New extractor fan in bathroom

[chrismcc]

Apologies before I begin on the rambling nature of this post. Moved into my house a year ago an it needed an emergency re-wire. All done and certified but we didn't really have a lot of time to think about what we wanted and now the missus wants the light in the bathroom changed and a fan fitted. So, it's the type of job I think I can cope with except the MCB bit (more later) and I would just like a bit of advice before I get onto LABC.

I currently have a single ceiling light with a pull cord which I plan to change for 4 low energy downlights all rated at IP44 (smallish room, bath no shower, that's downstairs, ceiling height is 2.4m), with the switch outside the door on the landing. I also want to put in an extractor fan above the bath. The fan is also rated at IP44 but will be in the roof space anyway, the switch will also be outside the door and an isolator will positioned outside above the door. We want to be able to run the fan independently of the light.

Now come the questions;

1. Can I use a 2 gang switch for both the light and the fan or is it better to use separate switches.

2. I will be running everything off the lighting circuit so I think I need to protect this circuit with an RCD. It is not currently, so do I get my electrician to move the MCB in the consumer unit or replace it with an RCBO? I think moving it might entail new bus bars as its a split load unit but consumer units are too scary for me so I don't look in them much.

3. I've drawn a circuit diagram (sorry if it's messy) of what I think it might look like and would welcome comments on colours, sleeving whether it's safe or anything else.

4. Do I need to do anything special as regards earth bonding.

Finally if I'm talking out of my a**e, let me know and I guess I'll have to fork out for a professional.

Thanks.

PS - earths not shown for clarity

 

[sparkyspike]

There's nothing much wrong with your circuit technically. However consider wiring without using junction boxes other than at accessible points such as through downlight holes. The fewer jb's the better. Try and make junctions at switches or light fittings.

Also, having a timer fan normally negates the need for a separate fan switch. You could consider using a 2 way switch as an overide switch, so that when the light is turned on, the fan comes on. Then if you want the fan on with no light, you can use the overide switch. You don't need two separate switches; a 2 gang will be fine.

If you want RCD protection, modifying the busbar is easy for an electrician and could be a cheaper option than a new RCBO. Your supplementary bonding should already be in place, so leave it as it is.

 

[chrismcc]

Thanks Sparkyspike. I hadn't thought of the override switch option. As for the junction boxes they would be screwed to the sides of the joists in the loft and easily accessible. However if it is likely my LABC would rather it was done the way you suggest I could change it. I'll give them a ring in the week and ask.

 

[sparkyspike]

I don't think LABC would be bothered about you using junction boxes. But if it's easy enough to route your cables without using jb's then do so.

If you want to use an override switch, then get a 2 gang switch. Wire the feed into COM of the light switch, and use L1 for the switched live to the light. Link L1 of the light switch to L2 of the override switch. Link COM of the light switch to L1 of the override switch. Use COM of the override switch to go to the fan. Connect neutrals and earths together. Job done!