Electrics in General - Stupid Question

[holmslaw]

..

 

[viewer]

No problem using 6mm if you choose the right sockets (Crabtree and MK will hold 2x6mm), although, because it is harder to make bends, you often need deeper boxes than with 2.5 or 4.

 

[ban-all-sheds]

I don't think a 20A RFC is recognised by the regs?

Yes it is, as is any other properly designed circuit.

What do you do about 523.8 and 433.4.2?

 

[Spark123]

I don't think a 20A RFC is recognised by the regs?

Yes it is, as is any other properly designed circuit.

The examples of ring and radial power circuits are options, i.e. there are other ways of skinning the cat.

It isn't the examples I was thinking of, it is the specific regulation regarding ring final circuits which includes protective devices, cable sizes etc.

 

[NotHimAgain]

The specific regulation you mention [433.1.5] does not preclude other designs.

'Industrial power rings' with an protective device of 200A or 100A were quite common - these would now be classed as distribution circuits, but the principle still applies. They are a poor mans alternative to bus-bar trunking - IMO not very nice - but they can be made compliant with BS 7671.

Some used overhead line taps as connection units. These can have an insulated cover placed over them but it sometimes drops off if disturbed - with electrifying results .

 

[ban-all-sheds]

The specific regulation you mention [433.1.5] does not preclude other designs.

No, but other designs would not comply with 433.1.5.

'Industrial power rings' with an protective device of 200A or 100A were quite common - these would now be classed as distribution circuits, but the principle still applies. They are a poor mans alternative to bus-bar trunking - IMO not very nice - but they can be made compliant with BS 7671.

Some used overhead line taps as connection units. These can have an insulated cover placed over them but it sometimes drops off if disturbed - with electrifying results .

What about final circuits for socket outlets, i.e. the type under discussion - what do you do about 523.8 and 433.4.2?

 

[NotHimAgain]

433.1.5 only considers ring final circuits protected by 30A or 32A devices, wired using conductors with a minimum CSA of 2.5mm². As such it does not apply to other designs.

A design using a 20A protective device might be wired using 2.5mm² and, subject to installation conditions, this could comply with BS 7671 generally, including 433.4.2.

523.8 does not preclude ring final circuits and the definition of these is not specific to cable or protective device sizes.

Now all you need to do is differentiate between a parallel circuit and a ring circuit, or prove that they are one in the same, and you might have a case against an industrial power ring .

 

[ban-all-sheds]

433.1.5 only considers ring final circuits protected by 30A or 32A devices, wired using conductors with a minimum CSA of 2.5mm². As such it does not apply to other designs.

No, but it's the only one which explicitly permits ring finals where the OPD is higher rated than the cable.

A design using a 20A protective device might be wired using 2.5mm² and, subject to installation conditions, this could comply with BS 7671 generally, including 433.4.2.

Indeed, but the whole point of a ring final is that the OPD has a higher rating than the cable, so I assumed that in any alternative RF design you'd still want that.

433.4.2 would not let you use a 20A OPD if the cable was not rated at 20A.

523.8 does not preclude ring final circuits and the definition of these is not specific to cable or protective device sizes.

No, it does not, but the only regulation which supports ring finals is 433.1.5.

Now all you need to do is differentiate between a parallel circuit and a ring circuit, or prove that they are one in the same, and you might have a case against an industrial power ring .

This discussion is about ring final socket outlet circuits.

 

[NotHimAgain]

Indeed, but the whole point of a ring final is that the OPD has a higher rating than the cable, so I assumed that in any alternative RF design you'd still want that.

433.4.2 would not let you use a 20A OPD if the cable was not rated at 20A.

Why is it the "whole point"? There are other consideration such as the number of load points that are traditionally connected; voltage drop; functional earthing to name a few.

The fact that a reduced cable size can be used under certain circumstances is useful, but it is not the only justification.

This discussion is about ring final socket outlet circuits.

Read the OP again BAS it is not that specific.

 

[martinxxxxxx]

This is great - the Titans of the forum clash

Who is winning?

 

[electronicsuk]

This is great - the Titans of the forum clash

Who is winning?

I think you know there can only be one winner, as the BAS-inator will not stop until all his enemies are dead, or at least completely belittled

 

[ban-all-sheds]

Why is it the "whole point"? There are other consideration such as the number of load points that are traditionally connected; voltage drop; functional earthing to name a few.

That's true.

The fact that a reduced cable size can be used under certain circumstances is useful, but it is not the only justification.

But it's always the case in domestic socket outlet ring finals, and it's always a main advantage, as things like volt drop are unlikely to be an issue.

Read the OP again BAS it is not that specific.

Hi guys, could someone gave me, or direct me to, a general overview of how a house is wired.

 

[GaryMo]

This is great - the Titans of the forum clash

Who is winning?

I think you know there can only be one winner, as the BAS-inator will not stop until all his enemies are dead, or at least completely belittled

Or bored?

 

[martinxxxxxx]

I have BAS ahead slightly on 1 technical point, ie what is the point of using a ring if it does not allow you to increase the cable current capacity. though the point about volt drop is valid, it is not a killer blow to BAS's argument.

Maybe it is all over and the victor is last man standing.

Hope the OP is looking all this up in his red book as we progress.

Martin

 

[londonboy]

I can't see where 523.8 and 433.4.2 say anything about ocpd size?!