Electrocution Case Cameron Highlands LPG Water Heater - What could be the causes?

Peace be upon all of us,

On 10th of March 2022, a couple was found dead  in their flat unit at Taman Puncak Tringkap, Brinchang, Cameron Highlands. Based on the post mortem, the couple is believed to have died from electrocution.

The water heater used was actually LPG (Gas) type water heater and not the electrical type instant water heater. Up to today, there has been no official investigation report on the cause of the incident i.e. how the gas water heater could have became Live with electricity.

LPG Type Water Heater

The LPG water heater uses gas as a fuel source to heat up the water. When the water reaches the magnetic switch, the sensor notifies the solenoid valve, which then turns on the gas pipeline. Once the gas flows into the burner, it triggers the igniter. The igniter sparks and gas flames appear. The cold water flows into the heat exchanger, which is then heated. For more details on how it works, please refer here.

The only electrical part within the LPG Water Heater is the igniter, which normally uses 1.5V or 3V battery as the ignition source. 

So, what are the possible causes for LPG Water Heater to become electrically Live?

Above is a typical electrical system in an apartment and its earthing interconnection. There

are a few assumptions here:

• LPG Gas Water Heater may be grounded or may not be grounded
• There are electrical wiring within the wall near position, where the gas water heater unit is installed. Most old building wiring may not be double insulated, i.e. the wiring is installed directly within the walls instead of within a conduit within the wall. There is possibility of the leakage coming from this wiring, which insulation may have been damaged or degraded over its lifetime.

Case 1: The LPG water heater is grounded

If it is grounded, when there is a leakage from the nearby wiring, the metal part of the LPG water heater will conduct electricity and render it Live. Since, the metal parts are grounded, these leakage will immediately be discharged through the grounding system, which will also trip the Residual Current Device (RCD) i.e. at 30mA of the apartment's distribution board. 

It could also be the case that the leakage is not big enough (<30mA) to trigger the RCD, the RCD leakage current setting is high i.e. 100mA, 300mA or the RCD itself is malfunction. Upon touch by someone, he may become the path to the leakage current. A human being is only able to sustain leakage current less than 10mA. For current 10mA or larger, it may cause muscle contraction and cardiac arrest.

Case 2: The LPG water is not grounded

If it is not grounded, upon any electrical leakage near the unit, the metal part of the LPG water heater will become Live. It will not trip the RCD since the earth leakage circuit is not complete yet. Upon touch by a person, he will complete the earth leakage circuit and be subjected to the current flow through him. Similarly, the leakage current may be too small to be detected by the RCD, but enough to cause injury or fatality, or the RCD itself is malfunction.

What can be done to avoid such mishaps?

1. Wiring installation to be inspected periodically by a competent person. 
2. As per Garis Panduan Pendawaian Elektrik Pepasangan Domestik (Domestic Installation Electrical Wiring Guideline) issued by Energy Commission Malaysia, section 10.5 Bahagian Yang Perlu Dibumikan (Parts Required To Be Earthed), all non-current-carrying metal structures within the wiring system and all exposed metals shall be earthed. The metal parts of the gas water heater and exposed gas piping shall be earthed.
3. Test your RCD regularly. Purchasing a RCD socket tester which you can get from Mr. DIY or online can confirm that your RCD and wiring system is working properly.

Note: For earth leakage protection and guideline on instant electrical water heater may be referred here.