No CPC on the lighting circuit but the customer wants a metal fitting!!

[Deleted member 26818]

Has the ECS guidance changed?
It always used to be that the departure was to install a 30mA RCD, Class II fittings, and a notice at the CU warning about the lack of CPC and not to install Class I fittings and accessories.

 

[brman]

Sorry to resurrect an old thread but I am curious about some of the comments here on the ESC guide.
I think the guide makes it clear that all class 1 fittings should have a cpc. BUT, if there isn't a cpc and the customer refuses a rewire or change of fitting what do you do?

The way I read it the guide is saying "do your best to reduce the risk as much as possible". ie. do your risk assessment and except that zero risk is not going to achievable!
So,
1) If there are simultaneous conductive parts accessible then it really is too high a risk, even with an RCD. (RCD being additional protection....). Therefore don't do the job.
2) If there are no simultaneous conductive parts, ie. a low risk of a good earth path then relying on an RCD is an acceptable reduction in risk from the current situation (i.e. not RCD) so do the CU change.

As already pointed out this is not relevent to adding a class 1 fitting to a circuit with no cpc. That is clearly increasing the risk and not acceptable.

Last comment. It has been stated that the cpc must follow the path of the L/N in this situation of fitting a class 1 accessory to an existing circuit. What reg (or logic) requires this?
Again, my logic is that the CPC is being supplied purely to protect the class 1 accessory. Not the circuit supplying it! So as long as there is a reliable earth at the accessory (however achieved) it is acceptable.
Obviously, if installing the circuit from scratch I would need the cpc to follow the L/N to protect the circuit (along with RCDs etc as necessary) but this is a different situation.

Anyone care to give the counter argument?

 

[Deleted member 26818]

The advice given by the ESC (unless it has changed to allow class 1 fittings), is a departure which would provide the same degree of safety as would be provided by compliance with the Regulations.
Care would have to be taken to ensure that there are no exposed-conductive parts, metal fitings, metal accessories or even metal accessory screw heads.
To my mind the fact that there are no exposed or extraneous-conductive parts within reach of an exposed-conductive part of a lighting circuit is not enough.
An earth path can be provided through walls, floors and ceilings.

I agree that there is no requirement for the earthing conductor to follow the L & N of the circuit, the conductor would not be considered as being a circuit conductor (CPC), as it would only be earthing the exposed-conductive part.

 

[brman]

Thanks spinlondon.
The advice in the current best practice guide 1 is that you can change a CU if there is a class 1 fitting without a cpc or earth, as long as there is no exposed or extraneous conductive part within reach - as long as the cct has an RCD fitting. Is this a change from previously?
Assuming this is an change to the advice it is clear it does not afford the same level of safety as the regs but it is certainly better protected than a (pre CU change) installation with no cpc, class 1 fittings and no RCDs. So I guess what they are saying is that the addition of the RCDs is a worthwhile improvement, even if it doesn't meet the intent of the regs.

 

[Deleted member 26818]

Obviously things change.
The ESC/NICEIC have taken the view, that if the metal fitting/s is/are existing, then changing the CU will not impair the safety of the installation, and that by providing RCD protection, safety will be improved.
The problem I have, is how this relates to the Regulations.
Whilst you are not required to update an existing installation, if it complied with the Regulations current at the time of design/construction.
I'm not aware that an unearthed exposed-conductive part has ever complied, certainly not within the last 46 years.
As such I would consider such a situation to warrent a code C2 if I were to conduct a Periodic Inspection.
To my mind providing RCD protection in such circumstances would not rectify the non compliance.
It may reduce the danger, so that a code C3 would be applicable, but would not remove it altogether, it would not comply with the current Regulations and would not be considered (to my mind) as an acceptable 'departure'.

This then poses problems when it comes to certification of the work.
Regulation 632.4 requires: "Defects or omissions revealed during inspection and testing of the installation work covered by the Certificate shall be made good before the Certificate is issued".
Whilst there is no requirement for you to upgrade the existing installation (if it complied at the time of design/construction) and it would be acceptable to note the defect/non-compliance under 'comments on the existing installation'.
If the installation of the RCD is intended to rectify the defect/non-compliance, it would fail inital verification, as the measure would not still not comply, and would not be acceptable as a departure becuse it does not afford the same degree of safety as would be achieved by compliance with the Regulations.

Then of course you have the fact, that by allowing such a situation to be rectified by the provision of RCD protection, you are effectively allowing any or all of the fittings and accessories to be changed to class 1.

I wonder what next the ESC/NICEIC will allow.
Cables concealed in walls outside of prescribed zones, as long as they are protected by RCDs?
Perhaps exposed live conductors, as long as they are protected by RCDs?

