Installing extra appliance, electric supply advice needed

[JohnW2]

Maybe, but the pre-amble to the Appendices says that, whilst Appendix 1 is 'normative', and "thus a requirement", all of the other Appendices are only for 'guidance'.

Indeed. Bizarrely though, A1 doesn't actually impose any "requirements" it's just a list of standards.

Not bizarre at all. If the list was "informative" then it could be ignored.

I have to say that I'm with BAS on this one. I don't understand what the pre-amble means when it say that the list of Standards is 'a requirement'. Nor do I understand what it would mean to 'ignore' a list of Standards, such as you suggest.

Kind Regards, John

 

[stillp]

I don't know what you mean by a "pre-amble". Presumably you mean the Note under the list of appendices, on p276? If so then I agree that the language is clumsy.
However, it is quite clear (or should be!) that if a normative reference is made to a standard, in the body of the document, then the details of that standard are also normative, and hence the Appendix listing those details for each standard is also normative. If it were not, the reader could choose to use a different version of a referenced standard, or even (depending on the exact wording of the requirement) possibly a different standard. So, for example, a reference to "ceiling roses complying with BS 67" means that they shall comply with BS 67: 1987 (1999), not the 1951 edition.
[The (1999) means that the 1987 standard was reviewed and reconfirmed in 1999]
I hope that's clear?

 

[EFLImpudence]

15B does depict the arrangement so it is just the connection to a ring that is disputed.

Playing 'DA' ... It's not quite that simple. 15B just shows a 4mm² branch of a 4mm² radial. That's rather different from a 4mm² spur originating from a 2.5mm² ring.

Yes, I realise but the branch is supplied by 4mm² and the spur by 5mm².
Which is better?

Would you still consider the arrangement to be non-compliant were it connected to the origin of the circuit?

No - but, again, I (or the 'DA''!) think that is 'different'. I don't think there's anything in the regs which says that one cannot have two 'circuits' (or 'sub-circuits'), in this case a 2.5mm² ring and a 4mm² radial, originating from (and protected by) the same OPD - so I think that would be compliant in most people's eyes.

Yes, but if a 2.5mm² spur is allowed there - a point on the ring, why would a 4mm² not be allowed at other points?

 

[JohnW2]

I don't know what you mean by a "pre-amble". Presumably you mean the Note under the list of appendices, on p276? If so then I agree that the language is clumsy.

Yes, that 'clumsy language' is what I'm referring to

However, it is quite clear (or should be!) that if a normative reference is made to a standard, in the body of the document, then the details of that standard are also normative, and hence the Appendix listing those details for each standard is also normative. If it were not, the reader could choose to use a different version of a referenced standard, or even (depending on the exact wording of the requirement) possibly a different standard. So, for example, a reference to "ceiling roses complying with BS 67" means that they shall comply with BS 67: 1987 (1999), not the 1951 edition. ..... I hope that's clear?

Yes, what you're saying is clear enough and, in the absence of any other/better explanation, I suppose that must be what the 'clumsy language' in the Note was trying/intending to say. It just seemed odd to me (and also BAS) that a list of Standards should be described as "a requirement".

Kind Regards, John

 

[stillp]

Yes, it's a group of requirements.

 

[JohnW2]

Playing 'DA' ... It's not quite that simple. 15B just shows a 4mm² branch of a 4mm² radial. That's rather different from a 4mm² spur originating from a 2.5mm² ring.

Yes, I realise but the branch is supplied by 4mm² and the spur by 5mm². Which is better?

Ah - but the 'equivalent CSA of a 2.5mm² ring is only 5mm² in the centre of the ring. The closer you get to one end of the ring, the closer does the 'effective CSA' get to just 2.5mm². As an extreme example, if the load is just 1% of the way around the ring, then only 1% of the current will go 'the long way around' - so that 'long' run of cable does very little to increase the 'effective CSA' of the two cables from that point, so that 'effective' CSA from that point' will be only fractionally above 2.5mm².

Would you still consider the arrangement to be non-compliant were it connected to the origin of the circuit?

