Confused by loop-in lighting fitting

[JohnW2]

Can't comment on the OP's product - but as far as I can see the Loop/Earth terminal on the MK model is just a 'parking' area for the cables, whichever one you use and is not linked to any of the metal parts of the rose itself.

I agree totally, on both counts. As you say, it's clear that the MK one has an 'isolated' terminal which can be used for 'parking' anything one wants. However, as you say, we can't (or shouldn't!) comment on the OP's product - which is why I think it very unwise indeed to advise him to connect the Ls to a terminal which, for all we know, might possibly be connected to exposed parts of the fitting, don't you?

Of course, it's an issue which could be resolved in 5 seconds if eitehr you or I were there with a meter.

Kind Regards, John

 

[JohnW2]

Exactly, reveralt. John, it's a plastic batten lampholder. Does it have any exposed conductive parts?

Dunno. If it's totally plastic, there's obviously no issue. However, that's far from a foregone conclusion ...

Untitled

• JohnW2
• 6 Nov 2013
• 1

Kind Regards, John

 

[stillp]

Every batten holder I've seen for the last few decades has a shroud to prevent contact with the metal part of the bayonet fitting.

 

[JohnW2]

Aha, so a real loop terminal is isolated, just a way to pass through without needing a connector block to join the wires. That would make sense.

Exactly.

I see. Who'd have thought a simple lamp-holder could be such a mine-field. It was a cheap brand but sold on screwfix and with a lot of positive reviews from (one assumes) knowledgeable people - reviews from people talking about buying dozens of the things.

There's probably nothing wrong with the product (although the instructions are unacceptable), provided one understands exactly what it is (i,e, what that third terminal is).

I can certainly get access to a multimeter to test although from memory the fitting is all-plastic other than the wired terminals and the actual bayonet push-terminals inside.

If it really is all plastic (with the exceptions you mention), then there is no issue. If the ring into which the bayonet lamp is inserted is metal, you would need to test with a meter on its continuity (or low resistance) range to make sure that there was no connection between that metal ring and the third terminal.

I'm leaning towards the approach in the diagram I posted in which case the suspicious loop/earth terminal would just be used for the earth wire anyway.

Do you mean by using a junction box? If so, then, yes, you'd then only be using the third terminal as a parking place for the earth wire, which would not be a problem.

Kind Regards, John

 

[JohnW2]

Every batten holder I've seen for the last few decades has a shroud to prevent contact with the metal part of the bayonet fitting.

Those I pictured are all brand new, relatively recently purchased, ones. I obviously removed the screw-on shrouds for the purpose of photography, but one can easily touch the metal part of the bayonet fitting (and simultaneously the pins) in all three cases, (if there is no lamp inserted) even with the shrouds on.

Kind Regards, John

 

[riveralt]

If the OP's Screwfix model is the Marbo Excel Loop in and Angled Batten Lampholder then these are the instructions in the packaging at the moment.

View media item 68606

 

[JohnW2]

If the OP's Screwfix model is the Marbo Excel Loop in and Angled Batten Lampholder then these are the instructions in the packaging at the moment.
View media item 68606

Agreed, IF that's what the OP has got, then there is no problem - so it depends upon what you are prepared to assume. It's at least good to see that they've now got the diagram correct. The OP will, of course, still have to terminate the earths/CPCs in something.

Kind Regards, John

 

[stillp]

one can easily touch the metal part of the bayonet fitting (and simultaneously the pins) in all three cases, (if there is no lamp inserted) even with the shrouds on.

So what. One could touch the live pin if there was no lamp inserted, and grap an earthed object with the other hand. Touching both pins, or one or both at the same time as the metal part, might cause a burn but there won't be any current flow through the heart.

 

[d000hg]

If the OP's Screwfix model is the Marbo Excel Loop in and Angled Batten Lampholder then these are the instructions in the packaging at the moment.

View media item 68606

Where did you get that from? It's the same product (not sure mine is angled but otherwise identical) and I bought mine only about 10 days ago.

Bad batch maybe?

 

[JohnW2]

one can easily touch the metal part of the bayonet fitting (and simultaneously the pins) in all three cases, (if there is no lamp inserted) even with the shrouds on.

So what. One could touch the live pin if there was no lamp inserted, and grap an earthed object with the other hand. Touching both pins, or one or both at the same time as the metal part, might cause a burn but there won't be any current flow through the heart.

Oh, c'mon - you're sounding a bit like me in my more 'pragmatic moments', but even I would not go anything like that far ....

(a) since when was it regarded as acceptable to have exposed nearby conductors at L and N potential, on the basis that a consequential shock would go through one's finger and (possibly) not through one's heart?

(b) if (a) is not enough for you, what if one touches the bayonet ring (connected to 'permanent live') at the same time as steadying oneself (on a ladder?!) by grasping a nearby water pipe with one's other hand (one's heart will then be at least partially in that current path!)?

I have a feeling that you must have been kidding

Kind Regards, John

 

[stillp]

(a) since when was it regarded as acceptable to have exposed nearby conductors at L and N potential, on the basis that a consequential shock would go through one's finger and (possibly) not through one's heart?

Since the invention of the bayonet lampholder?

 

[JohnW2]

(a) since when was it regarded as acceptable to have exposed nearby conductors at L and N potential, on the basis that a consequential shock would go through one's finger and (possibly) not through one's heart?

Since the invention of the bayonet lampholder?

Maybe I should have added that the 'L potential' in question (present context) was a 'permanent L', present even when the light was switched off.

In any event, what about my (b)? Do you really think it would be acceptable to have a touchable bit of metal which is 'permanently live' (unless the whole circuit was powered down or isolated), given that one cannot guarantee what else one's body might be in contact with simultaneously with touching it? The (frightening) analogies I could think of are endless!

Kind Regards, John

 

[stillp]

Where's this permanent live connection then John?

We've lived with these issues since the bayonet l/holder was invented. The metal bayonet ring doesn't need to be earthed since it is not exposed in normal service.
Many years ago they didn't even have those shrouds.

 

[riveralt]

Where did you get that from? It's the same product (not sure mine is angled but otherwise identical) and I bought mine only about 10 days ago.

Bad batch maybe?

I will have got it from Electrifix (Trade side of Screwfix).
I just opened it from my stock so could be several months old.
The straight loop in batten has the same instruction set.
I would take your instructions and product back to Screwfix and complain about the dangerous instructions they have given you.
I have emailed Electrium they make this brand for Screwfix.

 

[JohnW2]

Where's this permanent live connection then John?

This infamous 'third terminal', adjacent to an earth symbol. If, per the proposals, this was used to join the L supply feed to the permanent L of the switch cable, that terminal would obviously be 'permanently live'. If (and I accept that it probably isn't) that terminal were connected to a metal 'bayonet ring', that ring would also become 'permanently live'.

We've lived with these issues since the bayonet l/holder was invented. The metal bayonet ring doesn't need to be earthed since it is not exposed in normal service.

We've had to live with some things, but not anything (let alone the 'bayonet ring') which was live even when the light was switched off. However, you're probably right that those rings never are connected to an earth terminal. However, if it were me, seeing an earth symbol next to the terminal, I think I would spend the few seconds required to confirm that it wasn't connected to the ring before using it for an L conductor, rather than 'just assuming' - and I suppose I was thinking that the same "don't assume" philosophy should also be the basis of advice given remotely to an OP in this forum! I've certainly been taken to task in the past for much lesser deviations from 'giving safe advice' than that (although he didn't appear this Monday ).

Many years ago they didn't even have those shrouds.

As you know,I'm old enough to have experienced that era

Kind Regards, John