Which circuit for a bathroom extractor fan?

[HalfEatenFlapjack]

Hi

I want my bathroom extractor fan to come on when the bathroom light's on. Can I just connect it to the bathroom light switch?

Thank you.

HEF

 

[SaladFingersMKII]

Yes, you connect it to the light circuit and use that switched live to tell the fan to come on.

 

[Gutterball]

depends if the feed is to the switch or the light.

 

[JohnD]

it is more usual (and convenient) to connect it at the ceiling rose.

Very often it will not be possible to connect it at the switch.

 

[PrenticeBoyofDerry]

And very likely a fan isolator and a 3A FCU will be required.

 

[winston1]

And very likely a fan isolator and a 3A FCU will be required.

Not if it is on the lighting circuit.

 

[ericmark]

If you are asking if it can be controlled from the light switch only then if either there is no natural light or you have an opening window then you can use just the light switch. If however there is natural light and the window does not open then there needs to be an alternative method even if it runs in parallel with the light switch.

There are two basic ways to wire. Where only the light switch is used then normally wired from the ceiling rose with no opening window will need a permanent line and switched line supply and overrun built into fan.

The second method is to use a twin pole switch so although the same physical switch the electric bit is separate. This has the advantage a pneumatic timing switch can be wired in parallel this also means no overrun timer is required to comply.

Fans do go wrong and the standard fuse size is 3A but when run from lights often just the 6A MCB is used. In real terms a fault with fan will often cause it to burn out before either 3A fuse or 6A MCB will open the wire used to wire the motor is very thin. However what you do need is a means to isolate so if it does go wrong you can switch it off so you can continue to use lights. So either a FCU or special fan isolator is normally used.

If you are asking do you run wires to light switch then normally no but it will depend on how it is wired.

 

[HalfEatenFlapjack]

Ok thanks everyone. There's fuse in place anyway, and I'll incorporate an isolating switch.

Thanks

HEF

 

[Grenage]

And very likely a fan isolator and a 3A FCU will be required.

Not if it is on the lighting circuit.

I imagine he was referring to the fact that many (most?) fan manufacturers specify a 3A fuse in their specs.