I have fitted an Extractor fan with timer. It has a permanent live, a switched live and a neutral. My problem is the fan only comes on when the light is turned off and will continue to run until such time as we turn on the light, then it will switch off according to the 'timer delay'. Any idea as to what I might have done wrong?
Extractor Fan wiring error?
- Thread starter laughalot
- Start date
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Have you run the cable to the switch?
All I have done so far is remove an old faulty extractor fan and fitted a direct replacement assuming that I was connecting up correctly - the old fan used to work as intended until it packed up altogether - but my attempt at replacement has resulted in the fan operating in an unexpected way (only on when light is off)
If you've only replaced like for like, it would seem you have wired it up wrong.
What colour wires haved you connected to which terminals?
It is worth knowing that 3 core and earth cables usually connected to timed fans sometimes get connected the way some electricians think it should be, and not the actual correct way.
But don't let's go down THAT street...
What colour wires haved you connected to which terminals?
It is worth knowing that 3 core and earth cables usually connected to timed fans sometimes get connected the way some electricians think it should be, and not the actual correct way.
But don't let's go down THAT street...
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In that case the neutral connection is probably wrong.
What colour have you connected to neutral?
What colour have you connected to neutral?
Indeed. I think that the OP has almost certainly got the permanent live and neutral connections reversed - that would, I think, result in the unexpected behaviour he is experiencing.
Kind Regards, John
Does the light glow dimmly when turned OFF ?
The description suggests the fan's Live and Neutral have been taken from the cable to the switch and the fan's Switched Live taken from Permanent Live.
When the switch is OFF the fan is supplied with a Neutral via the lamp and Live from the Live to the switch. When the switch is ON the fan's Live and Neutral [*] are shorted by the switch
[*] it isn't a neutral even if the wire is blue or black
The description suggests the fan's Live and Neutral have been taken from the cable to the switch and the fan's Switched Live taken from Permanent Live.
When the switch is OFF the fan is supplied with a Neutral via the lamp and Live from the Live to the switch. When the switch is ON the fan's Live and Neutral [*] are shorted by the switch
[*] it isn't a neutral even if the wire is blue or black
All the OP has done is to connect the existing cable to a replacement fan, the previous fan having worked correctly when wired to the same cable. I therefore don't think there's anything wrong with the origins of that cable.
As I said, I think at simple neutral/permanent live reversal at the connections to the fan would result in the behaviour the OP is describing:
With light on or off:
N is connected to fan's P/L terminal
P/L (permanent 230V) is connected to fan's N terminal
there is therefore always the required 230V between fan's N and P/L terminals
With light on:
230V S/L is connected to fan's trigger ('S/L' terminal). The trigger terminal is therefore at the same potential as the fan's 'neutral' - so the fan sees no (N-S/L) trigger voltage, hence fan is not on.
With light off:
fan's trigger ('S/L') terminal is at N potential (via lamp), so the fan sees 230V between its trigger ('S/L') and 'neutral' (which is at 230V) terminals - hence fan is triggered to operate.
When light is turned back on, the trigger voltage disappears from it's S/L terminal (as above), so it over-runs for the timed period, then stops
... which I believe is the behaviour the OP has described.
Kind Regards, John
When I first connected I tried to ensure I was getting the cables connected correctly and so did a simple test on the wires - one wire showed to be permanently live i.e. showing current present when light is both off and on. The other 2 wires only showed a power supply when the light was switched on therefore I assumed one to be a switched live and the other to be neutral - assuming my identification of the permanent live to be correct, would an error on my part re getting the switched live and neutral the wrong way around, possibly give the resulting error I am getting?
What are you doing these tests with?
And you should be testing for voltage, not current(!)
And you should be testing for voltage, not current(!)
As TTC has asked, how did you do these tests (what with?)? What colours are the three wires?
As I've said, the only way I can think that you could get the behaviour you're seeing is if the permanent live and neutral had been 'swapped around'. If you'd got the S/L and N the wrong way around, the fan would never work, regardless of light switch position.
Kind Regards, John
Glad it's sorted- it's nice to be right for once
I suppose those colours aren't necessarily too irrational, provided that the blue was the neutral. Were these 'single wires' or in cable(s)? - you would not get those three colours in one cable.
Kind Regards, John
Single wires - in the same property I had to replace a 'spur' to the garage and on tracing it back to the main board I discovered that the previous occupant had used 'off cuts' and the wire colours changed 3 times from main board to socket in the garage. Not good but it's made me check all previous wiring in the property now
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