New Bathroom Extractor Fan - Wiring Query

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