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Stephen Jones · Dec 11, 2024

I have just had a new en suite installed off a bedroom.
I have a new in-line fan in the loft connected to a light switch outside the ensuite (via an isolator also in the loft) in the bedroom on the floor below.the loft. With the isolator in the 'on' position the fan and light come on using the en suite wall switch and all seems ok. Switching the light off does not stop the timer fan (which is set for a 5min extension). Turning off the isolator stops the fan. Also the fan remains 'electrically live' with the isolator off!!. Does this make sense? What is the problem? The fitter didn't know. Only sensible replies please. I realise there must be a wiring issue, I am getting an electrician but I'd like to know possible causes.

UNG · Dec 11, 2024

How have you established that the fan is electrically live with the isolator off in the off position

SPECIAL LOCATION · Dec 11, 2024

Welcome to the forum..

A timer fan has 3 wiring connections
A permanent live.. (to keep the timer function working)
A switched live.. (from a light or movement sensor or reactive switch, to start the timer once the switched live is turned off)
A neutral.. (because a neutral is required to complete the circuit for fan to work).
Most modern fans are plastic and do not require an earth connection..
(but an earth should still be taken to all accessories and if not required parked in a suitable terminal block / connector)

A fan isolator switch is a three-pole switch that should isolate all three wires..

Sounds like either your set-up is wired incorrectly, or you have a faulty switch that is not actually isolating all wires that it should isolate!!
[ I hope they haven't used the CPC as a switched live or neutral!]

Either way.. this is very basic and easy to identify what's wrong with a few tests and checks with suitable test meter(s), for a competent electrician.

Do I read it that your fan was fitted, connected, wired up by someone who is not actually an electrician? just a bathroom fitter?

If yes? Then part of your problem could be using a wrong tradesperson to undertake work outside of their scope of competence?

Side notes:
A 5-min run-on timer is probably much too short a time for all damp moist air to be removed from the duct.. and could result in problems later..
If there are no opening windows building regs recommend a 15min run-on timer..

Personally I think 15minuutes should be the shortest time considered if you are hoping to remove steam and moisture.

Also if selected by a bathroom fitter, it is possible that the fan could be under-powered as well for a duct if its longer than 1m total length to the external vent.

I come across these sort of problems all too frequently.. putting right incorrect wiring done by people who get confused with a 3-core & earth cable and Two lives!

ProDave · Dec 11, 2024

Not quite understanding the question. The fan you are talking about is a new fan in a new en-suite?

WHAT is the reference to the bedroom below? how does that relate to a new en-suite in the loft?

The fan is operating as it should with the over run timer. If you find the over run timer irritating at night, then I prefer 2 switches outside the en-suite, one for the light, one for the fan.

Stephen Jones · Dec 12, 2024

UNG said:
How have you established that the fan is electrically live with the isolator off in the off position

'With a tester Ung..I'm with a proper electrician now

Stephen Jones · Dec 12, 2024

SPECIAL LOCATION said:
Welcome to the forum..

A timer fan has 3 wiring connections
A permanent live.. (to keep the timer function working)
A switched live.. (from a light or movement sensor or reactive switch, to start the timer once the switched live is turned off)
A neutral.. (because a neutral is required to complete the circuit for fan to work).
Most modern fans are plastic and do not require an earth connection..
(but an earth should still be taken to all accessories and if not required parked in a suitable terminal block / connector)

A fan isolator switch is a three-pole switch that should isolate all three wires..

Sounds like either your set-up is wired incorrectly, or you have a faulty switch that is not actually isolating all wires that it should isolate!!
[ I hope they haven't used the CPC as a switched live or neutral!]

Either way.. this is very basic and easy to identify what's wrong with a few tests and checks with suitable test meter(s), for a competent electrician.

Do I read it that your fan was fitted, connected, wired up by someone who is not actually an electrician? just a bathroom fitter?

If yes? Then part of your problem could be using a wrong tradesperson to undertake work outside of their scope of competence?

Side notes:
A 5-min run-on timer is probably much too short a time for all damp moist air to be removed from the duct.. and could result in problems later..
If there are no opening windows building regs recommend a 15min run-on timer..

Personally I think 15minuutes should be the shortest time considered if you are hoping to remove steam and moisture.

Also if selected by a bathroom fitter, it is possible that the fan could be under-powered as well for a duct if its longer than 1m total length to the external vent.

I come across these sort of problems all too frequently.. putting right incorrect wiring done by people who get confused with a 3-core & earth cable and Two lives!

Thanks Trailer Boy..comprehensive reply brilliant. Very grateful. Your assumptions are all correct.
M Electrician with me now will post outcome

UNG · Dec 12, 2024

Stephen Jones said:
'With a tester Ung..

