Replacing a basic bathroom extractor fan with a timer one

Ashandiamo · 15 Oct 2008

Hi,
First time on here and really impressed with the site so I'm confident that someone can help with this one.

I'm in a house that is about 12 years old and looking to replace a basic bathroom extractor fan with a Marley Timer Fan NDx100T one. The supply to where the fan is positioned is two wires, live and neutral. Outside the bathroom is an on/off switch for the fan and a seperate isolator on/off switch.

The new fan has three terminals L, N and L1 which according to the instructions all need a feed in order for it to work.

Can someone please help with what goes where and where I will get the third wire from.

Thanks
Andy

bongos · 15 Oct 2008

You will require 3 core & earth cable. This will need to be run from either the switch or the existing light fitting (depending on how the circuit was initially wired). This should be connected via a 3 pole isolator to the new fan.

L - Live (brown)
L1 - Switched Live (black - sleeve brown)
N - Neutral (grey - sleeve blue)

Connect the green & yellow to the earth terminal.

This work may require notification and RCD protection as you are altering an existing circuit. Also make yourself aware of supplementary bonding. There is more information in the wiki.

Ashandiamo · 15 Oct 2008

Bongos,
Thanks for your response, seems a bit clearer but may just need to seek professional help as I just can't quite get the wiring clear in my head, if I understand what you are saying I will need to take a separate live feed from the switch, and route it through the isolator to the fan?
Please forgive me for being a bit slow on this one!
Thanks.
Andy

ban-all-sheds · 15 Oct 2008

Ashandiamo said:
Outside the bathroom is an on/off switch for the fan

So that switch must have permanent live going to it. Replace the cable from there to the fan with 3-core & earth so that you can supply permanent live, switched live & neutral to the fan.

You might also want to replace the switch, or switch base, with one with a neon, because once you've got a timed overrun fan you'll always be thinking "Did I turn it off or not......?"

and a seperate isolator on/off switch.

If that's an FCU you should replace it with an RCD one, assuming the circuit isn't already RCD protected.

All this work is notifiable, BTW...

ban-all-sheds · 15 Oct 2008

That's what happens when, having originally been first to reply, you then don't hit submit for ages....

Andy - is the "isolation switch" a 3-pole fan isolator, or a fused connection unit?

bongos · 15 Oct 2008

Did you look at the wiki? This image shows a timed fan wired to a ceiling rose but it can be wired to a switch if that is where you have L/N/E present.

Without the switched live the fan will not work as you require.

Ashandiamo · 15 Oct 2008

The isolation switch is a 3 pole fan isolator switch
Andy

bongos · 15 Oct 2008

From your description it seems that you have a twin core and earth feed to a switch which then continues to a 3 pole isolator and onto the fan?

If this is right then it sounds like you have loop in wiring at the switch. In this case you can run 3c+e between the switch and the isolator and then from there onto the fan.

In the switch (not isolator) the brown will connect to the permanent live terminal, black (sleeved brown) to the switched live terminal and grey (sleeved blue) to the neutral that will most likely be in a terminal block in your switch.

Are you sure you're happy to do this work? Have a good look at the wiki and it may help to draw a picture of the setup so you can work it out in your head.

Ashandiamo · 15 Oct 2008

Thanks everyone for all your help!
Much happier now and once I get some more cable I'll get the job done.
Thanks again.
Andy

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Replacing a basic bathroom extractor fan with a timer one

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