Extractor Fan Wiring

[mchaelh]

Hello, hoping someone can help me. I'm replacing a ceiling mounted standard extractor fan in a bathroom, which also has an electric shower (which has a pull cord). Fan comes on and off with light. Current fan has 3 connectors - I assume live, switched live and neutral (though don't know). The cables going into it are one black and 2 red. The model I've purchased (basic Selco extractor ie not timer), only has 2 connectors : 1 live, 1 neutral. So 3 wires from circuit, 2 connectors on fan. Any idea what I do? Don't need an earth on this model.
Thanks !

 

[JohnW2]

I'm replacing a ceiling mounted standard extractor fan in a bathroom ... Fan comes on and off with light. Current fan has 3 connectors - I assume live, switched live and neutral (though don't know). The cables going into it are one black and 2 red. The model I've purchased (basic Selco extractor ie not timer), only has 2 connectors : 1 live, 1 neutral. So 3 wires from circuit, 2 connectors on fan. Any idea what I do? Don't need an earth on this model.

One shouldn't really 'assume', but it's very probable that the black wire is the neutral and, as you say, the two red ones are probably live and switched live. If you had a test meter, you could ascertain which of the reds was which.

What you need to do is connect the neutral (assumed black) wire to the neutral terminal of the new fan and the switched live (one of the reds) to the live terminal of the new, non-timer, fan. If you don't have the means of testing (and much as some people here will probably complain) you could use 'trial and error', since no harm would come from getting it wrong. If you correctly connect the switched live to the fan, it will work as you wish (with the fan coming on/off with the light). If you connected the ('permanent') live to the fan, the fan would be on all the time, regardless of the light switch. The unused red wire would then have to be terminated in a small piece of connector block and tucked away somewhere safe within the fan housing.

Remember that you have to switch off the entire lighting circuit before doing any work on these wires, since one of them will probably always be live, even when the light is off.

Kind Regards, John

 

[stem]

Likely the original fan has a 'run on' timer that keeps it going after the light is switched off, so requires a permanent live, switched live and a neutral as you suggest. the only way to be sure is to test the existing installation with a multimeter.

If the new fan only has live and neutral terminals, it will not have the 'run on' facility and will just go 'on' and 'off' with the light. So the permanent live will not be required. If you want to keep this fan, the permanent live should be terminated and insulated separately.

If your bathroom doesn't have a window, I believe that the building regulations stipulate that the fan must 'run on' so you might be better taking the new one back and getting a more suitable replacement.