Changes to connect a 16A (hardwired) oven to 13A socket

[bengasman]

...As for connecting a 16A load to a 32A ring final circuit, the whole concept of such a circuit assumes that the 32A maximum load is reasonably distributed around the whole of the ring - and applying a 16A load at one point on the ring clearly goes against that concept...

How many kitchens in this country will have a 2kw kettle and a 2kw toaster running from one double socket?

 

[ban-all-sheds]

Why would you need a separate fuse on a circuit that already is protected by the mcb or other form of fuse on the board? I may have missed it but I'm not aware BS 7671 require more than one fuse to protect the wiring.

BS 7671 requires that only BS 1363 accessories, i.e. FCUs (which contain a BS 1362 fuse) or sockets which accept plugs which contain BS 1362 fuses be supplied by an undersized ring final.

Apart from that, I can get 16A as well as 20A ceramic cartridge fuses without any problem from stock.

BS 1362 ones?

Not saying you're wrong, just that I'm at a loss as to the why and how.

Because the traditional 2.5mm²/32A ring final should not be allowed. The regulations have to go into contortions of exemptions and special cases and special conditions to allow them to exist, and inconsistencies and anomalies arise.

 

[bengasman]

Apart from that, I can get 16A as well as 20A ceramic cartridge fuses without any problem from stock.

BS 1362 ones?

BS1361 which afaik is allowed as well.

Not saying you're wrong, just that I'm at a loss as to the why and how.

...Because the traditional 2.5mm²/32A ring final should not be allowed...

Truer words have not been spoken. I hate ring circuits and can not understand why anyone would still install them instead of using single cable when you get a decent 10-way CU for about 60 squid.

 

[JohnW2]

How many kitchens in this country will have a 2kw kettle and a 2kw toaster running from one double socket?

Obviously plenty - but in how many kitchens will both the toaster and the kettle be on continuously for an hour or two?

As BAS has been saying, the simplest answer to your question is that the regulations don't allow a '16A spur' - but not, I would say, without good reason.

Kind Regards, John

 

[ban-all-sheds]

BS1361 which afaik is allowed as well.

Allowed in what?

A BS 1361 fuse will not fit in a BS 1363 accessory - only BS 1362 fuses will.

 

[bengasman]

BS1361 which afaik is allowed as well.

Allowed in what?

Allowed to use for protection of the circuit with a suitable fuse holder installed in a suitable manner by a competent installer.
Might not be ideal but most customers would rather have a 'not ideal but legal' alternative to ripping out their kitchen or pulling up their expensive floor. We live in the real world rather than Utopia, where virtually no homes that I go into are wired up completely by the book.

 

[bengasman]

...the simplest answer to your question is that the regulations don't allow a '16A spur'

Do you know by any chance where it says that in the 16th edition? (didn't bother buying the 17th edition and only have the 16th here).
Just curious as I've never seen this prohibition.

 

[EFLImpudence]

Now you are planning contorted methods for something which is neither necessary nor needed.

 

[bengasman]

Now you are planning contorted methods for something which is neither necessary nor needed.

am a bit puzzled why you can't take a 16A spur from a 32A ring as long as the cable to the spur is big enough to carry 32A.
What am I missing?

Take two 'spurs' and extend the ring - simple.

But that isn't the question, nor is it likely to be easy to do in a fitted kitchen without opening the floors.
It's purely an academic question because I'd never heard of this being forbidden.

 

[EFLImpudence]

No, sorry, was getting confused by the purpose.

 

[JohnW2]

...the simplest answer to your question is that the regulations don't allow a '16A spur'

Do you know by any chance where it says that in the 16th edition? (didn't bother buying the 17th edition and only have the 16th here).
Just curious as I've never seen this prohibition.

As BAS has said, the 17th (snd I presume also 16th) edition only allows ring finals to supply BS1363 accessories - and you won't find a BS1363 accessory which can contain a 16A fuse or MCB.

Kind Regards, John

 

[EFLImpudence]

Now you are planning contorted methods for something which is neither necessary nor needed.

am a bit puzzled why you can't take a 16A spur from a 32A ring as long as the cable to the spur is big enough to carry 32A.
What am I missing?

Take two 'spurs' and extend the ring - simple.

But that isn't the question, nor is it likely to be easy to do in a fitted kitchen without opening the floors.
It's purely an academic question because I'd never heard of this being forbidden.

Not sure now if it is you or I who was confused.

As you were asking after reading the thread, I assume you were talking about a 16A spur to connect an oven - simply bad design.

As for the "nor is it likely to be easy to do in a fitted kitchen without opening the floors" then you wouldn't be able to fit the single spur either.

 

[bengasman]

Do you know by any chance where it says that in the 16th edition? (didn't bother buying the 17th edition and only have the 16th here)
If you don't know where it is in 16th, and only in the 17th, could you tell me what the section is called e.g.
531-01 overcurrent protective devices (in 16th)
that'll make it easy enough to read up about this in the 16th (I doubt anything changed in respect to fusing spurs in the 17th)

 

[bengasman]

Now you are planning contorted methods for something which is neither necessary nor needed.

am a bit puzzled why you can't take a 16A spur from a 32A ring as long as the cable to the spur is big enough to carry 32A.
What am I missing?

Take two 'spurs' and extend the ring - simple.

But that isn't the question, nor is it likely to be easy to do in a fitted kitchen without opening the floors.
It's purely an academic question because I'd never heard of this being forbidden.

Not sure now if it is you or I who was confused.

As you were asking after reading the thread, I assume you were talking about a 16A spur to connect an oven - simply bad design...

Yes, I know, but that doesn't make a '2nd choice solution" illegal or unsafe.
If I only accepted work from customers that are happy to fork out for a perfect solution and refused to carry out work that was not ideal but not illegal, I'd lose two thirds of my work.

 

[JohnW2]

Do you know by any chance where it says that in the 16th edition? (didn't bother buying the 17th edition and only have the 16th here) ... If you don't know where it is in 16th, and only in the 17th, could you tell me what the section is called e.g. 531-01 overcurrent protective devices (in 16th) ... that'll make it easy enough to read up about this in the 16th (I doubt anything changed in respect to fusing spurs in the 17th)

Like others, I'm getting a bit confused about what you are actually asking. In Amendment 1 of BS7671:2008 ('17th edition'), 433 is "Protection against Overload Current" and 433.1 is subtitled "Co-ordination between conductor and overload protection device". Within that subsection, 433.1.103 starts off:

"Accessories to BS 1363 may be supplied through a ring final circuit ... protected by a 30A or 32A protective device ...."

As I've said, you will not find a BS1363 accessory which can contain a 16A fuse or MCB.

Kind Regards, John