 

[brman]

I agree. In a periodic no earth on a class 1 would be a C2 regardless of RCD etc. I don't think RCDs and lack of extraneous conductive parts is enough to make it a C3.

So you are right, you are still leaving a potentially dangerous fault. However I think there are a few mitigating reasons why this is acceptable.
First, as I see it, a certificate for a CU change is not certifying the complete installation. It is certifying the work done (i.e. the CU change) plus the circuits as they affect the operation. So Max Zs, IR, bonding etc is needed to ensure the CU works properly. A good example of this is from my last elecsa assessment. On testing I found a spur of a ring with a Zs of greater than 1.14ohms. if this was something I had just installed I would be failing the test and working out how to get the max Zs down. However as I was just changing the CU I determined it was due to poor design (read as mutiple ring extensions and long spurs done over the years), not bad connections, and noted on the cert that it was high but still within that required by the RCD protection.
In the same way, if I came across cables out of zones I would still do a CU change.

And, to be fair to the ESC, they are not saying that fitting an RCD is rectifying the problem. You still need to inform the client in writing that there is a potentially dangerous fault and also label the CU that there is no CPC in the circuit so only class 2 fittings can be used. All they are saying is that doesn't stop you doing a CU change.

That is the way I read it anyway

 

[Deleted member 26818]

I've had a look at the BPG, and to be honest I'm not happy with it.
It looks like they've altered some of it to allow class 1 fittings, but not considered how that impinges on the parts they have not altered.
Some of it appears contradictory, and some is misleading.
On page 3 they mention that prior to 1966, there was no requirement to provide a CPC for lighting circuits.
However they fail to mention that there would have been no exposed-conductive parts on such a circuit.
The fittings and accessories would have been plastic or bakelite, and either plastic inserts would have been provided in the back boxes to isolate metal screws, or plastic screws would have been used.
On page 4 they mention that there is no legal requirement to upgrade an existing installation to current standards.
Then on page 6 they state that a disclaimer does not absolve the installer from responsibility if the customer does not want their existing installation upgraded.
Again on page 3 they indicate that a CU does not have to be replaced to provide RCD protection for instances where RCD protection is now a requirement. They indicate that there are other methods to provide the required RCD protection.
However on page 7, they indicate that if a CU is replaced, then RCD protection must be provided.
So whist there is no legal requirement to upgrade an existing installation and because of this,we don't have to upgrade the lighting circuit.
It appears that we do have to upgrade the RCD protection even though it is already stated that there are other methods which don't involve incorporating the RCD in the CU.

There is mention that the Building Regulations require that any alteration or addition does not leave the installation any worse in compliance with Section 1 of the Building Regulations, they also mention the Scotish Regulations.
However they do not mention the requirement of BS7671 that an alteration or addition does not impair the safety of an existing installation.
I know that the BPGis quite a small document, but I find it odd that they have left out this particular piece of information, especially as they later suggest that a risk assesment is conducted.
I also find it odd, that the suggest refusing to carry out the work in certain circumstances, despite the fact that conducting the work would not make the installation any less compliant with Building regulations and would not impair the safety of the existing installation. It would in fact improve safety if we were to install a CU with incorporated RCD protection.

I could probably go on, but I can't be asked.
To my mind they updated version is worse than the previous version, and needs looking at again.

 

[brman]

I agree! And I particularly find this bit annoying.....

I also find it odd, that the suggest refusing to carry out the work in certain circumstances, despite the fact that conducting the work would not make the installation any less compliant with Building regulations and would not impair the safety of the existing installation. It would in fact improve safety if we were to install a CU with incorporated RCD protection.

but at least if I follow guidelines from those that say they are experts in electrical safety then I have some small protection if things go wrong.....

 

[Octopus]

We have a duty to not leave a site in a more dangerous state than before we started and in this respect installing a new dual RCD board or one with RCBO's will only make it safer. Plus adding bonding.

So if the lighting doesn't have a CPC and a couple of fittings are metal so what????????????????????

 

[nickblake]

can you get a single earth back to the board and earth it like that or find the nearest earth and connect to that and label the board and note down on your cert ,there is to much relying on RCD's these days and they are not the be all and end all they do fail and often especially if no one tests them they can stick

 

[brman]

can you get a single earth back to the board and earth it like that or find the nearest earth and connect to that and label the board and note down on your cert ,there is to much relying on RCD's these days and they are not the be all and end all they do fail and often especially if no one tests them they can stick

yes, had to replace a crabtree CU the other day as it was reported that "when I push the test button nothing happens. Been like that for years.....". Turns out the side of the RCD was melted and the RCD not operating. Still worked as an isolator though so I am not sure what happened to it. And that was on a TT system so no ADS on the installation for years.