CPC as live conductor now OK?

[JohnW2]

I think there's a typo in there somewhere. 514.4.3 is about PEN conductor identification.

No typo, a green and yellow conductor oversleeved with blue is the identification for a pen conductor so presumably cannot be used for a cpc used as a neutral (should a plumber wish).

Ah, I see. Interesting one, that . 514.4.3 indicates the two possible means of colour-identification of a PEN, but nothing I can see in the regs specifically says that those colurs cannot be used to identify anything else (on the contrary, see my next paragraph). I agree, however, that it is odd ('naughty'?) if a particular means of identification by colours can have two different meanings.

In fact, it could be argued that 514.4.3 is the thing which is 'naughty', since the implication of everything else in 514.3 and 514.4 is that an oversleeving over-rides the colour underneath - i.e. that G/Y oversleeved with blue should indicate neutral and blue oversleeved with G/Y should indicate a protective conductor.

In any event, I would have to struggle pretty hard to think of a situation (at least, with 3-core cable) in which I would want to oversleeve a G/Y for use as a neutral. That would presumably arise only if I wanted the cable to carry two different neutrals and a L of some sort. With >3 cores, I suppose there might be some situations in which one wanted two separate neutrals (with corresponding Ls), but I would have thought that would be extremely rare. Even then, if one was hell-bent on oversleeving G/Ys, one could probably re-arrange things such that the G/Y was oversleeved with brown and something else oversleeved with blue.

As for the lighting circuit, I believe we recommend, no insist on, the fitting of only suitable accessories or rewiring.

If you replaced, say, a ceiling rose on such a circuit with a 'suitable accessory', would you feel able to sign a minor works cert, even though no CPC was run to that accessory, such that the end result was not BS7671-compliant?

Kind Regards, John

 

[EFLImpudence]

If you replaced, say, a ceiling rose on such a circuit with a 'suitable accessory', would you feel able to sign a minor works cert, even though no CPC was run to that accessory, such that the end result was not BS7671-compliant?

Yes, Just not compliant with the latest edition.

With the necessary recommendations, notes and warnings what else could you do?

 

[JohnW2]

If you replaced, say, a ceiling rose on such a circuit with a 'suitable accessory', would you feel able to sign a minor works cert, even though no CPC was run to that accessory, such that the end result was not BS7671-compliant?

Yes, Just not compliant with the latest edition. With the necessary recommendations, notes and warnings what else could you do?

Fair enough. For me it would be no problem - I just wasn't sure to what extent scheme-registered electricians had a problem with work which is not compliant with current regs.

Do I take it that you'd only do this if you believed the situation was compliant with the regulations operative at the time it was originally installed?

Kind Regards, John

 

[mfarrow]

I don't really understand that view. There is an explicit regulation which requires a CPC to be run to every accessory. There is even one explicit exception (insulated pendant lamholder) mentioned in the reg.

That specific regulation is under the sub-chapter 411 Protective Measure: Automatic Disconnection of Supply (ADS). That is just one of four protective measures against electric shock, which includes Double or Reinforced Insulation (including Class II equipment and accessories). Each may be used separately or in conjunction with each other, depending on the proposed application.

The limitation to using Class II on its own is stipulated under sub-chapter 412 in 412.1.3:

Where this protective measure is to be used as the sole protective measure... it shall be verified that the installation or circuit concerned will be under effective supervision in normal use so that no change is made that would impair the effectiveness of the protective measure. This protective measure shall not therefore be applied to any circuit that includes a socket-outlet, luminaire supporting coupler (LSC), device for connecting a luminaire (DCL) or cable coupler, or where a user may change items of equipment without authorisation.

Now, it's a shame the regulations don't define the term 'user', which I would mean to be someone not involved in carrying out replacement of accessories or equipment, but some others may interpret to be otherwise. However to me, whichever definition you apply, the chance of someone changing my Class II luminaire in the loft is no more than someone replacing the pendant lampholder for one of these, especially when it goes yellow and starts smelling of cigarettes or fish:

What makes you feel that there is room for exercising any discretion in deciding whether or not to comply with this regulation for accessories other than insulated pendant lampholders?

