Hiya

Presuming you are happy with one without a timer, and don't wish to take it back and get a timer model, then you can have it operate when the light comes on and go off when the light goes off.

If this is the case, you should have three or four cables, Red/Yellow/Blue/Green&Yellow stripey. Or you might have Brown/Black/Grey/Green&Yellow stripey.

Either way it's likely to be wired

Red/Brown = Permanent live (For timer fans)
Yellow/Black = Switched live (Only on when light is on)
Blue/Grey = Neutral
Green&Yellow stripey = Earth (Safety connection)

You need to connect yellow/black to the live on the new fan, and the blue/grey to the neutral on the fan. The other cables need to be safely connected into some small screw terminal block.

It may be that your cables have been coloured with insulation tape or sleeving to red & black or brown & blue. But providing you put the blue in the neutral, and one of the reds in the live it should work. If the fan stays on permanently then swap the reds over.

Make sure you turn the power off at the fuse board or consumer unit first. NOT just at the light switch as this won't turn off all power. If you find it too complicated or confusing call an electrician in for sure. Turn the light switch off and on once turned off at the consumer unit or fuse board to make sure the power is off to the light.

I've just installed a new one that I got from TLC, I am very impressed with how quiet it is.
Incidentally, can someone remind me why I need a fan isolator when the light swithch is outside the bathroom & the fan is in the loft (which has a completely seperate light source)? If someone wants this isolated they can pull the fuse (yes, it's is a real fuse, I've just moved!) for the lights!

Hi Twobarrows

An isolator is required so maintenance can be carried out safely on the fan should it be required. This should be wired independently from the supply to the light. For a timer fan you would need to isolate the permanent live, the switched live, and the neutral, hence the 3-pole isolator requirement. If you controlled the fan manually via a DP switch near to the fan, and it didn’t have an over-run/timer facility, then the DP switch would suffice.

Lectrician wrote on Mar 23^rd, 2009, 5:57pm:


That was why I asked, it would have been a pain to put an isolator above the door anyhow. I'll stick an switch in the loft whern I get round to it (isolating the feed for both live & switched live), in the meantime it will be the fuse!! Cheers.........