New ring circuit or spurs?

[AndyPRK]

But for the same current capability you would have to wire it with 4mm cable which is a waste of copper.

Is a 4mm radial a good idea for an upstairs socket circuit do you think?

 

[JohnW2]

Is a 4mm radial a good idea for an upstairs socket circuit do you think?

Probably not, in many 'regular houses' - but, for the same reasons, a 2.5mm² radial would often be adequate.

Kind Regards, John

 

[winston1]

Any ring circuit can be converted to two radials by removing a section of cable.
That section of cable is the waste.

True but you need to replace a 32A MCB with two 20A MCBs assuming you have extra room in the consumer unit. A few metres of cable is a cheaper than 2 MCB's and possibly a new consumer unit.

Ring finals are a great idea and we should be proud to have a superior system to those foreigners that still use radials.

 

[JohnW2]

Ring finals are a great idea and we should be proud to have a superior system to those foreigners that still use radials.

You will find plenty of dissenting voices. It's certainly very likely true, as often suggested, that had ring finals not become 'allowed', and hence 'established', way back, there is probably no way that that they would be accepted (as a 'new idea') today.

Since people are talking about saving cable/copper, using 5mm² worth of conductor for a ring when 4mm² would virtually always be adequate could be argued as a bit 'wasteful'.

Kind Regards, John

 

[AndyPRK]

I'm not sure about your last para John.

A 2.5mm ring will use less copper than a
4mm radial.

 

[JohnW2]

I'm not sure about your last para John. A 2.5mm ring will use less copper than a 4mm radial.

Yes, that was an ill-conceived statement . (I was thinking of something slightly different).

Of course, if one is comparing a 32A 2.5mm² RFC with 2 x 20A 2.5mm² radials, then (again depending on topology), the radials may well win in terms of copper per amp of capacity.

IMO, the greatest 'problem' with 20A sockets circuits (no matter what configuration) is that they are less flexible (in terms of use) than 32A ones - so one has to think carefully about positioning of sockets and likely loads. The main issue is that a 20A circuit cannot accommodate (should not be expected to accommodate!!) 2 x 3kW loads, or even one 3kW plus one 2k one, whereas a 32A circuit obviously can.

Kind Regards, John

 

[AndyPRK]

As wintson said, if you were to convert 2 rings into 4 radials that would add 2 MCB's to the CU with little advantage (and more confusion)

I appreciate 32A radials are great for kitchens though.

 

[JohnW2]

As wintson said, if you were to convert 2 rings into 4 radials that would add 2 MCB's to the CU with little advantage (and more confusion)

Sure - I would think that it rarely, if ever, makes any sense to convert existing rings into radials and, as I said, then one creates the 'problem' of circuits with only 20A capacity. 'Designed as such' 32A radials are a different matter.

I appreciate 32A radials are great for kitchens though.

Indeed. On t'other hand, 20A radials in kitchens strike me as bad news - but, even in my limited experience, I've seen a few.

In case it's not clear (since I mentioned that there would be 'dissenters'), I am not 'anti rings' (and have a house full of them). I suppose one of the greatest 'concerns' about them is that there can be faults in the circuit (particularly breaks in the ring) which will not be apparent to the user but which can, for example, result in overloading of cables.

Kind Regards, John

 

[AndyPRK]

sorry I didn't mean convert, I should have said adopt the principal of using radials in new build houses.

 

[EFLImpudence]

IMO, the greatest 'problem' with 20A sockets circuits (no matter what configuration) is that they are less flexible (in terms of use) than 32A ones - so one has to think carefully about positioning of sockets and likely loads. The main issue is that a 20A circuit cannot accommodate (should not be expected to accommodate!!) 2 x 3kW loads, or even one 3kW plus one 2k one, whereas a 32A circuit obviously can.

You are arguing against yourself having stated 20A.
Use 25A.


Two 32A / 4mm² radials will give you 64A to play with.

No one worries about wasting copper anywhere else.
Replace tails with 25mm² willy-nilly, 10mm² for cooker etc.

 

[AndyPRK]

2 radials connected to 1 25A MCB could work if 2.5mm used.


10mm cooker circuits are good for those that want an induction hob and elec oven.

tails are so short, is it really a waste of copper ?

I'm sure the size of bonding conductors could be reduced though !

 

[JohnW2]

You are arguing against yourself having stated 20A. Use 25A.

I realised that, but stuck to 20A since that seems to have become 'the norm' (and, of course, some silly people will argue that App 15 of the regs doesn't mention 25A radials!). A 25A MCB would, indeed, be fine, provided one is available for one's MCB and the cable is entirely 'clipped direct'. That certainly would alleviate, although not totally eliminate, the issues I mentioned about a circuit limited to 20A.

Two 32A / 4mm² radials will give you 64A to play with.

I suppose that, at least in theory, a logical extrapolation from the 32A 2.5mm² RFC would be a 63A 4mm² RFC - but then I'm sure that people would then moan about the 'terminal ratings' of the accessories!

No one worries about wasting copper anywhere else. Replace tails with 25mm² willy-nilly, 10mm² for cooker etc.

Quite so, but the 'copper argument' always gets wheeled out whenever there is a rings vs. radials debate!

Kindest Regards, John

 

[JohnW2]

2 radials connected to 1 25A MCB could work if 2.5mm used.

I wouldn't really call that 'two radials' - a radial circuit can have as many branches (or 'radiations from one point') as you like, including multiple originations at the CU ... but, of course, you'd still be 'limited' to 25A total load.

Kind Regards, John

 

[EFLImpudence]

2 radials connected to 1 25A MCB could work if 2.5mm used.

That would be no advantage.

10mm cooker circuits are good for those that want an induction hob and elec oven.

Only if you have a 44kW oven/hob
32A and 4mm² is good for any domestic arrangement.

tails are so short, is it really a waste of copper ?

Yes, if unnecessary.

I'm sure the size of bonding conductors could be reduced though !

Not reduced, but not fitting larger than needed.

 

[EFLImpudence]

I suppose that, at least in theory, a logical extrapolation from the 32A 2.5mm² RFC would be a 63A 4mm² RFC - but then I'm sure that people would then moan about the 'terminal ratings' of the accessories!

No, I meant two separate radials.