Shower fan/light wiring

[macka001]

Hi, Just bought a new shower fan light and have a question with regards to the switch that i should you. i don't want to connect it to the existing light switch but want to locate another switch outside the bathroom, do i need to use a double pole switch for this?
thanks for your help

 

[ban-all-sheds]

Is it just an on/off fan, or does it have a timed overrun?

 

[macka001]

Hi, yes it one of thoes with an over run timer

 

[ban-all-sheds]

Then you need to supply it with a permanent live, a switched live, a neutral (and possibly an earth - depends on the fan). You should use 3-core+earth cable for this.

It is common to use the bathroom light for all this, but there's no reason to, however I would suggest that you should still use the lighting circuit to power the fan.

You can either use junction boxes to join onto the lighting circuit, or connect to the permanent live of the existing light switch or the ceiling rose of the light - it all depends on where the cables and accessories are in relation to where you want to put the new switch.

The new switch does not have to be double pole, BUT you should have some means of isolating the fan completely. You can either use a 3-pole (Live, Switched Live, Neutral) isolation switch between the fan on/off switch and the fan, or you can put a DP switched FCU in the circuit before the fan on/off switch - this would also be a handy way to comply with any manufacturers instructions about using a fuse, which quite a few fans have.

 

[Bungalow Boy]

I've installed my timer fan as per your last instructions i.e. like an extra light but using triple and earth so I can also run permanent live to it. I've since read the instructions (I'm an engineer, so always know best) and found that the fan should have a double pole fused 3A isolator switch.

Given that my junction boxes are now fairly inaccessible and I can only get to the triple and earth wire to the fan I have bought a three way fan isolator switch that I'm about to place in the next room.

This is all very well, but I need to know if the fan has to be fused or will the 6A fuse in the consumer unit for the lighting circuit be enough?

 

[ban-all-sheds]

Remember I said "you can put a DP switched FCU in the circuit before the fan on/off switch"?

Now that you find yourself needing to put one after it, you will in fact need two, as you need to fuse both the permanent live and the switched live
The neatest solution would be to use a dual (not 2-gang) box like one of these:

then you could neatly mount a 2-module grid plate with 2 fuse modules and the isolation switch next to each other.

Other makes of accessories and other suppliers are available.

The 6A fuse in the CU will be fine for protecting the cable, but if the fan manufacturer says you should use a 3A fuse, and you do not, and something goes wrong with the fan, they will not honour the guarantee. IMPO they have these fusing requirements because they know that a lot of people won't bother, thus saving them money.

 

[Bungalow Boy]

Thanks 'ban all sheds'. I'll stop by the electrical shop on the way home tonight. I have three bathrooms to sort out, all have the same problem. This is what happens when an mechanical engineer builds a house!