Where using ADS as the main protective measure, I'm not suggesting there is, however if one wanted to consider it, there is always room for departure at the designer's consideration as described in 120.3 and 120.4.

 

[Iggifer]

Fair enough. For me it would be no problem - I just wasn't sure to what extent scheme-registered electricians had a problem with work which is not compliant with current regs.

Do I take it that you'd only do this if you believed the situation was compliant with the regulations operative at the time it was originally installed?

Kind Regards, John

http://www.esc.org.uk/fileadmin/user_upload/documents/industry/best_practice/BPG1v2_web.pdf

this has some good information on how to approach lighting circuits with no CPC's, it's mostly related to CU changes, good advice nonetheless

 

[JohnW2]

I don't really understand that view. There is an explicit regulation which requires a CPC to be run to every accessory. There is even one explicit exception (insulated pendant lamholder) mentioned in the reg.

That specific regulation is under the sub-chapter 411 Protective Measure: Automatic Disconnection of Supply (ADS). That is just one of four protective measures against electric shock, which includes Double or Reinforced Insulation (including Class II equipment and accessories). Each may be used separately or in conjunction with each other, depending on the proposed application.

That is all true. Most people have obviously been taking the last paragraph of 411.3.1.1 (which requires a CPC to be run to 'every point and accessory') as being something which applies generally, not only if one is relying on ADS. Are you suggesting that this regulation does not apply to circuits which do not (or cannot) rely of ADS as a protective measure?

The limitation to using Class II on its own is stipulated under sub-chapter 412 in 412.1.3:

Where this protective measure is to be used as the sole protective measure... it shall be verified that the installation or circuit concerned will be under effective supervision in normal use so that no change is made that would impair the effectiveness of the protective measure. This protective measure shall not therefore be applied to any circuit that includes a socket-outlet, luminaire supporting coupler (LSC), device for connecting a luminaire (DCL) or cable coupler, or where a user may change items of equipment without authorisation.

Now, it's a shame the regulations don't define the term 'user', which I would mean to be someone not involved in carrying out replacement of accessories or equipment, but some others may interpret to be otherwise.

Indeed - and, as you say, the definition of "under effective supervision" is crucial. I've always had some difficulty in understanding exactly what they intend to mean - and this, of course, applies equally whether or not there is a CPC run to the accessory/load in question. If what is at the end of the cable is Class II, then it will not (cannot) be utilising ADS - even if there is a CPC in the cable, it will not be connected (electrically) to the Class II equipment. It will therefore be relying on double insulation as its protective measure, which seemingly is only allowed if it is "under effective supervision" - and, as I said, that's seemingly true of any Class II equipment, regardless of whether or not a CPC is run to it.

What makes you feel that there is room for exercising any discretion in deciding whether or not to comply with this regulation for accessories other than insulated pendant lampholders?

Where using ADS as the main protective measure, I'm not suggesting there is, however if one wanted to consider it, there is always room for departure at the designer's consideration as described in 120.3 and 120.4.

True, but both 120.3 and 133.5 (which used to be 120.4) require that any such 'discretionary departures' do not result in a lower degree of safety than would be achieved by compliance with the regulations - so one would have to have a good argument that such was not the case.

Kind Regards, John

 

[JohnW2]

http://www.esc.org.uk/fileadmin/user_upload/documents/industry/best_practice/BPG1v2_web.pdf
this has some good information on how to approach lighting circuits with no CPC's, it's mostly related to CU changes, good advice nonetheless

Thanks. I'll take a look.

Kind Regards, John

 

[mfarrow]

Are you suggesting that this regulation does not apply to circuits which do not (or cannot) rely of ADS as a protective measure?

Yes, in the same way as you wouldn't apply anything you read in chapter 70, unless you had circuits in any of the special locations mentioned.

Indeed - and, as you say, the definition of "under effective supervision" is crucial. I've always had some difficulty in understanding exactly what they intend to mean - and this, of course, applies equally whether or not there is a CPC run to the accessory/load in question.

