2 core 1.5mm on lights.
- Thread starter Nugget75
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It very much does matter. The armouring is an exposed-conductive-part and must be Earthed. SWA must always be installed properly.
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I can see both points on earth or no earth, since 1966 we have required an earth to lights except for the suspended bit from the ceiling, however since the lights in this case plug in it would be considered as an appliance not a lighting circuit so it could be class II not requiring an earth, however any class II must comply with manufacturers recommendations, so to all bits, becomes a problem, so to in essence use an extension lead would be OK so in theroy an earth wire is run to the joint but no further, which may technically comply but is a little pointless if nothing else could use the extension, we use a two core extension lead with lawn mowers, so what is the difference?
I would use two core and shrink wrap the joint with epoxy lined shrink.
However it does raise technical questions as to when some thing is an appliance and when it is an installation. This could lead to pages of debate, no real cut and dried answer.
I did back in around 1995 get a couple of sets of Christmas lights which are in essence a set of festoon lamps, and I know when I lived in Hong Kong where it really rained not the sprinkle we get here, there were loads of festoon lamps set out and the seemed to survive the rain, however I am still a little wary about using festoon lights on a permanent basis, at work we will set out festoon lighting for an event, but the action of setting it out and collecting it again means the festoon is inspected. Also they are 110 volt (55-0-55).
The same when we use a lawn mover, we inspect the cable every time we put it away, cable will degrade in the sun over time, since the longest one can have between PAT tests is 4 years, I would say one would want to inspect and test at least every 4 years, the problem with domestic is how can the DIY man test, they are unlikely to have a PAT testing machine?
But in the main common sense, under these landers
any lamps would be protected from the rain, so not really a problem, but going branch to branch on the trees forming a hedge it would be very different. So more to do with common sense than trying to interpret the regulations to see if allowed. The wall lamp seen on the next wall (white) would get more of the weather as landers are higher at that point, but you must use common sense to decide is what I am doing safe.
At work the festoons set up for events are higher than any visitor can reach, and we would not re-bulb with lights switched on, so no chance anyone could touch them. I do have some festoon lighting at the rear of my house which can be touched, but around 5 volt, so no danger.
I would use two core and shrink wrap the joint with epoxy lined shrink.
However it does raise technical questions as to when some thing is an appliance and when it is an installation. This could lead to pages of debate, no real cut and dried answer.
I did back in around 1995 get a couple of sets of Christmas lights which are in essence a set of festoon lamps, and I know when I lived in Hong Kong where it really rained not the sprinkle we get here, there were loads of festoon lamps set out and the seemed to survive the rain, however I am still a little wary about using festoon lights on a permanent basis, at work we will set out festoon lighting for an event, but the action of setting it out and collecting it again means the festoon is inspected. Also they are 110 volt (55-0-55).
The same when we use a lawn mover, we inspect the cable every time we put it away, cable will degrade in the sun over time, since the longest one can have between PAT tests is 4 years, I would say one would want to inspect and test at least every 4 years, the problem with domestic is how can the DIY man test, they are unlikely to have a PAT testing machine?
But in the main common sense, under these landers
any lamps would be protected from the rain, so not really a problem, but going branch to branch on the trees forming a hedge it would be very different. So more to do with common sense than trying to interpret the regulations to see if allowed. The wall lamp seen on the next wall (white) would get more of the weather as landers are higher at that point, but you must use common sense to decide is what I am doing safe.At work the festoons set up for events are higher than any visitor can reach, and we would not re-bulb with lights switched on, so no chance anyone could touch them. I do have some festoon lighting at the rear of my house which can be touched, but around 5 volt, so no danger.
Not if none of it is exposed.
I don't see why if it is not actually being used for its SWA characteristics.
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For a start, as EFLI has implied, none of the armour would normally be 'exposed', in which case it could not be an 'eposed-c-p'. It's obviously true that it could become exposed (in places) if the outer sheth were mechanically damaged - but the same is true of anything within any cable that is mechanically damaged.
In any event, even if the armour were totally exposed, it surrounds a 'sheathed' cable which would be regarded as 'safe to touch' even if there were no armour - so, in common sense terms, there's really no reason why it must be earth.
