Sensitivity of ELCB

You don't. It's already done for you in your national electrical standards. All you have to do is hire a Qualified Electrician to follow them.

100mA? What's the point of that? The poor soul would be dead before it trips!

But on what basis national electrical standards select the sensitivity value?

Avoiding death by electrocution!

Ye gods....

Electrocution occurs at 30mA then why do we have ELCB of 100mAmp and 300mAmp

Er, could be that your circuits are not compliant?

Could be that these items are not intended for final circuits?

Could be that your national standards are out of date?

I can't see what you're doing. You tell me!

Hello RAMconsult. I wonder if you meant Ventricular fibrilation.? The reason I ask is that I have, and have had for several years now, Atrial fibrilation. It is a flaming nuisance, but doesn't seem too deadly.

Thanks for analysing the 92mA calculation. You are right healthy individual can tolerate 30mA till the time ELCB operates

One possibility is circuits for which human contact is unlikely, but electromechanical damage must be prevented. (And also minimizing nuisance trips.)

You've been coming here since 2012 and asking questions that any electrician should already know.

You appear to have "projects" which implies that other people are paying you to know the answers already.

I suggest that you either:

1. Stop taking money to do jobs for which you are not qualified.

2. Hire a qualified electrician, who is qualified.

3. Purchase the applicable code books and LEARN THE CODE REQUIREMENTS yourself.

Sorry lyn you are grossly mistaken. It is not about following electrician blindly. You may be doing not me. If you are not aware about the exact explanation I will furnish in this forum correct explanation with back up from IEC within next 24 hours.

Thanks & Regards

So, why on earth did you post if you already have the answers?

Why on earth I have posted it? Because to know the basis behind following electrician blindly or understand reasoning behind codes. Not only me everybody knows what are the standard sensitivity of ELCB used. Not everybody like you knows reason behind them. Some people acknlodge llke me and try to search some people do not like you and give out of context reply.

Thanks

I'm still waiting for you to, "furnish in this forum correct explanation with back up from IEC".

Where is your latest project? I'd like to monitor the progress.

24 hours have not elapsed yet.

Who's counting?

Lyn dont waste time writing crap. You may have plenty of time to waste, unfortunately I do not have. Other sincere people have responsibly given enough answers/inputs and there technical interpretation accompained by hands on experience. You can go through so that from next time onwards there is no dependency on electrician for proper selection of ELCB.

Good luck

Qualified Electricians follow national standards so that the risk of electrocution, injury, property damage, fires, loss of business, insurance claims and prosecution is negligible.

National standards are based upon best practice, predictive calculation, loss prevention and learning from mistakes.

It's all about liability.

Everybody already knows all of that. However, codes seldom if ever tell the specific whys for their provisions, which is what the OP was legitimately asking. Only RAM has offered any actual rationale, rather than snideness.

Thanks! That would be great.

It would also be great if you did that every time you come to the forum to ask questions that make it sound like you don't know the answers to those questions you ask.

Regards

What nonsense.

Your comment is non sense. Before writing something on technical forum think.

Thanks

30mA for adults,used in final circuits(BS) in CU.. In USA it is 6ma at sockets (receptacles).Infants will be hurt at low levels. There are higher ratings up to 500mA.

Sparky....hmmm

Refer BS 7671. We don't divide 230 by body resistance but by EFLI(earth fault loop impedance) from transformer including resistance of earth electrode,resistance of wires etc

Thanks Obouill IEC 60479 is informatve

This is my memory, I don't remember the which code has this application guidance -

30mA is best for human protection and is recommended for all sockets where hand tools / appliances can be connected and for those circuits dealing with water such as geyser in bathrooms.

100mA also can offer human protection to some extent and is recommended at a higher level (not at individual circuit / socket level). This is a practical necessity as the 30mA ELCB can maloperate with more extensive wiring (and corresponding leakage current exceeding the 30mA threshold under cetain conditions).

300mA can offer no protection for humans but is good enough as a protection against electrical fires.

Just to share.

Alternatively they can be used for effective discrimination-300mA at Main panel, 100mA at sub panel and 30mA at consumer unit or final circuit,6mA in each socket.

with respect, Raghun, yes 300mA is good enough for protetection against fires when those are due to earthe leakage, yes. But the ultimate protection against fires is AFDD (or CAFI, as named un the NEMA world).

About AFDD : http://www.electrical-installation.org/enwiki/Arc_Fault_Detection_Devices_(AFDD)

WHY? Because 6 millamps of electrical current is lethal for/to human beings.

This value is known from actual medical research testing and is not a disputable variable.

Body path resistance/impedance to current flow varies with ambient conditions, applied voltage level, and individual body characteristics.

This is not something anyone in their right state of mind would even consider altering or not complying with.

Back in the old days when the quality of insulation was often poor and suspect, especially heating elements, 100mA or more was required otherwise the ELCB (usually in series with the earth wire) would keep tripping out in normal use - and not helped by doubtful practice of earthing the neutral at point of use.

Modern wiring and equipment (made and tested to modern standards) have nigh on infinite insulation resistance, meaning there is little or no earth leakage to talk of, allowing RCD's with very low leakage protective currents with precise tripping times to be used.

Just as importantly, to be specified in the regulations to prevent people unwittingly inventing their own less safe standards.

Sncere thanks for giving technical inputs. I went through some catalog and IEC. I think:

1. 30mA for 30msec is deemed as the safe cut-off point to avaoid fatalities. 100mA is used to prevent fires. 300mA with adjustable time delay is used for the upstream device to provide discrimination between devices and to protect plant. 300 mA ELCB is used for apps like Lifts since its extremely isolated.
2. To be within zone of the IEC curve as shown in attached curve. It is necessary for the ELCB to operate within 50ms at 240 mA and 150ms at 80mA. Both these conditions are satisfied by 30mA ELCB For households, Individual outlets, Wet areas and temporary installations, ELCB with sensitivity not exceeding 30mA is advisable

When testing rCD in buildings as per BS 7671,at 50% of rated trip current=15mA,it should not trip and at 200% of trip current,it should trip within...mS.