Ring or radial . . . That is the question

[Steve]

Bought a 1950s ex council house with concrete downstairs floors. Three rooms downstairs, kitchen, living room and hallway.

Kitchen will have its own socket circuit, but the living room and hall will share a circuit with upstairs. It seems wasteful to run two cables down to each socket in the living room.

Which brings to mind having the downstairs sockets as spurs from sockets directly above.

But in a couple of locations in the living room I'll want two doubĺe sockets for AV equipment. Which rules out spurs. So a radial?

There are three bedrooms so for the four rooms and hallway we'd ideally need a 32A circuit, so 4mm would be required for a radial. Would voltage drop be an issue? Could the extra length of 2.5mm actually be cheaper than the shorter length of 4mm cable?

Obviously not me doing the design or install, just batting ideas about.

 

[EFLImpudence]

Obviously not me doing the design

Well, that is what you are doing.

You will need to measure distances and do the calculations.

There is a sort of discussion in another thread - start from my first post part way down on page one.
//www.diynot.com/diy/threads/socket-box-depth.465128/

 

[flameport]

for the four rooms and hallway we'd ideally need a 32A circuit,

Do you really expect over 7kW of equipment to be used in those rooms simultaneously?

 

[deadshort]

We don't know how the property is heated ………

DS

 

[Steve]

Obviously not me doing the design

Well, that is what you are doing.

You will need to measure distances and do the calculations.

There is a sort of discussion in another thread - start from my first post part way down on page one.
//www.diynot.com/diy/threads/socket-box-depth.465128/

I was inspired by that thread to ask my question. It just seems that a ring final is not the best/most logical choice here.

Maybe two 20a radials. . .

Flameport, no i do not expect that but you never know when the heating may break for a prolonged period and we need a few electric heaters. . .

 

[flyingsparks]

It seems wasteful to run two cables down to each socket in the living room.

.

Really?! All those extra metres, what probably about 30m more by doing the job properly? Not to mention future updates to the downstair sockets?
30m of 2.5 cost about £6...

 

[JohnW2]

Really?! All those extra metres, what probably about 30m more by doing the job properly?

Given the strength of feeling that various people have in different directions, I don't think it's very fair to suggest that the only way of 'doing the job properly' is to install a ring final. Pure rings, rings with spurs and radials all have pros and cons and their champions and haters, so there usually really is a choice. The individual situation may dictate that one approach is more appropriate, sensible or easy than others - but, assuming they are properly designed, all are 'fit for purpose'.

Kind Regards, John

 

[EFLImpudence]

It seems wasteful to run two cables down to each socket in the living room..

Really?! All those extra metres, what probably about 30m more by doing the job properly? Not to mention future updates to the downstair sockets?
30m of 2.5 cost about £6...

That's what I was arguing in the other thread.

It's NOT 'not properly'. Two cables running together to and from a socket is just pointless and wasteful.

How much money and/or copper is £6 for every house in the country? World? Oh no, they don't do it.

 

[Iggifer]

Radial upstairs 20A
Radial downstairs 20A
Kitchen socket radial 20A
Cooker radial 32A (depends on cooker)
Appliance radial for washing machine/tumble dryer etc (20A - depends on appliances, maybe more than one radial)

Job done. IMO there is no excuse for poor design like dropping spurs/branches down to each socket. There's do difference to capping one cable down to two.

Agree with EFLI on ring finals though, we basically never install them anymore

 

[JohnW2]

Agree with EFLI on ring finals though, we basically never install them anymore

I may be wrong, but I don't actually think that was what EFLI was saying!

Kind Regards, John

 

[Iggifer]

I was under the impression he doesn't like them? I'll admit I didn't read all of the other thread, but that's the impression he's given in this one.

 

[EFLImpudence]

Yes, that is my fundamental belief.

I was inspired by th²at thread to ask my question. It just seems that a ring final is not the best/most logical choice here.

Oh, not sure inspired is the right word.

Anyway, in layman's terms:

Ring circuits are a remnant of the days of rewireable fuses when, compared to now when we have MCBs, 'the next size up' cable had to be used.
For example, in today's cable sizes.
15A fuse - 2.5mm²
16A MCB - 1.0mm²
20A fuse - 2.5mm² at a push
20A MCB - 1.5mm²
25A MCB - 2.5mm²
30A fuse - 6mm²
32A MCB - 4mm²
45A MCB - 6mm²
So they devised the ring circuit which wass in effect 30A fuse - 5mm² (2x2.5 although the imperial was nearer 6) but because of imbalance, restriction had to be made. 1.5mm² is still not allowed on rings even though it meets all the requirements with a 32A MCB.

So, you see, unless the circuit is actually a ring from and back to the CU with very little run to the first and last socket then a ring is hardly worth the bother.

 

[Steve]

It seems wasteful to run two cables down to each socket in the living room.

.

Really?! All those extra metres, what probably about 30m more by doing the job properly? Not to mention future updates to the downstair sockets?
30m of 2.5 cost about £6...

Your point about future updates is invalid. Since you could spur off a ring main socket or a branch off a radial socket equally.

 

[EFLImpudence]

Yes, but their point is you should have all the sockets on the ring in case one day you want to spur off one of them.

I.e. not have any spurs now.

 

[Steve]

Radial upstairs 20A
Radial downstairs 20A
Kitchen socket radial 20A
Cooker radial 32A (depends on cooker)
Appliance radial for washing machine/tumble dryer etc (20A - depends on appliances, maybe more than one radial)

Job done.

Sounds good to me. The only mod I'd make is to have the front bedrooms and the living room on one radial so the living room sockets can branch off the upstairs bedroom sockets. Otherwise one may have to use JBs or such, or run two cables down the wall, making this entire thread pointless. . . The back bedroom and bathroom would share a radial, as well as the dining end of the kitchen.