No - but, again, I (or the 'DA''!) think that is 'different'. I don't think there's anything in the regs which says that one cannot have two 'circuits' (or 'sub-circuits'), in this case a 2.5mm² ring and a 4mm² radial, originating from (and protected by) the same OPD - so I think that would be compliant in most people's eyes.

Yes, but if a 2.5mm² spur is allowed there - a point on the ring, why would a 4mm² not be allowed at other points?

I'm not sure that I really understand your point/question. As above, if the point were very close to one end of a 2.5mm² ring, then the 'effective CSA' of the cable from the origin (OPD) to that point (where it changed to 4mm² for the spur) would not be a lot more than 2.5mm².

Kind Regards, John

 

[JohnW2]

Yes, it's a group of requirements.

If that's what it means, then that's what it means - but I find the language very far from clear!

Kind Regards, John

 

[deadshort]

Hi all,

I am wanting to install a dishwasher in a kitchen which doesn't already have one. It will go under the sink on the opposite side to the washing machine. I would ideally like to connect it up without disturbing any tiling.

I currently have one 13A FSU above the washing machine with an unswitched socked below. The FSU I assume is on the ring main as it has 2x2.5mm feeds with 1x2.5 supply to the socket below.

I am aware you cannot connect more than one appliance into a single socket/spur, so I was wondering if there is anything I can fit in lieu of the FSU which will act as 2 FCUs supplying 2 spurs down to 2 sockets below? The hope being it can be a straight swap!

Apologies if there is an obvious solution to this, I'm kinda new to household electrics

On a side note regarding plumbing, I was going to buy one of these http://www.screwfix.com/p/washing-machine-y-piece-bsp/81000 and also one of these http://www.screwfix.com/p/mcalpine-appliance-trap-40mm-white/95241. I trust they will do the job?

Thanks

You can change the FCU to a 32a DP switch and change the single socket to a double using a 'converta'socket. No additional cables and no mess
And it complies with regs as it's a spur.

 

[EFLImpudence]

Having a double socket is not the problem,

It is that it is not advisable to have a WM and DW together in the double socket and two single sockets are not allowed on a 2.5mm² unfused spur.

 

[deadshort]

The regs permit a double socket on an unfused spur. I have not suggested 2 single sockets. How many utility rooms have a double socket with the WM and TD plugged into them? or are we using the 'selective diversity" argument

Kind regards,

DS

 

[EFLImpudence]

Ah - but the 'equivalent CSA of a 2.5mm² ring is only 5mm² in the centre of the ring. The closer you get to one end of the ring, the closer does the 'effective CSA' get to just 2.5mm². As an extreme example, if the load is just 1% of the way around the ring, then only 1% of the current will go 'the long way around' - so that 'long' run of cable does very little to increase the 'effective CSA' of the two cables from that point, so that 'effective' CSA from that point' will be only fractionally above 2.5mm².

Yes, I know all that but you are introducing red herrings.
No one would query two 2.5mm² from close points on the ring; you have suggested two spurs from the same point.

Because there is conduit in place I have proposed 4mm² and, even though you actually agree, we have ended up having a prolonged discussion although it was BAS who disagreed and it was to him that my justification was aimed.


There is no doubt that my proposal is electrically safe.
The debate concerns whether the regulations allow it or not because they do not expressly show it - but then - nor do they expressly forbid it.

 

[EFLImpudence]

The regs permit a double socket on an unfused spur. I have not suggested 2 single sockets. How many utility rooms have a double socket with the WM and TD plugged into them? or are we using the 'selective diversity" argument

No, but I am proposing and we are discussing a safe and compliant way to install two single sockets on a spur.

 

[ban-all-sheds]

Yes, it's a group of requirements.

What does it require you to do?

 

[ban-all-sheds]

The regs permit a double socket on an unfused spur.

But you may not use one to simultaneously supply a WM & TD.

How many utility rooms have a double socket with the WM and TD plugged into them?

All those exceeding the rating of a double socket.

 

[deadshort]

Ah, the selective diversity rule is applied !



DS