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Recommended wiring topology for multiple lamps on one switch?

Nicholas Lee
As having an array of mains downlighters or spotlights in a ceiling is now fashionable, (rather than a single central luminaire), this begs the question of how to optimally and correctly wire them all up to the light switch.

In the case where one light switch operates multiple lights (as powered by from the domestic lighting circuit), there are several possible ways to wire from the switch to each of the lamps.

[It is taken as obvious that each lamp needs to be wired in parallel, with connections to the mains neutral and the switched-live wires.]


The (twin-and-earth) cable routing from the switch to all the lights and could be one of:

1) Daisy-chain   (the cable goes from the switch to one lamp, and then on to the next lamp, until all lamps are connected)

2) Ring    (like the daisy-chain wiring, but the final connection then links back to the switch to create a "ring main")

3) Star   (separate cables go from the switch to each lamp)

4) Tree   (i.e. a balanced spanning-tree, where the cable goes from the switch to two lamps, and each of them connect to two lamps, branching until all lamps are connected)

Each topology has different implications regarding the current distribution, and its associated heating losses in each segment of cable.

For example, a Daisy-chain topology has the highest current loading in the cable segment closest to the switch, but it uses the least cable; whereas the star topology has equal current loading in all its cable segments, but it uses the most cable.


Do the IET regulations recommend a particular wiring topology for particular scenarios, and what does everyone use in practice?

Thank you
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    Ok, not sure where the kitchen is, assume the table goes under the larger of the 2 skylights.


    If fed from above, then two runs of three and earth between the switch locations, and one T and E to the kitchen and two to the one by the patio - I don't like shared lives, but it would be possible at a push to away with less 3 core.


    If fed from above the lines from the switches become T and E switch lines. Steady live feed to the lights nearest these . Then centre fed chain from the patio doors for the perimiter and  either star or chain the 4 to minimise joist crossing.

    If fed via switch box, then it gets quite full at the 3 way switch, as you need an L + N and the three cores becomes L1.L2 and N from the supply end and L1.L2 and switched live to lamp at the slave end, and need cutting in part way along, and you end up with a black switched live and a black neutral at that point, assuming black is the slider core and Brown and Grey are the L1 L2 'strappers' between the fixed contacts.

    I'm sure there is an infinite sea of alternative right answers.



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  • 0
    Ok, not sure where the kitchen is, assume the table goes under the larger of the 2 skylights.


    If fed from above, then two runs of three and earth between the switch locations, and one T and E to the kitchen and two to the one by the patio - I don't like shared lives, but it would be possible at a push to away with less 3 core.


    If fed from above the lines from the switches become T and E switch lines. Steady live feed to the lights nearest these . Then centre fed chain from the patio doors for the perimiter and  either star or chain the 4 to minimise joist crossing.

    If fed via switch box, then it gets quite full at the 3 way switch, as you need an L + N and the three cores becomes L1.L2 and N from the supply end and L1.L2 and switched live to lamp at the slave end, and need cutting in part way along, and you end up with a black switched live and a black neutral at that point, assuming black is the slider core and Brown and Grey are the L1 L2 'strappers' between the fixed contacts.

    I'm sure there is an infinite sea of alternative right answers.



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