Bathroom fan permanently on

[pauldalgarno]

Just replaced a noisy fan with new quiet one, but it's permanently on.

One cable with three core wires and a earth core running into the fan. I've wired the brown to live, black to switched live, and grey to neutral, and this leaves the fan permanently on. Have I ballsed it up with colours?

Should have looked before I disconnected the old one of course but had assumed the correct colours were wired up, and a diwnstairs fan is wired this way and working correctly.

Swopped brown and black around as thought lives may be mixed up, but fan buzzed quietly so assuming that's not good, and swopped them back.

The fan is on the same circuit as the light switch.

Any advice folks? I have a multimeter if that's what I need to identify things.

 

[undistilled]

Get a volt stick and work out which is permanent live and which is switch live. You can also do this by experimentation; with light off switch off at circuit fuse leave for 10 seconds then switch fuse back on. If correctly wired then fan should not come on. If it comes on then switch live and permanent live are reversed. Neutral must be correct otherwise nothing would work.

 

[pauldalgarno]

Get a volt stick and work out which is permanent live and which is switch live. You can also do this by experimentation; with light off switch off at circuit fuse leave for 10 seconds then switch fuse back on. If correctly wired then fan should not come on. If it comes on then switch live and permanent live are reversed. Neutral must be correct otherwise nothing would work.

Thanks, any thoughts why the unit would buzz quietly when I swopped the two "live" wires? When I did this it did work properly, but was a bit concerned by noise.

 

[pauldalgarno]

ps - to check for permanent and switched live I turn off the power, bridge across neutral and "live" with multimeter on continuity with light switch off, and then on to detect continuity?

 

[undistilled]

Make sure the blades are not impeded by any debris or distortion of the unit. Although they spin quickly they are very easily stopped by any foreign object such as a tiny fragment of plaster between blade and body. If you are still unhappy with it take it back as faulty and get a replacement. What make/model is it?

 

[undistilled]

You can check it this way - not bridge just one prong to neutral and one to the live cable. If you have a functional earth it would be better to test to that.

 

[undistilled]

keep power on (just be careful) and have meter set to voltage not continuity.

 

[pauldalgarno]

Make sure the blades are not impeded by any debris or distortion of the unit. Although they spin quickly they are very easily stopped by any foreign object such as a tiny fragment of plaster between blade and body. If you are still unhappy with it take it back as faulty and get a replacement. What make/model is it?

Thanks again, it's a Vent Axia vasf 100b, much quieter than old unit. Maybe some distorsion, so I'll check that too.

 

[undistilled]

By the way, you would want to do this testing with the cables disconnected from the fan.

 

[undistilled]

Vent axia = good product

 

[ban-all-sheds]

volt stick

 

[Taylortwocities]

Have I ballsed it up with colours?

Yes.

Although you have , probably, connected it up as it should be there's no guarantee. You'll need a multimeter to determine what is live, neutral and switched live.

As BAS has indicated, a volt stick is not going to help you. My guess is black=neutral, brown = live, grey = switched live. But guessing isn't the way we do things, is it?

 

[PrenticeBoyofDerry]

Yes I would assume (never assume out loud) that the black core could be neutral.
As stated previously, referring readings across the brown, grey, black cores, is likely to cause confusing, if you are assuming the grey core is a neutral, when it could possibly be a line conductor, so if you have a CPC/earth continuous back to earth, use that to reading across the three cores.
You could also do some investigation at light fitting and at fan isolator.
Also the fan is an overrun fan and will overrun for a period before it stops, are you sure that you have been patient enough for fan to complete it's overrun cycle (which will depend on the time it has been set to)?

 

[riveralt]

As PBOD said use the earth (hopefully still at the fan) to determine which is which.
Since this is a live test, put the four cables at the fan into separate terminals on a connector block.
Set your multi-meter to volts.
Turn the light on - put one probe on the earth and test for voltage between it and the other three - the neutral wire should be 0v while the two line wires should be 230v.
Having identified the neutral - now turn the light off.
Now test between the earth and the two remaining wires - one of them the switch live should be 0v and the other permanent live at 230v.

 

[undistilled]

Volt stick = extremely useful indicator for those who know how to use them and know their limitations . Neutral must be correct otherwise there is no circuit therefore fan could not have come on.