SOLVED Old extractor fan has TNL; new only has NL

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DOIDIY

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Hi everyone!

I’m replacing a broken extractor fan. It has three wires - T, N and L

I understand this is because the old fan had a timer.

My new fan only has N and L as it doesn’t have a timer.

Do I need to:

A) Put the mains N to the fan N and mains L to fan L, THEN put the mains T wire in with the L of the fan

OR

B) Put the mains N to the fan N and mains L to fan L, THEN just keep the mains T isolated by putting into a connector box that doesn’t connect it to anything else?

I’m thinking it’s A. I’ve replaced cookers and bathroom mirrors, built my own loft bedroom and bathroom but this is new to me lol

Many thanks in advance
 
jj4091 said:
B
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It depends upon what the 'L' and 'T' were. I would imagine that 'L' was probably the permanent live and T the 'switched live' ("Trigger") from the light.

If that's the case, then doing 'B' would result in the fan being on continuously, regardless of whether the light was on.

Again if my assumption is correct what is needed in neither 'A' nor 'B' but, rather, connecting 'T' (switched live) to the fan's L, and putting the 'L' (permanent live) safely into a bit of connector block or suchlike, connected to nothing else.

Of course, I could possibly be wrong about the nature of T and L.

Kind Regards, John
 
Got it all sorted now - above suggestion of B was correct. Thanks so much too John!
 
DOIDIY said:
Got it all sorted now - above suggestion of B was correct. Thanks so much too John!
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Glad it's sorted !

So (assuming that the fan now goes/on/off with the light switch) my 'assumption'/guess was clearly wrong :-).

I have to say that it does seem (at least to me) very odd that the permanent live was identified as 'T', which usually means 'Trigger' (a.k.a switched live - 'switched' by the light switch) !

Kind Regards, John
 
RandomGrinch said:
The original fan was reported to be broken - who's to say it was wired correctly to begin with! :)
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True, but I had assumed (yes, I know :-) ) that, although now 'broken' and needing replacement, it had (wired as it was) once 'worked' in the past - and not 'worked' in the sense of the fan being on continuously ;)

Kind Regards, John
 
RandomGrinch said:
If PL was connected to LT, and SL to L - wouldn't the fan have turned on and off with the switch, and have no run-on?
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It would - but I suppose I was 'assuming' (again!) that, before becoming 'broken', the timer fan had been worker properly as a timer fan

... but perhaps not - these 'assumptions' are problematic ;)

Kind Regards, John
 
Every timer fan I've ever installed has needed the permanent live connected to the timer which then keeps the fan running after the switched live is removed but switches it off after the set time. That is what I was understanding the Op. to mean in his suggestion B
 
jj4091 said:
Every timer fan I've ever installed has needed the permanent live connected to the timer which then keeps the fan running after the switched live is removed but switches it off after the set time. That is what I was understanding the Op. to mean in his suggestion B
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All I can say, to anyone else viewing this thread - read the manual for your specific fan! :)

Screenshot_20240331-080110_Adobe Acrobat.jpg
 
Last edited:
JohnW2 said:
Glad it's sorted !

So (assuming that the fan now goes/on/off with the light switch) my 'assumption'/guess was clearly wrong :).

I have to say that it does seem (at least to me) very odd that the permanent live was identified as 'T', which usually means 'Trigger' (a.k.a switched live - 'switched' by the light switch) !

Kind Regards, John
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It’s working as it was before and has an isolator switch so can be left on with the light off.

Though the old one had a timer, it never worked since we moved in two years ago.

I’ve put off this job for about 6 months whilst completing another project - next step is to remove all the mould that’s built up without it (no window)!
 
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