DIY a new ring main

[JohnW2]

Yes, two radials would certainly be an option, although in all likelyhood oversized for the expected demand. They‘d probably use less cable than a ring.

As you say,that's certainly an option.

As I always say, although I'm sure that it will usually not be an actual problem in practice, I am personally not all that comfortable with 20A (or 16A) radials, since it doesn't seem ideal to have umpteen "13A" outlets on a circuit when, at least in theory, just two loads could 'overload' the circuit.

I'm perfectly happy with 32A (4mm) radials or, if devices are available for the CU, 25A ones, since, cable-loading-wise, there are no worse than 32A rings.

 

[AndyPRK]

While I love a ring (in a kitchen for example or to cover a whole floor area), and also I love a 25A radial.

but OP please don't use 4mm in your living room! It's good for a kitchen. But not one living room

 

[JohnW2]

While I love a ring (in a kitchen for example or to cover a whole floor area), and also I love a 25A radial.

As I said, I'm also happy with 25A radials,and even more so with 32A ones.

... but OP please don't use 4mm in your living room! It's good for a kitchen. But not one living room

What do you mean by that?

I would have no problem with a 32A radial supplying anywhere, including a living room. For those who favour radials, 25A devices are not available for many CUs, leaving one stuck with a maximum of 20A - and, as I've said, I'm not totally comfortable with 20A radials, so would much prefer 32A (4mm²) ones, in any room(s).

 

[AndyPRK]

using 4mm for a living room is
1 A waste of money
2 Possibly a bit more of a pain to terminate at the sockets.

Worse case the central heating fails. You get 2 heaters. 10A each I think they are.

2 heaters and the tiny current drawing devices you find in a living room are unlikely to trip a 20A mcb. (Especially with thermostats operating )

 

[JohnW2]

using 4mm for a living room is 1 A waste of money

It obviously depends upon the situation, but a 4mm² radial does not necessarily cost more (or 'use more copper) than a 2.5mm² ring final (which would be the 'traditional' situation)

2 Possibly a bit more of a pain to terminate at the sockets.

I suppose experiences vary, but I personally find 4mm easier and nicer to work with than 3.5mm.

Worse case the central heating fails. You get 2 heaters. 10A each I think they are. 2 heaters and the tiny current drawing devices you find in a living room are unlikely to trip a 20A mcb. (Especially with thermostats operating )

Probably true, but a circuit is usually unlikely to supply just one room (other than a kitchen), so what if one gets 3 or 4 heaters - or what if someone does some vacuuming, hair drying, ironing or whatever whilst the heaters are running?

I'm sure that, in practice, one would virtually always 'get away with it' but it really does not 'feel right' to me to have a dozen or more "13A" socke outlets on a circuit which theoretically cannot take even 2 x 13A loads.

 

[AndyPRK]

But if we were to stay on topic, the OP is wanting to power 1 living room and a couple of hall way sockets.

I think in this case 4mm, would use more copper.

While the sockets are 13A capable, it's a rareaty these days to have things that actually use 13A.

If someone is foolish enough to do hoovering while the heating is broken then I have no sympathey for an MCB trip.

(Can't believe I'm arguing against rings, this has never happened before)

 

[JohnW2]

But if we were to stay on topic, the OP is wanting to power 1 living room and a couple of hall way sockets. I think in this case 4mm, would use more copper.

It depends upon the layout/topolgy, not the nature oof the room(s) supplied.

In the extreme case, with sockets all in a straight line radiating from the CU, a 2.5mm² ring would use 25% more copper than would a 4mm² radial - since 2 x 2.5 = 5.

 

[EFLImpudence]

In the extreme case, with sockets all in a straight line radiating from the CU, a 2.5mm² ring would use 25% more copper than would a 4mm² radial - since 2 x 2.5 = 5.

It is more than that. I make it 36% because with 2.5mm² there is also twice as much CPC.

 

[AndyPRK]

I was comparing a 2.5mm radial. And 4mm radial.

 

[flameport]

4mm² T&E is a poor choice as it's disproportionately more expensive than other sizes as very few people buy and use it.

Also not forgetting this is a lounge/diner which will have tiny loads plugged in.
A single 20A circuit is almost certainly adequate. Perhaps two of them if additional division is desired for convenience or other reasons.

 

[JohnW2]

It is more than that. I make it 36% because with 2.5mm² there is also twice as much CPC.

Yes, that as well.

 

[JohnW2]

4mm² T&E is a poor choice as it's disproportionately more expensive than other sizes as very few people buy and use it.

That#s true, but if 32A radials become more common, then your logic would suggest that the price of 4mm² would fall.

Also not forgetting this is a lounge/diner which will have tiny loads plugged in. A single 20A circuit is almost certainly adequate.

Indeed, I have acknowledged that.

Perhaps two of them if additional division is desired for convenience or other reasons.

The problem of that is that it then becomes a matter of 'pot luck' other than for people (probably not mny) who know how the circuits have been wired - someone with two (or more) large loads is as likely to plug both into the same circuit as into different ones.

 

[Ragnar_AT]

I spend a lot of time in a country where 13 A radials are the norm. The only time I‘ve ever seen one of then overloaded was with multiple electric heaters plugged into one circuit. Had it been one circuit per room everything would have been fine but this circuit supplied two bedrooms. Overloading a 20 A radial (except in a kitchen) should be pretty much impossible in a home.

 

[Harry Bloomfield]

I would have no problem with a 32A radial supplying anywhere, including a living room. For those who favour radials, 25A devices are not available for many CUs, leaving one stuck with a maximum of 20A - and, as I've said, I'm not totally comfortable with 20A radials, so would much prefer 32A (4mm²) ones, in any room(s).

It is a completely unnecessary waste of money, effort, and copper.

 

[EFLImpudence]

Except that it could cost less money, take less effort and use less copper.