Skyjuice

Instantaneous Heater – Electrocution in the Shower

2 September 2014


There was a report that a Singapore teen was found dead while taking a shower. It was not immediately known if he was electrocuted or just scared to death as an electrical outlet that was connected to the instantaneous heater was shown charred in this picture.



Observation

There was no further report on the death but it was said the family just replaced the instantaneous heater themselves. They found the boy dead, lying on the floor when they forced open the bathroom door after hearing the boy's screaming. The resuscitation did not help the poor child.

The picture showed that the heater wires, run on ordinary 3 core cable, might be directly connected directly to a heater switch which could have burnt out.  This did not quite indicate the boy was electrocuted.

The heater switch is also not a common one that use double-gang socket outlet box. The picture also shows that the house wiring is a very old type with exposed wirings running on the surface using wood battens. This sort of wiring type is only found in very old HDB flats or perhaps in SIT flats that have never been replaced. But this flat in Block 1 Hougang Avenue 3 is a HDB 3 room improved unit which was built in the 70/80.

It was also reported that the socket outlet box was installed inside the bath room.  This is not allowed under the present electricity codes in Singapore.

What could be wrong?

There may be many reasons causing the boy’s death. It is not known until the investigation has been completed.

But from the picture, it may be clear that the wirings and system was not a typical installation in HDB’s flat built in the 70/80. This suggests that the owner could have re-wired the installation.

PUB, the former utility board, made the installation of earth leakage circuit breaker (ELCB) a mandatory requirement for every new residency electrical installation in the 70s.

If the boy has been caused by electrocution, it may be highly possible that either the ELCB is not working properly or the re-wiring of the apartment has removed the ELCB.


What is an ELCB?

An earth leakage circuit breaker (ELCB) is an electrical switch that can sense current flow or leakage of electricity and trip the main switch to the apartment before anything damage could happen.

Most Singaporean homes are installed with such ELCB that can trip when the earth leakage is more than 30 milli-amperes.


In the past, the ELCB must have saved many innocent lives. If it is true about the electrocution,  this poor boy would have been saved if the ELCB had worked and trip the electrical supply.

Could it be a failed ELCB?

The ELCB could fail to operate because it is basically an electro-magnetic switch with mechanism that might get stuck in the closed position during operation. It is for this reason that all ELCB will have a test button.



Testing of ELCB should be done regularly. The best is once a month. This is because ELCB or the main switch board are often enclosed somewhere out of view and may subject to all sort of environmental exposures including possible moisture attacks,  rusting the mechanism.

Besides Testing ELCB, what can be done?

One could ensure always that electrical appliances are connected to the earth so that if there is any electrical leakage to earth from the appliance, it will first trip the electrical main before any human could touch them; also, if there is any human contact, the current created will have enough power to trip the ELCB.


How to ensure there is a proper earthing?

Invest in a multi-tester that would cost not more than SGD$30 from most electronic shops.  The meter is also available from many $2/= neighbourhood shops with a separate price tag.



Set the tester to the lowest ohmic range, say 1 to 100 ohm. Using one test lead touching the metal part of the appliance, the other test lead touching any metal part of the water pipe or tap. The meter should show some readings around 10 ohms and below. If it is more than 50 ohms, most likely one would have a faulty earthing requiring attention or rectification.

In the case of instantaneous heater, using one lead touching the metal part of the piping connector of the shower head and the other lead touching directly to the water facet that is connected to water heater.    

In case where instantaneous heater has a PVC outlet connector that does not expose the metal part of the heater such as those shown here having an insulated PVC connectors,  carry out as follows:


First, switch off the power supply, then remove the outer protective casing of the heater (usually fixed onto the heater with a bottom screw). Using one cable lead touching the metal boiler unit or any other metal part and the other lead touching the water facet directly.   When fixing back the casing, make sure it is fixing back to the original position.

Why test cable must touch water pipe or facet?

It is a mandatory requirement in Singapore that all wiring installations must have their earthing bonded to the water piping at the incoming mains.



By having one lead touching the metal part of the appliance and the other lead to the water pipe or facet, one can test roughly the integrity of the earthing system within the apartment.

If the earth readings are more than 10 ohms, it is good to check the earthing of the appliance or the actual electricity earth for safety sake.

The electrical installations in Singapore are always installed with an effective earthing resistance having less than 1 ohm.  There should be test reports submitted to the authority.


What if the water piping has a section consisted of PVC?

Water pipings are mainly metal pipes but sometimes, a section of PVC may be inserted. It may give false reading especially when there is no water in the pipes. If there is water, the multi-ohm meter should still give some good readings because water is electricity conductive. If there is any doubt about the integrity of the earthing, place the test lead to the water pipe before the PVC section.

