Help with 4 colour wiring

[Sard]

Hi,

I'm looking to replace the ceiling rose below with a new light and a little confused by the wiring. I have worked out conductors belong to the ring main and disconnected those from the ceiling rose and reconnected them and the other lights on this circuit all work fine. The 4 colours on this other cable are Red, Yellow, Blue and unsleeved Earth. My new light fitting has L, N, E terminals. This circuit also has an extractor fan that comes on with the wall switch. I have bought a J804 Hager 4 way Junction Box to make this a bit easier, so I can run a conductor from the junction box to the new light, once I have the 4 cable figured out.

Thanks in advance!

 

[pete01]

Double check inside the fan but I think the...

The Yellow and black are switched live

The 3 reds together are permanent live

The blue and black are neutral.

 

[Sard]

Thanks Pete. Just to clarify, the cable I need to figure out has Red, Blue, Yellow and Earth. So I assume Red is Live, Blue is Neutral, Yellow is switched Live. When I wire in my new light fitting, I will connect the Red from the light fitting to the Yellow, again assuming it's switched live.

Does that sound ok?

 

[pete01]

. Just to clarify, the cable I need to figure out has Red, Blue, Yellow and Earth. So I assume Red is Live, Blue is Neutral, Yellow is switched Live

It looks that way, check in the fan to confirm it.

 

[ericmark]

Red, yellow, and blue, today brown, black, and grey, are the colours used for three phases, but electric does not mind what colour is used, and it is easier to work out what is what when three colours are used. In the main, people use red for line, but which colour is used for switched line or neutral is up to the installer.

From the picture, it seems yellow is switched line, and blue is neutral, but the only way to be sure, is to test.

 

[Sard]

Tried yellow as switched live but it tripped the RCD. I also remembered there is an isolator on this circuit for the fan. Does that change things?

 

[pete01]

Post a pic of what you've done

 

[Sard]

Going clockwise
Top left Grey - spur from lighting ring main acting as supply
Top right white - Assumed to be switched cable, neutral, live and earth connected to corresponding blocks. Yellow assumed to be switched live, connected to loop terminal on JB
Bottom right grey - load going to new ceiling rose, with live wired into switched live terminal above
Bottom left grey - load going to illuminated mirror. Not switched.

 

[endecotp]

Why have you not just copied what you had before?

 

[Sard]

I need to add an illuminated mirror to the circuit, which would have been difficult to replicate exactly in the new light fitting.

 

[endecotp]

It’s not safe to assume that blue in a R/Y/B cable is neutral.

Don’t try to fix this by guessing. Look in the switch, and the extractor fan.

 

[Sard]

Yes sure, I will investigate. Shall I also look in the isolator switch?

 

[endecotp]

Double check inside the fan

check in the fan to confirm it.

the only way to be sure, is to test.

You ignored all that, didn’t you?

 

[sparkwright]

Why have the cables with red and black suddenly become brown and blue?

 

[Sard]

You ignored all that, didn’t you?

Not ignored, the fan was tricky to take apart to check the wiring but I get your point.