New Bathroom Extractor Fan - Wiring Query

[Colin47]

Hi,

I'm looking to install a new bathroom extractor fan in my bathroom as I have a windowless bathroom and the current one I have installed in bathroom ceiling is just a standard one and isn't powerful enough so looking to change this to a Manrose MF100t inline extractor fan.

Now I originally spoke to 2 electricians to get quote and both said same thing in that they would only put a junction box in there to connect existing wiring to terminal box and new 3 core and earth wire from terminal box to loft. Our loft is a storage room where the new unit is already mounted to the wall and the flexible duct is already there for current one so quite easy to connect to new one. Access to floor boards is also not a problem either. One electrician told me you don't need a electrician to put junction boxes in to connect to existing to new one however I wanted to give this one a go.

Attached photos of the Hager J804 4 way terminal maintenance free box and also image of current existing wiring in current extractor fan. I have the 3 core and earth 1.5mm.

Looking at the current wiring in current fan, we have red, blue yellow and black wire.

The 3 core and earth cable have 4 wires - grey, black, brown and a bare wire without sleeve.

I have done minor repairs before to hedge cutters with broken wires but first time in doing anything with lighting / extractor fan.

Just wanted to check, looking at the terminal box we have 4 terminal blocks with each block have 2 ports (not sure why).

Would this work as follows:

N - blue existing wire (one end) , grey wire oppostite end

Not 100% sure but 2nd terminal block appears to be for earth - yellow existing wire (one end), bare wire with a yellow / green sleeve on other end

L1 - red existing wire one end , brown wire opposite end

L2 - I am unclear on this one. We have black wire currenting exisiting and on new 3 core and earth. Would these connect together?

Also does anyone know why 2 ports per terminal block?

Thanks.


Colin

 

[westward10]

The yellow is not earth I would strongly recommend you get an electrician to do this.

 

[Colin47]

Thanks. Is the reason for advising using a electrician due to the complexity of the wiring? The two quotations that I got from electricians were on the basis they would only using junction box with existing wire and if replacing existing cable wires from ceiling light it will take 2 hours to do as it becomes a bigger job. If the yellow wire in not earth, then what is it?

 

[westward10]

The yellow is the trigger wire to activate the fan.

 

[MDJ]

Thanks. Is the reason for advising using a electrician due to the complexity of the wiring? The two quotations that I got from electricians were on the basis they would only using junction box with existing wire and if replacing existing cable wires from ceiling light it will take 2 hours to do as it becomes a bigger job. If the yellow wire in not earth, then what is it?

I assume and am rarely wrong by your last question you intend to do the job yourself, you have had 2 electricians look at it and IMO either get one of them to do it or get a third quote. I can assure you the yellow wire is probably a switch wire, the red a feed and the blue a neutral, well possibly, but it is not an earth. Get a spark in colin, long term it will save you any grief.

 

[Colin47]

The earth has been taken out. No earth wire from the looks of it but the current extractor fan has been running for 7 years.

 

[DPG]

The insulation also looks damaged on the yellow wire.

 

[DefyG]

I presume that where you have mounted the new extractor renders the existing cable too short (hence the need for a junction box) which would be perfectly acceptable providing the existing cpc is maintained into the fan assembly (which of course will not used but should still have earth continuity within the cable) and confirmed during testing/certification.

You mention running a new cable to the light? which would indicate no isolator. I would recommend installing an isolator switch whilst upgrading the fan.

The junction box actually has 4 ports for cables 4xL1 4xL2 etc. This allows for various termination scenarios and not just a straight cable one in one out junction.

 

[davesparks]

Does the existing cable have an earth wire in it?

 

[pc1966]

Does the existing cable have an earth wire in it?

I think it has been cut off just at where the outer sheath has been stripped back to (I think I see a hint of copper between the blue and yellow). That is not a good sign of past installation, and I would not be too surprised if the other end had been treated much the same.