Can anyone tell me why lighting isn't generally wired as a ring and whether there would be any advantage in a ring if the physical layout meant that it was easy to do it?
Lighting Circuits - Ring/Radial
- Thread starter AdamCH
- Start date
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afaik, rings were devised to save copper... IE using 20A cable to supply a 32a circuit by creating two paths back to the consumer unit.
Given the smallest available T&E is typically sufficient to wire a lighting circuit as a radial, you'd simply end up using more cable and gain nothing.
What do you expect to gain from wiring the lighting circuit as a ring?
Given the smallest available T&E is typically sufficient to wire a lighting circuit as a radial, you'd simply end up using more cable and gain nothing.
What do you expect to gain from wiring the lighting circuit as a ring?
Or - split the ring and have two 25A radials.
That's what I was asking. Is there an advantage if the additional cable was negligible?
For example would a 1mm ring be better than a 1.5mm radial?
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1mm² cable has a current carrying capacity of 16A and your lighting circuit has a 5A fuse or 6A mcb.
This is because of the fittings and accessories connected to it.
There is no point doubling the cable.
From my above post you can see the Ring Circuit isn't such a brilliant idea.
This is because of the fittings and accessories connected to it.
There is no point doubling the cable.
From my above post you can see the Ring Circuit isn't such a brilliant idea.
It was a bit cryptic for me! "two 25A radials"? on a lighting circuit? Or are you saying that two 25A radials are better than a 32A ring so rings themselves aren't such a good idea?
'Twas, as stated, a copper saving exercise dreamt up after we won the last war. Most of, if not all, of the rest of the world run radial circuits.
Personally, I think, for sockets, rings are a good idea, it doesn't matter where the high current draw (fire) is plugged in.
As a plus its easier to do your continuity/R1+R2 tests!!
Personally, I think, for sockets, rings are a good idea, it doesn't matter where the high current draw (fire) is plugged in.
As a plus its easier to do your continuity/R1+R2 tests!!
Actually it does matter where things are plugged in - that's one of the drawbacks of rings. With radial circuits it doesn't matter because they don't have unbalanced undersized cables in parallel supplying each point.
Rings do have the advantage of a "high integrity" CPC. With a radial one loose screw in an earth terminal can break the CPC continuity to down stream sockets. With a ring it requires two loose screws to remove the CPC from any sockets. ( or one screw in the CU but that applies to radials as well )
And exactly the same "feature" is twice as likely to be a disadvantage (as there are 2 live conductors vs 1 cpc) and get you a potentially overloaded cable.
Have you never heard of MCBs and fuses ? Believe it or not these operate or melt long before the copper in the "overloaded" CPC can melt.
Or are you saying that with two live conductors leaving the MCB there can be twice the MCB's rated current coming out of the MCB terminal ?
Ib ≤ In ≤ Iz
No, I'm saying that if you get a break in L or N continuity you suddenly have a 32A radial using 2.5mm² cable.
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