Lighting circuit 1st fix

[jfb]

I am ready for first fix electrics in a very small barn/office with mezzanine bunk bed and shower room and would welcome any advice on the lighting plan.

I have an electrician on board but he is currently out of action/contact with covid symptoms.


S1 – switch for 24v LED strip lighting under the mezzanine bed
S2 – main switch for lighting
S3 – positioned at mezzanine/bed level it is a 2 gang switch – one switch as 2 way with S2 and other switch for bed reading lights
S4 – switch for lighting in shower/toilet room positioned outside the room

Avoiding any ceiling roses with circuit wires being brought into the switch.
All wiring 1.5mm 2 core except wire from S2 to S3 in 1.5mm 3 core.

Questions:

1. Anything wrong with the layout? (especially the 2 way switch S2/S3 and then going on to S4)
2. Could I use 1mm 2 core for all wires from switches to lamps? (most lighting would be from S2 – 4 small lamps on the purlins with overall length under 10m)
3. Would 35mm back boxes be sufficient? 25mm?
4. Minimum distance of wiring from EPS insulation? (only couple of sections where this is relevant)

 

[ProDave]

If S3 and S2 form a 2 way switching pair, then you will need a 3core & earth (for the 2 way switching) AND a 2 core and earth (to feed power to the other lights) between them.

 

Use 1mm for everything.  1.5 is simply not necessary for 99% of domestic lighting and in some cases is awkward in some light fittings.

 

Remember safe zones.

[jfb]

That is most helpful Dave - the three core being additional to the main feed makes sense.

And using 1mm everywhere is good to hear as I have seen some pretty busy back boxes!

[ProDave]

35mm deep back boxes are much better for "loop at switch" lighting,