Bulgaria and RCD

Jimj40 · Dec 16, 2014

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!

davesparks · Dec 16, 2014

Gardner said:
davesparks said:

Gardner said:

And that may have been the case, but is still dangerous. In the US TN-C was never allowed for general sockets or circuits. Up until the 1960s we had 2 wire none earthing sockets, however when installing new 3 wire sockets on those circuits we must install an RCD. We CAN NOT jumper the neutral to ground. If we did any electrician could loose their license. It is well known that a neutral can never be guaranteed to function as a grounding conductor passed the service.

Here is how we install 3 wire sockets on old 2 wire circuits:

http://ecmweb.com/site-files/ecmweb.com/files/archive/ecmweb.com/mag/410ecm17fig2.jpg

http://ecmweb.com/site-files/ecmweb.com/files/archive/ecmweb.com/images/201ecmCQfig1.gif

DIY vid, but very detailed and explains the correct way to do it:

https://www.youtube.com/watch?v=twhzCgVst80

First part: The 10 Worst Grounding Mistakes You'll Ever Make | Design content from Electrical Construction & Maintenance (EC&M) Magazine

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Click to expand...

Those pictures show a circuit without an earth, not a TNC installation.

Very different things!

It is still common to find lighting circuits without an earth in the uk, the correct course of action in this situation is to rewire the circuits. Unfortunately there is a tendancy for people to accept RCD protection as an alternative to this.

Click to expand...

Gardner · Dec 16, 2014

davesparks said:
Those pictures show a circuit without an earth, not a TNC installation.

Yes, because you will not find a TN-C installation in the US. And if TN-C was so safe, then why disallow jumping the neutral wire to the earth wire at the socket? Why disallow that but allow a GFCI?

Very different things!

Yes, one concept is safer than the other.

It is still common to find lighting circuits without an earth in the uk, the correct course of action in this situation is to rewire the circuits. Unfortunately there is a tendancy for people to accept RCD protection as an alternative to this.

Rewiring the circuit is the BEST option. I am not arguing that and the OP should do the same. However, if you could not rewire the circuit you only have 3 options:

1. Leave everything ungrounded

2. Jump the neutral to the earth terminals at all lights

3. Or add an RCD

#3 is safer than #2 in that if a neutral broke every light fitting is not energized at 240 volts. Lights just go out. If a fault occurred in the lights a leakage of ever 30ma would trip it.

The installation the OP has would have never flown in the US. Such earthing means came from the Soviet Union (from my understating) and passed to other countries where influence spread. As for the UK I dont think that was the case, but is it safe to say that in the UK if I had a circuit without a ground that I just could not connect the neutral to the frame?

Gardner · Dec 16, 2014

From the article the hazard is clearly spelled out:

There are several ways you can complete this upgrade, many of which are erroneous and strictly against the Code. For example, never apply the following non-NEC-compliant solutions:

Hook up a new grounding receptacle on the theory that this is a step in the right direction. This can lead future electricians and occupants to believe they are fully protected by a non-functioning ground receptacle.
Connect the green grounding terminal of a grounded receptacle via a short jumper to the grounded neutral conductor. This practice is totally noncompliant and dangerous because when a load is connected, voltage will appear on both the neutral and ground wires. Therefore, any noncurrent-carrying appliance or tool case will become energized, causing shock to the user, who is typically partially or totally grounded.
Run an individual ground conductor from the green grounding terminal of a grounded
receptacle to the nearest water pipe or other grounded object. This “floating ground” presents various hazards. It is likely that this ground rod of convenience will have several ohms of ground resistance so that, in case of ground fault within a connected tool or appliance, the breaker will not trip — and exposed metal will remain energized.

Gardner · Dec 16, 2014

4:05 of this video, perfect explanation of why the OPs set up is dangerous:

https://www.youtube.com/watch?v=pObsSoI4-yE

davesparks · Dec 16, 2014

Gardner said:
Yes, because you will not find a TN-C installation in the US. And if TN-C was so safe, then why disallow jumping the neutral wire to the earth wire at the socket? Why disallow that but allow a GFCI?

Yes, one concept is safer than the other.

Rewiring the circuit is the BEST option. I am not arguing that and the OP should do the same. However, if you could not rewire the circuit you only have 3 options:

1. Leave everything ungrounded

2. Jump the neutral to the earth terminals at all lights

3. Or add an RCD

#3 is safer than #2 in that if a neutral broke every light fitting is not energized at 240 volts. Lights just go out. If a fault occurred in the lights a leakage of ever 30ma would trip it.

The installation the OP has would have never flown in the US. Such earthing means came from the Soviet Union (from my understating) and passed to other countries where influence spread. As for the UK I dont think that was the case, but is it safe to say that in the UK if I had a circuit without a ground that I just could not connect the neutral to the frame?

