Earth funnies and phantom voltages on lighting circuit

[JohnW2]

Read what I put. I was talking there about Class I luminaires.

You were, but you seemed to be talking in the context of your repeated mentions of 412.2.3.2, which refers to (any) items of Class II equipment", not just luminaires. Apologies if I misunderstood.

Where you have a cable in and a cable out, an earth terminal is needed to ensure earth continuity round the circuit to comply with the reg.

not "to comply with the reg". 'The reg' ( 412.2.3.2) merely requires that a CPC be run to every point/accessory, so is really only relevant if there could otherwise be no CPC at all (since connected Class II equipment did not require one). If there are two (or more) CPCs going 'in' and 'out' (i.e. a looped cable/CPC), then there is obviously a need for them to be joined together (to achieve continuity), but that's nothing to do with the requirements of 412.2.3.2 (which would, in any event, strictly speaking be satisfied even if the two CPCs were not joined).

 

[securespark]

You've lost me.

This is getting ridiculous!

"Run to and terminated".

That would not be terminated if they were just present but not connected to each other.

 

[SimonH2]

.Despite what Harry says I don't think this was an 'amateur' job at the time*. Most of it seems legitimately done - as part of a big loft and kitchen extension job- just a question of trades maybe cutting a few corners here and there. . . . . I expect they were getting fed up with being told to install yet ANOTHER 2-way light switch . . . . .

* 'at the time' in this case probably means late '90's or early 22000's.

Back then, the building trade was a wild west when it came to electrical work - with anyone who thought they knew one end of a screwdriver from the other doing the electrical work. Kitchen fitters had the worst reputation for that.
The result was the changes to building regs in 2005 making most electrical work notifiable - and allowing a new class of charlatan to appear.

So you can't make any assumptions about the competence of those doing the electrics then.

As the regulation states, it is purely in case it is needed in the future.
A daft reason for a regulation in my opinion.

I disagree.
Just in this one thread we've had mentioned multiple items of equipment thatvare not safe on a lighting circuit unless earthed.
Given plenty of evidence that such things do get fitted regardless - and "metal light switches that SWMBO likes" being a common one - I think it makes sense to require there to be a functional earth to be available anywhere that such an item might be fitted.

 

[securespark]

You've lost me.

This is getting ridiculous!

"Run to and terminated".

That would not be terminated if they were just present but not connected to each other.

I think Sunray was more successful in being diplomatic than I.

The classic situation is a lighting circuit with loop and CPC terminal at the rose providing continuity to the switch and of course subsequent roses and switches

 

[EFLImpudence]

... but Class II fittings will not have an earth terminal.

What? Like the Aurora AU150? Double Insulated with earth terminal to provide continuity......

That's a 'transformer'.

 

[EFLImpudence]

This could be debated as well:

 

[securespark]

That's a 'transformer'.

It has the double insulated symbol on it....

 

[securespark]

This could be debated as well:

View attachment 393789

What is there to debate?

 

[EFLImpudence]

What is there to debate?

Well - as the regulation states and with that definition in mind, the (unwanted) CPC shall be run to and terminated at the point, not necessarily to the current using equipment itself which is not a point.

It not being a good idea to have an earthed conductor in Class II items.

 

[ericmark]

That would not be terminated if they were just present but not connected to each other.

That was my thought, unless changed it did say 411.3.1 A circuit protective conductor shall be run to and terminated at each point in wiring and at each accessory except a lampholder having no exposed-conductive-parts and suspended from such a point.

Many thermostats and the like have a parking terminal for the earth wire. Down lights in the main are not suspended, so do need an earth wire, even if class II.

In real terms, folding the earth wire over, and putting a bit of earth sleeve on it, where it does not feed onwards is not going to cause a problem. But the regs, at least in 2008, say terminated not just run. A chock block would likely comply, as would one of the maintenance free units.

I have looked at many down lights, and thought they are simply not compatible with the UK regulations. Why are they offered for sale? Some thermostats also seem to be lacking the parking terminal.

