bedroom wiring challenge...

[Marc Bowler]

Hey guys


I’m new to the forums and this is my first post, I’m undertaking a reasonable wiring job in my master bedroom whilst I should point out I’m definitely not an electrician (I guess that’s kinda obvious otherwise I wouldn’t be here asking advice!) but I am an aerospace engineer, so I’m fairly competent at most types of manual work. I think I’ve got most of it worked out and I just need a few final pointers if you guys wouldn’t mind.


I’ll give you some background on what I’m doing, what I’ve already done and then I’ll move on to the questions, so please bear with me whilst I explain...


So I’m installing the following in my main bedroom...


main lighting:


3 x recessed down lights

Under bed and behind headboard strip lighting


These both are to be controlled via a switch by the door as you enter the room, and from both sides of our bed.


Secondary lighting:


A small wall mounted reading lamp either side of our bed

A custom made full length LED mirror


I’m confident that I’ve done the wiring correctly for the light switches. As I understand it 3 way switching is configured by the wiring between the 3 switches (I’ve got a 2 gang 2 way switch on the wall as you enter the room, a 2 gang intermediate switch in the middle of the circuit on one side of the bed and another 2 gang 2 way switch at the end of the circuit on the other side of the bed) aside from the first light switch in the sequence it’s not affected by the wiring in the loft coming from the junction box (previous light in another room)


My plan is to have this junction box as a 6 terminal 20A and by my workings out there will be 6 cables wired to it (originally would have been but I’ll come back to this.


Power in (power coming from previous light from another room)

Power out (going to a second JB to supply power to reading lights and mirror)

Switch 1 (1.5mm T&E going to 1st gang on the first light switch)

Switch 2 (1.5mm T&E going to 2nd gang on the first light switch)

Light 1 (cable going to ceiling down-lights, this is one of the questions for later)

Light 2 (1.5mm T&E going down inside the hollow walls to under bed lighting socket)


So here are the questions


Question 1:


Assuming I can fit them in is it ok/safe to have 6 cables in a junction box, I noticed on the back of the JB it has printed 4 x 1.5mm max?


If I’d have done it my original way there would have also been the power for for the reading lamps and the mirror which would have been 8 Cables, I thought this to be far too excessive


Question 2:


According to the manufacturer instructions for installing the down lights it says that you can use 0.75mm - 1.5mm cable for the lighting, I have already put the lights in (coming from a 4 terminal junction box) and connected them together via 0.75mm flex rated at 6A, and assuming that’s ok (please say so if it’s not) my question revolves around the first light in the sequence (the one coming from that junction box) can this cable also be 0.75mm flex? I’m asking because I read somewhere (can’t remember where) that all the cables coming from a JB should be of the same size and although I could fit 1.5mm T&E in the boxes that attach to the down lights I would have to cut away some of the plastic casing to make that happen.


Question 3:


The wife wanted the mirror hard wired in so as to not have any cables showing so in this instance I'm simply treating it as another light, much like the wall mounted reading lamps they dont require the switch wire as they have thier own switch (the mirror also has its own touch switch built into the mirror surface) incidentally the reading lamps are of a flush wall design and as such all their wiring and workings go inside the hollow wall, these are to be mounted a few inches above the light switches on either side of the bed, and all the cabling from the light switches is just about running up behind the lamps


The mirror has a short length (about 4 inches) of 3 core 0.75mm coming out of the light Transformer at the back so my plan is to extend this by linking the same cable type to it so I have say at least metre of flex to play around with (this is only so I can physically remove it from the wall and unwire it if i need to, the excess will be hidden by the rear recess of the mirror) then to attach that length of flex to the cable within the hollow wall via a terminal block, I'll then hide the terminal block in a backbox behind a simple face plate behind the mirror, that way the cable will apear to be coming straight out of the wall. There’s not enough space for a plug socket behind the mirror without making the mirror sit proud away from the wall.


So this question is kinda the same as the last one: can the connection Between the terminal block and the last junction box be 0.75mm flex cable as oppose to running another length of 1.5mm T&E? I only ask this because the mirror is to be mounted next to the side of the bed that has the intermediate lightswitch and there's already an abundance of cables concealed within the wall, and although it wouldn’t be impossible for me to get 1.5mm T&E up inside the wall it would certainly be a squeeze...thus far all cables have been placed in designated safe zones


Running up the safe zone from the intermediate light switch (and behind the reading lamp) are 4 x 3C & E (two go to the first switch, and the other 2 go to the last switch) and 1 x 1.5mm T&E for the reading lamp, so there’s already five cables there four of which are quite large


I apologise for the length of this post but I wanted to give as much detail as possible so that you guys understand what I’ve done.


Do my questions make sense and does what I’ve explained sound reasonably above board?


Many thanks for taking the time to read it

 

[Taylortwocities]

Sorry, CBA to read all of your thesis..

I would use 1mm² T&E cable throughout.

This "flex" is it 3-core? Don't forget you must have an earth (CPC) running throughout your wiring.

I noticed on the back of the JB it has printed 4 x 1.5mm max?

This is the max number of 1.5mm² conductors in each terminal. As I say, 1mm is easier and youll soon run out of terminal space with 1.5mm². (Someone will probably mumble about saving the Earth's mineral resources too).

Any junction boxes must be accessible.

 

[Marc Bowler]

The flex currently wired between the down lights is 2 core, I'll attach a picture of the installation booklet page and and the wire coming from the back of the mirror is 3 core.

As for the junction box it is in the lift and my loft is only a crawl space, so yes technically it's accessible, but it will be attached to one of the rafters

 

[Taylortwocities]

The only bit of wire that can be 2-wire is the (supplied) short bit from the downlight to its terminal box.
All the other cabling must be 3-core and the third core connected to earth, all the way through so you can test earth at the last light in the string. You'll need an earth there to do your final testing before energising the whole enchilada.

Did you not wonder what the earth terminal on the junction box might be for?

 

[Marc Bowler]

Well I did wonder... that might seem like a silly statement and I have no issue with being told something is incorrect, and your right I didn't specify how many wires the lighting flex had (my apologies) but going by the installation booklet it only shows 2 wires (a live and a neutral) despite there being an earth terminal in the terminal box it doesn't mention an earth wire in the picture nor in the description of the wire colours underneath it, it's not a major job to replace the cable with 3 core though, so I'll make that a first job tonight