It doesn't matter whether TNC is allowed now or not, of how relatively safe it is or is not.

The OP has an existing TNC installation.

Basing my answers on the current uk wiring regulations, which provide rules for TNC installations, it is incorrect to install an RCD into the installation and disconnecting the earth then relying on an RCD as the sole means of protection is not allowed.

If TNC has never been allowed in the USA and the NEC does not contain any rules for TNC installations then I don't see how this can be used as a point of reference for the OPs situation?

I don't know what installations in the USA are like, other than the usual rumours, but around here spontaneously breaking neutral (or any other) connections are very very rare. Is it a fault you come across with much regularity?

davesparks · Dec 16, 2014

I just don't get why they are advising the replacement of a socket without an earth with a socket with an earth, gfci and a sticky label? Over here the only thing it would get replaced with is a blanking plate!

And as for the comment at 3:30 in the video about the test button being the only legal test for a gfci? Unless your gfci devices are a lot better than RCDs then that sounds like a recipe for disaster.

Gardner · Dec 17, 2014

davesparks said:
It doesn't matter whether TNC is allowed now or not, of how relatively safe it is or is not.

The OP has an existing TNC installation.

Existing does not make it safer, in fact worse. However, my point is that the only way to get an RCD to work is removing the N-G connection at the sockets. And if such were done it would be safer than what existed. Nothing beats a dedicated earth wire, but that is not the case here.

Basing my answers on the current uk wiring regulations, which provide rules for TNC installations, it is incorrect to install an RCD into the installation and disconnecting the earth then relying on an RCD as the sole means of protection is not allowed.

From a BS7671 perspective you may be correct. Do you have the exact section or link? But going by US codes that is exactly what we must do if we found a "boot legged" ground (TN-C system). Any electrican would have to break the jumper and instal either a non grounding outlet or GFCI.

If TNC has never been allowed in the USA and the NEC does not contain any rules for TNC installations then I don't see how this can be used as a point of reference for the OPs situation?

TN-C used to be allowed for ranges and clothes dryers yet disallowed because even though far fewer points of failure existed between the panel and ranges/dryer outlets their were still reports of people being shocked (and even killed) from loose PENs. In once case a PEN was loose and the dryer was energized, the person reached over to the earthed washer and was killed. In Canada TN-C was never allowed for ranges and dryers.

I have personally seen/felt electrified dryers because of loose PENs even though the odds of it breaking on a high capacity circuit with few connections are slim compared to a branch circuit.

And as for people jumping neutral to ground in old house there are well documented cases of both shocks and death resulting. Its even mentioned in the Mike Holt video.

Its not that Americans never used or encountered PEN and are ignorant of how safe or dangerous they are, its that we have encountered them in real life first hand and know full well the risks associated with using them. Those risks have been well documented.

And keep on thing in mind. This is all at 120 volts, often on wood framed floors. The OP is in Bulgaria where most floors are conceret or at least conductive at 220 volts. A shock here is many, many times more likely to be fatal. So the risk is that much greater.

I don't know what installations in the USA are like, other than the usual rumours, but around here spontaneously breaking neutral (or any other) connections are very very rare. Is it a fault you come across with much regularity?

It is a fault I come across every now and then. But you can not tell me it does not happen in other parts of the world. All connections fail here and there. If PEN was so safe it would still be allowed for new installations in the regs.

AND FWIW, PEN was popular in the soviet union. But I know for a fact the soviet union was far away from human progress or logical thinking. The soviet way of thinking destroyed everything it touched, so I am not to keen to take anything they devised seriously.

Gardner · Dec 17, 2014

I just don't get why they are advising the replacement of a socket without an earth with a socket with an earth, gfci and a sticky label? Over here the only thing it would get replaced with is a blanking plate!

Because if the only option is keeping the existing circuit that is the safest option at hand. The best thing to do is replace the whole circuit with 3 wires, but that is often not practical. Nearly all US homes before the mid 60s had 2 wire circuits and 2 wire none earthing sockets. To re-run all those circuits is impossible. Millions of homes would need to be remodeled (opening up plastered walls) to do so.

Perhaps the UK never had none grounding sockets, and that is ok. But in the US millions still exist in older homes. A GFCI circuit is safer than a non GFCI circuit when a ground is absent in both cases.

Yes we could jumper the neutral to ground so we now have a grounding socket, but that is more dangerous than just leaving an appliance ungrounded. Connections fail, and such can kill someone. Again, a broken neutral will electrify all metal.

And as for the comment at 3:30 in the video about the test button being the only legal test for a gfci? Unless your gfci devices are a lot better than RCDs then that sounds like a recipe for disaster.

Our GFCIs have a resistor that when the test button is pushed closes the resistor which puts an imbalance across the coil. Some GFCI will not reset unless the GFCI circuit works adding extra safety.

