Will an RCD offer any protection in a building with NO earth circuit?

[AmatuerinCambodia]

I live in Phnom Penh, Cambodia and people die here regularly by electrocution. There is no earth wiring in the buildings, just live and neutral.

I am a member of an expats forum and the question arises: Will using an RCD device offer any protection at all?
I understand RCD's will go off with any leakage and that may have to include the human being the earth. At the moment my apartment has 8/16/32 amp circuit breakers and nothing else.

I can buy plug-in type RCD units to go between an appliance (like the washing machine) and the wall socket. Will this offer any protection even it is me being the earth!

 

[brianmoooore]

the problem is, the off button or test button on the rcd will use the earth to create a small imbalance between the L and N to test the internal circuits of the rcd.
if you have nothing connected to the earth terminal then this will not work.
the rcd should still work but you will be unable to test it.

That's not how the test button works on any RCD that I've encountered. The test circuit takes current from the 'in' side of one pole and the 'out' side of the other, so the 30mA that flows when the test button is pressed only flows through the sensing coil on the side where the test current is taken from the 'out' pole.
This arrangement does not rely on any earth connection, allows the RCD test circuit to operate whichever end is used for supply and load, and disconnects the test circuit as soon as the RCD trips, allowing the resistor in the circuit to be rated at much less than the 7W it would otherwise need to be rated at in case someone held the test button in.

 

[timhoward]

If the appliance is not connected to earth then the RCD will not have any earth leakage current to detect, until your body provides a path when you touch it. So the RCD with no earth won’t trip.

Welcome to the forum by the way!

Also, a tip for the speed readers - the above comment is one that people need to read carefully in the context of the direct question above it (about whether an RCD provides any early warnings of no earth connection) as opposed to the original question in this post about whether an RCD improves safety if there's no earth connection at all.

 

[brianmoooore]

Also, a tip for the speed readers - the above comment is one that people need to read carefully in the context of the direct question above it (about whether an RCD provides any early warnings of no earth connection) as opposed to the original question in this post about whether an RCD improves safety if there's no earth connection at all.

Agreed! I failed to do the above, which is why my answer to the question has been edited into rambling gibberish.

 

[Mike Johnson]

@Rockingit Your research would tend to indicate that a neutral earth connection at the transformer does exist, although not guaranteed, How can this be verified by the home owner?

 

[ipf]

@Rockingit Your research would tend to indicate that a neutral earth connection at the transformer does exist, although not guaranteed, How can this be verified by the home owner?

It seems there is only one answer to that......but not recommended looking at past records over there.

 

[Rockingit]

International distribution systens are fascinating, and completely dispel the myth that Brit is best, too. For example I'm currently in Australia, in basically a Brisbane city suburb. Walking down the road and I realised when glancing at the poles that the same pole is carrying both HV and LV - Conventional delta HV on top and then intermittently it drops down via a TX onto the LV lines and appears as 3PN. Earthing (that I've seen, anyway) is TT. A simple idea that must save on costs massively whilst delivering constancy over long distances.

 

[Mike Johnson]

The power providers in France leave the earthing arrangements to the home owner so TT systems are the norm, most electricians carry large SDS drills for that purpose.

 

[ElectroChem]

International distribution systens are fascinating, and completely dispel the myth that Brit is best, too. For example I'm currently in Australia, in basically a Brisbane city suburb. Walking down the road and I realised when glancing at the poles that the same pole is carrying both HV and LV - Conventional delta HV on top and then intermittently it drops down via a TX onto the LV lines and appears as 3PN. Earthing (that I've seen, anyway) is TT. A simple idea that must save on costs massively whilst delivering constancy over long distances.

Australia's LV distribution is almost exclusively PME/TNCS, here called MEN (Multiple Earthed Neutral). You'll find very few TT systems here.

 

[pc1966]

Australia's LV distribution is almost exclusively PME/TNCS, here called MEN (Multiple Earthed Neutral). You'll find very few TT systems here.

But you do have single-wire eath return HV systems where the Earth is your return path?

That is about TT as you can get LOL!

 

[GeeGee50]

If the appliance is not connected to earth then the RCD will not have any earth leakage current to detect, until your body provides a path when you touch it. So the RCD with no earth won’t trip.

But isn't there still a leakage / loss of current if the appliance develops a ground fault (i.e. the active/live wire touches the appliance chassis/casing)? Therefore, this will create an imbalance of current between Live and Neutral and therefore the RCD will still trip?

 

[brianmoooore]

But isn't there still a leakage / loss of current if the appliance develops a ground fault (i.e. the active/live wire touches the appliance chassis/casing)? Therefore, this will create an imbalance of current between Live and Neutral and therefore the RCD will still trip?

Only if the unearthed appliance is in contact with the general mass of earth, which is by no means certain, since many appliances sit on rubber or plastic feet.

 

[westward10]

But isn't there still a leakage / loss of current if the appliance develops a ground fault (i.e. the active/live wire touches the appliance chassis/casing)? Therefore, this will create an imbalance of current between Live and Neutral and therefore the RCD will still trip?

Not if it is not connected/isolated from earth. Live will touch the casing, have no where to go and not create an imbalance.

 

[Thrubstack]

Surely when you touch a live circuit, your body provides a path to earth, that will result in an imbalance and the RCD trips.

 

[brianmoooore]

Yes, there's a good chance that your body will provide a path to earth and imbalance the currents, with the result that the RCD trips.
This will probably save your life, but it will still hurt.

 

[HappyHippyDad]

Yes, there's a good chance that your body will provide a path to earth and imbalance the currents, with the result that the RCD trips.
This will probably save your life, but it will still hurt.

Can you really say a 'good' chance? If you see post number 9 your body will only provide a pathway to earth if the neutral point of the transformer is earthed. I have absolutely no idea if this would be common practise in the OP's country.

I suppose it couldn't actually do any harm by using a plug in RCD. It would either not work, so you're no worse off, or it would work and probably safe your life. So I guess it's a good idea. However, by using an RCD you may feel a sense of security and take greater risks!