16amp blue socket wired off a socket spur

Dad's garage had a C16 for the welder on the RFC
As you go on to mention middle, we can be pretty certain that you mean a "Ring FC" -
plus, of course for some inexplicable reason in our bizarre world, it does not stand for "Radial FC".

- mounted on a metal box with a C16 MCB in it. Not regs compliant,
Why not?

but if you apply logic and electrical knowledge then you'd have to agree that it was perfectly safe
Of course.

(it was a short RFC, and the C16 socket would be not far of the middle of it).
Yet the assumed 2.5mm² conductors of the ring and spur have a CCC of 27A so to all intents and purposes it did not matter where on the ring it was and the C16 was being used solely as a low current limiter.
 
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Indeed. However, I wonder whether the fact that (as so often!) the OSG does not (cannot?) cite a regulation in BS7671 which actually says that may, perhaps, "say it all"?

Kind Regards, John
That reminds me of someone on this forum. He has the same atttibutes.
 
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Indeed not - but "So what?". As I said, if one believes that the (40A or whatever) OPD is there only to protect teh fixed wiring (and NOT to act as a 'current limiter'), the fact that the plug/socket was unfused would be irrelevant.

Indeed, even if you did think that 'current limitation' was one of the purposes of the OPD, a B20 would allow about 29A to flow for an hour, or appreciably more than that for shorter periods - hence not all that much use for 'limiting' current to 16A!


Do you believe that it is not permissible to have one (or morew) 15A BS546 socket(s) on a circuit with an OPD ofd >15A/.16A?

Kind Regards, John
Permissable or not, I would do everything in my power to avoid anything over 15A fuse/16A MCB for a single 15A socket and only to the 20A for multiple sockets.
However one of the council owned theatres I worked in had a Strand Junior8 lighting board running 8x 500W lights, the power to it was plugged into a 15A socket. When the lights were replaced with 1000W units and the fuse blew several times it was ungraded to 30A fuse wire in the fuse box. It had been running like that for several years when I started working there and there were no noticeable problems despite regularly running at 222% of the sockets rating.
 
As EFLI has asked, what makes you think that?
433.1.204 ?
Otherwise, you have to consider 433.4 which would preclude there being any spurs off an RFC. 433.4.2 could be tricky to comply with for an RFC because of the unknown distribution of currents due to unknown load values and placements. 433.4.1 won't apply as it's known in advance that current sharing will be unequal.
And then you get to 523.7, and hence to 523.1
While technically it might be permissible - I doubt many people would care to "prove compliance" with the regs for such an installation.

As an aside, based on the same logic of "why not ?", a 32A socket on an RFC would also be acceptable - without local current limiting. Personally I'd not see a problem electrically if it's located sensibly on the ring - but demonstrating standards compliance is another matter.
 
433.1.204 does not apply to spurs.
433.4 and 523.7 do not apply; rings are not considered conductors in parallel.
523.1 - not sure why you think your arrangement is any different to lots of sockets.

You had a 16A OPD protecting a 27A spur cable which is fine. It is less than a double socket might be.

Asking about a 32A socket is taking things too far although - if there were no sockets on the ring...
 
I get what you're saying but it doesn't quite work like that does it? Thinking about the number of 13A plugs and sockets I've replaced [and not only the cheap makes] which are also considerably more than 1mm² where they struggle to run at 13A on a regular basis, demonstrates that to me on a regular basis.
The Post Office (before BT) downgraded 13 amp sockets to 8 amps on their premises for a reason.
 
Permissable or not, I would do everything in my power to avoid anything over 15A fuse/16A MCB for a single 15A socket and only to the 20A for multiple sockets.
Fair enough - but you must be thinking of the OPD as having some purpose other than protecting the cable.

As with all sockets circuits (which, in some senses, are a designer's nightmare), the designer has to use his/her judgement of likely loads on such circuits - and certainly should not rely on OPDs to 'limit' loads which could have been anticipated. In the OP's case, where the only load he is likely to plug into any 16A socket (probably the only thing he has with a 16A plug!) is his welder, but (as he says) he wishes to be able to 'plug it in' in different places - in which situation I think it would not be unreasonable for the designer's judgment to be that it was unlikley that the total load would ever exceed 16A, no matter how many 16A sockets there were.

