Loft wiring curiosity - any sparks seen this before?

[Bodie]

Hi all

Could any sparks lend an ear to my situation?

In my loft, I have a square black junction box from which all the lighting switches/roses/circuit goes into.

The lighting circuit doesnt seem to radial around the roses like most other lighting wiring that is discussed.

I am going to wire in a timed shower light fan (3 Pole isolater, etc etc - all covered) but my question is;

When looking at the attached diagram, would it be possible to take the power from the cable that is used to power the digital high pressure mixer shower (via a 20 amp 4 way J/B between the "Main black" junction box and the FCU) and then use the switch wire on the bathroom light so the fan comes on with the light only?

Ive never come across a lighting circuit like this before hence all the questions!

Many thanks in advance for any advice/help you give.

 

[OwainDIYer]

no, you need to have the switched live, permanent live, and neutral for the fan circuit run together (in the same cable)

Locate those inside the junction box and run a 3+e from the box through the fan isolator to the fan.

A photo of the junction box would be nice.

 

[Bodie]

Brilliant, thanks.

So basically open up the black box?

Strange looking beastie.

Thanks for your help.

 

[RF Lighting]

It's just a central joint box. It's the most common way of wiring lights and has been used on virtually every lighting installation from the invention of electricity, until about 1960.

Other methods tend to be fovoured now, but central JB is still a common way of wiring lights.

It makes it really easy for you to wire your new fan supply too

 

[Steve]

Nobody else concerned about the potential age of this installation? Especially after what RF said . . .

 

[sparkwright]

Nobody else concerned about the potential age of this installation? Especially after what RF said . . .

Not really, still a common method of doing it even today.

Never used the central jb method myself, always worried too many cables near the loft hatch, and the possibility someone's gonna want it moved.

Good method for only having one cable at the light and one cable at the switch. Lot of earth wires to join together.

This may help answer Steve's query; are there earth wires in the big junction box? And is the cable PVC, as opposed to rubber?

 

[securespark]

To be fair, I think that's why Owain said:

A photo of the junction box would be nice.