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"3 Core and Earth" to led downlights
jimmyhorns
16 Posts
Question
I had already planned out the lighting cable runs for the 4 'chains' of LED downlighters for the reasonably large (7x8m) kitchen / diner / living room.
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There continues to be a bit of uncertainty as to exactly which downlights to have in each cable run - I wont bore you all with the exact details, but on some occasions we think that having a simple 4 quadrant design would be better, and at other times we think it would be better to have 2 main halves and then two areas covering the dinning room table and the kitchen island.

We have to make a decision pretty quick as we are days away from the plasterboard going up and so the 1st fix electrics being in.

Then I had a thought - maybe we dont have to make a choice at all, maybe there can still be flexibility at each light as to which of two circuits the downlight takes its live from.

If 3 core and CPC is looped in and out of each downlight, would I not be able to choose post installation. - I mean I know I would be able to - thats just basic circuit design, the question is if it is allowed? There is space within each downlighter's connection block to do this, (there are 4 terminals, N, E, 1 and 2 - all of which have a loop in and loop out). This suggests to me that I am not the first person to have this thought?

Any thoughts? - I appreciate the downsides of a longer cable run but paradoxically it wont actually be that much longer.
3 Replies
Chris Pearson
2495 Posts
Well, you cannot have two circuits supplying the same luminaire, but you could have two switches on the same circuit supplying it.

If you put small groups of luminaires on a number of grid switches (say, eight) there is nothing to stop you from turning them on in whichever combination suits the circumstances at the time. Heck, you could even switch each one individually if you wanted to!
jimmyhorns
16 Posts
Chris Pearson:
Well, you cannot have two circuits supplying the same luminaire, but you could have two switches on the same circuit supplying it.

If you put small groups of luminaires on a number of grid switches (say, eight) there is nothing to stop you from turning them on in whichever combination suits the circumstances at the time. Heck, you could even switch each one individually if you wanted to!


The live and neutral (there is no earth lead off the connector block) to the actual luminaire are by default connected to N and 1 in the connector block. If I am only looping in and out of the connector block with the other conductors presumably this wouldnt count as supplying the luminaire with two circuits as the connector block is effectively a junction box?

mapj1
3421 Posts
So long as both switched live options are on the same MCB or fuse at the CU, it is all one circuit. If you do not do this, then you need to transfer the neutrals as well.
It is perfectly OK to bring  switched L1, switched L2 and N to each fitting, and decide later which pair to hook the lamps between
Go for it.
Mike.

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