I know that sockets are normally wired in ring finals but is there ever any need for lighting to be wired in a ring?
Just Interested....
- Thread starter wreck-it-steve
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They can be found wired in a RFC but as above not in domestics.
why would you want to?
I'm not saying you would want to but I just wondered if that's how it was done in big factories or offices where they have lots of lights on one circuit but lighting terminals would only accept certain cable sizes.
Com/Ind lighting a little more accommodating for cable cores.
Voltage drop with large installations?
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314.1 Every installation shall be divided into circuits, as necessary, to:
(i) avoid hazards and minimize inconvenience in the event of a fault
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
Because of these rules lighting circuits are not that big. One may find there is a contactor or relay so although one switch may switch on a huge amount of lights one can still switch off small groups by opening a distribution board.
The whole idea of the final ring was to save copper after the second world war and the main component was the fused plug system. There are lighting systems with similar fused plugs which allow for maintenance a single lamp to be isolated without switching off the whole system but this is normally part of lighting track often around 16A so even with reasonable long runs there is no need for a ring.
The final ring is not the only ring system it is common to have two supplies so that areas can be isolated for maintenance but unlike the final ring the cable can take the whole load of the circuit.
I have seen lighting rings in domestic but I suspect it is because some one working on it did not realise why we use a ring circuit and wired it that way in error.
As to volt drop that has been disused many times. When using HF florescent fittings able to run on any voltage between 200 and 250 there is no real need to worry about volt drop. The old inductive control however was very different.
(i) avoid hazards and minimize inconvenience in the event of a fault
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
Because of these rules lighting circuits are not that big. One may find there is a contactor or relay so although one switch may switch on a huge amount of lights one can still switch off small groups by opening a distribution board.
The whole idea of the final ring was to save copper after the second world war and the main component was the fused plug system. There are lighting systems with similar fused plugs which allow for maintenance a single lamp to be isolated without switching off the whole system but this is normally part of lighting track often around 16A so even with reasonable long runs there is no need for a ring.
The final ring is not the only ring system it is common to have two supplies so that areas can be isolated for maintenance but unlike the final ring the cable can take the whole load of the circuit.
I have seen lighting rings in domestic but I suspect it is because some one working on it did not realise why we use a ring circuit and wired it that way in error.
As to volt drop that has been disused many times. When using HF florescent fittings able to run on any voltage between 200 and 250 there is no real need to worry about volt drop. The old inductive control however was very different.
One advantage of a ring for the lighting is that a single fault such as a loose connection in a ceiling rose does not result in loss of lights. I accept it is a fault that will go undetected but it is a fualt that does not present a high risk. Both sides of the fault are connected via the ring to the same potential ( live or neutral ) so no significant current can flow through the fault.
The same fault in a radial would have live on one side and neutral on the other with some lamps in series with one of them. The load current for those lamps would need to pass through the fault. If the fault was a resistive connection and not open circuit then current could flow through the fault and create heat at the fault.
I have only come across a RFC on a lighting circuit twice.
Once when a plumber asked me to take a look at his wifes new shop where he had added new lights and couldn't get them to work. He had wired a ring......from the off peak board
And I came across a ring on a caravan park - a 16mm SWA looping around all the street lights. I was locating a fault causing the 60amp fuse feeding this to blow, loosing ALL lights. A poor design.
IMO there is simply no practical reason why you would consider using a RFC for lighting, domestic or otherwise!
Lighting is generally grouped *fairly* close together, and if it a long way from the DB, then wiring a ring to combat voltage drop/loop impedance issues is pointless - It just means a second long run of cable.
Once when a plumber asked me to take a look at his wifes new shop where he had added new lights and couldn't get them to work. He had wired a ring......from the off peak board
And I came across a ring on a caravan park - a 16mm SWA looping around all the street lights. I was locating a fault causing the 60amp fuse feeding this to blow, loosing ALL lights. A poor design.
IMO there is simply no practical reason why you would consider using a RFC for lighting, domestic or otherwise!
Lighting is generally grouped *fairly* close together, and if it a long way from the DB, then wiring a ring to combat voltage drop/loop impedance issues is pointless - It just means a second long run of cable.
that would be ok for an all night shop!Once when a plumber asked me to take a look at his wifes new shop where he had added new lights ............ ..........from the off peak board
It does have its merits though, assuming its a big park and lots of lights, to wire smaller radials woud probably resulted in quite a lot of 6 / 10mm runs and overall quite a bit more copper
And once the damaged bit had been found, it could be isolated and the rest kept live untill ground works could be scheduled, granted some of them might be a bit dim and if you are really unlucky some might struggle to strike.
Of course the single cable fault blacking out the lot is the downside, but I guessed they assued that was unlikely to occur. Did you find what had caused the damage?
I believe one of the schools round here has its site distribution on a ring, looping in and out of busbar chambers in various blocks via a pair of isolators.
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