# Wiring diagram help - Replacing inline fan with timed inline fan

#### AmateurChris

I'm replacing an inline extractor fan with the exact same model with a timer function but I'm having trouble understanding the wiring diagram. I've removed the wires from the old fan and got the new one ready but I'm struggling to understand what to do next.
The previous wiring setup was shown below in 21, and I'm trying to get to 22. I'm confused by a few things, firstly why the bulb exists on the diagram, secondly the switch from L to L3 and lastly how I'm supposed to link L to L2/3/4. Is it as simple as running L to L2 and another wire from the L2 terminal to L4?

Thanks!

You may have a problem.

How it the fan currently switched on?
Does it come on when the light does and go off when the light does?

If that is the case then you have a neutral and a switched live going to the fan in parallel (google me) with your room light (possibly fed from it?).

You now need to have a permanent live fed into the fan so that when the light goes off, the fan has permanent power to run the timer and the fan while the timer is on.
If you can get access to the light ceiling rose/fitting you may find a permanent live in it that you can use.

The lamp shown on 22 shows you where the room light goes in the circuit so that it operates using the room light switch.

The double pole switch that is in both the L and N lines is to enable you to isolate the fan, I am sure others will agree that although they are recommended many do not fit this and power it directly from the lighting circuit.

The single pole switch that goes to 22 terminal 3 is your room light switch.
I don't know what the link to 4 is for, the documentation should tell you.

An electrician may be along shortly to advise you better and tell you I'm wrong because I'm just a DIY'r

EDIT:
N1 = Permanent Neutral.
L2 = Permanent Live.
3 = Switched Live.

#### Taylortwocities

AS Mattylad says. You need to provide a permanent live, switched live and neutral to the fan. So you have some extra wiring to do, becuase the new fan has a timer and the old one doesnt.
The online instructions are appalling, but there seem to be three wiring variations ET, FT and GT and the position of the link enables the fan speed in some models. So for your fan to run at high speed there must be a link installed as shown between L2 and 4.

#### AmateurChris

You may have a problem.

How it the fan currently switched on?
Does it come on when the light does and go off when the light does?

If that is the case then you have a neutral and a switched live going to the fan in parallel (google me) with your room light (possibly fed from it?).

You now need to have a permanent live fed into the fan so that when the light goes off, the fan has permanent power to run the timer and the fan while the timer is on.
If you can get access to the light ceiling rose/fitting you may find a permanent live in it that you can use.

The lamp shown on 22 shows you where the room light goes in the circuit so that it operates using the room light switch.

The double pole switch that is in both the L and N lines is to enable you to isolate the fan, I am sure others will agree that although they are recommended many do not fit this and power it directly from the lighting circuit.

The single pole switch that goes to 22 terminal 3 is your room light switch.
I don't know what the link to 4 is for, the documentation should tell you.

An electrician may be along shortly to advise you better and tell you I'm wrong because I'm just a DIY'r

EDIT:
N1 = Permanent Neutral.
L2 = Permanent Live.
3 = Switched Live.

Thanks for the replies, I agree that the instructions are appalling. Sorry I meant to include this, the fan is switched on and off from an 'isolator switch' above the door on the outside of the bathroom. There's no light or lightswitch involved at all - switch on the fan operates, switch off the fan doesn't and it's normally off for obvious reasons.
I think I'm following, it's normal have a timer fan wired into the lighting circuit as the 'permanent live' and that's the extra icons that 22 includes but doesn't reference anywhere. I hadn't considered that, I was quite happy just switching it on/off when I need it but I guess the moment I turn off the isolator the fan will die even with the timer?
This a bigger job than I'd hoped, might be professional electrician time.

Last edited:

#### Taylortwocities

You didn’t need a timer fan then.

to make it work in non timer mode

connect up neutral and live to N1 and L2

You then need to link The live from L2 to 3 and 4.

the fan should then just work switched on and off from your switch.

let us know if that works.

#### AmateurChris

Thanks Taylor, that's my current setup with the previous fan. I was hoping to use the timer function along the process of: Switch on, take shower, switch off, timer runs until finish. I think I'm now appreciating that the fan doesn't keep all the power it needs to continue running on timer internally, hence the switched/permanent live.

#### Taylortwocities

Then you need to run a permanent live to L2 (linked to 4) on the fan.the live from your switch goes to 3.

#### endecotp

Have you unscrewed your fan isolator switch?
How many wires are there? Any unused ones?

#### Taylortwocities

Have you unscrewed your fan isolator switch?
How many wires are there? Any unused ones?
Yes. A photo of the wiring. And how many wires in the cable at the fan too please.

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