Bathroom light/extractor fan problem

[magill]

Evening all

Posted this in blogs by mistake!!

Bit baffled with current situation, maybe someone here has experienced before?
Just wired up a bathroom light with the extractor fan as normal practice. All works fine until light is switched off and during the 15 minute over run the light blinks on and off every few seconds. when the fan is switched off at the isolater the blinking stops, so it definately has something to do with the fan wired via the switch live. Any thoughts before i start fault finding?

Thanks

 

[ipf]

Is it ELV with the XFR outside the bathroom ?
If not, sounds like faulty fan/timer.

 

[Moses]

Evening all

Posted this in blogs by mistake!!

Bit baffled with current situation, maybe someone here has experienced before?
Just wired up a bathroom light with the extractor fan as normal practice. All works fine until light is switched off and during the 15 minute over run the light blinks on and off every few seconds. when the fan is switched off at the isolater the blinking stops, so it definately has something to do with the fan wired via the switch live. Any thoughts before i start fault finding?

Thanks

what make and model fan is it?

 

[Guitarist]

Definitely voltage getting back to the light via the fan then. I would guess at either the perm live touching the switched live at the fan, or a faulty circuit board in the fan.

 

[Moses]

Definitely voltage getting back to the light via the fan then. I would guess at either the perm live touching the switched live at the fan, or a faulty circuit board in the fan.

Then the light should stay ON

 

[Guitarist]

Then the light should stay ON

Not if it is touching but not connected. Seen plenty of cables over the years making an intermittent contact. I'm sure that you have too with all your experience Moses

 

[bethelec]

moses and the parting cables. lol

 

[telectrix]

an, but didn't moses part the brown sea. the bible said red, but europe says brown. shows what heathens the EU are.

 

[Moses]

Not if it is touching but not connected. Seen plenty of cables over the years making an intermittent contact. I'm sure that you have too with all your experience Moses

You don't mean touching, but adjacent to each other, but electrically separate, hence allowing electromagnetic pickup.

The lamp will only flicker if its a CFL.

May be the OP should try an incandescent lamp and see if it still flickers.

 

[Guitarist]

You don't mean touching, but adjacent to each other, but electrically separate, hence allowing electromagnetic pickup.

The lamp will only flicker if its a CFL.

May be the OP should try an incandescent lamp and see if it still flickers.

No, I mean TOUCHING. Sometimes, when cables are connected to small terminal blocks such as one finds in fan units, it is not uncommon to find that someone has stripped too much insulation off, or even that there is a strand from a stranded cable touching an adjacent cable.

Why are you always so obtuse Moses? Do you like just winding people up are do you have a superiority complex?

 

[magill]

Some interesting theories there lads. There is definately no touching of wires anywhere. Fan is a Airflow Q100HT. What i did try though was to pull the switched live from terminal 1 (delayed start/15 min over run/humidity) and place in terminal 2 (constant run) and bingo, no light flicker, BUT dissappointing as it was purchased for the delayed start and humidity control! Prob looking more likely that there is a prob with the board. The bulb is a CFL so i will dig out a incandescent lamp in the morning and see if that has any impact.

Thanks so far

 

[Moses]

No, I mean TOUCHING. Sometimes, when cables are connected to small terminal blocks such as one finds in fan units, it is not uncommon to find that someone has stripped too much insulation off, or even that there is a strand from a stranded cable touching an adjacent cable.

Why are you always so obtuse Moses? Do you like just winding people up are do you have a superiority complex?

Not being obtuse. sorry if it comes across as that way.
But if the switched wire was touching the permanent then the lamp would stay ON? or not?

 

[Rockingit]

Not being obtuse. sorry if it comes across as that way.
But if the switched wire was touching the permanent then the lamp would stay ON? or not?

The Pd would be the same, therefore no.

Edit: Just realised that's wrong, the light could potentially stay on if the union was downstream of the switch.

 

[GLENNSPARK]

an, but didn't moses part the brown sea. the bible said red, but europe says brown. shows what heathens the EU are.

well....i`m starting to think if he was the spring Tel....the brown sea that is...

 

[Moses]

The Pd would be the same, therefore no.

May be I am not understanding what you are trying to explain.

As the switched wire connects the 230V from the switch to the lamp, to supply the L to the Lamp to light it, and then this switched L is fed to the fan. So if this switched wire connects/shorts to the permanent L in the fan, then surely that permanent L connects through the switched L to the lamp supplying it with 230V. The Lamp already has a permanent N, and now has a L.

I am sure if the Permanent L and Switched L were connected/shorted any where then the lamp would stay on.

What PD are you talking about?

 

[Rockingit]

May be I am not understanding what you are trying to explain.

As the switched wire connects the 230V from the switch to the lamp, to supply the L to the Lamp to light it, and then this switched L is fed to the fan. So if this switched wire connects/shorts to the permanent L in the fan, then surely that permanent L connects through the switched L to the lamp supplying it with 230V. The Lamp already has a permanent N, and now has a L.

I am sure if the Permanent L and Switched L were connected/shorted any where then the lamp would stay on.

You are correct, hence my previous edit.

 

[Moses]

You are correct, hence my previous edit.

Thankyou.

 

[Guitarist]

Not being obtuse. sorry if it comes across as that way.
But if the switched wire was touching the permanent then the lamp would stay ON? or not?

After a 4 year apprenticeship and over 20 years in the field, there have been many times when I have come across cables "touching" without being connected, causing intermittent supplies to loads. This can often be caused by vibration, and would result in a "flicker" in this instance.
If this is a difficult concept for you to understand then I can only apologise for confusing you with my suggestion.

 

[magill]

Replaced the CFL with a low watt halogen and hey presto! all works fine according to plans. Absolutely no flicker. Big thank you to Moses for the idea, saved a lot of hassle. This is one of those scenarios that nobody can teach you so many thanks to all members for input.

 

[trev]

I had this problem once on a job for a council in a school, after a lot of head scratching it turned out that my mate had marked up the cables wrongly. Stripped everything out, traced which cable was which reterminated and it worked fine.