Ceiling downligts replacement.

bengasman · 30 Apr 2018

Good day leccy gurus and thanks for your help in advance.
I'm replacing the old, cheap rubbish downlights with new model that meets energy, fire and sound requirments.
Apart from the construction being a pain it the you-know-what to put in, I found they are wired up with regular 3-core flex. Is that: fine, not ideal but no problem or really not acceptable and have to be rewired with T&E.
The new ones are 5 Watt led so virtually not heat production compared to the old halogens.

Taylortwocities · 30 Apr 2018

3-core flex is fine. I guess the old and new lights are mains (230volt)?
If so, don't forget that the earth connection may be necessary for the new lights, even if the lights are Class II, the earth should be continuous through to the last light.

bengasman · 30 Apr 2018

Muchas gracias senhor. The new ones are metal case so do need all three wires any way.
I very much doubt that whoever stuck them in originally had the foggiest idea what he was doing any way. Fire regs were breached. Metallic parts not earhted. Cables run hither and yon, partially as spurs partiaclly in series, and so on so I don't have to worry too much about maintaining the line but will test each one seperately just to be sure when it's all done.

Taylortwocities · 30 Apr 2018

Even though they have a metal case, they may be Class II (Double Insulated). If so you MUST NOT attach an earth to them.
Double insulated items have a symbol like this on them.

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Taylortwocities
30 Sep 2009
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bengasman · 30 Apr 2018

There is not class II mention but there is an earth provision on the connector and an earth symbol on the housing.
I never knew that it was a no-no to connect an earht to doubled insulated items. What is the bad thing/danger/risk about it?
It is very common for boiler controls etc to be class II now but often the wiring was originally for metal housings. What should I do with the obsolete earth/cpc or whatever you want to call it in the old cables? You'e not supposed to just cut them off or even 'terminate' them on a floating terminal strip, I know that much.

Taylortwocities · 30 Apr 2018

If there is no Class II sign, and an earth connection, then the item needs to be earthed.

If youintroduce an earth to a class II item you may be creating a PD that should not exist.

The manufacturer’s instructions will tell you if to earth, or not. And you gas men always follow the MIs, don’t you?

Taylortwocities · 30 Apr 2018

bengasman said:
You'e not supposed to just cut them off or even 'terminate' them on a floating terminal strip, I know that much.

Terminating strip is fine. The earth will be needed for testing of the wiring. You know, EFLI, etc.

bengasman · 30 Apr 2018

Taylortwocities said:
...If youintroduce an earth to a class II item you may be creating a PD that should not exist....

PD???
Wossathten? A Pouble Denetration? What does it stand for?
As for the doing things to MIs, they never mention something like: 'This is a class II item so no earth needed, and if you're existing cable has an earth included, this is what you should do'.
RFM is possibly my most used expression but I was referring to the old cable, not to the newly connected item. What do I do with that bit of yellow/green that was needed on my old Honeywell zone valve but not necessary for the new class II model?

Taylortwocities · 30 Apr 2018

PD=Potential Difference.
Just put the redundant earth lead into a bit of insulated terminal block. Or disconnect it from the wiring centre.

ban-all-sheds · 30 Apr 2018

bengasman said:
As for the doing things to MIs, they never mention something like: 'This is a class II item so no earth needed, and if you're existing cable has an earth included, this is what you should do'.

I think he meant in general. Like putting boilers on 3A fuses even though nobody has a clue as to why.

EFLImpudence · 30 Apr 2018

bengasman said:
As for the doing things to MIs, they never mention something like: 'This is a class II item so no earth needed,

They do generally (always?) state "This {appliance} must not be earthed".

JohnW2 · 30 Apr 2018

EFLImpudence said:
They do generally (always?) state "This {appliance} must not be earthed".

I keep seeing that said, but is it actually true?

A lot of Class II items do not really have anything metal to earth, so such a statement would be a bit moot. Even when there is metal, they will presumably not normally be supplied with any 'earth terminals' which connect to that metal, so I'm not sure how anyone would be expected to 'earth it' without in some way modifying the item, even if they wanted to.

I have even seen it said that some Class II items come with an instruction that an earthed conductor 'must not enter' them - but I've certainly seem some which provide a terminal (connected to nothing) in which one can park a 'not needed' earth conductor.

Kind Regards, John

EFLImpudence · 30 Apr 2018

We've been through all this before.

JohnW2 said:
I keep seeing that said, but is it actually true?

Yes.

A lot of Class II items do not really have anything metal to earth, so such a statement would be a bit moot.

It would, but it would stop people coming on here to ask about it.

Even when there is metal, they will presumably not normally be supplied with any 'earth terminals' which connect to that metal,

Presumably because the manufacturer considered a connection to do what should not be done is not necessary.

so I'm not sure how anyone would be expected to 'earth it' without in some way modifying the item, even if they wanted to.

They are are not expected to do it nor want to do it.

I have even seen it said that some Class II items come with an instruction that an earthed conductor 'must not enter' them - but I've certainly seem some which provide a terminal (connected to nothing) in which one can park a 'not needed' earth conductor.

Presumably not in the Class 2 parts.

JohnW2 · 30 Apr 2018

EFLImpudence said:
Yes.

I can't argue with what you've seen, but, for my part, I'm sure that I have seen plenty of Class II items which do not come with an instruction that it "must not" be earthed (in at least some cases probably because there isn't really anything 'earthable').

EFLImpudence said:
Presumably not in the Class 2 parts.

I can't say that I've ever come across any item which indicates that some parts of it are Class II and some aren't.

Kind Regards, John

winston1 · 30 Apr 2018

bengasman said:
partially in series,

I very much doubt that that is the case. They'd be very dim if so. Are some of the lights very dim?

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Ceiling downligts replacement.

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