hope your question is regarding earth leakage relay and elcb. ELR is used to trip the circuit with contacts and ELCB/RCB is directly connected in the circuit.

No, my question is 'is either better than an earthed 3 wire circuit, without breaker'. There are many two wire circuits here, no earth or ELCB or other breaker. I think that fitting with an ELCB provides better protection than earthing, but am willing to be proven wrong. All ears!

English 101 is just down the hall. "Better" is subjective. ELCB and earth are for 2 different things. -- JHF

Please read these:

Earth leakage circuit breaker - Wikipedia, the free encyclopedia

Working Principle of Earth Leakage Circuit Breaker (ELCB) and ...

Thanks Joshi, I am aware of the way these operate. I am wondering what are the arguments in favour of these, vs the usual three wire active / neutral / earth? The reason I ask is that some jurisdictions are ordering earths to be installed on old two wire systems. My guess is that and ELCB / RCD is a better way to go.

I would think an ELCB is better as more sensitive. A fuse works by blowing and thus isolating the circuit, if a low enough resistance is put between live and earth. Also blows if the appliance overloads, but main protective function is against live getting in contact with the earthed body of the appliance, which is readily touched. But fuse blows at about 2 x rating (100% overload) and if you touch a live terminal it could kill you without blowing the fuse.

An ELCB or similar works by detecting earth current or imbalance between live and neutral currents, and trips at a non-lethal 30ma, typically. A fuse (or MCB) is still needed to blow on appliance overload, which does not cause earth current or current imbalance .

You do realise an ELCB needs an earth?

Jim, My ELCB only has two wires in, and two out - active & neutral. No provision for any other connection.

What Jimrat is saying is that you need the earth/grounding wire also.

Every plug should have an earthed wire coming to it, NOT through the ELCB /RCD but from your distribution board or the like. This will allow the appliance to be earthed so that any leak to the housing of the appliance (If metallic ...) will be detected by the RCD/ELCB before any person touches it, and trip off the power supply to the offending item.

In that case it's not an ELCB, it's an RCD, which trips on detecting imbalance between live and neutral currents (if I've got my terminology right, maybe RCD covers both).

Not sure which is considered better by the experts, current imbalance has the advantage that if you touch a live terminal and external earth with your other hand, it will trip, but ELCB wouldn't. Neither protects if you touch live and neutral, but anybody crazy enough to do that probably needs a shock.

You explained what i was intimating. E (earth ) L ( leakage ) C ( circuit ) B ( breaker ). I also now believe it to be an RCD. Still, the house needs an earth.

No, it doesn't. Not at the device.

However, it won't work if the supply isn't earthed at the local distribution transformer.

I concur.

look my friend , first earth is for protection against electrostatic charges , and protection for machines But ELCB is a protection for people against shock

so this is for purpose and the other for another purpose

if the equipment isn't eartherd then you can't use elcb because it's principle of work depends on earth

regards

Better or worse, you need to follow the electical practices in your country, Boss, because your building insurance company can wriggle out of a claim if you don't and there is an incident because of it. Wrigging out of claims is what Loss Adjusters do for a living.

Don't you need proper earthing for an ELCB to work too?

For a time, there were voltage-operated ELCBs and current-operated ELCBs now called RCCB (Residual Current Circuit Breakers) or RCDs (Residual Current Devices). Voltage-operated ELCBs are not now permitted by IEE regulations or other standards because accidents occurred where the earth connection was lost, leaving the supply on with a false sense of security.

The answer to the question is that the two supply wires, line and neutral, should be connected through the RCCD AND the earth wire connected directly through a connector or earth bar.

Some appliances will have an earth terminal or a third (earth) wire in their cable, some - all insulated like a plastic hair dryer or transformer insulated like a laptop power supply - will have two wires in their cable.

AND

No you don't. You can infer a ground leak by Kirchoffs first law, then break the circuit.

I am also of the opinion that ELCB doesn't require earthing (earthing of the equipment to be precise)to work, as it is based purely on the unbalance b/w phase & neutral.If a person touches a faulty unearthed equipment,the ELCB will still trip if the current goes above its rated leakage tripping current.

I meant system earthing

In the UK it depends what class of equipment you are supplying. Something in a plastic type enclosure (class ii double insulated) can never become live so a 2 wire supply is ok. Anything with exposed metal work (class i - metal kettle) needs an earth connection as well.

RCDs can and do fail. We are supposed to regularly test them .........

the old ELCB was banned. If the earth became disconnected the unit failed but more likely a fault on a neighbours equipment would bring your kit out.

If there is any exposed metal work about give it a better path to earth than your body - it usually pays off.

A little bit of knowledge is a dangerous thing! When I talked of ELCB, I was speaking generically & was thinking of two wire RCD, such as I have. Yes, ELCBs do require an earth. RCDs do not. So let me rephrase the question; in an older building fitted only with 2 wire power, what would be better - fit it with an RCD, or add the third (earth) wire? What can be said in favour of either option? Thanks, Stuart. P.S. No real 'laws' here -

I do understand what you are asking. I only hope that you understand that the answer is an unequivocal " fit an effective earth wire."

As an aside. What part of the world are you in? To not have laws to keep people safe must provide for some interesting statistics re cause of death. I could also envisage a sound argument for removing the less wary from the gene pool and your country should be able to prove the efficacy that an absence of 'nanny laws' provides. You should have a very sound gene pool by now.

Slightly left of due North from you, but we can still see the Southern Cross at midnight around Songkran.

Gene pool shows no improvements - wet season floods continue to kill from exposed wires in public spaces. And some at home.

The best solution would be to rewire it and bring it up to the latest standards, as embraced within British Standard 7671.