Extending a Ring Circuit

[plugwash]

I’ve not come across these type of sockets. Can you provide a link please. Thanks

MK part numbers:

K5830 - 13A BS1363
K5831 - 16A Schuko
K5832 - 15A american style (made to a Saudia Arabian standard, so presumablly intended for markets in the middle east)
K5833 - 5A BS546
K5834 - 16A French.

Scholmore part numbers (replace xx with BK or WH for black or white).

MM010xx - 13A BS1363
MM020xx - 16A Schuko
MM030xx - American style, Unlike MK scholmore list a US standards body, but strangely they list the current rating as 16A.
MM033xx - 5A BS546
MM038xx - 15A BS546

 

[ericmark]

A Schuko socket is not permitted in the UK.

 

[EFLImpudence]

Says who?

 

[plugwash]

From some googling I would guess he is reffering to

"553.1.2 Except for SELV or a special circuit from Regulation 553.1.5, every plug and socket-outlet shall be of the non-reversible type, with provision for

I think there may also be a reg requiring sockets to be from a particular list of standards (effectively ruling out foreign sockets) but i'm not sure.

 

[ericmark]

Says who?

From some googling I would guess he is reffering to

"553.1.2 Except for SELV or a special circuit from Regulation 553.1.5, every plug and socket-outlet shall be of the non-reversible type, with provision for

I think there may also be a reg requiring sockets to be from a particular list of standards (effectively ruling out foreign sockets) but i'm not sure.

Yes, the odd thing is not allows a socket, but can use socket adaptors, we had problems where I worked with German imports where there was a Schuko socket inside the panel to power the laptop when working on the PLC, the BS 1363 is larger, and not easy to fit in the same space, we decided to regard it as current using equipment rather than part of the installation and turned a blind eye to the socket. It was only used by electricians anyway.

One thing when extending a ring final is of course to make sure it is a ring final, I came across a lovely job where two sockets fitted to split the ring, and extended around the room with 2.5 mm² cable, only problem was it was not a ring final but a 4 mm² radial so we had under sized cable quick cure was use a 20 amp MCB instead of a 32 amp.

Clearly the electrician had not done the inspecting and testing, the loop impedance results showed the supply was a radial, but until I started to work there, there was no look impedance meter.

 

[winston1]

A Schuko socket is not permitted in the UK.

Plenty of them at Heathrow airport above the desks labelled for phone charging.

 

[Jupiter01]

One thing when extending a ring final is of course to make sure it is a ring final

A continuity test using an MFT would establish that? We can also use this to ensure that the ring is intact.
May be also check the breaker to see that it has two legs in the breaker.

 

[JohnW2]

A continuity test using an MFT would establish that? We can also use this to ensure that the ring is intact.
May be also check the breaker to see that it has two legs in the breaker.

Indeed. The latter is the obvious first step - if there is only one cable at the origin, it cannot be a ring (but it could, I suppose, be a 'lollipop' circuit).

If there are two cables, then, as you say, continuity tests will establish whether it is an (intact) ring (rather than two radials, both originating at the breaker, or a 'broken' ring).

Kind Regards, John

 

[ericmark]

Plenty of them at Heathrow airport above the desks labelled for phone charging.

There are silly plastic lumps without the BS 1363 marking on them shoved into 13 amp sockets in dentist and doctors in spite of the NHS officially banning them, and web sites like http://www.fatallyflawed.org.uk/ pointing out the dangers of using them.

They allow children to access exposed live parts.

Just because one silly idiot does some thing, that does not mean we should copy them. Of course for all we know they may be supplied from an isolation transformer.

 

[ericmark]

As @JohnW2 and @Jupiter01 say, testing is important, in the main with power off with a ring final there should be continuity between both line, both neutrals, and both earths.

This was clearly not the case with the office I found the extra sockets in, and since there was an electrician on site it seems highly unlikely it was a DIY job.

