Flashing LEDs when fan and lights off

clanky boy · Aug 5, 2023

Good afternoon everyone.
I have fitted an extractor fan in my bathroom with an overrun timer, to start when the bathroom led lights are turned on. I have wired the feed to the fan via an adjustable overrun timer and DP isolator with the SL for the fan timer coming from the light switch.

The issue is with lights and fan off the LEDs are flickering dimly - this stops when the DP switch is opened. I assume there is a small leakage to N from somewhere in the timer causing the sensitive LEDs to flicker, which when the DP switch is opened cannot occur hence the flicker stops.

I have bought and fitted a 47nF 100r capacitor and connected it to all possible combos in the timer - no change. The only thing that stops it is if I disconnect the SL from light switch yo timer - but obviously the fan wont run now.
I have spoken to a qualified sparky who's only suggestion was the capacity action as a snubbed - he doesn't know what to do now!

I am stumped and would appreciate any advice please.

Mike Johnson · Aug 5, 2023

To stop the stray voltage in my kitchen flashing the LED's I had to use snubbers on four of the twelve lights.

The one way switch as opposed to a two way would only make a difference if wired two way.

clanky boy · Aug 5, 2023

clanky boy said:
I have, on the first LED in the run, where I switched them. I'll try one of the others now though. I have just changed the switch to a 1w as opposed yo the 2w that I was using - back soon!

I have fitted the capacitor across one oc yhe other LEDs and no change and swapped 2w for 1w switch.

clanky boy · Aug 5, 2023

clanky boy said:
I have fitted the capacitor across one oc yhe other LEDs and no change and swapped 2w for 1w switch.

Managed to upload screenshot of wiring - sorry for rubbish art skills!!!

clanky boy · Aug 5, 2023

clanky boy said:
Managed to upload screenshot of wiring - sorry for rubbish art skills!!!

Not drawn on sketch is DP switch just before timer (between 1st LED JB and timer on sketch).

Mike Johnson · Aug 5, 2023

Put on an additional snubber and re-draw your sketch.

clanky boy · Aug 5, 2023

Mike Johnson said:
Put on an additional snubber and re-draw your sketch.

Mike, please see a better diagram. I have now fitted two capacitors (only have 2) and no change. I would have thought two capacitors and a gu10 should quash any stray V? As soon as I disconnect the timer SL the flickering stops. Can I fit a 10a 250v diode to stop any voltage leakage back from the timer SL to the SL connection at the light switch, which is the only way I can see and voltage getting to the LEDs.

Avo Mk8 · Aug 5, 2023

clanky boy said:
Can I fit a 10a 250v diode to stop any voltage leakage back from the timer SL to the SL connection at the light switch, which is the only way I can see and voltage getting to the LEDs.

It's ac mains. A diode will just rectify it, the result of which probably won't do what you want!
Is the S/L from switch to timer accessible? Would it be practical to use a 2 pole light switch and switch the timer S/L separately from the LED's? That would obviously stop the problem!

Could you confirm if the GU10 is LED or halogen. If LED could you try a halogen?

Sorry about all the questions - your circuit diagram rather neatly separates the wiring of the timer and fan from the wiring of the lights, but in reality are the physical cables jumbled together? That could lead to an induced voltage being the problem.
But if they are actually separated, I'll stick with the suggestion it might be the timer creating the voltage.

clanky boy · Aug 5, 2023

Avo Mk8 said:
It's ac mains. A diode will just rectify it, the result of which probably won't do what you want!
Is the S/L from switch to timer accessible? Would it be practical to use a 2 pole light switch and switch the timer S/L separately from the LED's? That would obviously stop the problem!

Could you confirm if the GU10 is LED or halogen. If LED could you try a halogen?

The gu10 is a halogen, which I thought would sort any voltage leakage.

Avo Mk8 · Aug 5, 2023

clanky boy said:
The gu10 is a halogen, which I thought would sort any voltage leakage.

I absolutely agree. I can't see how it can be induced voltage from other wiring with a thumping great filament load across it.

clanky boy · Aug 5, 2023

I am now confused. I will look for a DP switch and try that if you think that is ok?

Avo Mk8 · Aug 5, 2023

clanky boy said:
I am now confused. I will look for a DP switch and try that if you think that is ok?

Well it would stop the flashing, but doesn't explain why it's happening!

Have you got a multimeter or MFT?

Mike Johnson · Aug 5, 2023

Have you disconnected the SL from the L in the fan?

clanky boy · Aug 6, 2023

Avo Mk8 said:
Well it would stop the flashing, but doesn't explain why it's happening!

Have you got a multimeter or MFT?

Yes, a multimeter

Avo Mk8 · Aug 6, 2023

clanky boy said:
Yes, a multimeter

Thought it might be worth measuring voltage on Manrose S/L, both connected and disconnected.
Also try Mike Johnson's suggestion above.

clanky boy · Aug 6, 2023

Avo Mk8 said:
Thought it might be worth measuring voltage on Manrose S/L, both connected and disconnected.
Also try Mike Johnson's suggestion above.

Good morning everyone. As mike suggested I disconnected the SL at fan - no change.
I have fitted a different timer - no change.
Cables are not particularly close or bunched - so I think unlikely it's inductive from an adjacent cable.
Showing between 7v - 11v between L/N at one of the LEDs.

I have wired a pendant with 100w lamp across one of the LEDs L/N and problem gone, but obviously I can't keep that there!

I'm using .47uf 100r capacitor as snubber, but are these large enough (or whatever), as the 100w lamp appears to be able to dissipate the stray voltage.

Yet again I appreciate all the help.