What if the Ohmic reading is Still high?

Try pulling a power extension cord that has an earthing connector from the nearest power socket outlet  to somewhere nearer to the heater and measure the resistance between the extension cord's earth and the heater's earth.   If the reading is still high,  there is a poor earthing connection to the heater and one should call an electrician to fix the problem immediately.

Update 1:   2 Sept 2014



This picture showed clearly the heater was connected to a 3 pin plug.   Understand the switch socket outlet of a double gang type was removed by the Police for investigation.  This switch socket outlet, installed outside the bath room,  was connected to the supply using another 3 core cable.  The wiring is an illegal addition according to the local codes which required all fixed wiring (e.g onto the walls) must be carried by licensed electrical worker e.g. an electrician and proper wiring method consisted of conduits or trunking should be used.  No flexible cables should be used.

What can I do if the house does not have an ELCB installed?


The Electricity ACT 1974 mandates the installation of ELCB in all new apartments including HDB flats.  Those built before this date might not have ELCB installed as a standard.  One should install the ELCB immediately for these electrical installation at the main switch panel.  It may cost around SGD $200/= including labour but it will save some life. 
However,  one could also install power socket extension plug with ELCB protection.  In such case,  it is better to check if the power socket extension plug has proper testing certificate from recognised institutions.  This extension plug might not be cheap.



Update:  The Coroner's court 

The Coroner's court in March 2015 found that the boy could have come into contact with an electrically energised metallic shower outlet hose that was attached to a water heater.   The court added that the boy's father installed the water heater about three months earlier. The simple installation work did not fulfil the strict definition of 'electric works' regulated by the Energy Market Authority.

http://www.straitstimes.com/singapore/courts-crime/teenager-electrocuted-in-shower-died-of-misadventure-coroner-finds




27 March 2017

 Installing New Instantaneous Water Heaters


1.  Never trust anyone whosoever install the electric instantaneous water heater for you. Even if it is a qualified electrician or LEW, they might make mistakes.   He may also be color-blind making wrong wirings;

2.  Make sure you see that person who install the water heater test the earthing system in your present. If possible, ask the person to perform a earth leakage test using method just described to ensure that your house's earth leakage circuit break (ELCB) or residue current circuit breaker (RCCB) is working properly;

3.  Also make sure the water heater has PSB/SPRING – Singapore or approved testing label.



8 comments:

JB Cheong said...

When we press the TEST button on the ELCB, do we essentially caused a trip on purpose? I was told a power trip is quite damaging to big home appliances such as the refrigerator. How true is that?

I suppose to minimize damage, would it be alright to turn off every electrical things in the house before I press the TEST button? Will the reduction in power usage gives false testing result?

Thank you.

Sky Juice said...

Most electrical appliances are designed to handle sudden loss of power without causing any damage. This is particularly so when they are required to work in remote villages where power outage is almost a daily event.
The test button of ELCB simulate and cause an unbalance current within the ELCB for tripping purpose. Testing of ELCB can still work properly without any external loads

asd pipeplast said...

Hi there! I'm at work browsing your blog from my new iphone 6!
Just wanted to say I love reading your blog and look forward to all 
your posts! Carry on the fantastic work!

Steven H said...

As shown in your picture (portable RCD Adaptor) is only rated at 13A. Is it safe to be used for a instant water heater of 3.3KW?

I think connecting an RCCB (20A with tripping sensitivity of 10mA) will be a better choice.

Just my view only. Thanks.

Steven H said...
This comment has been removed by the author.
Sky Juice said...

Hi Steven H,
It will depend on the quality of the RCB. 3.3KW for 240 volts will be drawing around 10 Amperes. There is very little safety factor left for continuous load but showering is not a continuous load. Good to check the heat emitted at the RCB just to ensure there is over heating due to bad connection.

JB Cheong said...

Concerning instant water heater with section made of PVC, would you recommend using the below kind of device as an added precaution?

https://item.taobao.com/item.htm?id=522799141872&_u=5ceiu137af7

I hope you read Mandarin.

Thanks.

Sky Juice said...

Sorry for the late reply. The brochure appears to suggest an alternative by installing the device in between the heater outlet and the shower pipe. It said that water has a resistivity of 1300Ω.cm and by special construction, the current flow in the water can be reduced to 0.02mA/kw.
Lets assume that this alternative will work but it is not comfortable to assume that water resistivity is always constant and would not change with impurities and also, the device would not impede water flow. I would prefer and will trust only the conventional wisdom.