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

Snubber across the LED connection.

Avo Mk8 · Aug 5, 2023

If I understand correctly, rather than a fan with an integral run-on timer, you have a standard fan with a separate external timer unit connected in the wiring to the fan. Could you confirm it's done as the circuit below (with the neutral not switched) but with the timer connected after the switch to the three fan feeds?
If the run-on timer has any significant leakage from its live input to its switched live out, this could be the cause of the led's illuminating.
as above re snubber - but It may not be like an induced/ghost voltage that can be shunted, so that may not be the solution.

What is the model of the run-on timer for interest, because I'm thinking at the moment that may be the culprit?

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

clanky boy · Aug 5, 2023

Avo Mk8 said:
If I understand correctly, rather than a fan with an integral run-on timer, you have a standard fan with a separate external timer unit connected in the wiring to the fan. Could you confirm it's done as the circuit below (with the neutral not switched) but with the timer connected after the switch to the three fan feeds?
If the run-on timer has any significant leakage from its live input to its switched live out, this could be the cause of the led's illuminating.
as above re snubber - but It may not be like an induced/ghost voltage that can be shunted, so that may not be the solution.

What is the model of the run-on timer for interest, because I'm thinking at the moment that may be the culprit?

View attachment 109798

Thank you for replying.

The timer is a Manrose 1351. The fan, buried in the ceiling! has a built in timer set to max (30mins), and i adjust the overrun time on the external timer. The supply to the fan isolator DP switch is last on the lighting radial. It then goes to the timer and the output from the 1351 timer to the fan. The 1351 timer needs a SL so I have taken a SL from the light switch to timer, to control the timer start function. Output from the timer then to fan. The fan needs a SL in its JB so i have looped the fan L to SL in the fan JB.
All functions correctly except the LEDs flicker dimly unless the DP switch is open.

I have two bathrooms with the same issue, all wired the same.

I tried to load a wiring diagram but it was 3.2Mb and it wouldn't accept it I'm afraid!

Thank you for helping.

James · Aug 5, 2023

Is the circuit protected by and rcd?

clanky boy · Aug 5, 2023

The circuit is protected by an RCBO.

Mike Johnson · Aug 5, 2023

You have complicated the connections unnecessary.

https://www.tlc-direct.co.uk/Technical/DataSheets/Manrose/BGDT20_1351.pdf

Avo Mk8 · Aug 5, 2023

clanky boy said:
All functions correctly except the LEDs flicker dimly unless the DP switch is open.

I think it's significant that the Manrose timer spec gives not only a maximum load, but also a minimum load of 15W!
I'm suspicious of leakage current coming out of the switched live terminal of the Manrose timer when the lights are off, causing the led flickering effect.
If a snubber across the bathroom led's doesn't fix it, I'm not sure what's next best.
You could fit a relay across the lights and use the n.o. contact to energise the Manrose SL input!
If the bathroom LED's are of an interchangeable type, eg GU10 holders, as a bodge you could put a single halogen bulb in one of them, which should stop the flickering of the rest!
Or use a double pole light switch with one pole for the Manrose SL and the other for the lights!
Or try a different overrun timer!

I tried to load a wiring diagram but it was 3.2Mb and it wouldn't accept it I'm afraid!

If using a tablet or PC you might try taking a screen shot, editing out anything spurious round the edges, and uploading that!

Avo Mk8 · Aug 5, 2023

Mike Johnson said:
You have complicated the connections unnecessary.

https://www.tlc-direct.co.uk/Technical/DataSheets/Manrose/BGDT20_1351.pdf

I understood that's what's essentially been done, but the switch shown is also the light switch!

Mike Johnson · Aug 5, 2023

I have the same unit to control my shower fan, it switches two independent LED GU10's in the shower cubicle without any flickering, but then I did wire it in accordance with the wiring diagram in post 7 between the SL and N into the Manrose unit after the switch.

Mike Johnson · Aug 5, 2023

Avo Mk8 said:
I understood that's what's essentially been done, but the switch shown is also the light switch!

And I think that is where the problem is, Ghost voltage from the main switch, a snubber should sort it out, two way by chance?

Avo Mk8 · Aug 5, 2023

Mike Johnson said:
I have the same unit to control my shower fan, it switches two independent LED GU10's in the shower cubicle without any flickering, but then I did wire it in accordance with the wiring diagram in post 7 between the SL and N into the Manrose unit after the switch.

So the switched feed to your LED's is connected to pin 2 of the Manrose thing, they are less than 15W, and they don't flicker!
So much for my theory!

clanky boy · Aug 5, 2023

Mike Johnson said:
And I think that is where the problem is, Ghost voltage from the main switch, a snubber should sort it out, two way by chance?

The timer is wired as per instructions and ligjting load is 4x4.8w LEDs, and to act as a snubber I wired the shower light which is a gu10 as the last lamp on the run. I have also tried two (in case one was duff!) 47uF 100r capacitor across every combo of terminals - I'm baffled.
I'm going to try a 1 way switch at the light switch as I am using a two way but in 1 way config.

I really appreciate all the help and advice - I'm struggling with this one!!

Mike Johnson · Aug 5, 2023

Have you tried the capacitor across one of the LED's?

clanky boy · Aug 5, 2023

Mike Johnson said:
Have you tried the capacitor across one of the LED's?

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!