Indeed. The reg in question is
EITHER daft (by introducing the anomaly we have been discussing)
OR very badly worded (in not making it clear that the "20A minimum CCC" does not apply to unfused spurs, if that were the intent)
Kind Regards, John
Myths
- Thread starter EFLImpudence
- Start date
Kind Regards, John
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I believe we all interpret it as 'EITHER' working on the basis that one DSSO is rated at only 13 or 20A but truth be told I don't know which option it is.
There is no consensus about such things, but the 'rating' of the socket does not limit the possible overload current, which (until an OPD operates) is determined solely by the load.
BS1362 fuses being as they are, if two loads were plugged into a double socket with plugs which both had 13A fuses, a total of around 44A could theoretically flow for an indefinite period of time!
Kind Regards, John
Oh yes, I know the folly of such set-ups. and the B32 MCB should hold it too.
35 years ago I stayed with a friend while on loan to London Telephones and while there she moved house, my 'rent' being rewiring, plumbing new kitchen/bathroom etc. (the lead piping removed entirely payed for the whole of the total replumbing and full CH sytem with what is now known as a combi boiler with some to spare). While there was no CH, electric heaters were being used. I got in one evening and immediately detected the smell of hot PVC cable; 2 fan heaters running on one extension lead, it was so hot the PVC was on the verge or running/dripping.
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WOW,
first of all let me declare what I said and why I said it.
I was making the point that, whilst the scenarios I described might be described as contravening the special requirements of OPDs on a ring final circuit, would not in my opinion make them suddenly become dangerous.
It , to me, seems illogical to imagine a compliant circuit is reasonably safe yet removing part of it (the ring portion) now makes it become less safe.
I had expected, initially, a bit of a "gut reaction" from some and indeed in the past I have likewise an initial gut reaction to some scenarios only to then look a bit deeper and think "Hmm, I am struggling to find anything actually non-compliant/dangerous".
I had not expected, in the slightest, such a reaction to my theoretical scenarios though.
So, the question was really "does removing the ring from the equation make this circuit become dangerous?"
I say it does not, that would not be logical to suggest it does.
I am not mentioning whether it now becomes non-compliant, that is a different question.
first of all let me declare what I said and why I said it.
I was making the point that, whilst the scenarios I described might be described as contravening the special requirements of OPDs on a ring final circuit, would not in my opinion make them suddenly become dangerous.
It , to me, seems illogical to imagine a compliant circuit is reasonably safe yet removing part of it (the ring portion) now makes it become less safe.
I had expected, initially, a bit of a "gut reaction" from some and indeed in the past I have likewise an initial gut reaction to some scenarios only to then look a bit deeper and think "Hmm, I am struggling to find anything actually non-compliant/dangerous".
I had not expected, in the slightest, such a reaction to my theoretical scenarios though.
So, the question was really "does removing the ring from the equation make this circuit become dangerous?"
I say it does not, that would not be logical to suggest it does.
I am not mentioning whether it now becomes non-compliant, that is a different question.
I`m not really sure that I follow that John.
any Overcurrent Protective Device might be connected for 1, 2 or 3 reasons.
1/ Overload.
2/ Short circuit
3/ Earth fault.
One twin socket might have two plugs drawing current and both would have overload protection from a 13A max fuse.
So that leaves us with short circuit protection being required and possibly earth fault protection too (we might/might not consider any RCD if connected)
I am strugging to follow the logic of the "electric board people"
Agreed
DittoI hope someone asked him "so what?"
Kind Regards, John
Agreed
I`m not disagreeing with that, I am questioning solely "has it now become dangerous" because the ring was removed.
Yes I agree with you on that one too John, they have decided quite sensibly that the CCC should be adequate in this case.
In other words, very rarely could it become a problem therefore allowed in this case but not allowed on bog standard radials because it could open up the "flood gates" to other scenarios.
Whoops, even I am drifting off my "Has it now become (more) potentially dangerous if the ring is removed from a compliant circuit?"
Anyway, compliance aside, my opinion is NO it has not become any more risky/dangerous to remove the ring and leave everything else as it was.
It can`t be.
Electrons do not care about topology.
Anyway, example, 3 twin sockets on the ring itself, 1 twin socket spurred from a ring socket, 1 twin socket jointed to a ring cable and 1 twin socket spurred from the fuseway.
Everybody happy?
If yes, then anybody now unhappy (regarding potential danger) with 6 twin sockets each on its own radial to the one fuseway instead?
32A MCB in both cases!
It can`t be.
Electrons do not care about topology.
Anyway, example, 3 twin sockets on the ring itself, 1 twin socket spurred from a ring socket, 1 twin socket jointed to a ring cable and 1 twin socket spurred from the fuseway.
Everybody happy?
If yes, then anybody now unhappy (regarding potential danger) with 6 twin sockets each on its own radial to the one fuseway instead?
32A MCB in both cases!
There was a requirement for switches for fixed appliances in bathrooms to be of the pull cord type, but only if the switch was in the bathroom, and that last appeared in the 13th edition in 1962.
However even then it was permitted for the switch to be located outside the room, so the 'electric board' person was still wrong.
That requirement was removed in the 1966 edition.
This may be where the 'pull cords required for bathroom lights' mess originated from, although it was only ever a requirement for fixed appliances. Lights never needed a pull cord in bathrooms or anywhere else.
Well, not usually "1, 2 OR 3" reasons - isn't it usually 'all three of them' ?
I thought I have made it fairly clear that I was talking specifically about overload protection (so, by implication, also {L-N} 'short-circuit' protection, since a 'short circuit' is merely an extreme case of 'overload').
The need for ('earth') fault protection is (a) a separate issue that I was not talking about and, more important (in context) is not influenced by changes in the CCC of a cable of given CSA - i.e. the fault protection will be the same with Method C 2.5mm² T+_E (27A) as when the CCC of such a cable is reduced to 20A by 'de-rating factors.
Quite so. And if one is considering 'worst case scenarios' one has to assume that the downstream protection is 2 x 13A (i.e.26A)
Eh? As above, 'short-circuit protection' is merely an extreme case of 'overload' - if the device is adequate to protect against 'overload' currents which are 'appreciably greater than 26A', it can certainly protect against the probable 'hundreds of amps' in the case of a 'short-circuit'.
As above, that's a different issue, but obviously a requiremeng. If fault protection is provided by an OPS (i.e. as usual in a TN installation), then adequate fault protection would mean 'at least adequate' short-circuit protection - since, with the exception of 1mm T+E, R1+Rn is less than R1+R2.
Kind Regards, John
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