Ring Finals Vs Radials

[PrenticeBoyofDerry]

The ever popular ring final circuit seems to be on it's way out.
So what benefits does/did the ring final ever have to offer over the radial circuit.
Was the ring final circuit ever that great?
Is/was it a waste of time installing these circuits?
What are the pros and cons between these two circuits?

 

[ColJack]

who says they are going out of fasion?

ring were introduces to save on copper..
the alternative is the 4mm radial, or more circuits at a lower current such as 16A radials..

the pro's are that if you happen to break a ring earth at some point, the earth is still present at all the sockets..

 

[Click-Sure]

But break a live conductor at any point and you get a potential overload situation with no visable effects to the end user.

Thats why they're out for me!

 

[PrenticeBoyofDerry]

who says they are going out of fasion?

ring were introduces to save on copper..
the alternative is the 4mm radial, or more circuits at a lower current such as 16A radials..

the pro's are that if you happen to break a ring earth at some point, the earth is still present at all the sockets..

I'm having a heated discussion with someone who believes that ring final circuits are a waste of time and money, this was prompted by a third party suggesting that rings are being phased out(excuse the pun)for radials.

 

[Click-Sure]

They will dissapear with a revision of the regs, they nearly did with 17th, as a result, along with my own concerns about their safety, I no longer install them, and often split rings into two 20A or 16A radials as appropriate where I get chance.

 

[sparkyspike]

The good thing about rings is that the last outlet on the circuit isn't compromised because of its distance from the fusebox, mainly because all sockets on a ring are the same distance away.

Other than that they can cause problems like, as mentioned, undetected loose or broken connections. I did a PIR yesterday which located SEVEN broken connections caused by a kitchen fitter badly crimping conductors on a ring circuit and leaving it buried in the wall behind tiles.

The trouble is, before I arrived with an installation tester, nobody had a clue there was a problem.

If our UK fuseboxes weren't so miserly, there would be more room for nice short radial circuits, all on RCBOs.

 

[flameport]

Rings were ok when they were introduced.

However with RCDs now required on virtually all socket outlets, and many modern appliances having significant leakage currents, the idea of putting large numbers of appliances (e.g. a whole floor of a house) on a single circuit is flawed.

RCBOs and several smaller radial circuits would be much better. Perhaps one circuit per room? 2 for a kitchen or utility.
Whether people are prepared to pay for that is another matter.

 

[PrenticeBoyofDerry]

The good thing about rings is that the last outlet on the circuit isn't compromised because of its distance from the fusebox, mainly because all sockets on a ring are the same distance away.

are they though, you get same readings on contiuity test but that's because test is set up that way.

 

[ColJack]

the following is an example based on exagerated numbers..

for a 10m ring with 3 sockets on it, evenly spaced at 1/4 way, 1/2 way and 3/4 way round it..

ring continuity, you get 10 ohms end to end.. ( exagerated 1 ohm per meter )
mid point would be 5 ohms and 5 ohms.. ( resistors in parallel )
so
1/rt = 1/5+1/5 = 2.5 ohms..

3/4 point on one side would be 7.5 ohms and 2.5 ohms

1/rt = 1/7.5+1/2.5 = 1.875 ohms ( which would be the same for the 1/4 socket )

now, the same sockets on a radial of 7.5m ( as there is no return leg.. )
for arguments sake lets say it's 0.5 ohms per meter because you used a larger csa..
at the first socket it would be 1.25 ohms
second would be 2.5 ohms
and third would be 3.75 ohms..

 

[scousespark]

Other than that they can cause problems like, as mentioned, undetected loose or broken connections. I did a PIR yesterday which located SEVEN broken connections caused by a kitchen fitter badly crimping conductors on a ring circuit and leaving it buried in the wall behind tiles.

Crimping to extend cable is lazy, but it's not restricted to rings.

As for the sizxe of the CU, I find the restricted space in most houses more of a factor. On a recent job I fitted the CU on it's side. Looked a bit odd, but job done. Option B was to knock a partition wall down 1978 house so could have done this with a Stanley knife.

 

[ban-all-sheds]

http://www.theiet.org/publishing/wiring-regulations/ringcir.cfm

 

[RF Lighting]

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.

 

[LiamPope]

http://www.theiet.org/publishing/wiring-regulations/ringcir.cfm

That must have been a blast. Wish I'd been there!

 

[sparkyspike]

Crimping to extend cable is lazy, but it's not restricted to rings.

The point I was making was that broken connections on a ring can remain undetected.

 

[industryspark]

Scousespark wrote

Crimping to extend cable is lazy, but it's not restricted to rings

Thats a bit harsh isnt it? I understand where your coming from in that a new leg of cable is better than crimping but its not always possible to avoid crimping. There is nothing wrong with a correctly crimped joint.