Socket for vacuum cleaner from lighting circuit?!

[JohnW2]

Sorry, I was referring to the double socket off a ceiling rose in a public area off a lighting circuit (if that indeed is what it actually is).

Oh, fair enough. In that case, as I went on to say, although not something that most of us would do, or than many of us 'like' seeing (perhaps just because of habit) the arrangement could well be compliant with regs (give or take the couple of caveats I mentioned) and does not really represent any significant 'safety' issue.

Surely anyone carrying out an EICR can use his discretion if someone is clearly stupid whatever the wording of the regs.

Opinions will obviously vary as to what is 'stupid' but, in general, if something is 'coded' (as a 'defect') on an EICR that should relate to s non-compliance with some regulation in BS7671. The inspector's discretion comes into it in deciding which code to give. To code as "C2" (which is the 'lowest' code which 'requires' remedial action, the inspector's opinion has to be that the defect is "Potentially dangerous - urgent remedial action required" - and I would suggest that it would probably be difficult to argue that such was the case with what we are talking about.

I can understand a socket on a lighting circuit in a discrete place feeding say an under cupboard light but a double socket in a public place in a hotel is something altogether different. Yes an overload will ‘only’ trip the lights but frequent ‘power cuts’ as seen by customers is not good for customer service.

As I've said, in a hotel it's probably unlikley that the lighting circuits are only 6A. They could well be 16A - and, to put that in context, if the socket were supplied by a 20A radial, no-one would be complaining at all. In any event, if there were ever any 'power cuts' as a result of the arrangement,they would surely be extremely rare (not 'frequent'). In fact, as I've said, the only likely large load I can imagine being plugged into that socket is a vacuum cleaner, and that would usually not be being used whilst the restaurant was occupied by any customers.

Kid Regards, John

 

[JohnW2]

What about my other point of why does the circuit have to (still ?) have a 6A OPD?

The actual number are obviously pretty arbitrary but, as you go on to say, I can but presume that the reason why 5A was chosen (subsequently changed to 6A, because of 'preferred number' considerations) was to allow smaller cable to be used than had all circuits been 15A or 30A.

Now in the day of LEDs, I imagine that if the regs allowed cables of 'tiny CSA' to be used in installations, we might well be seeing "1A lighting circuits"

Kind Regards, John

 

[JohnW2]

I wonder if we refered to them as X circuits (x representing the fuse or breaker nominal rating) might be more helpful?

We sometimes do - and, as I have recently written,I think that our absent friend's concerns relate primarily to "6A circuits", not "lighting" ones.

Kind Regards, John

 

[EFLImpudence]

The actual number are obviously pretty arbitrary but, as you go on to say, I can but presume that the reason why 5A was chosen (subsequently changed to 6A, because of 'preferred number' considerations) was to allow smaller cable to be used than had all circuits been 15A or 30A.

Yes. Exacerbated by the derating factor of BS3036 fuses.

That still does not answer why we still use a 6A MCB on 16A and 20A cable, or -

conversely, why we don't use 6A cable.

Now in the day of LEDs, I imagine that if the regs allowed cables of 'tiny CSA' to be used in installations, we might well be seeing "1A lighting circuits"

Still using 16A and 20A cable?

 

[JohnW2]

Agreed, indeed another problem arises because the earth itself is not very conductive per unit part .

Indeed.

In fact, attempting to scrape the barrel (probably incorrectly!) of what ancient knowledge I once had about this aspect of physics, I think that 'conduction' through the body of the earth is a far more complicated (and 'difficult to get one's head around) business than is the simple conduction down a discrete conductor (e..g. 'a bit of wire') that we are used to thinking about.

In thee latter case, if we push one electron fractionally into one end of the conductor, then that nudges sech successive electron to move a tiny fraction along the conductor, with the eventual effect that one pops out (a tiny fraction) at the other end.

When we're talking about 'the body of the earth', I think it's more a question of the 'input electron' disappearing (essentially 'unnoticeably') into an almost-infinite pool of electrons, and the 'output electron' similarly appearing (again,essentially 'unnoticeably') out of a near-infinite pool of electrons at the other end, with far less certainty/clarity (at least in my mind!) as to what is going on in the earth between those two endpoints.

However, there's so much dust on those vague recollections that I may be totally wrong!!

Kind Regards, John

 

[JohnW2]

That still does not answer why we still use a 6A MCB on 16A and 20A cable, or - conversely, why we don't use 6A cable.

I can but presume because,for whatever reason (maybe 'mechanical robustness'?), BS7671 does not allow 'tiny cables' to be used anywhere in LV installations?

Still using 16A and 20A cable?

No - as I wrote (with new emphasis) ... " IF the regs allowed cables of 'tiny CSA' to be used in installations"

Kind Regards, John

 

[EFLImpudence]

I can but presume because,for whatever reason (maybe 'mechanical robustness'?), BS7671 does not allow 'tiny cables' to be used anywhere in LV installations

You are missing my point and reading it the wrong way round.

Why not 16A OPD?

 

[JohnW2]

You are missing my point and reading it the wrong way round.

i was not missing your 'point', but was only responding to half of it/them (there were two points, with an OR between them). As for the other one ....

Why not 16A OPD?

Well, that,of course, is 'allowed' (by BS7671) and,as you are presumably implying, would be OK with 1.5mm² cable (and 1.0mm² if Method C) - so I suppose it's the electricians, rather than the regs, that you would have to blame for our not having 16A 'lighting' circuits.

As for the reason it started, that is anyone's guess (the reason it 'continued is obvious - sheep without brains doing things 'because that;'s how they have always been done' ! ). Was it perhaps because of the 'ratings' of accessories available for use on lighting circuit?

I suspect, but obviously don't know, that the main reason was that, even in the days of incandescent bulbs, 5A/.6A was nearly always 'enough' (at least, in domestic environments), so perhaps no-one saw a need for 'more' ?

Kind Regards, John