Thee outer surfaces of PVC cables (whether T+E, flex or whatever) frequently come into contact with metal objects. Do you therefore feel that any such metal objects must be regarded as 'exposed-c-ps', and therefore 'earthed'?
Kind Regards, John
You will find that cable armouring is always considered to be an exposed-conductive-part, whether or not it is exposed to the touch. Likewise metallic conduit/trunking is always considered to be an exposed-conductive-part. Indeed the IET Guidance Notes explicitly state this.
As I asked, if that is the case, then does the same apply to anything else metallic which might come into contact with the outer surface of an insulated-and-sheathed cable? ... and if not, why the inconsistency?
Kind Regards, John
just to add that with SELV no earth should be present
I would think that depends upon what you mean by "present". If the cable is insulated and sheathed, there is nothing prohibiting its outer surface coming in contact with earthed items (whether it is carrying SELV, some other type of ELV or LV), so I don't see why it would not be acceptable for it to have an earthed covering (outside of the sheathing) as part of the structure of the cable. After all, I don't think anyone is suggesting that it is not permissible to put an SELV cable within earthed conduit, are they?
It's in some senses the opposite of the issue I'm trying to get some sense about from Risteard. When an outer earthed armour/covering is not required, it is quite possible that the outer surface of an insulated-and-sheathed cable will come in contact with metal objects, particularly in the case of flexible cables (metal door knobs, metal furniture etc.) but it would neither make sense, nor be practical, to regard all such objects as "exposed-c-ps" which were required to be earthed - and I don't see why earthed armour within the structure of a cable (outside of the sheath) should be any different from any other 'metal object'.
Kind Regards, John
What? What does exposed mean?
When earthed, does that not then make it a CPC?
Are parts (correctly) considered to be extraneous-conductive-parts whether or not they are extraneous?
Is it?
John, by earth present,, i was meaning yes it`s ok and good for it to be close by and useable if needed in future. However not so close by and useable to be touchable whether deliberately or accidentally whilst touching a SELV wiring system , the S in SELV means separated and this must be preserved for safety. in other words a selv system is completely floating in respect to earth voltages at all times upon the whole system.
indeed the world could be a lot safer if all our mains voltages were completely floating in respect to earth (think bathroom shaver socket for example), however just one connection (resistive, capacitive or inducive) albeit accidentally means we have an earth which is the opposite polarity of any Live conductor except the N. In most situations we can not maintain an earth free system
indeed the world could be a lot safer if all our mains voltages were completely floating in respect to earth (think bathroom shaver socket for example), however just one connection (resistive, capacitive or inducive) albeit accidentally means we have an earth which is the opposite polarity of any Live conductor except the N. In most situations we can not maintain an earth free system
Yes, most of us ('regulars') probably understand all that, but it doesn't really alter what I said. If (as is the case) the outer surface of an insulated-and-sheathed cable carrying SELV is 'allowed' to come into contact with earth, or earthed items, then I don't see why it should cease to be 'allowed' if the 'earthed item (outside of the sheath of the cable) were part of the construction of the cable.
Again, I imagine that most of us agree with that. Other than in very localised environments, having an earth-referenced supply is an inevitable and unavoidable evil. If we attempted to have a floating supply network, I would expect that the incidental/accidental connections to earth would apply roughly similarly to both sides of the supply, in which case both sides ought to end up at potentials relative to earth of roughly half the 'between-sizes' supply potential.
Kind Regards, John
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Ok, (the regulators seem to considered that important).
What am I missing?
Isn't that the point of SELV so that it doesn't matter if you touch an earth; be it an installation earth or anything touching the planet?
Right, so what did you mean by the above?
OK. with SELV no part of the supply should have any reference to earth at all so that any power is one polarity or the other polarity and nothing else and all such voltages are extra low
No argument with any of that, but I still don't see why that precludes having an earthed conductor within the physical cable (separated from the SELV conductors by two layers of insulating material), provided that earthed conductor is not in any way connected to either side of the SELV supply.
If you're going to say that capacitive 'connection' to the earthed conductor is an issue, then there should be a (totally impractical) requirement to avoid a cable carrying SELV to get anywhere near anything earthed !
Kind Regards, John
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