Some basic lighting circuit questions

[d000hg]

Sorry for the really novice questions - I've done mains sockets before but never lighting and a few little things are confusing me...

1)I keep wondering, why do you run the cable from supply -> light -> switch rather than supply -> switch -> light? It seems like both should work just fine but the first one is the only way I've seen instructed... even though it means using more cable.

2)If I want one switch to control multiple lights, I just run the cable supply -> light1 -> light2 -> switch i.e. in series, right? Will the light fitting pass current on even without a bulb in or will one blown bulb mean they all go dark?

3)The bayonet fittings I have only have live/neutral terminals, what happens about earth... not used? My light-switch has a metal body with an earth terminal, if there's no earth through the lighting what do I do here to be safe?

Thanks!

 

[riveralt]

Sorry for the really novice questions - I've done mains sockets before but never lighting and a few little things are confusing me...

1)I keep wondering, why do you run the cable from supply -> light -> switch rather than supply -> switch -> light? It seems like both should work just fine but the first one is the only way I've seen instructed... even though it means using more cable.

You can do either.

2)If I want one switch to control multiple lights, I just run the cable supply -> light1 -> light2 -> switch i.e. in series, right? Will the light fitting pass current on even without a bulb in or will one blown bulb mean they all go dark?

You need to look up the difference between series and parallel lighting. House lights are wired in parallel.
//www.diynot.com/wiki/electrics:lighting:parallel

3)The bayonet fittings I have only have live/neutral terminals, what happens about earth... not used? My light-switch has a metal body with an earth terminal, if there's no earth through the lighting what do I do here to be safe?

Plastic accessible fittings are Class 2 and therefore do not need an earth. For metal fittings you must run an earth from the switch earth terminal to the back box which itself should be connected to the Main Earthing Terminal.

For further information look here:
//www.diynot.com/wiki/electrics:lighting

 

[d000hg]

Ah, I see about the parallel thing. I was wondering if light fittings acted as a simple junction box, but if the bulb is the only thing making the connection clearly lights in series won't work very well

The light fittings I have don't seem to look like the ones in most circuit diagrams (thanks for the link). They have 3 terminals but according to the instructions, it should be done like this
[code:1]
---------------| LOOP |-----------------
SUPPLY SWITCH
___________________|____________________
[/code:1]

It seems a bit weird to me. In my very simply setup I just really want something like this:

[code:1]FCU=========/switch/========light[/code:1]

Is that workable? It would also mean I have an earth from the FCU to connect up to the switch, and I just connect a cable directly from the switch to the light and on that stretch, ignore earth entirely.

My switch is actually a 3-gang switch, it supports 1-way or 2-way but for my needs, doing as described above to 3 separate lights would be just fine and gives me more control anyway.

 

[stillp]

just connect a cable directly from the switch to the light and on that stretch, ignore earth entirely.

You should run an earth to the location of the light fitting, in case you or someone else decide to change the light fitting for a metal one.

 

[d000hg]

Sorry, I'm using 2-core and earth so by ignore I meant "leave it in place but don't attach to the light fitting".