Our GFCIs have one down fall in that they contain electronics, so a large transient like a lightning strike can harm them. But still this is why we are told to test them frequently, as all RCDs should be.

We all believe, and are all taught in the US, that when no ground wire exists, it is safer to add a GFCI, than to jumper the neutral to the case.

davesparks · Dec 17, 2014

Gardner said:
Because if the only option is keeping the existing circuit that is the safest option at hand. The best thing to do is replace the whole circuit with 3 wires, but that is often not practical. Nearly all US homes before the mid 60s had 2 wire circuits and 2 wire none earthing sockets. To re-run all those circuits is impossible. Millions of homes would need to be remodeled (opening up plastered walls) to do so.

Perhaps the UK never had none grounding sockets, and that is ok. But in the US millions still exist in older homes. A GFCI circuit is safer than a non GFCI circuit when a ground is absent in both cases.

Yes we could jumper the neutral to ground so we now have a grounding socket, but that is more dangerous than just leaving an appliance ungrounded. Connections fail, and such can kill someone. Again, a broken neutral will electrify all metal.

Our GFCIs have a resistor that when the test button is pushed closes the resistor which puts an imbalance across the coil. Some GFCI will not reset unless the GFCI circuit works adding extra safety.

Our GFCIs have one down fall in that they contain electronics, so a large transient like a lightning strike can harm them. But still this is why we are told to test them frequently, as all RCDs should be.

We all believe, and are all taught in the US, that when no ground wire exists, it is safer to add a GFCI, than to jumper the neutral to the case.

There were 2 pin sockets in use once upon a time, and unearthed circuits allowed to feed 3 pin sockets but that is all pre 60's. Any installation of that date will be well beyond the point of needing to be rewired by now!
The 2 pin sockets will predate the unfused round pin plugs which were in general use before our current fused plugs.

The only 2 pin plugs in common use are shaver supplies fed from isolating transformers.

That test button doesn't tell you what time it operated in or what current it operated at though does it? How do you record this on the installation certificates, or is it just a tick box?

Creating a PEN conductor wouldn't even be considered in the uk as a solution to a circuit having no earth.

As I have said the regulations exist for the use of PEN conductors purely to allow for the possibility of installations still using this system.

We are taught that the only solution to a circuit having no earth is to install an earth, either as a separate conductor or by rewiring.
The idea that fitting an RCD and double insulated fittings throughout such a circuit is an absolute last resort if you come across the problem part way through a job etc and the customer refuses to have it out right. If you come across it before you start a job and it affects your work and they refuse to have it put right then you walk away and don't do the job.

Gardner · Dec 17, 2014

davesparks said:
There were 2 pin sockets in use once upon a time, and unearthed circuits allowed to feed 3 pin sockets but that is all pre 60's. Any installation of that date will be well beyond the point of needing to be rewired by now!

But surelly its not practical to rewire every old instillation?

The 2 pin sockets will predate the unfused round pin plugs which were in general use before our current fused plugs.

The only 2 pin plugs in common use are shaver supplies fed from isolating transformers.

Ok, makes sense.

So in truth its not likely that a 2 pin socket will be found anywhere 240 volts 13 amp power is needed?

That test button doesn't tell you what time it operated in or what current it operated at though does it? How do you record this on the installation certificates, or is it just a tick box?

Just a tick box. I know we are not perfect here. The rumors are true, we suck (really bad) at testing. We do have GFCI testers, but usually are just a resistor and nothing fancy.

I do admire your RCD testers in that they will gradually pull more current until a trip takes place. Then it can be recorded down.

Creating a PEN conductor wouldn't even be considered in the uk as a solution to a circuit having no earth.

Thats my point, a reason exists for that. IMO the OP basically has a 2 wire circuit forced to run a 3 pin socket.

As I have said the regulations exist for the use of PEN conductors purely to allow for the possibility of installations still using this system.

How were these existing systems implemented? What were they used for. This has me genuinely curious

We are taught that the only solution to a circuit having no earth is to install an earth, either as a separate conductor or by rewiring.

I agree this is best. But not always doable. If the wires in the OPs case are plastered in the wall, it might not be possible without breaking up the wall. But the OP should definitely try to get a ground.

In the US a separate ground is viewed with mixed feelings. Having a ground outside the cable or raceway increases its impedance. I would imagine in the UK that might effect RCD disconnect times? New NEC installations do not allow a separate earth wire outside of the conduit or cables.

The idea that fitting an RCD and double insulated fittings throughout such a circuit is an absolute last resort if you come across the problem part way through a job etc and the customer refuses to have it out right. If you come across it before you start a job and it affects your work and they refuse to have it put right then you walk away and don't do the job.

This is where practices change. Just the way it is I guess.