What is wrong with rings

[bernardgreen]

In another thread one person expresses surprise at finding a ring on the lights supply.

And another comments that those who do ring lighting circuits soon learn not to.

So my question is what is wrong with a ring ?

( I have my flak jacket on )

Bernard
Sharnbrook
UK

 

[securespark]

Lighting circuits are not rings. They are radials.

 

[CookyMan9999]

the reason we do sockets rings is beacause a 2.5 mm cable can only carry 28amps of current but having it in a ring effectivley increases the surface area of cable allowing it to carry more.

In a lighting circuit this is not needed as 1.0 or 1.5mm will be sufficient to bare the load as a radial

 

[RF Lighting]

Nothing is wrong with using a ring circuit to supply lights as such, but it is completely unnecessary to use a ring circuit. A radial is more than sufficient, and as such it is the convention to fit a radial.

 

[JohnD]

A Ring is a good way of carrying quite a heavy load on a fairly light cable, and avoiding a big voltage drop at one end because it does not have an end.

However, lighting circuits carry very little current, and even a 1mm T&E would carry it with ease. The usual 1.5mm cable will carry 20A before applying de-rating factors and can be bunched, buried in insulation, and pass through hot areas and still be safe to carry 6A.

The ring brings an extra level of complication and can hide faults with broken conductors, because it still works (unlike a broken radial) but can have excessive load if that happens.

 

[bernardgreen]

The ring brings an extra level of complication and can hide faults with broken conductors, because it still works (unlike a broken radial) but can have excessive load if that happens.

Putting lights on a ring does make them tolerant to one fault of loosened connection ( tolerant in that all lights remain functional ) and the defective joint does not have to carry the full current of downstream lights so the arcing / heating at the joint is very much reduced if not eliminated.

I was told ( years ago ) that this reduction of arcing / heating at a loose connection wasone of the major benefits of ringed power circuits.

Yes I am aware that any fault needs to be noticable and faults on rings can be "hidden".

On a radial with a loose connection in the first socket and full load at the far end the loose connection is going to get hot. If this first socket is out of sight and not used then until the electrician arrives to sort out the intermittant power this socket is a hazard.

Bernard
Sharnbrook

 

[jj4091]

the reason we do sockets rings is beacause a 2.5 mm cable can only carry 28amps of current but having it in a ring effectivley increases the surface area of cable allowing it to carry more.

In a lighting circuit this is not needed as 1.0 or 1.5mm will be sufficient to bare the load as a radial

Do you mean cross sectional area?