Underground earth from supplier but overhead supply?

[bernardgreen]

Was it?

non compliant to have two RCDs

I recall the meter installer's boss saying at first that two RCDs were not compliant.

 

[aptsys]

Hi Securespark,

What advantages over TT does TN-C-S have?

Thanks!

Lower Ze, but that's it. A fault to earth is unlikely to trigger overcurrent devices on a TT supply, but may on a TN-C-S or TN-S supply

 

[securespark]

What advantages over TT does TN-C-S have?

Well, back in the days when regs were different, a TT - TN-C-S conversion was a relatively easy way to make a dangerous situation safe.

When I was a maintenance electrician, I would often come across a TT install with an old Wylex board and no earth electrode or RCD or alternatively a defunct VO- ELCB.

Fitting bonding and getting the DNO to provide an earth terminal would provide the bare minimum for safety. Granted, there would still be no RCD protection, but my job in this situation was to leave the installation a whole heap safer than it was.

 

[John D v2.0]

Was it?

No, it's non compliant not to have 2, as it's not adequate separation of circuits. Perhaps the objection was that there was no single main switch to isolate the whole installation.

 

[ban-all-sheds]

non compliant to have two RCDs

I recall the meter installer's boss saying at first that two RCDs were not compliant.

Yes, I know that's what you said they said.

Which is why I asked if it was non-compliant.

 

[bernardgreen]

Which is why I asked if it was non-compliant.

The man in the office with the authority to over-ride the decision of the meter installer told me that having two RCDs was the reason the meter installer was justified in not installing the meter. Does this not suggest that having two RCDs made the installation non compliant with the regulations in force at that time. ?.

The man in the office with the authority to over-ride the decision of the meter installer told me that having two RCDs was sensible when safety on site was taken into account and for that reason the meter installer would be told to install the meter. Make of that what you will.

Now you have the information there is no need for you to ask for the information again.

Perhaps the objection was that there was no single main switch to isolate the whole installation

There was a single switch, The meter fed a 4 way consumer unit ( no RCD but main switch ) 2 MCBs one fed the caravan via RCD 1 and the second MCB fed the site sockets via RCD 2. The caravan was a single ring final with lighting plugged into socket. This was acceptable to the man in the office. I recall the metal work of the caravan had to be bonded to the PME earth even though this would have been a serious shock hazard if the network Neutral had failed. Hence a very low impedance ground rod was installed.

 

[ban-all-sheds]

The man in the office with the authority to over-ride the decision of the meter installer told me that having two RCDs was the reason the meter installer was justified in not installing the meter. Does this not suggest that having two RCDs made the installation non compliant with the regulations in force at that time. ?.

It suggests that that could be the case.

And, of course, if you are certain that people like the meter installer, and the person in the office, could not possibly have been wrong about what the regulations prohibited, a certainty which you could reasonably hold if you have never, ever encountered or heard of situations where people have been wrong, then the answer is "Yes, it did contravene the regulations".

The man in the office with the authority to over-ride the decision of the meter installer told me that having two RCDs was sensible when safety on site was taken into account and for that reason the meter installer would be told to install the meter. Make of that what you will.

What I make of that is that it is quite possible that the regulations did not prohibit having two RCDs.

Now you have the information there is no need for you to ask for the information again.

Well, I don't have the "information", as in an answer to my question.

You've just repeated, for the second time, i.e. imparted for the third time, the information that the meter installer told you that 2 RCDs was forbidden, and that someone else later said it was OK to have them.

You still have not answered the question about whether it really was forbidden.

OK - fair enough, you don't know. And neither do I, which is why I asked the question.

From a position of not knowing, you could have said "I don't know". But instead you decided to keep repeating what you had already said about being told it was forbidden, and claim that I now had the answer, and didn't need to ask again.

Quite why you decided that that was the appropriate way to respond to my question I cannot begin to imagine. But you are excused from any more involvement. The combination of you not knowing the answer and writing obfuscating replies is of no value or interest to anyone.

 

[ban-all-sheds]

it was non compliant to have two RCDs

Does anyone here other than Bernard know if it was?

 

[securespark]

What are you getting at?

What Bernard installed was akin to a "17th Ed" consumer unit, but of course this installation was erected under the 14th.

 

[ban-all-sheds]

What I am getting at was did the 14th Edition forbid having a split-load CU with 2 RCDs? The fact that something was not required until a particular Edition does not automatically mean that it was forbidden in all earlier ones.

 

[flameport]

What I am getting at was did the 14th Edition forbid having a split-load CU with 2 RCDs?

No. While nothing is specifically mentioned about split load or any other type of CU, the applicable regulation states 'one or more earth-leakage circuit-breakers'.

Two or more was probably an unusual arrangement at the time, but was permitted.

Image from 14th edition, 1976 reprint including amendments, which was the last 14th edition, the next being the first 15th edition in 1981.

 

[securespark]

Can't find it in the 14th Ed at the moment, but latter day regs say something like, these regulations are a minimum standard, there is nothing to say the standard cannot be exceeded.

314.1 in current regs concerns division of installation to avoids danger and hazards.

I cannot find any equivalent regulation in the 14th except for this footnote to Table A.2:

Note 2 -- In the interests of good planning it is undesirable that the whole of the fixed lighting of an installation should be supplied from one final sub-circuit.

 

[ban-all-sheds]

No. While nothing is specifically mentioned about split load or any other type of CU, the applicable regulation states 'one or more earth-leakage circuit-breakers'.

Two or more was probably an unusual arrangement at the time, but was permitted.

Thanks.

It what I thought would likely have been the case.