Confused about switching for a electric shower extractor fan.

[me]

It seems to me that ideally the shower extractor fan should come on automat ically when the shower is switched on using the power control on the shower unit itself. But I don't see being able to do that because it would involv e getting into the shower unit and connecting to the switched side of the s hower unit switch. Now I could probably do this but it seems it's not what is normal practice.

So what's the normal way of doing things? If I connect to operate from the light switch then what about in the daytime when you use the shower and wan t the extractor running but don't need the light on? Is it just expected th at any time you use a shower you must have the light on no matter the time of day?

And as the regs require this ventilation when the shower is in use surely t here's no point operating the extractor from a light switch because then it doesn't have to be used.

All seems odd to me and as I said...I'm confused.

[Harry Bloomfield]

on 13/05/2018, me supposed :

Fit a PIR operated fan. That would cover the bath, or shower, or toilet being used in a room. Mine includes both a built in PIR and a humidity sensor. It comes on if you walk in the door and it continues to run after the bath or shower has been used, until the excess moisture has been dispelled to the outdoors.

[Brian-Gaff]

Seems alittle bit ad hoc though. I have no fan, I open a window! Brian

[spuorgelgoog]

You can use a current sensing relay on the mains supply to the shower.

Owain

[me]

But then you've got the situation where you go in to get the towels to wash , open a window, kill a fly etc., and the damn thing turns on unnecessarily for half an hour!

It just seems to me this hasn't been thought through properly. There should be a connection in the shower unit provided by the manufaturer which provi des power when the electric shower is turned on. It's only an extra ten or twenty watts after all so you wouldn't need to uprate the shower cable.

Anyway, reading around a bit it appears that most fans are switched from th e light switch and I'm not sure how that gets past building control when it can obviously be left off when showering?

[Harry Bloomfield]

me brought next idea :

As you say, 20watts running for 20 minutes - so what!

If the shower in use were the only time the fan might be needed, I agree, but for most people it is needed when the bathroom is occupied, so an occupation switch (PIR) works better.

[me]

I was an electronics engineer but my days of being bothered to cobble toget her electronic circuits are well gone. The principal is what I was after th ough. I just wish the shower manufacturer would build something into the sh ower itself. All it would need is an extra output on the shower power switc h and a bit of 1mm T&E could be run from it to the fan...job done.

[me]

Ah right. In my case though it's just a shower room, nothing else.

[Jim]

You could join into the output side of the switch with some suitably sized cable, take that to a fused spur and then power the fan off that.

I've always thought that an auxiliary contact on the shower switch would be the easiest solution.

[ARW]

Put the fan on it's own switch.

Turn on fan when you want the fan on.

Turn off after use.

[Jimmy Wilkinson Knife]

I thought the regs only needed fans in bathrooms with no window? In which case you'd always have the light on unless you were having kinky sex in the shower with an ugly mistress.

[ARW]

Why would anyone have an ugly mistress?

Come on you have not thought this one through have you?

[Jimmy Wilkinson Knife]

Maybe she has other qualities?

[ARW]

You have never been married and had a mistress have you?

I have.

[Jimmy Wilkinson Knife]

You managed to find TWO worthwhile women!? In the UK?!

[ARW]

Have you found one woman?

[Jimmy Wilkinson Knife]

One woman or one worthwhile woman?

[newshound]

That's what I do. It's only a couple of 6 watt CFLs

(and not an electric shower, apart from the pump).

[Andrew Gabriel]

I did a shower room for someone else. For that, the fan is on a run-on timer with the light as usual, but to get a longer run after a shower, it's also triggered by a pipe stat on the shower hot feed, so it will stay on until the pipe cools. That part of pipe has an

8mm parallel pipe which snakes up behind the bathroom mirror, so that when you use the shower, the mirror is heated. When the shower is finished, this loop up behind the mirror convects via the piece of pipe with the pipe stat on it, to cool that pipe down.

When I get around to it, I will write this up with diagrams.

[Harry Bloomfield]

Andrew Gabriel formulated the question :

An interesting way of doing it, thanks..