Fan with timer

16 Mar 2011
Reaction score
United Kingdom
Hi I wonder if you can help, although there are many previous posts on this matter I cannot seem to find my particular scenario.

I want to install a fan with integral timer, the unit has the usual connections , ie neutral, permanent live and switched live.
The current ligthing arrangements are as follows, 3 spotlights and 1 switch all looped on a switch wire.

I have no access to the junction box for the permanent live, I think its buried under the tiles in the bathroom above this one, so my question is this.

In the absences of a ceiling rose or junction box for the permanent live, would the following work

1. take a 3amp fused spur from a socket outside the bathroom, run this into a 3 pole isolator ,( both installed outside of bathroom)

This bit im unsure of ,,,

2. take a single core and connect one end to one of the spotlights , the other to the l2 in on isolator this being the switched live.

3. Run a 3 core from the isolator to fan, ending up with the following connections.

3 amp fcuto --> 3 pole isolator -- > fan

N--> N IN --> Nout-> N
L --> L1 IN -->L1 out --> L permanent

spotligtht to --> 3 pole isolator -->fan

L--> L2 In--> L2 out -->L swithched
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Had a job to understand the last bit, are you saying the fan will be supplied by both the lighting circuit and the socket circuit?

My apologies if I have misunderstood you.

Is there another part of that lighting circuit you can obtain a permanent live? The switch will have one for a start. Or another room if on the same circuit.
Thanks for the response, I cannot get access to the junction box feeding the circuit , so in essence what I suggested was feeding the fan from both the ligthing and the fused spur. Take it from what you are suggesting that this way wont work, if not could you take time to explain why, it would be much appreciated.

I can get access to the switch, so if I connected a cable either side of the switch and ran this back to the isolator as the permanent and switched live, would that work

Thanks in advance
A bit difficult to understand as sparkright says, but you cannot take connections from different circuits, I e lighting and sockets, you have to come from the same one. If you take a neutral from the lights you could use the line from the lights as a switched live and a permanent live from the supply side of the switch. Hopefully you have RCD protection?
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you could just put a humidi fan in or a fan wth a pull cord?
As Wingcoax says.

You will get your neutral from the spotlight.
You will get your permanent live from one side of the switch.
And switched live either from the spotlight or the other side of the switch.

Where you were talking about using sing core cable, make sure it is double insulated. You could use ordinary twin and earth cable.
Thanks for all the response, and apologies for the lack of clarity, i never have been any good at explaining myself. Think I have it now thanks again.
You must not mix up feeds from separate circuits.

At the very least it will cause real problems later when the electrics are tested and/or upgraded as it will make what is called a shared neutral. This will cause RCDs to trip.

At the worst it could be dangerous. For example, you turn off the circuit that is marked "upstairs lighting", but part of the circuit will still be energised from the fused spur.

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