Bulgaria and RCD

[Jimj40]

Hi, All - and greetings from a newbie in Bulgaria!

I wasn't sure if this should go in the DIY section or here, since both are relevant, so apologies if I made the wrong choice.

In a nutshell, our house in Sofia is "old", ie 1990(!) and very substantial. There is a supply coming in which is earthed but, as is often the case here, the circuits themselves aren't earthed as such but what would be the earth is actually tied to the neutral. Just to make things more "interesting" all the cables, even new ones, are just plastered into the walls.

We have some stainless steel outside lights, which are welded onto a ss balustrade around the garden. Obviously, I wanted to get some sort of RCD protection at least for the outside lights but our local well-qualified electrician said there was no point since there was no real earth in the circuit. I have to assume that he is correct but I'm none too crazy about lights outside without any means of guarding against grabbing a metal balustrade and becoming the new earth conduit myself....

So, any thoughts about how I might be able to build in better protection without gutting the whole house would be gratefully received!

 

[ImpededLoop]

Welcome!

It would give you better protection to install an RCD, even if the circuit has no CPC (earthing). However, the installation should be tested first to ensure that there are not any faults that would cause nuisance tripping frm an RCD.

 

[Jimj40]

Thanks - that sounds a lot more reassuring than I was dreading!

Now I just have to work out HOW to get it into that circuit (I'm pretty sure that putting one in the consumer unit would give me nuisance trips all day long). It's all stuffed into the one round continental-type hole for a double switch with power coming in and then 2 circuits going out to different sets of lights - oh, and I didn't mention that the switch is set into wood panelling...at least the smoke-alarm might tell me when I have a short!

 

[davesparks]

You say what would be the earth is tied in to the neutral, do you mean it is operating as a TNC arrangement with a single PEN conductor operating as both neutral and earth?

 

[Jimj40]

You say what would be the earth is tied in to the neutral, do you mean it is operating as a TNC arrangement with a single PEN conductor operating as both neutral and earth?

I'd love to answer that if I only understood the question!

Basically, the earth terminal in any given socket is connected to the neutral, ie there are 2 wires connected to neutral. Likewise, back at the consumer units, earth and neutral are connected to neutral. Apparently it's fairly normal here, especially in older properties, but it doesn't thrill me particularly....

 

[davesparks]

Sounds to me like a TNC installation, they were allowed in the uk up until the end of the 13th edition.
The current regulations include requirements for them should an existing installation need to be repaired or modified. From memory I think one of the requirements is that RCDs must not be fitted.

 

[ImpededLoop]

You've answered Dave's question well. He wanted to know if the neutral conductor was also being used as earth which you confirmed.

In the UK the electricity suppliers use this method, but inside the property we have 3 separate wires for live, neutral and earth.

Edit.. Dave answered whilst I was typing!

 

[Jimj40]

You've answered Dave's question well. He wanted to know if the neutral conductor was also being used as earth which you confirmed.

In the UK the electricity suppliers use this method, but inside the property we have 3 separate wires for live, neutral and earth.

The new/decent installations here also have "normal" 3-wire connections but not the older properties As you may imagine, there are also plenty of cowboy sparks over here, some of them from the UK, I'm sorry to say. It's interesting that some expats insist on having a UK electrician installing UK-spec ring mains here, which I believe are illegal here - although the insurance companies love them as non-EU-standard installations are a get out of jail free card for them.

 

[ImpededLoop]

Sounds to me like a TNC installation, they were allowed in the uk up until the end of the 13th edition.
The current regulations include requirements for them should an existing installation need to be repaired or modified. From memory I think one of the requirements is that RCDs must not be fitted.

Regulation 543.3.3 says "A switching device shall not be inserted in a protective conductor...."

So as Dave says, an RCD shouldn't be used for combined neutral and earth installations.

This might be a situation where a single pole RCBO would be useful to just isolate the line conductor.

 

[davesparks]

This might be a situation where a single pole RCBO would be useful to just isolate the line conductor.

Now there's an interesting point!

 

[ImpededLoop]

Now there's an interesting point!

I thought that might attract your attention.

 

[Gardner]

Hi! And Welcome!

An RCD does not need an earth to function. It is purely a differential devices. The sum delta of current. I would add a 30ma 230 volts GFCI the breaks both poles and call it good.

 

[ImpededLoop]

Hi! And Welcome!

An RCD does not need an earth to function. It is purely a differential devices. The sum delta of current. I would add a 30ma 230 volts GFCI the breaks both poles and call it good.

It does, but if the neutral is also the cpc you can't break that.

 

[davesparks]

Hi! And Welcome!

An RCD does not need an earth to function. It is purely a differential devices. The sum delta of current. I would add a 30ma 230 volts GFCI the breaks both poles and call it good.

It may not need the earth to function, but it certainly shouldn't be installed such that it breaks the earth.

We have established that the installation is using a PEN (protective earthed neutral) conductor rather than having a seperate earth and neutral earlier in the thread. Advising him to now install a protective device which breaks this conductor is very I'll advised.

 

[Gardner]

It does, but if the neutral is also the cpc you can't break that.

I agree, but in this case the ground to neutral bond must be removed at the sockets protected in order for the RCD to function without sporadic tripping.

It may not need the earth to function, but it certainly shouldn't be installed such that it breaks the earth.

We have established that the installation is using a PEN (protective earthed neutral) conductor rather than having a seperate earth and neutral earlier in the thread. Advising him to now install a protective device which breaks this conductor is very I'll advised.

I agree that a PEN should never be broken, but useing TN-C all the way to a socket passed the main incomer is a very bad idea. He will need to remove the jumper and convert the PEN to a neutral. Even if his RCD never broke the PEN it will always trip. You can not use an RCD on a TN-C system even if it does not break the PEN.