 

[JohnW2]

You've lost me. .... This is getting ridiculous! ... "Run to and terminated".
..... That would not be terminated if they were just present but not connected to each other.

I'm sorry that I seem to have caused confusion which, as I've suggested, seems to be due to the fact that we have been talking 'at cross purposes'.

It is now apparent that you have been thinking and talking about a situation in which there is 'looping' of cables at the point/accessory/luminaire/whatever - and in that situation I agree with everything you've been saying.

However, I have been thinking and talking about 'all other situations' (i.e. no 'looping'). In those situations, there is only one cable and one CPC, so nothing 'to connect to each other' and no consideration of 'continuity' between anything and anything else - so all one can do (to satisfy the reg) is 'park' an unused CPC ('terminate' it in a 'floating' terminal, or whatever) . It was because I was thinking of that ('one cable') situation that I did not understand why you kept talking about 'continuity'.

Does that help to explain the reason for the confusion?

 

[JohnW2]

.... and "metal light switches that SWMBO likes" being a common one - I think it makes sense to require there to be a functional earth to be available anywhere that such an item might be fitted.

Maybe - but, as always, I think one needs to think/debate how far it is reasonable to go in anticipating changes to an electrical installation which might be implemented in the future.

It's also almost academic in terms of any new wiring, since (unless it's wired in 'singles') it would inevitably be done with T+E - so, unless some idiot 'cut the CPC back', there inevitably would be a CPC available at every 'point' in a circuit.

 

[JohnW2]

View attachment 393792

Well - as the regulation states and with that definition in mind, the (unwanted) CPC shall be run to and terminated at the point, not necessarily to the current using equipment itself which is not a point.

I think that's probably verging on semantic 'quibbling' since it could probably be argued that, say, the 'input terminals' of an item of current-using equipment constituted "a point" (as defined).

It not being a good idea to have an earthed conductor in Class II items.

I see no problem with an earthed conductor being "in" (inside) a Class II item, per se. What is theoretically 'not a good idea' is to have that conductor electrically connected to anything 'touchable' - which would not be the case if the earthed conductor were merely 'parked' somewhere within the item.

 

[SimonH2]

Maybe - but, as always, I think one needs to think/debate how far it is reasonable to go in anticipating changes to an electrical installation which might be implemented in the future.

In this case we know it's fairly common, so perfectly reasonable to anticipate that such changes are likely.

It's also almost academic in terms of any new wiring, since (unless it's wired in 'singles') it would inevitably be done with T+E - so, unless some idiot 'cut the CPC back', there inevitably would be a CPC available at every 'point' in a circuit.

Sadly, we know it's all to common for corner cutting clueless ****wit idiots to do just that. It's one thing if they just don't connect the CPC - then it's possible (if you can find all the ends) to go round and connect them. It's another thing if they cut the ends back.

And then we get situations like at our church. Lights in PVC twin sans CPC - and then you need to modify a circuit. Rewiring isn't an option so that means adding a CPC by whatever means is practical.

 

[JohnW2]

In this case we know it's fairly common, so perfectly reasonable to anticipate that such changes are likely.

As I said, "maybe".

Sadly, we know it's all to common for corner cutting clueless ****wit idiots to do just that.

I'm not really sure what you're suggesting. The regs already require that at least one CPC is run to every 'point'/accessory etc. If someone installs wiring that does not achieve that, they have simply contravened the regulation - and I can't see what more the regs can do, beyond 'requiring it' (which they already do). What did you have in mind?

It's one thing if they just don't connect the CPC - then it's possible (if you can find all the ends) to go round and connect them. It's another thing if they cut the ends back.

True - but I have to say that, in my person experience, it has very rarely been the case that there is a 'cut back' CPC and so little slack in the cable that it's impossible to expose/retrieve enough of the CPC to 'connect' to it.

And then we get situations like at our church. Lights in PVC twin sans CPC ...

As you presumably noticed, I was talking specifically about 'new wiring' and that would hopefully not done using cable without a CPC (even if one could find some), would it?