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.

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.

Avo Mk8 · Aug 6, 2023

clanky boy said:
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.

Thanks for all the info. It doesn't get any clearer!
Have you tried disconnecting S/L from the timer and measuring the voltage on the 'Manrose' S/L terminal (if any).

I'm presuming all the lamps (by which I mean the bulbs themselves) on this circuit are mains voltage, there's no led driver or electronic transformer on this circuit, no shaver socket or charger, or anything we're missing?

Avo Mk8 · Aug 6, 2023

It would help me if you could disconnect the entire LED string (complete with the shower light) from its supply, eg at the terminal block or whatever it is that you show in your diagram, and measure the resistance of the lamp chain between L and N. I would expect it to be very low, eg 10 or so ohms with the shower halogen bulb in circuit.

clanky boy · Aug 6, 2023

Avo Mk8 said:
Thanks for all the info. It doesn't get any clearer!
Have you tried disconnecting S/L from the timer and measuring the voltage on the 'Manrose' S/L terminal (if any).

I'm presuming all the lamps (by which I mean the bulbs themselves) on this circuit are mains voltage, there's no led driver or electronic transformer on this circuit, no shaver socket or charger, or anything we're missing?

I will measure the V at the SL at the timer.
The spots are 240v ovio inceptor nano5.
The Halogen is not mains voltage, it's 12v from a Tx just before the light that is set into the extractor inlet over the shower.
I might disconnect the Tx and see if that does anything.

clanky boy · Aug 6, 2023

Avo Mk8 said:
It would help me if you could disconnect the entire LED string (complete with the shower light) from its supply, eg at the terminal block or whatever it is that you show in your diagram, and measure the resistance of the lamp chain between L and N. I would expect it to be very low, eg 10 or so ohms with the shower halogen bulb in circuit.

I'll go and do that now - back shortly.

Avo Mk8 · Aug 6, 2023

clanky boy said:
I'll go and do that now - back shortly.

Sorry, sent you on a wild goose chase!
I had the feeling the shower light couldn't be mains halogen with what we've seen, as it's not acting as a snubber!

If you put a mains halogen somewhere in that chain, that would be one way of solving the problem.
I think Mike is right, it just needs more snubbers until the effect goes away.

clanky boy · Aug 6, 2023

clanky boy said:
I'll go and do that now - back shortly.

The voltage at SL is 11.4v.
All LEDs and halogen, 2 snubbers and 100w lamp - approx 100M ohms
All LEDs and halogen, 2 snubbers- 90M ohms
All LEDs and halogen, 1 snumber- 100M ohms
All LEDs and halogen, - 120 - 150M ohms.

clanky boy · Aug 6, 2023

clanky boy said:
The voltage at SL is 11.4v.
All LEDs and halogen, 2 snubbers and 100w lamp - approx 100M ohms
All LEDs and halogen, 2 snubbers- 90M ohms
All LEDs and halogen, 1 snumber- 100M ohms
All LEDs and halogen, - 120 - 150M ohms.

I have taken a picture of the 2 snubbers I have - are these suitable or can you recommend something else please.

Avo Mk8 · Aug 6, 2023

clanky boy said:
I have taken a picture of the 2 snubbers I have - are these suitable or can you recommend something else please.

The 47nf is maybe a little low. I think 100nF (0.1uF) or more with say 120 ohms in series is the usual sort of thing.
There have been threads on this forum before about this.

This has been a suggestion before:

PMR209ME6220M470R30 | KEMET RC Capacitor 220nF 470Ω Tolerance ±20% 250 V ac, 630 V dc 1-way Through Hole PMR209 Series | RS

uk.rs-online.com

You may still need more than one!

Mike Johnson · Aug 6, 2023

I use these from RS Components:

[ElectriciansForums.net] Flashing LEDs when fan and lights off

Avo Mk8 · Aug 6, 2023

Mike Johnson said:
I use these from RS Components:

That's the one! I think it was your post I was thinking of.

Mike Johnson · Aug 6, 2023

@clanky boy notwithstanding any of the last four pages, somewhere you have a Ghost voltage on your supply to these lights, this can be caused by many different reasons, but usually its a two way switch somewhere on the loop with an induced voltage between the two switch's, a clean supply or snubber/snubbers are the only way to cure the problem IMO.

clanky boy · Aug 6, 2023

Avo Mk8 said:
The 47nf is maybe a little low. I think 100nF (0.1uF) or more with say 120 ohms in series is the usual sort of thing.
There have been threads on this forum before about this.

This has been a suggestion before:

PMR209ME6220M470R30 | KEMET RC Capacitor 220nF 470Ω Tolerance ±20% 250 V ac, 630 V dc 1-way Through Hole PMR209 Series | RS

uk.rs-online.com

You may still need more than one!

I have ordered a few 150nF and I'll try that - if no joy I'm off to tie a noose!!!
Thank you everyone for the help and advice - if the new snubbers don't work I'll pick this up again.

clanky boy · Aug 7, 2023

Mike Johnson said:
I use these from RS Components:

View attachment 109812

That is a nice tidy setup - I will try these if what I have ordered doesn't work.
Thank you.

Mike Johnson · Aug 12, 2023

@clanky boy any news?

clanky boy · Aug 12, 2023

Mike Johnson said:
@clanky boy any news?

Not yet Mike. The snubbers arrived Fri and not had a chance to fit them yet. When I do I'll post the outcome- it's always nice to close a problem down and not leave it open ended

clanky boy · Aug 15, 2023

Mike Johnson said:
@clanky boy any news?

Mike, apologies for delayed reply, but I finally got round to fitting the snubbers today. I got 8 x .1uF 120ohm and fitted all of them, one more each time. It has vastly improved but problem still there - that equates to .8uF and 960ohms! I disconnected them again and tried my 100w bulb again - problem goes instantly yet it equate to 500ohms and .41A, if my maths serves me correctly. Am I missing something or do I need much bigger snubber(s) say .22uF (220nF),470ohm snubbers- your thoughts please, kind regards, Mark.

Mike Johnson · Aug 15, 2023

If you know where the main power for the downlighter runs, put the snubbers as close to the first lamp as you can.

clanky boy · Aug 15, 2023

Mike Johnson said:
If you know where the main power for the downlighter runs, put the snubbers as close to the first lamp as you can.

I have put 7 snubber s into the first light JB. Flickers and then peters out over 30 seconds.

DPG · Aug 15, 2023

There's got to be more to this than just needing more and more snubbers chucking at it surely?

Not sure what though I must admit.

Mike Johnson · Aug 15, 2023

The snubbers need to be on each individual light not all bunched together, see post No 39 that is just one light connected at the lower end of the junction box.

Its the bulb that is picking up the Ghost voltage not the circuit.