2-way light switches using 3 core unconventionally

[echoes]

All,

I have 2 lights, both of which need to be under 2-way control. I am looping in at the switches where there is therefore always a line and neutral available.

I am proposing this arrangement:
[code:1]

SWITCH BOX 1 SWITCH BOX 2

----------L---------o---------------------------o-------L----------
----------N---------o---------------------------o--------N----------


o------------N
LAMP1 /o-------------------------o
o-------SL-----o o---L
o-------------------------o/
N----------N------o
/o-------------------------o LAMP2
L--o o--------------SL------o
o-------------------------o/
[/code:1]

(Inside the switch boxes, all L's, N's and CPC's are connected together (not to each other!).)

Between the 2 switch plates (and disregarding CPCs), I therefore need line and netural, plus 2 switched lines for each lamp (6 conductors).

Question is: I can use 3 runs of T & E or 2 runs of 3-core and earth. But with the latter, the SL's for one lamp will be carried in different cables - one with the lighting circuit's L & N, and the other with the other lamp's SL's. With correct sleeving, is this perfectly acceptable, OK, but asking for confusion, or just bang out of order?

I am aware that there are various other arragments of wiring this, but this is one of the more economical in terms of cable.

Thanks in advance - what do you think?

 

[Chri5]

Run 1mm 3 core x 2 between the switches and do it right.

Cable sharing isn't right, each part of the switch should be considered separate to one another.

Having 3 x 2 core (on a TE NEVER use the earth) where each side of the switch uses 3 wire is messy, maybe outside rules and could be a source of mystery to anyone working on it in future years.

Keep things standard, which is 3 core 1 x switch A to B, 3 core 1 switch B to A.

See wiki on the title bar for clear wiring diagrams should you need.

 

[ban-all-sheds]

Run 1mm 3 core x 2 between the switches and do it right.

It's just as right to use twin & earth strappers as he shows.

I agree, mixing things up to use 2 x 3C+E instead of 3 x T+E isn't right, but using 3 x T+E is perfectly OK.

 

[echoes]

Thanks Chri5 - the cable sharing wasn't sitting right with me, hence the post.

I will keep things standard and easy to identify.

I think this has less potential for confusion, but switch box will have 5 cables entering (6 if I need to loop out). Bit of a challenge, but I'm sure it can be done...I'll post a pic when I've wired that up.

[code:1]
SWITCH BOX 1 SWITCH BOX 2

----------L-------o----------------------------------------------
----------N-------o----------------------------------------------


L---o-----------------------------o
\o-------------------------o/
o--SL--------o-----------------------------o
LAMP1
o--------N


L---o-----------------------------o
\o-------------------------o/
o--SL--------o-----------------------------o
LAMP2
o--------N

[/code:1]


Using the CPC as a line was never going to happen!

 

[echoes]

@b-a-s

Thanks - I agree that the cable sharing was a poor idea. Thanks for confirming. T&E strappers is going to save me some space inside the back boxes and will therefore require less swearing.

Running 4 X T&E and 2x 3-core&E through 2 knockouts in a single back box would be a bit challenging. Thank God I decided against 1.5mm2, and with it, any prospect of a flood of halogen downlighters (result!).

 

[electronicsuk]

Worth noting that the cable sharing you describe could also be a recipe for future problems with low energy lamps, as capacitive coupling from the other live cores can generate just enough current to cause such lamps to flicker dimly even when turned off.