Extractor fan relay

[StorminBen]

Afternoon all,

A quirky query that I'm hoping someone may be able to assist with

Intention
I would like to wire in an extractor that only comes on when needed but does so in an automated manner (I know I could just wire in a manual switch)

Considerations
I hate bathroom extractors that come on with the light. 90% of the time you are in the bathroom you dont want/ need them on.
The shower switch does not get turned off every time so simply wiring into their has also been discounted

Thoughts
I recall from school days the old reed-relay which worked on the principle that current flowing through one side would activate the other side.
Is there anything similar that would work for AC and sense the current when the shower was turned on?

Any and all thoughts greatly appreciated

Thanks
Ben

 

[chivers67]

Get a Fan with a delay timer?

 

[Taylortwocities]

Buy a water flow switch to enable the fan when water is running.

Something like THIS maybe.

PS RCD protection essential!

 

[JohnW2]

You could install a flow sensor in the water feed to the shower.

Kind Regards, John
Edit: Arrgggh - typed too slowly again!

 

[StorminBen]

Wow, that was quick -and a very nice solution to boot.
Only minor glitch is that most of them are designed to work in a vertical alignment whereas the feed to the shower does not have an easily accessible vertical component

 

[JohnW2]

Wow, that was quick -and a very nice solution to boot. Only minor glitch is that most of them are designed to work in a vertical alignment whereas the feed to the shower does not have an easily accessible vertical component

That's true, and one sometimes has to tweak the pipework a bit to create a fairly vertical bit. Most of them say vertical ±15°. I've tried using them semi-horizontal, but they are then not totally reliable. If semi-horizontal, when water is flowing, they switch 'on' OK, but they usually rely on gravity to return them to the 'off' position when water flow ceases, and that may not happen if the device is not fairly vertical.

Don't forget that the sensor does not necessarily have to be physically close to the shower, provided that it is a pipe supplying only the shower. There might be more convenient pipework in which to install it more distant from the shower.

Kind Regards, John

 

[endecotp]

I recall from school days the old reed-relay which worked on the principle that current flowing through one side would activate the other side.
Is there anything similar that would work for AC and sense the current when the shower was turned on?

Yes, see e.g. http://www.kele.com/power-monitoring-and-protection/current-switches.aspx

 

[PBC_1966]

As you mention the shower switch not being turned off every time, presumably this is an instant electric shower. You could just tap from a switched point inside the shower unit and (via suitable fusing) use that for the control line to the fan.

 

[JohnW2]

As you mention the shower switch not being turned off every time, presumably this is an instant electric shower. You could just tap from a switched point inside the shower unit and (via suitable fusing) use that for the control line to the fan.

He could, but I hesitated to suggest that, for reasons which you can probably imagine.

Kind Regards, John

 

[OwainDIYer]

You can make your own
http://wiki.diyfaq.org.uk/index.php?title=Current_activated_switch

 

[Steve]

I wired my fan through a momentary action switch to get 20 mins run out of it using its internal overrun timer. Switch must be outside the room or out of zones.

 

[magicmushroom666]

You could also get an extractor with a humidistat, but I think the flow switch combined with the fans own timer would be better, preemptive rather than reactive.

 

[bernardgreen]

A thermal sensor on the waste pipe from the shower ?

A PIR sensor with its "vision" limited to the inside of the shower cubicle ?

An accoustic sensor to detect the sound of water hitting the shower tray ?

Whatever is used the sensor must operate on an ELV supply ( less than 50 volts and prefereably only 12 volts or less ) and relay switching mains be in a dry area and preferably not in the shower room ( unless the room is large enough to have a non hazardous zone )

 

[Simon35]

http://uk.rs-online.com/web/p/flow-sensors-switches-indicators/0256578/

or this...

http://uk.rs-online.com/web/p/flow-sensors-switches-indicators/0256562/

One is for 15mm pipework, one is 22mm. I have the 22mm mounted horizontally in the cold water feed to my thermostatic mixer shower...works a treat, and has done for 10 years, Just wire the switched live to the fan through the normally open contact on the flow switch.

All up in the roofspace away from any zones.

 

[Simon35]

A thermal sensor on the waste pipe from the shower ?

A PIR sensor with its "vision" limited to the inside of the shower cubicle ?

An accoustic sensor to detect the sound of water hitting the shower tray ?

Whatever is used the sensor must operate on an ELV supply ( less than 50 volts and prefereably only 12 volts or less ) and relay switching mains be in a dry area and preferably not in the shower room ( unless the room is large enough to have a non hazardous zone )

I might be mis-reading you here Bernard, but are you saying it needs to be ELV regardless of location, or just if its in a bathroom zone?