Missing neutral for the Bathroom Fan Installation

[Papillion]

Hi,
I am newly qualified and would very much appreciate some advice on this. I few days ago I've purchased one of those low noise bathroom extractor fans with a timer and humidity sensor and run a three core cable from it to the loft which I was planning to connect to the 3 pole isolator.

Once in the loft, on closer inspection by removing part of the floor boards, the wiring for the bathroom light has a conductor from the pull cord switch with the (a)red wire connected to the live (brown) of the light and (b)black wire connected together with the red coming from the next light and both connected to the neutral (blue) of the light.

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There doesn't seem to be a neutral wire coming from the next light and the extractor fan needs a permanent live, neutral and switched live to connect. Any advice on how to wire this would be greatly appreciated.

 

[Sparky Ninja]

what do you mean by...

and both connected to the neutral (blue) of the light

??


It sounds like you have a S/L & N supplying a secondary light?


Just seen the image you've now added. Those connections make no sense so I think you may have incorrectly identified some.

 

[telectrix]

the diagram you show cannot be right. you need to identify the permanent live, switched live, and neutral

 

[Sparky Ninja]

Are you farmiliar with switch lines?

 

[Papillion]

Hi Widdler, I can't make sense of it either, that's why I've added the diagram. That's what I found under the floor boards (connected by terminal blocks too)..

 

[accordfire]

I'll hazard a long shot guess......

The "Red" you've identified as running from N to the next light fitting is probably actually a Neutral running to a 2 way switched landing light.

I'm GUESSING here - but it seems likely that someone when installing, decided they needed a Neutral, probably on the landing and only had Twin RED and Earth left. Damn naughty, but it happens.

Use a test meter, would be my suggestion - and identify that it is, indeed a Neutral and not a Live - other way is to open the landing light rose and see what you've got in there....

 

[james hanley]

should have been as easy to use four core cable from the bathroom ceiling rose to the fan ,brown for your permanent live ,blue for your return ,green for earth and yellow for the fan switched live ,i would advise you rewire the circuit properly as for you to find that the red is in fact used as a neutral and you wired the fan to the wiring like this ,you would be just as bad as the idiot who wired the mess in the first place ,you would also be helping any future spark who works on the circuit if you redone it correctly

 

[james hanley]

thats damn cowboys for you mate,its what were up against

 

[james hanley]

should have been as easy to use four core cable from the bathroom ceiling rose ,brown for per live ,blue for return ,green for earth and yellow for the fan switched live.i would advise you to rewire the lights as for you to just find if the red is being used for neutral and wire up the fan with the wiring like that you would just be as bad as the nutcase who done it in the first place

 

[accordfire]

should have been as easy to use four core cable from the bathroom ceiling rose ,brown for per live ,blue for return ,green for earth and yellow for the fan switched live.i would advise you to rewire the lights as for you to just find if the red is being used for neutral and wire up the fan with the wiring like that you would just be as bad as the nutcase who done it in the first place

Um...did I miss something in the colour coding somewhere?

Where do you get four core mains cable with a yellow core and a green core?

If you mean four core flex, it's not suitable for a lighting final anyway, and the colours would be Brown, Black, Grey, and Green/Yellow striped....

If you mean 3 Core and Earth, well, that's pretty well Brown Black Grey, and bare CPC sheathed green/yellow striped.

Bit puzzled as to where you get the colours from....

 

[Papillion]

Thank you for all your replies. I guess I'll have to remove all the floorboards and check this out properly. Judging by this discovery (and the state of the crumbling conductors), it does look like a complete re-wiring is required.

 

[Wiredspark]

The drawing defo shows some "Home improvements" looks to me like your (RED) neutral is a "borrowed" neutral for the next light. I can only see from your drawing a switched live which suggests to me that you need to find your supply. Is it at your switch?????? If not, you need to find it. Looks like you might be onto a wee can of worms here mate.

 

[james hanley]

if you have ever done intermediate wiring you would know about wiring colours blue and yellow are used there respectively for strapping and switching

 

[Izzy's Dad]

if you have ever done intermediate wiring you would know about wiring colours blue and yellow are used there respectively for strapping and switching

James, red, blue and yellow were the old colours for multiple live conductor systems, ie 2 way/intermediate switching. They are now brown, black and grey.

 

[james hanley]

i am 15 edition mate i left the trade some years ago to do electronics sorry if i mislead anyone pal but at least they did use it i am now in the middle of updating to the 17th edition in january (thank god i hear you say).

 

[accordfire]

if you have ever done intermediate wiring you would know about wiring colours blue and yellow are used there respectively for strapping and switching

Yes, James, I've done a little, in the last 25 years or so. Blue and yellow used to be the colours, but that stopped a few years back when CENCELC harmonisation came upon us. Blue was replaced by Black, and yellow by Grey. Solid green hasn't been used as a CPC colour since, ISTR the 70's.

It was a question, was all - no need to be so defensive.....

 

[james hanley]

apologies mate i didn t realise i was being so defensive.

 

[denpicardo]

The most common way to install a new exhaust fan is to put it in place of an existing ceiling light, controlling it from the light's wall switch.If you are really ready to take some step by step instructions,I can give you a little more time tonight and can talk you through this.Since I have some time invested in your project,I would love to see it resolved too.

 

[malcolmsanford]

Um...did I miss something in the colour coding somewhere?

Where do you get four core mains cable with a yellow core and a green core?

If you mean four core flex, it's not suitable for a lighting final anyway, and the colours would be Brown, Black, Grey, and Green/Yellow striped....

If you mean 3 Core and Earth, well, that's pretty well Brown Black Grey, and bare CPC sheathed green/yellow striped.

Bit puzzled as to where you get the colours from....

Why not suitable as long as you apply regulation 521.9.1

 

[telectrix]

Yes, James, I've done a little, in the last 25 years or so. Blue and yellow used to be the colours, but that stopped a few years back when CENCELC harmonisation came upon us. Blue was replaced by Black, and yellow by Grey. Solid green hasn't been used as a CPC colour since, ISTR the 70's.

It was a question, was all - no need to be so defensive.....

surely it was yellow replaced by black and blue by grey, or is it me getting confused now