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Life Ranger
06-01-2006, 11:21 AM
Have you checked your home's ELCB lately ?

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Electric Shock

The primary variable for determining the severity of electric shock is the electric current which passes through the body. This current is dependent upon the voltage and the resistance of the path it follows through the body. An approximate general framework for shock effects is as follows:

Electric Current (1 second contact) = Physiological Effect
1 mA = Threshold of feeling, tingling sensation.
10-20 mA = "Can't let go!" current - onset of sustained muscular contraction.
100-300 mA = Ventricular fibrillation, fatal if continued.


FOR YOUR SAFETY, kindly check your home electric circuit if there is a working ELCB at the main electric panel by prushing the test button. If this main ELCB is rated 100mA, you are advised to change it to a 30mA ELCB. And if you are using INSTANT WATER SHOWER, you are STRONGLY ADVISED to install a 10mA ELCB right before the device !

orchipalar
06-01-2006, 11:49 AM
Have you checked your home's ELCB lately ?

FOR YOUR SAFETY, kindly check your home electric circuit if there is a working ELCB at the main electric panel by prushing the test button. If this main ELCB is rated 100mA, you are advised to change it to a 30mA ELCB. And if you are using INSTANT WATER SHOWER, you are STRONGLY ADVISED to install a 10mA ELCB right before the device !Err...30mA would not be sufficient to operate 1 household aircond...whilst the electric cattle is boiling water...n the maid is trying to do ironing...n 4 little Orchis needs to take a hot shower...so how ar?

kwchang
06-01-2006, 01:05 PM
This should be in the DIY channel and I will be moving it there later.

As for ELCB, I remember touching the exposed live wire of my water heater while it was installed. I felt a buzz where I touched the wire and the power tripped. That water heater was brand new with its own ELCB. I don't think the house ELCB tripped, only the one at the heater. Great stuff. I live to tell the tale.

Life Ranger
06-01-2006, 02:05 PM
Err...30mA would not be sufficient to operate 1 household aircond...whilst the electric cattle is boiling water...n the maid is trying to do ironing...n 4 little Orchis needs to take a hot shower...so how ar?

Orchipalar, the 30mA is the rated leakage current (which current flows from the Live wire thru your body to earth). Normally the current should flow from Live wire thru your electric device and flow back thru Neutral wire. If you touch the Life wire accidentally, current leakage occurs. The rated load current you mentioned here should be about 60A for a normal household.
Just check your ELCB at the main panel, you should see the characters 60A & 100mA labelled on it. Please note that most ELCBs provided by the developer is rated 100mA which does not make provision of proper protection to human body.

Take care.

Life Ranger
06-01-2006, 02:14 PM
This should be in the DIY channel and I will be moving it there later.

As for ELCB, I remember touching the exposed live wire of my water heater while it was installed. I felt a buzz where I touched the wire and the power tripped. That water heater was brand new with its own ELCB. I don't think the house ELCB tripped, only the one at the heater. Great stuff. I live to tell the tale.


kwchang, it was lucky that you were installing the ELCB equipped water heater whose tripping rating may be about 15mA. This also could have proved that your main ELCB is of a higher rated one like 100mA. And if this is true, you would have acquired a much bigger shock, and worst, it wouldn't tripped.. kindly check the main ELCB out...

CCY
06-01-2006, 02:27 PM
Orchipalar, the 30mA is the rated leakage current (which current flows from the Live wire thru your body to earth). Normally the current should flow from Live wire thru your electric device and flow back thru Neutral wire. If you touch the Life wire accidentally, current leakage occurs. The rated load current you mentioned here should be about 60A for a normal household.
Just check your ELCB at the main panel, you should see the characters 60A & 100mA labelled on it. Please note that most ELCBs provided by the developer is rated 100mA which does not make provision of proper protection to human body.

Take care.

Will 30ma rated elcb increases the incidences of those nuisance trip ? You do not want your mains to trip every other day as well just because we want it to be more sensitive. I do not know how much of an instantaneous differential imbalance current that can arise from all your normal electrical appliances added together. But a slight lightning in the vicinity can easily generate enough of such low threshold imbalance current.
Who want to come back after a 3days holiday and find that the meat in the fridge turns bad because of a trip.

keith
06-01-2006, 03:02 PM
Will 30ma rated elcb increases the incidences of those nuisance trip ? You do not want your mains to trip every other day as well just because we want it to be more sensitive. I do not know how much of an instantaneous differential imbalance current that can arise from all your normal electrical appliances added together. But a slight lightning in the vicinity can easily generate enough of such low threshold imbalance current.
Who want to come back after a 3days holiday and find that the meat in the fridge turns bad because of a trip.
In fact, in Singapore it's a requirement for ELCB/RCCB to be rated at 30mA. But in Malaysia, I think it's not practical, as the our wiring is not "clean" enough and 30mA will cause lots of nuisance tripping. Just my 2 sens...

