Ring Finals Vs Radials

[ericmark]

I can't imagine a situation where an electrician would be confused about what the circuit was, and what size cable to use.

I don't need to imagine. I have worked in factories which have always employed electricians so all electrical work was done by electricians.

I found a room where the single socket outlet had been changed to two singles and a 2.5mm cable went around the room from one to other where some one had tried to extend the ring. Had it been a ring it would have been considered as a good professional job. But it was a 4mm radial on a 30A cartridge fuse.

I changed to 20A MCB it was only option which also resulted in the fan heaters no could longer be used together.

Sorry to say not all electricians are as careful as they should be. Until I started there was no earth loop impedance meter on site and not PAT testing records. I was employed in the main to get site to a standard the HSE would accept.

It was not the only company I had worked for where there was no earth loop impedance tester available for the electricians. Often the mega was only specialist tester.

Although in the main factories were better than domestic as far as plans were concerned and many had good plans. Where as in domestic the plans to show what is fitted and where is often missed.

I can see the ring going. It is illegal in some countries to have parallel conductors of unequal length. But the 13A socket is still the best in the world and to remove it and still comply with regulations as to reversibility and cable sizes would mean duel sockets with the old 5A and 15A sockets so light 0.75mm flex can still be used. The 2.5A lead set is very common these can't be safely used with the German Schuko sockets.

I can see new sockets being marketed, which can better take the thicker 6mm cable and so the ring main can become history. MK sockets already take larger cables than many of the cheap ones.

I also see the need for a FCU able to take larger fuses than 13A for supplying hobs and the like as at the moment only the consumer unit can take units over 13A which means two feeds for hob and oven etc.

 

[AndyPRK]

I wonder how the rest of the world copes without fuses in their plugs ?

 

[ericmark]

I wonder how the rest of the world copes without fuses in their plugs ?

Thick cable

 

[ebee]

I wonder how the rest of the world copes without Ring Final Circuits?

That Great British invention that has stood the test of time.

A few basic rules, a good amount of common sense and off we go - superior

 

[plugwash]

I wonder how the rest of the world copes without fuses in their plugs ?

Thick cable

Not really, afaict their low current flexes are often just as thin as ours are. They seem to rely on the MCB to provide short circuit protection and rely on the characteristics of the load to prevent overloads. Probablly works ok as long as the flexes stay reasonably short.

AIUI the main purpose of the fused plugs was to make 30A ring circuits (which don't forget were protected by rewirable fuses which afaict provide far less protection than the MCBs we use today) reasonablly safe. Providing better protection for small flexes than the old system (which would often see thin flexes protected by a 15A fuse) was just the icing on the cake.

The 30A ring circuit was itself created as a copper saving measure, not to try and improve safety.

 

[ban-all-sheds]

I wonder how the rest of the world copes without Ring Final Circuits?

And I wonder why you felt the need to resurrect a 2½ year old topic....

 

[ebee]

 

[securespark]

Rings have their uses, as do radials.

It's all about designing an installation properly, and using either type of circuit where it is most apropriate given the circumstances.

For something like the upstairs socket circuit in a standard domestic house, there is no circuit more suited to this application than a ring final, whereas a circuit in a kitchen to supply the washer / dryer / dishwasher / oven etc would be much more suited to a radial.

I often see older houses with a 20A radial for upstairs sockets. Generally they are not hugely loaded.

 

[ericmark]

Nearly 3 years ago but oddly it has just come up again where my son has bought a house.
Unlike some of the comments before there is no issue with workmanship and we both have a full test set.
The recording of loop impedances really means there is no longer a problem with broken rings a quick test soon shows any error.
However other than kitchen can't really see where we need more that 20A and since the idea is one room at a time a RCBO per room makes a lot of sense.
The only question is consumer unit loading. Two rings and lights plus oven and impossible to ever exceed the capacity of the supply. (Gas hob and he's an electrician!) Heating all gas so no shower or immersion to consider.
Main load is washing machine. Which in the past ran from a 3KVA inverter so that's not a problem.
But how many sockets per room. OK could run track and fit and remove at will but in real terms how many?
Stick 4 sockets for TV and sods law she will want it moved so still ends up with a 4 or 8 way adaptor to run video, Sky etc. So is it worth anything more than 4 doubles per room?
Dado sockets for kitchen maybe but all other rooms is it really worth more than 4?
To wire one room at a time then radials seems to make sense? Ceiling to be replaced so wire from below.
Just can't see any reason to use a ring except for kitchen?

 

[ban-all-sheds]

Why not use a 30 or 40A radial for the kitchen?....

 

[ebee]

Are the terminals on sockets OK for 40A ?

 

[JohnW2]

Why not use a 30 or 40A radial for the kitchen?....

Are the terminals on sockets OK for 40A ?

Quite apart from the CCC, the terminal capacity is quite likely to be an issue. As far as I can make out, even for a 32A radial, unless it's all clipped direct, you'd be having to use 6mm² - and for a 40A radial, unless it was all clipped direct, you'd have to use 10mm². I think some sockets (e.g. MK) have terminals rated to take 2 x 6mm², but I don't think any would take 2 x 10mm².

Kind Regards, John.

 

[EFLImpudence]

Clipped direct it is then.

 

[securespark]

Why not use a 30 or 40A radial for the kitchen?....

Ban, I thought you took a dim view of anyone suggesting a non-standard circuit arrangement...

 

[securespark]

I changed to 20A MCB it was only option which also resulted in the fan heaters no could longer be used together.

Better off to replace the 2.5 with 4. With today's regs, you could have had a spur off a 4 milli radial in 2.5, but I take it this was in the days of the 15th?