Too true, and IIRC, although I don't have a BGB in front of me, the regulations also request trained supervision (or words to that effect) for any IT circuits. Now, I can imagine why this is the case for IT circuits with IR monitors, as you'd need to know what to do when the buzzer on the box sounds and you send someone out to investigate the first fault. The question is, is that really the same thing as a user having a piece of fixed equipment on the wall which they shouldn't be removing unless they're (in the eyes of BS 7671) competent to do so anyway, and which would require the use of tools etc?

My personal opinion is that in 20 years time ADS will start to be phased out in fixed installations (perhaps starting with lighting circuits), in much the same way as it has on portable appliances. It will certainly save a lot on copper costs, which can only continue to rise.

 

[JohnW2]

Are you suggesting that this regulation does not apply to circuits which do not (or cannot) rely of ADS as a protective measure?

Yes, in the same way as you wouldn't apply anything you read in chapter 70, unless you had circuits in any of the special locations mentioned.

I can sympathise that logic - which, of course, would change a fair bit of what has been written in this thread (in a direction that many people wouldn't like!).

My personal opinion is that in 20 years time ADS will start to be phased out in fixed installations (perhaps starting with lighting circuits), in much the same way as it has on portable appliances. It will certainly save a lot on copper costs, which can only continue to rise.

Who knows, but I personally somewhat doubt it, not the least because of the cables themselves. After all, there are some people who would like a move in the opposite direction, to insist on a CPC in cables/leads supplying portable Class II equipment. Admittedly this is mainly about 'additional protection' (i.e. RCDs), but a CPC is a CPC.

Kind Regards, John

 

[plugwash]

Some devices are very difficult to design in a class 2 manner. Switched mode power supplies are one example. To meet EMI regs there needs to be a high frequency path between input and output, for class 1 devices that's no problem you put capacitors between the input and mains earth and either tie the output to mains earth or put capacitors between output and mains earth

For class 2 devices the capacitors have to be placed between input and ouput. This causes a major design conflict, the safety people want small caps for less input-output leakage, the EMI people want large capacitors to minimise high frequency impedance. For small PSUs a compromise can be found that works for both groups but for larger PSUs this can be difficult. Furthermore even if the capacitors are small enough to satisfy the safety regulators they can still cause problems.

Ever wonder why most laptop PSUs now have an earth connection?

So while I could see a potential for phasing out earthing on lighting circuits phasing it out on socket circuts seems a whole lot less practical.

 

[EFLImpudence]

Do I take it that you'd only do this if you believed the situation was compliant with the regulations operative at the time it was originally installed?

You would have to presume that it was, wouldn't you?

Even if it were installed yesterday (by a plumber) you can't issue a compulsory rewiring order.

 

[JohnW2]

Do I take it that you'd only do this if you believed the situation was compliant with the regulations operative at the time it was originally installed?

You would have to presume that it was, wouldn't you?

I don't really understand. You might, for example, know it had been originally installed recently enough for it to have been non-compliant with the regs even then. I was essentially asking whether you would still feel able to issue a certificate (with the deviation from current regs mentioned in it) if that were the case.

Even if it were installed yesterday (by a plumber) you can't issue a compulsory rewiring order.

No-one is suggesting that you could. My question was about the circumstances under which a scheme-registered electrician could issue a MWC (or an EIC, come to that) in relation to work which ended up with an installation which is not compliant with current regs (with 'deviations' noted).

To clarify my thinking .... I would have thought that, in general, it would makes little sense (and hopefully wouldn't be regarded as 'acceptable') for an electrician to issue a certificate noting deviations which render the installation totally unsatisfactory/unsafe (e.g. {extreme example!!} "Shower isolator switch replaced. Deviations: supply cable noted to be of far too small CSA and fed via an RCD but no OPD other than service fuse"). However, I accept that one situation in which there might be a 'reasonable excuse' is if the deviant parts of the installation were compliant with regs when originally installed.

Kind Regards, John

 

[EFLImpudence]

I think this might be a bit too hypothetical.

Do I take it that you'd only do this if you believed the situation was compliant with the regulations operative at the time it was originally installed?