Really it does narrow it down a bit then, I have quite a few bits of test kit that will indicate a piece of equipment is possibly live but it won't tell me at what voltage and if all the conductors are properly connected

Stephen Jones said:
I'm with a proper electrician now

Stephen Jones said:
M Electrician with me now will post outcome

Do you have an alter ego or am I missing something
It sounds odd that a proper electrician is getting an electrician in to sort an electrical problem.

Stephen Jones · Dec 12, 2024

UNG said:
Really it does narrow it down a bit then, I have quite a few bits of test kit that will indicate a piece of equipment is possibly live but it won't tell me at what voltage and if all the conductors are properly connected

Do you have an alter ego or am I missing something
It sounds odd that a proper electrician is getting an electrician in to so⁹rt an electrical problem.

I'm not an Electrician. Turns out the bathroom fitter had
Incorrectly wired at least one of the 21 wires coming
through the ceiling (from the fan unit, isolator etc in the loft).in
to the light fitting. Also the two-speed fan unit had
to be replaced with a timer -based. unit .Think the fitter masqerading
as a sparky might have known this! All sorted. Thanks for replies.

SPECIAL LOCATION · Dec 12, 2024

Stephen Jones said:
Think the fitter masqerading
as a sparky might have known this! All sorted. Thanks for replies.

Thanks for the update and glad you got it sorted...

I think most of the other electricians on here like myself see far too many botched up wiring jobs, where all the customers sees is a switch, socket, fan, light etc.. that all looks wonderful, installed by a non-electrically competent person!

But in the loft, under the floor, inside the stud wall is an absolute rats-nest of sub-standard joints and faults waiting to happen.

The old phrase "Jack Of All Trades And Master Of None" tends to be very true with bathroom fitters, kitchen fitters, builders, landscape gardeners etc.. who all say they can "do the electrics for you" to save you money!!

But my advice, especially on any project costing thousands rather than hundreds of pounds, is always get proper tradespersons for the key tasks..
Construction, Joinery, Plastering, Plumbing, Electrical, Tiling, Heating etc...
There can be a bit of overlap between a few areas, but on the whole the greater the over-lap, the bigger the mess-up..

(I spent three hours on Wednesday this week putting right some messed-up kitchen electrics that "The customers friend" said he could do.. Grid switch with the wrong yoke, so the face plate couldn't fit on.. Cooker switch wired back to front so the neon indicator was always on.. Broken earth continuity on the ring... Lose terminations in the back of multiple sockets, so live or neutral wires popped out when opening them up while investigating the earth fault.. All fixed and sorted, ring continuity verified, earth loop impedance & RCD trip times etc.. all checked... So the customer then had to pay extra for my time rectifying her "my friend can help to save you money as electricians always overcharge" solution!!!)

Stephen Jones · Dec 13, 2024

SPECIAL LOCATION said:
Thanks for the update and glad you got it sorted...

I think most of the other electricians on here like myself see far too many botched up wiring jobs, where all the customers sees is a switch, socket, fan, light etc.. that all looks wonderful, installed by a non-electrically competent person!

But in the loft, under the floor, inside the stud wall is an absolute rats-nest of sub-standard joints and faults waiting to happen.

The old phrase "Jack Of All Trades And Master Of None" tends to be very true with bathroom fitters, kitchen fitters, builders, landscape gardeners etc.. who all say they can "do the electrics for you" to save you money!!

But my advice, especially on any project costing thousands rather than hundreds of pounds, is always get proper tradespersons for the key tasks..
Construction, Joinery, Plastering, Plumbing, Electrical, Tiling, Heating etc...
There can be a bit of overlap between a few areas, but on the whole the greater the over-lap, the bigger the mess-up..

(I spent three hours on Wednesday this week putting right some messed-up kitchen electrics that "The customers friend" said he could do.. Grid switch with the wrong yoke, so the face plate couldn't fit on.. Cooker switch wired back to front so the neon indicator was always on.. Broken earth continuity on the ring... Lose terminations in the back of multiple sockets, so live or neutral wires popped out when opening them up while investigating the earth fault.. All fixed and sorted, ring continuity verified, earth loop impedance & RCD trip times etc.. all checked... So the customer then had to pay extra for my time rectifying her "my friend can help to save you money as electricians always overcharge" solution!!!)

Sound comments and I agree with all that. It's all about those raboo words Health and Safety at the end of the day. Wise words Trailer. Why take chances with leccy?! It'll all end in tears eventually

binky · Dec 13, 2024

I would also check it is actually venting to the outside and not pumping damp air into your attic. Seen that far too many times.

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