There has been debate about lollipop systems, when I did my C&G 2391 I was taught to test for them, and to list as a fault, however I can find no regulation to say should not be used. The problem with the ring final is we moved from 7/0.029 to 2.5 mm² and so we have gone from approx 3 mm² down to 2.5 mm² and so a large drain near the CU or the split on a lollipop can over load the cable, this is why now they say over 2 kW non portable should have a dedicated supply.

 

[EFLImpudence]

A Schuko socket is not permitted in the UK.

...but as far as the "not permitted" is concerned; who is going to do anything about it?
The police are only likely to get involved these days if you misgender the Schuko plug and socket or deride its ethniticty.

Seriously, though, as far as BS7671 is concerned, there is:

120.3
"Any intended departure from these Parts requires special consideration by the designer of the installation and shall
be recorded on the appropriate electrical certification specified in Part 6. The resulting degree of safety of the
installation shall be not less than that obtained by compliance with the Regulations."

and:

511
"511.1 Every item of equipment shall comply with the relevant requirements of the applicable British or
Harmonized Standard, appropriate to the intended use of the equipment. The edition of the standard shall be the
current edition, with those amendments pertaining at a date to be agreed by the parties to the contract concerned
(see Appendix 1).
Alternatively, if equipment complying with a foreign national standard based on an IEC Standard is to be used, the
designer or other person responsible for specifying the installation shall verify that any differences between that
standard and the corresponding British or Harmonized Standard will not result in a lesser degree of safety than that
afforded by compliance with the British or Harmonized Standard. Such use shall be recorded on the appropriate
electrical certification specified in Part 6.
511.2 Where equipment to be used is not covered by a British or Harmonized Standard or is to be used
outside the scope of its standard, the designer or other person responsible for specifying the installation shall confirm
that the equipment provides at least the same degree of safety as that afforded by compliance with the Regulations.
Such use shall be noted and appended to the appropriate documentation specified in Part 6."

 

[Harry Bloomfield]

I have a ring circuit using 2.5mm T&E and protected by a 32Amp MCB.
I want to add 3 more sockets to the existing ring but maintain all of the existing sockets. The floor is concrete.

Having read the other comments above, I think the main detail which is missing, is details of the physical layout of these extra three sockets.

For instance, if there are two sockets on one wall, tested and proven to be wired adjacent on the same ring, the easy method would be to simply disregard/disconnect the existing cable linking the two and run a new cable from original socket one, new socket 2, then 3, then 4 and on to original socket two. You would thus have all your socket as part of a continuous ring.

 

[JohnW2]

There has been debate about lollipop systems, when I did my C&G 2391 I was taught to test for them, and to list as a fault, however I can find no regulation to say should not be used.

I see nothing in the regs which say that they cannot or should not be used, provided that the CSA of the cable forming the 'stick' of the lollipop (i.e. from OPD to 'the ring' is adequate - which will usually require it to have a greater CSA than the cable of the ring' itself. I have one is my house, a not-needed old 10mm² (don't ask me!) cooker circuit being used as a feed to a (2.5 mm²) ring (and a lighting circuit) in my large cellar/workshop.

The problem with the ring final is we moved from 7/0.029 to 2.5 mm² and so we have gone from approx 3 mm² down to 2.5 mm² and so a large drain near the CU or the split on a lollipop can over load the cable ....

With the regulation as it currently is (and has been for a long time - maybe 'for ever'?), a ring final is allowed with cable with a CCC (with prevailing installation method and any de-rating factors) as low as 20A (provided it is at least 2.5 mm², or 1.5 mm² if MICC) - so it wouldn't matter whether it was 7/0.029 or 2.5 mm².

Kind Regards, John

 

[JohnW2]

Seriously, though, as far as BS7671 is concerned, there is: ....

We've discussed this a lot in the past, and I think the issue which causes most 'debate'/disagreement probably is ....

"511.1 ................ will not result in a lesser degree of safety than that afforded by compliance with the British or Harmonized Standard.

...since some will probably argue that a reversible plug/socket does not provide the same 'degree of safety' as does a BS1363 one.

Kind Regards, John

 

[EFLImpudence]

The regulation does not state "unless some people argue..."

Some people argue the world is flat.