Philips LED oyster fitting flashing when off

Hello everyone.
Not CBus related but I am having some trouble with a Philips LED oyster fitting.
http://www.simply-leds.com.au/phili...iling-17w-led-luminaire-350mm-warm-white.html

The light is switched by a 30 series mech and there is no dimmer.
I have replaced the fitting and checked the switch and wiring insulation resistance but it is still flashing according to the customer.
Faintly about once per second when switched off.

I tested the suspect fitting in my office and cannot notice any flashing in the off state so I suspect the problem is some induced voltage in the cable to the light.
The cable to the light is well clear of other cabling and only parallel to live power running down to the switch.
Perhaps it could also be leakage across the switch mechanism but my megger says no.

I believe the property may have some electromagnetic rodent repellent devices.

I had in mind to test the Clipsal 31LCDA to see if it would help.
Has anyone seen this before or have any other suggestions.

Thanks
Daryl

 

I just tested the same light fitting connected to a CBus leading edge dimmer expecting to see it flash or glow in the off state but is does not.
This suggests to me that it is not terribly susceptible to stray voltages and I am now even more perplexed.

 

After some more testing I found that this LED light fitting will illuminate dimly with only an active and earth connected.
Therefore if it was connected with incorrect polarity it would glow when switched off.

So now I am off the find out why and how much potential between the neutral and earth in this installation.

 

Hi Ashleigh
Thanks for the feedback

I tested 3 of these fittings and they all glow with only active and earth connected.
The glow is so dim you have to be in darkness to see it.
Probably just a tiny amount of leakage.

I tried 31LCDA across the lamp with neutral disconnected and it still glows.

Insulation resistance to earth is infinity.

Not much more I can do until I can test the installation but I can't get access until next week.

 

I have a random issue with some LED drivers, I believe it is as a result of 240V always being there on a dimmer channel, but current is negligible, and for normal (Tube/Filament) lights there is enough internal resistance to collapse the circuit.

However when it comes to some LED drivers the current draw of the components isn't enough to collapse the circuit so you get flicks occasionally, when "off".

If I have 2 on a channel, no issues, presumably the load is enough.

 

Hi Chromus
Thanks for the suggestion.
Yeah I can understand that problem but this is a bit different.
CBus dimmers have voltage at the output even when off.

The light fittings in question don't have a problem with that and I deliberately tested them on a CBus dimmer output to evaluate.
The customer's site has conventional wiring with 30 series switch mechs.
Switched active power is disconnected and I have tested that.

I have tested a couple of the Philips LED oyster fittings on a CBus dimmer and they are not giving any trouble even though the dimmer is providing a voltage in the off state to active and neutral terminals.

The Philips LED oysters in question do display an unusual property of illuminating when there is a potential between neutral (or un switched load conductor) and earth.

When there is any load on a circuit there will be voltage drop in the cables and a potential difference between earth and neutral.

I'm sure most electricians will be familiar with shorting a neutral and earth and tripping an RCD or sometimes not if there is no load.
So some potential difference will often exist between neutral and earth.

In this case I'm sure the potential difference between neutral and earth is causing the light to flash.
I've yet to determine whether it is caused by a wiring fault or stray voltages in the neutral or earth due to interference.

Bad feature Philips Lighting.
I will certainly be letting everyone know the outcome because if a light is flashing or glowing with the active positively switched off, the first thing anyone would look for is an active to switch wire fault.
Not a neutral to earth fault.

What I have yet to test is whether the potential difference between neutral and earth in the installation is due to a wiring fault or some induced voltage.
The fittings are certainly behaving correctly at my workshop during testing.

 

The voltage potential in this installation between neutral and earth was due to a fault with the earthing system.
The flashing in the off state has stopped once that was rectified.