You would have to presume that it was, wouldn't you?

I don't really understand. You might, for example, know it had been originally installed recently enough for it to have been non-compliant with the regs even then.

If I did know for certain because I saw it being installed yesterday (why wasn't I doing it?) then I would refuse to connect the light (why wasn't whoever did it fitting the light?).

However, if it was already there and merely requiring a light to be replaced, what else could I do apart from as I said above?

I was essentially asking whether you would still feel able to issue a certificate (with the deviation from current regs mentioned in it) if that were the case.

I can only note in 'comments on existing installation' any defects found and explain to customer.

As long as the certificate records the situation correctly it is correct.
As long as my work has no 'deviations' then it is correct.

(You do mean 'deviations' (i.e. not to current regs.), don't you? 'Departures' are another thing - just being sure.)

Even if it were installed yesterday (by a plumber) you can't issue a compulsory rewiring order.

No-one is suggesting that you could. My question was about the circumstances under which a scheme-registered electrician could issue a MWC (or an EIC, come to that) in relation to work which ended up with an installation which is not compliant with current regs (with 'deviations' noted).

Yes it is done all the time as long as the tests on what is there are satisfactory.
This is still applying to the lighting circuit.

To clarify my thinking

I'm sure that's not necessary.

.... I would have thought that, in general, it would makes little sense (and hopefully wouldn't be as 'acceptable') for an electrician to issue a certificate noting deviations which render the installation totally unsatisfactory/unsafe (e.g. {extreme example!!} "Shower isolator switch replaced. Deviations: supply cable noted to be of far too small CSA and fed via an RCD but no OPD other than service fuse"). However, I accept that one situation in which there might be a 'reasonable excuse' is if the deviant parts of the installation were compliant with regs when originally installed.

Ah, but that's completely different than just 'newer regulations'.
The shower example is actually dangerous and if not allowed to rectify I would not touch it.
I would probably leave disconnected.
A lighting circuit which has been there for years without a cpc and fitted with only class II equipment is completely different.

I think you have chosen a bad example for comparison.
A better one would have been an old car without seat belts.

Clunk, click. Whoops.

 

[JohnW2]

I don't really understand. You might, for example, know it had been originally installed recently enough for it to have been non-compliant with the regs even then.

If I did know for certain because I saw it being installed yesterday (why wasn't I doing it?) then I would refuse to connect the light (why wasn't whoever did it fitting the light?).

Well, the customer might well tell you when it was installed, particularly if you asked. Anyway, particularly for those cases in which one is not sure as to when the work was done, I can think of a slightly more 'relaxed' criteria which one might apply - namely whether what has been done in the past would ever have been compliant with the prevailing regs during credibly recent decades.

I was essentially asking whether you would still feel able to issue a certificate (with the deviation from current regs mentioned in it) if that were the case.

I can only note in 'comments on existing installation' any defects found and explain to customer. As long as the certificate records the situation correctly it is correct. As long as my work has no 'deviations' then it is correct.

Fair enough.

(You do mean 'deviations' (i.e. not to current regs.), don't you? 'Departures' are another thing - just being sure.)

I meant "not to current regs" - but, as above and below, I was thinking of things which, at some point in history, would have been compliant with the prevailing regs.

.... (e.g. {extreme example!!} "Shower isolator switch replaced. Deviations: supply cable noted to be of far too small CSA and fed via an RCD but no OPD other than service fuse").

Ah, but that's completely different than just 'newer regulations'. The shower example is actually dangerous and if not allowed to rectify I would not touch it. I would probably leave disconnected.

Exactly. As above, I think there is a big distinction to be made between "has become non-compliant (with currentg regs) because of newer regulations' (but would have been compliant at some point in history) and "never would/could have been compliant with prevailing regulations".

[
A lighting circuit which has been there for years without a cpc and fitted with only class II equipment is completely different.

Again, exactly. That is an example of the first of the two scenarios I just mentioned ('newer regulations'), whereas the hypothetical shower scenario would be an example of the second one ('would never have been compliant').

I actually think that we are more-or-less agreeing.

Kind Regards, John