What is the best configuration to add a these additional sockets?

[uptoyou]

*in case this has a bearing (as things stand)
Spur 1 - 150W electric toilet heater
Spur 2 - double socket for OLED TV, maybe a soundbar/PS5 (this will be housed behind the TV so nothing else with be going into these sockets)
Fused switch - 1.35kW heater
Main double socket - PS5/Receiver/Subwoof
>>>extension maybe for additional Amazon Firestick/Buray...

 

[EFLImpudence]

I have traced it to a 150W electric heater in the downstairs toilet.

Ok.

So, can I have 2 separate 4mm spurs on the same socket,

Yes, you can - if there is room.

or should I rewire the toilet heater into the fused switch/back of the new double socket?

Same difference.

 

[uptoyou]

Thanks EFL, think this has wrapped this one up!

 

[JohnW2]

Taking multiple socket-outlets/points off the spur in 4mm^2 cable risks concentrating the load of the ring too much around one of the ring cables, rather than a more even distribution. ...

As EFLI has said, that would be equally true of multiple sockets in close proximity inserted 'on the ring' at the same point.

I would not consider it a strictly compliant method of alteration.

With which regulation do you consider it would not be strictly compliant?

 

[Risteard]

Then you would be wrong.

I most certainly would not.

 

[SUNRAY]

Is there not a requirement something like fusing a spur at 13A or 16A MCB when adding more than a single or a double socket?

 

[JohnW2]

Is there not a requirement something like fusing a spur at 13A or 16A MCB when adding more than a single or a double socket?

Only if it is 2.5²mm cable. If 4mm², then (just as with a 4mm² radial) there is no limit to how many sockets can be supplied (but the examples shown in Appendix 15 fail to mention that!)

Kind Regards, john

 

[EFLImpudence]

Is there not a requirement something like fusing a spur at 13A or 16A MCB when adding more than a single or a double socket?

Only if the cable requires it for electrical reasons; not "just because".

Incidentally, I have never seen it stated in the regulations that a 16A MCB should be used.
Presumably someone said that would also be electrically satisfactory and people just accepted that solution - but why 16A and not 25A?

I do not understand why any discussion is required on the subject.
Does Ib ≤ In ≤ Iz not apply to spurs from rings but is alright from radials?

 

[SUNRAY]

I don't have a copy of the regs here at the moment and if I did have mine here it would be 2001 version. I have 2001 OSG which simply states: "A non fused spur feeds only one single or one double socket or one permanently connected equipment."
and then goes on: "Permanently connected equipment is locally protected by a fuse complying with BS1362 of rating not exceeding 13A or by a circuit breaker of rating not exceeding 16A..."

So that clearly states a fused spur is restricted to 13A fuse but a piece of fixed equipment to 13A fuse or 16A MCB.

Oh and according to 2001 definitions
"Spur. A branch from a ring final circuit." I believe this places different rules on ring and radial finals appendages.

I fully understand there is little electrical difference between a row of sockets on a ring or on the end of a 4mm² spur but it goes against all I've ever learnt and the only document I have available to read.

I assume the information contained in OSG is correct [yes I understand it is a guide] and, unless the regs have changed, it is clearly wrong to have more than a double socket on an unfused spur regardless of what size cable it is.

 

[JohnW2]

I don't have a copy of the regs here at the moment and if I did have mine here it would be 2001 version. I have 2001 OSG which simply states: "A non fused spur feeds only one single or one double socket or one permanently connected equipment."
and then goes on: "Permanently connected equipment is locally protected by a fuse complying with BS1362 of rating not exceeding 13A or by a circuit breaker of rating not exceeding 16A..." ... So that clearly states a fused spur is restricted to 13A fuse but a piece of fixed equipment to 13A fuse or 16A MCB.

Indeed - but, as so often, the OSG is not telling the whole story (and nor, probably, does the person who writes it even understand 'the whole story'!). What the OSG is talking about is a spur wired with 2.5mm² cable - which, as I said, is the only type of unfused spur which is depicted, or mentioned, in the guidance of appendix 15.

I fully understand there is little electrical difference between a row of sockets on a ring or on the end of a 4mm² spur but it goes against all I've ever learnt and the only document I have available to read. .... I assume the information contained in OSG is correct [yes I understand it is a guide] and, unless the regs have changed, it is clearly wrong to have more than a double socket on an unfused spur regardless of what size cable it is.

No - and that's because "the only document you have to read" is not "the regulations". Nothing in the regs themselves says anything about spurs from ring final circuits, other than to say that such circuits may have 'unfused spurs' - so absolutely nothing about what may, or may not, be supplied by any sort of spur, and the only stipulation about the cable (by implication, this applies to spurs as much as to the ring itself) is that it must have a CCC of at least 20A and must have a CSA of at least 2.5mm² (unless it is MICC, in which case 1.5mm² is allowed).

