Wired new Fan and Isolating switch but fan running

[divvy]

Hi,

Please help I've just fitted and new Timer fan with an isolating swicth outside the bathroom, but the fan runs when the light is off and vice versa when tunred on.

Thought I had wired it correctly but wonder if the problem with the cables in the isolating switch.

Used 4 core from fan to isolating switch and then to the connection in the light fitting.

I hope this is enough informtation.

Divvy

 

[securespark]

Need piccys of your connections to fan and where you have connected into the supply and the isolation switch connections.

 

[PrenticeBoyofDerry]

Yes need more detail.
How have you wired it, what core to which terminal at light, isolator and fan?
Sounds like you have your switch and permanent lives in reverse.

 

[Greenie9657]

Hi,

Please help I've just fitted and new Timer fan with an isolating swicth outside the bathroom, but the fan runs when the light is off and vice versa when tunred on.

Thought I had wired it correctly but wonder if the problem with the cables in the isolating switch.

Used 4 core from fan to isolating switch and then to the connection in the light fitting.

I hope this is enough informtation.

Divvy

Hi there

When i did my bathroom about 4 months ago i wired up a similar set up.
I put the supply into a 10A fan isolator switch outside the bathroom, then from the switch i wired the fan. N, E and L. The switch live i took from my light switch. Therefore, the light switch controlled the fan coming on and when you turned the light off the perminant live kept the fan on for the time set with the timer. Everything is usually labeled up L, N and E. I dont know how you could have wired it wrong. You could have put the perminent live into the switched live on the fan but that would just keep the fan running all the time. Im sure if you get a picture sorted then people will be able to assist further.

 

[PrenticeBoyofDerry]

This is how it should be done:
//www.diynot.com/wiki/electrics:lighting:fan

 

[JohnW2]

Sounds like you have your switch and permanent lives in reverse.

Reversing permanent L and S/L (from light cct) connections would normally make it function as a non-timer-fan - i.e. just come on whilst the light was on. The 'trigger' input of the timer unit would always be live (from the permanent L), but the power feed to the triac (from the S/L), hence fan, would only be present when the light was switched on. This does not appear to be what the OP is experiencing.

Kind Regards, John

 

[Greenie9657]

This is how it should be done:
//www.diynot.com/wiki/electrics:lighting:fan[/QUOTE]

Hi mate.

I remember seeing that diagram when I was wiring mine up but there's something I don't understand which is why I wired it the way I did. Perhaps you could clear this up.

On the diagram it shows the live, neutral and switched live coming from the lights ceiling rose into the fan isolation switch. Aren't those switches 10A?? And the lighting Cct 5A? Therefore if the fan draws more than 5A but not as much as 10A things would blow even though there isn't a fault?

Just a thought as I'm an aircraft electrician and not a domestic one.

 

[ban-all-sheds]

Switches are just switches, not breakers. The current ratings are what they can handle.

And why would you put a humongous fan which draws more than 6A on a 6A lighting circuit?

 

[PrenticeBoyofDerry]

On the diagram it shows the live, neutral and switched live coming from the lights ceiling rose into the fan isolation switch. Aren't those switches 10A??

Generally the 3 pole fan isolator is 10A

And the lighting Cct 5A? Therefore if the fan draws more than 5A but not as much as 10A things would blow even though there isn't a fault?

Does not work like that, you need to take the output of the load of the fan, which is often about 20W, so not asking for more than 1A.
So you don't have an overload issue and you don't have fuse blowing.
The amp rating of the switch and isolator, refer to the safe current they can endure before they start to breakdown.

Question:
The switch that operates the lights/fan in the bathroom.
I guess it,s a one way function but is it a two way plate?
Have got switch live for light in L1 and fan in L2?
Therefore when one turn on the other turns off?

 

[Greenie9657]

Switches are just switches, not breakers. The current ratings are what they can handle.

And why would you put a humongous fan which draws more than 6A on a 6A lighting circuit?

I wouldn't but that is what it looks like from the diagram. Which is why I did it a different way.

 

[RF Lighting]

How did you do yours then??

 

[ban-all-sheds]

I wouldn't but that is what it looks like from the diagram.

You think the digram shows a fan which draws more than 6A on a lighting circuit?

WHY??

 

[EFLImpudence]

I wouldn't but that is what it looks like from the diagram.

How can it be? - It's smaller than the ceiling rose.

 

[Greenie9657]

It's just the way I see the diagram. You have the 5A lighting circuit and then the 10A fan isolation switch is spurred from that. I don't understand that or I'm seeing the diagram different to everyone else.
I had a 10A wire straight from my consumer unit into the bathroom which supplied an immersion heater in a previous life but the wire was just left there in the airing cupboard hanging down. ( I've only live here 4 months). So I used that.

 

[ban-all-sheds]

It's just the way I see the diagram. You have the 5A lighting circuit and then the 10A fan isolation switch is spurred from that.

If I took your car and put 'Y' rated tyres on it would that suddenly make it capable of going at 180mph?

I don't understand that or I'm seeing the diagram different to everyone else.

Both.

I'm an aircraft electrician.

I'm gobsmacked.

And more than a little worried.

I had a 10A wire

No such thing.

• //www.diynot.com/wiki/electrics:flatpvccables
  
  
• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://www.tlc-direct.co.uk/Book/4.3.11.htm
  
  
• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  

So I used that.

And the rating of the MCB/fuse compared to the rating of the switch and what the fan maker specifies is.....?