Life Ranger
06-01-2006, 03:04 PM
Will 30ma rated elcb increases the incidences of those nuisance trip ? You do not want your mains to trip every other day as well just because we want it to be more sensitive. I do not know how much of an instantaneous differential imbalance current that can arise from all your normal electrical appliances added together. But a slight lightning in the vicinity can easily generate enough of such low threshold imbalance current.
Who want to come back after a 3days holiday and find that the meat in the fridge turns bad because of a trip.

Some electric workers did provide me with such answer as nuisance tripping might take place. My finding is negative. Actually I have installed an ELCB rated 10mA/40A in my old folk home in Seremban early last year, and so far has no such problem. I have also replaced my USJ house 100mA to 30mA and feel that it trips even fewer during the lightning.....

Any EE specialist here to comment about tripping when lightning ? I once heard a comment saying it is the poor Earthing of the house that causing the ELCB to trip easily...

keith
06-01-2006, 03:06 PM
Err...30mA would not be sufficient to operate 1 household aircond...whilst the electric cattle is boiling water...n the maid is trying to do ironing...n 4 little Orchis needs to take a hot shower...so how ar?
Leakage current is the current flowing in the earth line. It happend when the electrical equipment is not properly insulated, and there is some current flowing to the earth. What you have just described is a situation of potential over-loading, it's different from current leakage.

Life Ranger
06-01-2006, 03:30 PM
Protection Against ELECTRIC SHOCK with Earth Leakage Circuit Breaker (ELCB)
[ ELCB is also called Residual Current Circuit Breaker (RCCB) or Residual Current Device (RCD). ]


ELCBs are devices capable of sensing earth leakage current and interrupting the circuit automatically when these currents exceed a predetermined value. An earth leakage current is the current flowing to earth from live parts of an installation. ELCBs are the core balance type which monitor the difference in the current flowing in the live and neutral conductors. Under healthy conditions the vectoral sum of the currents in the live and neutral conductor will equal zero and no operation is necessary. If an earth fault occurs the live and neutral currents will not balance and the difference will be detected by the ELCB. This imbalance is used to open the circuit and thereby stopping the current flow.

EARTH LEAKAGE TRIPPING CURRENT (SENSITIVITY)

This is measured in milli-amperes (mA) and is referred to as the degree of protection in an accidental shock hazard situation.


The IEC Standard 1008/1009 of 30 mA sensitivity for domestic and personal protection with the tolerance of 30 mA plus zero and minus 50%, that is, a range from 15 mA to 30 mA. ELCBs are manufactured to operate in the tolerance band of 19 to 26 mA.


For personal protection 30 mA offers a high degree of protection and will operate by cutting off the earth fault current well within the time specified in the IEC Publication 1008/1009.


TEST BUTTON

All earth leakage units are provided with a test button. When pressed, the test button causes an imbalance to simulate an earth fault operation. The test button should be pressed often to prove the unit is in working order. If the unit does not trip instantly, expert advice should be sought to check the electrical installation.

CCY
06-01-2006, 03:41 PM
What difference does it make if the threshold is reduce and the response time is increase. You can have a 10ma sensitivity but a delay response to the fault condition. The safety isn't only in the threshold current of 30ma or 100ma but also how fast the elcb is suppose to trip. Current x Time factor will come into play as well and is used by manufacturer to ensure as stable an elcb is to be in normal usage.

orchipalar
06-01-2006, 03:52 PM
Err...the term ~ earth leakage circuit breaker(ELCB)...is incorrectly used...

A residual current circuit breaker(RCCB) can improve the safety of an electrical system but cannot remove all risk of electric shock or fire. In particular, an RCD will not detect overload conditions, phase to neutral short circuits or phase-phase short circuits. Some sort of over-current protection (fuse or circuit breaker must be employed to guard against these occurrences. Combined RCD/circuit breaker units are available, and these combine the functions of an RCD with those of a conventional circuit breaker, responding appropriately to fault currents and overload conditions. These are known as RCBOs, and are available in 1, 2, 3 and 4 pole configurations. RCBOs will typically have separate circuits for detecting current imbalance (RCD function) and for detecting overload current (circuit breaker function); however the device for interrupting the flow of current will be common to both functions.

An RCD will help to protect against electric shock where current flows through a person from a phase (live / line / hot) to earth. It cannot protect against electric shock where current flows through a person from phase to neutral or phase to phase, for example where a finger touches both live and neutral contacts in a light fitting. It is virtually impossible to provide electrical protection against such shocks as there is no way for a device to differentiate between current flow causing an electrical shock to a person and normal current flow through an appliance. Protection against electrical shock of this nature must be through mechanical means (guards or covers to protect against accidental contact) and procedure (e.g. switching off power before undertaking maintenance).

http://en.wikipedia.org/wiki/Residual_current_device

Err...perhaps there is much to learn for everybody here...