was detected.
The water heater drew electricity from the older wiring system, which was not protected by the RCCB as there was no such requirement at the time the system was installed, said Mr Goh.
He said that if the RCCB had been installed in such a way that it protected the household’s entire circuitry, it would have detected the earth leakage during the incident, tripped and cut off the current.
ADVICE TO HOMEOWNERS
Asked by State Counsel Ong Xin Jie to give advice to homeowners who want to install water heaters on their own, Mr Goh said they should first ensure the appliance has the SAFETY Mark certification given by Enterprise Singapore.
They should not use three-pin plugs or 13-amp fuses to power water heaters. Instead, they should check that the bathroom provides a connection point to a double-pole switch.
If there is no such connection point, they should engage a licensed electrical worker to carry out wiring work for a standalone circuit for the water heater.
After that, they should engage a qualified technician to install the water heater to the connection point.
Homeowners are also recommended to do monthly tests of the RCCB installed in their households, said Mr Goh.
If the RCCB does not trip the power supply when they press the test button, they should engage a licensed electrical worker to rectify the problem.