Neutral went bang - can someone explain this wiring to me?

[westward10]

In your drawing I would use the brown as the live to the switches and the black as one of the returns plus in a three core and cpc you have no blue it is grey. Three plate doesn't have to have a rose the connections can be within the light fitting. The term three plate is used because years ago there were three terminals on a batten holder back plate hence three plate. Prior to this with only two terminals at the base you had two plate.
There are multiple ways lighting circuits can be wired some of them quite baffling and over complicated.

 

[Electrics]

In your drawing I would use the brown as the live to the switches and the black as one of the returns plus in a three core and cpc you have no blue it is grey. Three plate doesn't have to have a rose the connections can be within the light fitting. The term three plate is used because years ago there were three terminals on a batten holder back plate hence three plate. Prior to this with only two terminals at the base you had two plate.
There are multiple ways lighting circuits can be wired some of them quite baffling and over complicated.

Well this has definitely baffled me!

There is zero chance of me figuring this out without taking the sensor out and the key switch and looking at the cabling.

Since the light literally only had a 3 core and earth in the fitting, it couldn't have been wired like my drawing above even if the principle is the same.

This is going to really wind me up.

I think from memory the sensor had red black and earth in the back of it but i only briefly glanced at it on my way past, someone else took it out and was looking at it.

We need to change the sensor since it's naffed (they linked the line and switch line together so the light is now permanently on (it's in a store cupboard) until the sensor is changed) so if i get sent back there next week i'll take some pics of the wiring at both switch and sensor.

Thanks for taking the time to try to explain it to me, definitely owe some beers!

 

[westward10]

Imagine the sensor as the switch which it essentially is so you were correct previously where you said it replaces SW1 in my drawing the only slight difference being it also requires a neutral to function.

 

[Electrics]

Imagine the sensor as the switch which it essentially is so you were correct previously where you said it replaces SW1 in my drawing the only slight difference being it also requires a neutral to function.

I get how it works in your drawing, like if i had to wire it in singles i could, quite easily. I just can't get my head around exactly how it was wired in the light i was replacing! Hopefully i get to go back and can have a proper look.

 

[westward10]

It will all become clear don't try and cram too much in, once you get the basic principles you will eventually see how it all works.

 

[Vortigern]

A sensor would have a L N and a L out to the light so you should have seen three wires, not just black and red and earth. Shame there is no pics. The light you were working on, just to be clear, there was only four wires going in to it? Not eight wires, i.e. looping to the next fitting in line???

 

[nicebutdim]

This is going to really wind me up.

Don't let it - if you get the opportunity to figure it out, then well and good. If not learn what you can and add to that at each subsequent opportunity.

There's a mountain to climb and the only way to the top is one step after another.

 

[Electrics]

A sensor would have a L N and a L out to the light so you should have seen three wires, not just black and red and earth. Shame there is no pics. The light you were working on, just to be clear, there was only four wires going in to it? Not eight wires, i.e. looping to the next fitting in line???

The light was fed by 3 core + earth flex, one cable in, push fit connections at the fitting and black, blue, brown and earth.

I think it was the last on the circuit from the lighting in the room next door since that room was a main shop front but the light i was changing was in a store cupboard so maybe added as an afterthought. Might be why i still got a bang since the cupboard was only turned off at the keyswitch and not the MCB - when the MCB was turned off the lights in the main shop room went off.

I'll draw a pic of the set up.

 

[Electrics]

You know thinking about it, the wires were really short and when i took the neutral out it's possible some of the other wires touched.

I'm wondering if the line from the sensor has shorted which is why the sensor is now broken and doesn't work. It's not a coincidence imo that the sensor stopped working immediately after this.

If the sensor was still live then it's going to switch live as soon as it senses my movement in the room isn't it? Normally i think you switch off the light and then kill the emergency switch so the emergency light comes on the battery power but if it's a sensor and not a switch then you can't kill the power unless at the MCB, which was still on?

Still confused mind as to how the RCD never tripped.

 

[westward10]

A flex indicates a coupler in the ceiling void.

 

[Electrics]

A flex indicates a coupler in the ceiling void.

Coupler? You mean like a connector block or such like?

 

[westward10]

Coupler? You mean like a connector block or such like?

No some kind of luminaire coupler like a Klix socket or similar. In fact if this is the case then it makes replacement easy as you just unplug it.

 

[Electrics]

No some kind of luminaire coupler like a Klix socket or similar. In fact if this is the case then it makes replacement easy as you just unplug it.

Yes i know exactly what you mean - i replaced several of those on the same day. Oh man that would be hilarious and maybe slightly tragic if one of those was tucked inside the ceiling panel and we didn't see it.

 

[ipf]

Don't worry about it......it's all done different in Essex, anyway...

You're not the first to 'em to be flummoxed.

 

[Electrics]

Don't worry about it......it's all done different in Essex, anyway...

You're not the first to 'em to be flummoxed.

Looks like there was probably stuff tucked up in the ceiling that we didn't see, whether that be a coupler or a JB or whatever. Probably easy to figure out if you have a good poke around. If i get sent back there this week i'll update with some pics.

 

[ipf]

An EICR lately had something similar. The light fittings, moved from original positions, were fed with a 3c flex. If you've got access or can obtain it, fair enough. If not, as in the EICR, it's dependant on the test results and, in many cases, a bit of 'hit and hope'. There's no saying what state the joints are in. Fully testing is important.

 

[Lister1987]

Have a look here; Lighting Circuits Introduction - https://www.flameport.com/electric/lighting_circuits/index.cs4

A variety of lighting setups explained with useful illustrations.