... and, in any event, even if several welders were plugged into several sockets on the circuit, and all used simultaneously (if the OP had enough hands!), if correctly specified the cable would still be safe, and the worst that would happen would be that the MCB would trip.

Kind Regards, John
 
While technically it might be permissible - I doubt many people would care to "prove compliance" with the regs for such an installation.
I would like to think of it as "innocent until proved guilty" (aka "conformant unless proved non-conformant") (I use that terminology because of BS7671's new-fangled definition of "non-compliance"!). As EFLI has pointed, none of the regs you cited are really relevant/applicable to what we are discussing - so, unless/until someone can indicate an explicit reg with which the proposed arrangement would not conform, I would continue to regard it as 'conforming', and would not feel the need to 'prove' that it was!
As an aside, based on the same logic of "why not ?", a 32A socket on an RFC would also be acceptable - without local current limiting. Personally I'd not see a problem electrically if it's located sensibly on the ring - but demonstrating standards compliance is another matter.
Well, particularly if there were other sockets on the circuit, the designer would have to be careful in deciding that it was "unlikely that any cable in the circuit would be overloaded for long periods of time" but, if the designer were so satisfied, what is the problem you perceive? Silly though it would be, from the POV of the circuit, why would one 32A socket on the ring be any worse than, say, 3 double sockets in close proximity at a similar point on the ring (either 78A or 60A total, depending on how you care to count it)?

Kind Regards, John
 
The Post Office (before BT) downgraded 13 amp sockets to 8 amps on their premises for a reason.
Proof please, I've asked before and didn't receive an answer then.


I've still not been able to find any evidance that BT had any such downgrade, we certainly had 3KW appliances in pretty much every building that I worked in and I certainly found no evidence of any restriction while doing PAT for a number of years.
 
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Fair enough - but you must be thinking of the OPD as having some purpose other than protecting the cable.

As with all sockets circuits (which, in some senses, are a designer's nightmare), the designer has to use his/her judgement of likely loads on such circuits - and certainly should not rely on OPDs to 'limit' loads which could have been anticipated. In the OP's case, where the only load he is likely to plug into any 16A socket (probably the only thing he has with a 16A plug!) is his welder, but (as he says) he wishes to be able to 'plug it in' in different places - in which situation I think it would not be unreasonable for the designer's judgment to be that it was unlikley that the total load would ever exceed 16A, no matter how many 16A sockets there were.

... and, in any event, even if several welders were plugged into several sockets on the circuit, and all used simultaneously (if the OP had enough hands!), if correctly specified the cable would still be safe, and the worst that would happen would be that the MCB would trip.


Kind Regards, John
Only common sense, good practice and experience.

And of course there is nothing wrong with designing a circuit with the OPD serving 2 purposes.
 
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The Post Office (before BT) downgraded 13 amp sockets to 8 amps on their premises for a reason.

@winston Do you have any evidence to support this claim or is it another one of your made up “facts”?

<edit> apologies @SUNRAY i didn’t see you had also asked for the same thing.
 
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Only common sense, good practice and experience.
I really don't get it.

If I understand correctly, you're only saying this because the 15A/16A plugs/sockets don't have fuses, but I don't see what difference that makes, given that, even when plugs have fuses, there could be many of them connected to the same circuit simultaneously. Although BS1363 plugs each contain a fuse which cannot be more than 13A, on a typical 20A or 32A circuit one would have a dozen or two outlets into which a dozen or two such plugs, and their loads, could be plugged (representing a massive theoretical total load).

Would you say that to have multiple 13A (BS1363) outlets on a 20A radial was contrary to common sense, was bad practice and was outside of your experience?

Kind Regards, John
 
Proof please, I've asked before and didn't receive an answer then.


I've still not been able to find any evidance that BT had any such downgrade, we certainly had 3KW appliances in pretty much every building that I worked in and I certainly found no evidence of any restriction while doing PAT for a number of years.

I said the Post Office not BT.

It has been discussed and confirmed on these forums before.
 

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