Nothing in the regulation which permits ring finals ('with or without unfused spurs') (433.1.204) over-rides the general provisions of 433.1.1, the effect of which is to allow a 4mm² cable protected by a 32A OPD to supply as many sockets as one wants - whether that cable is a spur from a ring final, a radial or anything else you can think of!

Those who point out that an unfused spur supplying multiple sockets which originates close to the origin of a ring could theoretically result in overload of part of the cable are correct - but exactly the same risk exists if multiple sockets are installed 'on the ring' close to one end of it. As required by 433.1.204 t is for the designer to minimise such risks by appropriate selection of the location of sockets 'on the ring', or of the location of the origin of a spur from the ring.

Kind Regards, John

 

[EFLImpudence]

I don't have a copy of the regs here at the moment and if I did have mine here it would be 2001 version. I have 2001 OSG which simply states: "A non fused spur feeds only one single or one double socket or one permanently connected equipment."

I don't read the OSG other than looking up mistakes that people have relayed. I would advise throwing away the OSG.

and then goes on: "Permanently connected equipment is locally protected by a fuse complying with BS1362 of rating not exceeding 13A or by a circuit breaker of rating not exceeding 16A..."So that clearly states a fused spur is restricted to 13A fuse but a piece of fixed equipment to 13A fuse or 16A MCB.

Does it not depend on the rating of the equipment?
Surely you cannot consider that as definitive and exhaustive.

Oh and according to 2001 definitions
"Spur. A branch from a ring final circuit."

Oh, latest BS7671:
Spur: A branch from a ring or radial final circuit.

I believe this places different rules on ring and radial finals appendages.

In a way, the requirements for rings do not apply to spurs; how could they?

I fully understand there is little electrical difference between a row of sockets on a ring or on the end of a 4mm² spur but it goes against all I've ever learnt and the only document I have available to read.

Ok. I repeat: Ib ≤ In ≤ Iz

I assume the information contained in OSG is correct [yes I understand it is a guide]

No, it is a dreadful publication.

and, unless the regs have changed, it is clearly wrong to have more than a double socket on an unfused spur regardless of what size cable it is.

I don't think they have changed but let's say "Yes, they have changed".

I cannot believe this even needs discussing.

 

[SUNRAY]

Well if we're talking about the number of errors, perhaps we should throw the regs book away too.

 

[JohnW2]

Well if we're talking about the number of errors, perhaps we should throw the regs book away too.

The regs book is the regs book - so, even though it always has contained some 'errors', it has to be regarded as "the regs book", whether we like it or not.

Some other publication which purposes to be 'guidance on the regulations', but which repeatedly 'makes up its own rules' (which don't exist in the regs) and/or under- or over-interprets what the regs actually say is, in my opinion, best ignored!

Kind Regards, John

 

[SUNRAY]

The regs book is the regs book - so, even though it always has contained some 'errors', it has to be regarded as "the regs book", whether we like it or not.

Some other publication which purposes to be 'guidance on the regulations', but which repeatedly 'makes up its own rules' (which don't exist in the regs) and/or under- or over-interprets what the regs actually say is, in my opinion, best ignored!

Kind Regards, John

Fair enough but I always thought it was an official publication and I did include this:

I assume the information contained in OSG is correct [yes I understand it is a guide]

 

[JohnW2]

Fair enough but I always thought it was an official publication and I did include this:

I suppose that depends upon what one means by "an official publication".

It is certainly true that it is written by one of the co-authors (IET) of "the regulations" (BS7671). However, no matter who it is written by, it is, in my opinion, a worrying "guide to the regulations" (any regulations) that makes up things which are not actually in those regulations and which also sometimes 'over-interprets' things which are in the actual regulations. As the document says itself ...

The scope generally follows that of BS 7671 . The Guide includes material not included in BS 7671, it provides background to the intentions of BS 7671 and gives other sources of information. However, it does not ensure compliance with BS 7671 . It is a simple guide to the requirements of BS 7671; electrical installers should always consult BS 7671 to satisfy themselves of compliance.

In my opinion, the 'intentions' behind regulations should be clear from what is actually written in "the regulations", and should not be mentioned only in some "non-normative" 'guidance' document.

We repeatedly see instances here of people believing that things are "required by the regulations" because they are mentioned in the OSG, whereas the truth is that the regulations say no such thing. Exactly the same problem arises with the 'Approved Documents' published in relation to various parts of the Building Regs (Like Part P, Part B, Part M etc.) - again, those Approved Documents merely offer guidance/recommendations, yet many people think they are indicating what is required in order to comply with the relevant Part of the Building Regs.

If people actually read the 'Introductions/Prefaces/Forewords' of these 'guidance' documents, they might perhaps be less likely to misunderstand what they are!

Kind Regards, John