Stupid electician? Sky light and extractor fan

[Lectrician]

Ok, with electric OFF, remove the switch from the wall, and tell us how many cables, what colours, and if there are any terminal blocks inside the switch box.

A photo would be ideal.

Also, is it just a single light fitting?? Could you tell us what cables are feeding this (colours, and any other terminal blocks present)

 

[benjiman]

Ok, with electric OFF, remove the switch from the wall, and tell us how many cables, what colours, and if there are any terminal blocks inside the switch box.

A photo would be ideal.

Also, is it just a single light fitting?? Could you tell us what cables are feeding this (colours, and any other terminal blocks present)

Yup have done so, heres what I see:

One black wire with a red sleave, one red wire and one earth.

I have taken the back box out and theres nothing there apart from the wire feed. I put my hand up there but I cant feel any terminal blocks, just the wire.

The light is a standard rose fitting. The extractor fan is a few foot away from the light.

I have opened the rose fitting and this is what I see:

4 RED wires all going to 1 block.

4 earth wires.

1 YELLOW wire with a red sleeve and
1 BLACK wire with red sleeve both going to 1 block.

2 BLACKS and 1 BLUE going to 1 block.

Sorry can get photo with the house being in a mess at the moment - everythings being re-decorated and I cant find the camera and leads etc.

 

[ban-all-sheds]

Sounds as if the cable for the fan has been taken directly off the ceiling rose.

What is access to the lighting circuit like? Can you easily get at the wiring from above?

Also you said "I put my hand up there but I can feel any terminal blocks, just the wire" - does this mean that there's a hollow wall, down which you could drop another cable?

 

[benjiman]

Sounds as if the cable for the fan has been taken directly off the ceiling rose.

What is access to the lighting circuit like? Can you easily get at the wiring from above?

Also you said "I put my hand up there but I can feel any terminal blocks, just the wire" - does this mean that there's a hollow wall, down which you could drop another cable?

Where the light switch is there is a partition wall. If I take the back box out I can feel the wire going up. But I cant really do much else. Everything has been plastered up now so I can only get at the wire by taking the back box out.

Yup I may be able to drop cable down the hollow wall where the switch is and take it out from the bottom if that would help.

 

[ban-all-sheds]

Yup I may be able to drop cable down the hollow wall where the switch is and take it out from the bottom if that would help.

Well if you want the fan separately switched, then you will need a separate cable running to another switch.

I don't know whether you'd prefer this to be on the same plate as the light switch (you could replace it with a 2-gang), or a pull switch on the ceiling inside the bathroom.

If there are noggins in the wall it might not be easy to drop another cable down it. How do you plan to decorate the plastered wall? If papering is to take place then you should be able to cut holes in the wall and patch them up afterwards and not have it show.

You will also need to get access to where the cable runs between the switch and the rose - just unscrewing the rose to get at the connections won't be enough.

 

[benjiman]

Hey thanks for your quick replies.

So suppose I could run the cables where do they need to be run between and how many. I want a two gang to replace the 1 way.

With a bit of hard graft and flexible conduit and a few holes in the plasterboard I may just be able to run the cables.

Also what type of cable to use? And how will the connections be done?

 

[Lectrician]

BAS has it covered.

If it was me i would replace the 2 core and earth (red and black) cable from the rose to the switch with a peice of 3core and earth cable. Do this by taping it onto the 2 core, and pulling it up.

Then, connect to a new 2 gang switch, the red and blue of the new cable as the red and the black where (blue as black). Link the two terminals marked common together with scrap bit of red cable. The L1 from the secong gang of the switch will connect to the yellow of the 3core cable.

In the rose, put the red and blue where the red and black was. The yelow will need a terminal block connecting to the RED and YELLOW of the fan cable.

If this sounds a little confusing - it is!!! A diagram may help more, especiaaly when connecting the switch. (has 2 commons and 2 L1's - link commons to the red, one L1 to blue, and the other to the yellow.)

BAS is good at diagrams, and has more time than me

When you have finished, and you switch the fan switch on, it will delay for a second or so before starting, but will turn off instantly when you turn the switch off.

 

[ban-all-sheds]

In the rose, put the red and blue where the red and black was. The yelow will need a terminal block connecting to the RED and YELLOW of the fan cable.

I'd leave the Red of the 3-core cable going to the fan where it is, and simply join the Yellow of that cable to the Yellow of the new one, so as to keep the timed overrun feature.

I would also install 3-pole fan isolator.

BAS is good at diagrams, and has more time than me

Not right now I'm afraid....

 

[Lectrician]

If you have a seperate switch, i see no reason for the over run - its a sod a night, this is where we have had complaints.

A 3 pole isolator is only really needed for a room with no windows, or for a loft mounted fan - NICEIC have never picked us up for not using one on new builds, neither has the NHBC. They are a good idea, but not essential i dont think.

I have no time a for a diag either, lets wait and see what benji thinks first

 

[benjiman]

Cheers guys your help is very much appreciated.

At the moment im trying to pull a 3 core wire from the switch to the rose. Not as easy as it sounds. Taking very long just to do this. A batton came on the way so had to make a hole in the wall to guide the 3 core in.

Currently taking the coving off so I can get into the ceiling of the shower room. Mission or what!

Once again many thanks lecy and BAS and others for the advise.

 

[ban-all-sheds]

If you have a seperate switch, i see no reason for the over run - its a sod a night, this is where we have had complaints.

Overrun is useful to finish clearing the room after you've left the shower.

I'll bet the complaints you've had are where it's been wired to the light switch, and someone gets up in the night to use the loo, turns on the light, and then can hear the fan running for a while after they've gone back to bed....

 

[Lectrician]

We have installed 2 gang switches for ages, with fan over run, its these they moan at...."we will switch it off when ready, its not as if the lights are left on"

 

[ban-all-sheds]

[shrug]

 

[benjiman]

evening all, quick question. Why are there 4 wires going into the rose? (Excluding the one I have just added)

There is 1 three core and three 2 cores.

Of them I know this:

1 is for the switch.
1 for the extractor fan (3 core)
1 for the rose (I think)

Whats the other one for?

 

[benjiman]

Just drawn the diagram of the wiring as it is at the moment:

(Earths havent been drawn on diagram)

Ive run the 3 core, what needs to be done next? It will be easier for me to understand now that you all know exactly how the wiring is at the moment. Refer to them as 2core (1) (2) or (3) then ill find it much easier.

Cheers