Sensible way to switch extractor fan with shower switch??

[roganty]

Hi all,

I am after a way to switch on an extractor fan using the shower switch.

Now before I get flamed, and told to wire it into the lighting circuit, I have a very "forgetful" OH who will forget to turn the extractor on each and every time she gets in the shower.
By wiring it into the shower, she can't forget to turn it on.

I've read B-A-S's post (from 2005) //www.diynot.com/forums/viewtopic.php?t=20386#123601 is this an acceptable way of wiring it all up?

If I use a none timed-overrun fan then I can just wire an FCU from the load side and then to the fan. Simples.

By using a timed-overrun fan I will obviously need a permanent live and neutral, so I would need to wire an FCU from the supply side of the switch.
For the switched side I will only need the live, is it fine to run just a live to a second FCU and then to the fan?

Thanks for any help you can provide.

 

[333rocky333]

What about a flowswitch in the pipework

 

[JohnW2]

If I use a none timed-overrun fan then I can just wire an FCU from the load side and then to the fan. Simples. ... By using a timed-overrun fan I will obviously need a permanent live and neutral, so I would need to wire an FCU from the supply side of the switch. For the switched side I will only need the live, is it fine to run just a live to a second FCU and then to the fan?

Functionally, I can see no reason why not.

The only issue is that it would be necessary to switch off both FCUs to make the fan safe to work on - at the very least, I would want to see warning labels on both FCUs to that effect. I suppose the 'proper' way to do it would be to take the permanent live, switched live and neutral all though a 3-pole isolator before they fed the two FCUs. Some people would then probably say that a standard 3-pole fan isolator would not be 'rated' for connection to a shower circuit; if you subscribed to that view (I would say more theoretical than real, given the nearby downstream FCUs with small fuses) , you would have to use a 'heavy duty' 3P+N isolator, such as used at the origin of 3-phase installations. On the basis that I've just mentioned, I would personally probably just use a standard 'fan isolator' if I were taking that approach.

Kind Regards, John

 

[roganty]

What about a flowswitch in the pipework

Thanks, but that is not an option as most of the pipework is buried in the wall, where it comes out of the wall it more-or-less joins up straight away with the supply for the sink.

 

[roganty]

Functionally, I can see no reason why not.

The only issue is that it would be necessary to switch off both FCUs to make the fan safe to work on - at the very least, I would want to see warning labels on both FCUs to that effect. [...] I would personally probably just use a standard 'fan isolator' if I were taking that approach.

@John, thanks for the info.
By using a fan isolator I'm assuming I could use an unswitched FCU. Or would you recommend I use switched FCU's anyway?

 

[JohnW2]

Functionally, I can see no reason why not. .... The only issue is that it would be necessary to switch off both FCUs to make the fan safe to work on - at the very least, I would want to see warning labels on both FCUs to that effect. [...] I would personally probably just use a standard 'fan isolator' if I were taking that approach.

@John, thanks for the info. ... By using a fan isolator I'm assuming I could use an unswitched FCU. Or would you recommend I use switched FCU's anyway?

I would think it would actually be safer to have unswitched FCUs - that way there would just be one switch to isolate everything. If you had 'switches all over the place', someone might switch off one of the FCUs and think they had made the fan safe to work on.

You may get some people debating whether you should use massive cables (which would probably be too big to connect to a fan isolator, and maybe even FCUs) up as far as the FCUs. If that happens, I'll join in the debate - and will remind them that the regulations do allow for a cable to be protected by a fuse downstream of where there is a reduction in cable size

Kind Regards, John

 

[roganty]

I would think it would actually be safer to have unswitched FCUs - that way there would just be one switch to isolate everything. If you had 'switches all over the place', someone might switch off one of the FCUs and think they had made the fan safe to work on.

You may get some people debating whether you should use massive cables (which would probably be too big to connect to a fan isolator, and maybe even FCUs) up as far as the FCUs. If that happens, I'll join in the debate - and will remind them that the regulations do allow for a cable to be protected by a fuse downstream of where there is a reduction in cable size

Kind Regards, John

@John, thanks for all of your help.

