Evening chaps, sure we have a few sparkies here. Just doing the bathroom ATM and wish to fit an extractor fan. I've chosen one that's suitably large for the bathroom and an inline 240v model, this was for a few reasons but mostly for a safety aspect. It requires a switched live permanent live and neutral.

We have an electric shower and the instructions recommend to use the supply from the lighting. This means everytime the lights go on for a wee the timer will be on for 20 minutes, seems a bit silly. So I thought I could utilise the shower switch.

Pre switch live=permenant live

Post switch live= switched live

Pre switch neutral=neutral

Does that seem acceptable? Should I fit a fused isolator for the fan supply?

I think it means take a live feed prior to the light switch.

 

That's how I wired my bathroom extractor.

Yeah pre switch is constantly live, post switch is switched live. I've used the same wiring diagram really just transferred the power source.

Thought we had more electrians than this...

Yes, in theory you can. However, the shower supply will be massive in comparison to what you need for the fan.

You'll definitely need to fuse it down to 3A but you'll physically struggle to fit what is likely to be at least a 6mm twin and earth cable into a fused connection unit.

A potential idea...

Stick a shower rated downlighter in your shower and put a pull cord next to the shower cubicle. When you use the bathroom just the bathroom lights come on. When you want to use the shower the shower light and fan come on. After, turn it off and the fan overruns.

Also, I'd recommend one of these for a centre light in your bathroom... http://www.britektechnologies.com/products/commercial/95-down-light-8inch-slim

Simple and easy to fit, perfect spread of light, nice and bright and minimal power consumption.

Cheers Dave, I did think about that, space is pretty tight as it is. The trouble is there's already two pull cords in there already, one for the lights one for the shower. I was going to use some 1.5mm three core to wire the fan up, it's 25w. Will it cause an issue then the far lower load of the fan running on the same circuit(if I can get it in there).

I may just have to wire it up in the lighting circuit as per the manufactures recommendation and live with the silly overrun.

Yes, you really shouldn't tap off of a higher rated circuit. Your shower circuit will have around a 40 amp potential whereas 1.5mm cable is only rated around 15 amps.

If you want to run it off your shower supply you'd be safer enlisting the help of a local electrician.

Better safe than sorry when it comes to electricity. Especially in a bathroom.

Yeah it's a pretty high draw isn't it. I guess it's not the end of the world if the fan runs when not necessary. So il run from the lighting circuit, junction box is in a handy spot anyway. So I just need to define each cable, should take too long then run the three core across. The only thing that confuses me is I'd need two fuses, one for each live. Normally the fused isolator only contains live neutral earth doesn't it.

You can get specific fan isolators from any electrical wholesalers. It's basically a 3 pole switch.

The extractor fan can be provided with its own 3 amp fused spur supply for PL and N, with only the SL taken from the lighting circuit to turn it on and off with the lights.

Generally most extractors have an adjustable timer on them, they can be set for much lower than 20minutes, IIRC mine can run for as little as 1, got it set to around 5.

Ok il go grab one tomorrow.

 

I've got to replace the down lighters which I picked up today, the previous owner fitted normal ones in the bathroom gu10 240v types aswel. I only realised what they had done when they got damp. Bloody idiot. I've now got some fire rated ip65 12 mr16 type ones.

The extractor fan can be provided with its own 3 amp fused spur supply for PL and N, with only the SL taken from the lighting circuit to turn it on and off with the lights.

Generally most extractors have an adjustable timer on them, they can be set for much lower than 20minutes, IIRC mine can run for as little as 1, got it set to around 5.

 

Yeah it can, just want to clear the steam after a shower as without extraction it's ridiculous.

I may be a little late here, but I wouldn't see a problem with running it off the shower if it was fused, you could just get an inline fuse holder from maplins or somewhere (or 2 to fuse both lives) and you could proably fit them in the shower pullcord along with your 1.5 3core and earth.

 

I'm imagining a big deep 30mm white plastic box for the shower pull cord. if it's not then you may struggle to fit them in, but I'd just then fit the inline fuses and tape them up all nice and just push them into the loft above.

 

It'd annoy me to death if I could hear the fan from the bedroom on a night, just nip in for a quick wee then can't get back to sleep for 20mins.