Installing a new bathroom fan help?

[gerlep]

Hey there, i uninstalled my old bathroom fan as it was too noisy. I waited a year to get the new one, and hence forget my wiring instructions.
I bought an Envirovent Silent T-100 fan. It has 3 connection terminals, L, N and Ls.
My existing cable has 4 colours, Red, Blue and Yellow, (and Earth, which apparently is not needed according to the unit assembly instructions. I did a voltage test and got current across Red and Blue.
I installed R=L, B=N, Y=Ls, that didn't work, i then tried Y=L, B=N, R=Ls which didn't work either.
I opened my wall switch as the fan works in tandem with the light, all that was in there was Red and Black connection wires. Leading me to believe there has been some work done cable wise above the ceiling, which I can't access.
Anyone any ideas?
Separately is there anyway this fan can be tested before i even install with an old cable plugged into my wall socket? thanks in advance.

 

[Aragorn84]

You will have three connections:

Live
Switched Live
Neutral

Live is always live
Switched live will become live when the light is on
neutral is neutral.

You need to use a multimeter to find out which wire is which unless you can find the wiring to the fan inside the ceiling rose or in the roof space. Dont go connecting them willy nilly to different terminals trying to get it to work, and make sure the power is off when your poking around with the meter.

If you would like to test the fan separately, connect the brown wire from a flex to the L terminal, and place a wire jumper between L and Ls. Connect the blue wire to the N terminal, and plug it in ideally with a 3A fuse.

 

[gerlep]

Thanks for replying so quickly Aragorn 84. Fan works well. I just found the old fan too, with a connector block attached with existing cables, would you be able to deduce the live switch wire if i posted a quick image of that?

 

[ericmark]

make sure the power is off when your poking around with the meter

How will that work? Can hardly measure if neutral or line if switched off?

It is clearly important the neutral goes to correct point. Even a simple neon screwdriver will likely show two line wires and one neutral.

Now here I will stand to be corrected but assuming neutral is correct the getting L and Ls mixed up will be unlikely to cause any damage so using trial and error on the L and Ls is unlikely to cause a problem.

Of course if neutral has been connected to Ls and Line to L during experiments then it is very possible the unit has been damaged.

So yes I would try with neon screwdriver you should get with it switched on two lines and one neutral i.e. two wires light neon one does not. However with lights switched off you may get two lines still as the inductance in cable may be enough to light a neon.

I would normally say use a meter but you need a reference point and there is likely more danger finding a reference point than using a neon screwdriver which uses your body as the reference point.