What sort of circuit do I have?

[flipper81]

I just moved into a new house and I need to change the bathroom light; it has no cover on the back or front so steam is getting both into the fitting and into the void above it.

The wiring is a bit unexpected though, and provides no earth to the light itself. Can anyone tell me what this type of circuit is, and whether it can provide an earth so I can fit the new light myself? Or do I need to get my nice electrician round? I have attached a diagram of what I have.

Many thanks!

Untitled

• flipper81
• 31 Jan 2014
• 1

 

[diyer56]

The cable on the far right probably goes to a bathroom fan with an overrun feature and therefore needs both a switched and permanent live. In your diagram the switched live is yellow.

The three shorter cables in your diagram are as follows:

Left - cable to the switch. The red is the permanent live and the black is the switched live coming back from the switch. This black cable should have a red sleeve.

Middle/Right - these cables are the incoming supply and the supply to the next light.

If you need an earth connection to your new light this can be obtained from the terminal with yellow/green cables in the central choc block.

 

[flipper81]

Thanks diyer, you are totally right - there is a fan with an overrun and I had completely forgotten that. So I can just run an additional earth from the 'third' choc block to the light?

 

[diyer56]

The third terminal in the lower choc block.

You should really check that all these 'earth' (CPC) cables are actually connected to the main earthing terminal at your consumer unit. More information can be found in this post thread:
//www.diynot.com/forums/electrics/light-switch.382626/#2933670

 

[flipper81]

I replaced the light, with an earth, and everything is rosy.

However, the bathroom is now incredibly steamy - far beyond the capabilities of my old fan - so I am replacing it with a new Xpelair DX100H since that has a humidistat. But what keeps me awake at night is the thought of all the steam that must have been disappearing through the light socket and up into the cavity between the downstairs ceiling and the upstairs floor.

Does anyone know of any kind of damp/rot/mould prevention I should use? I spotted the problem as soon as we moved in but it was previously a rented property, it might have been open like that for years.......

Thanks!

 

[ban-all-sheds]

What sort of circuit do I have?

A traditional one.

//www.diynot.com/wiki/Electrics:Lighting-Circuit-layouts

Does anyone know of any kind of damp/rot/mould prevention I should use?

Nothing you can do now will undo any damage already done.

First step is to lift some floorboards and see what state the joists etc are in.

 

[securespark]

From my experience only, my guess is that you will find minimal damage.

Take some pics and post them here if you want an opinion.