I assume something like this would be overkill!?

Could I get away with using 2 FCU's (neutral and live; and switched) or would I need 1 for each (neutral; live; and switched)?

 

[JohnW2]

@John, thanks for all of your help. I assume something like this would be overkill!?

Well, as I've implied, I personally certainly would. In fact, your shower circuit may have a 45A or 50A MCB protecting it, in which some might even try to argue that the 'overkill' 40A isolator was not OTT enough!

Could I get away with using 2 FCU's (neutral and live; and switched) or would I need 1 for each (neutral; live; and switched)?

Two would be fine. As you suggest, one for the permanent live and neutral, the other just for the switched live (but make sure that you use the 'L' side of the latter one, otherwise it will 'miss' the fuse!).

Kind Regards, John

 

[JohnD]

Now before I get flamed, and told to wire it into the lighting circuit, I have a very "forgetful" OH who will forget to turn the extractor on each and every time she gets in the shower.

Do you mean she showers in the dark?

 

[roganty]

Well, as I've implied, I personally certainly would. In fact, your shower circuit may have a 45A or 50A MCB protecting it, in which some might even try to argue that the 'overkill' 40A isolator was not OTT enough!

That's alright, they also do a 25A isolator

Two would be fine. As you suggest, one for the permanent live and neutral, the other just for the switched live (but make sure that you use the 'L' side of the latter one, otherwise it will 'miss' the fuse!).

Thanks for confirming what I was thinking!

 

[roganty]

Do you mean she showers in the dark?

@JohnD, yes thank you very funny

More often than not the showers are during the day, so its easy to miss turning the light on.
Plus, the bathroom is right next to our son's bedroom, and having the extractor fire up every time we use the toilet during the night is not a good idea!

I get blamed enough for missing the toilet during the day, it's no fun doing it with the light out at night!!!

 

[JohnD]

ah, you mean you have a noisy extractor fan.

You could change it for a new, near-silent one. There are now a number of ball-bearing extractors on the market, and a new generation which have been redesigned to minimise noise.

Do you have access to the space above the bathroom ceiling?

 

[ban-all-sheds]

I am after a way to switch on an extractor fan using the shower switch.

Is it an instant-heat electric shower, or a mixer one with a pump?

Now before I get flamed, and told to wire it into the lighting circuit, I have a very "forgetful" OH who will forget to turn the extractor on each and every time she gets in the shower.

Make her clean the mould off the grouting - she'll start to remember.

By wiring it into the shower, she can't forget to turn it on.

Indeed not. But will she remember to turn it off?

I've read B-A-S's post (from 2005) //www.diynot.com/forums/viewtopic.php?t=20386#123601

Without the aid of photos, thanks to Imageshack linkrot.

is this an acceptable way of wiring it all up?

I think so, but I wouldn't do it that way again - too much rsing about fusing down the shower circuit to supply the contactor coil. If I were to do it again I'd still use a contactor, but I'd have that switch the shower supply. So the fan, and the contactor coil would be on the lighting circuit which means a light switch is all that's needed, not a clunking great 50A shower switch.

But ideally I would use either a flow-switch in the pipe, or if it were a mixer shower, a temperature sensor on the hot supply pipe.

If I use a none timed-overrun fan then I can just wire an FCU from the load side and then to the fan. Simples.

A timed overrun fan is what you want though.

 

[ban-all-sheds]

There are now a number of ball-bearing extractors on the market, and a new generation which have been redesigned to minimise noise.

But he doesn't want to extract ball bearings, he wants to extract air.

 

[JohnW2]

ah, you mean you have a noisy extractor fan. ... You could change it for a new, near-silent one.

He could, and that might help to avoid problems from nocturnal trips to the loo - but it wouldn't help the fan to come on when his other half showered during the day, when she didn't need the light on.

Kind Regards, John