I have low energy bulbs at top and bottom of my domestic staircase, controlled by conventional three-way switching. When "on" they perform normally, but when "off" they flicker for much of the time, sufficiently brightly for me to see my way around at night. Similar bulbs in single-switch circuits do not do this.
I am well away from industrial sources of radiation, although many neighbours probably have wireless broadband,(perhaps in 3GHz region).
Has anyone else experienced this, and what is the explanation ? If you reply, do you really know, or are you just speculating ? No offence meant; I am simply anxious to know, and R.Feynman warned about the difficulty !

Peter,

I did a quick search on the net to see if there is any obvious explanation(s) and the only ones I have seen, as I suspected, is dodgy wiring.

Apart from that, low energy bulbs can flicker for a few seconds after switching off, which is apparently normal.

The recommendation is to get an Electrician to check the wiring.

Almost certainly caused by the slight capacitive leakage between cores of the 3-way-and-earth 2-way switch cable.
The electronic inverters in CFL lamps will run well enough from a high impedance source that they cause intermittent striking of the fluorescent tube - like a neon relaxation oscillator. Some lamps seem to be worse than others. You might try wiring a couple of series-connected 100k resistors in parallel with the lamp. You may even be able to squeeze them inside the lampholder. (Suggest 0.25W resistors and use two in series to keep within their voltage rating).
The resistors should shunt away any capacitive leakage current.

Alan

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Alan Kay, CEng MIEE

Thanks Alan,
Sounds reasonable, but still leaves the question as to why these bulbs flicker sometimes and sometimes not. I cannot observe any pattern.
I wonder why you said "almost certainly"; have you come across it elsewhere ?
PeterP.

Just completed a full house rewire where the stairs had a 2 way intermediate circuit etc .All dead tests passed all live tests passed . Put in some CFL's and they did exactly the same as your problem.
Me and the builder looked at them on when they should be off and laughed like kids.
the make were phillips 20watt.
swapped them for another make now they are off when they should be off , no problems since.
I could only come to the conclusion that the lamps were storing some energy and discharging for a small amount of time when switched off

Padwad,
Thanks for news of your Philips CFLs. However, for me it is not "a small amount of time". They flicker periodically throughout the night, and day !
PeterP

One particular cfl lamp was to be controlled using an X10 switch. These switch units have a local-overide facility triggered by switching the connected load off then on again. Detection of that action depends upon a small resistor-limited continuous load current. With this particular lamp that current was enough to make the cfl strobe randomly.

HTH

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Alan Kay, CEng MIEE

Every time I hear about this problem it is on a landing light. That would be because that is the most common light on a two way switch in this country. Have to agree completely with Alan Kays first post.

Bob

Do they continue to flicker when you turn off the main switch???, when they flicker try switching off the whole houses electrics, and note wether they are flickering, if they only do it with the main switch on then I would suspect they are wired wrong, could be induced voltage IMO

Same problem experienced twice:at home on a single-way switched bedroom ceiling light which flashes periodically after switch off,the lamp being a Philips Genie 11w Energy Saver.
Also when staying in a hotel in France recently the light over the mirror flashed every 7 seconds throughout the night.New it was a low energy bulb by the way it started up but could not identify it as it was in a concealed fitting.
Both were only visible in a very dark environment.
Looks like its not a rare occurance.
George Stallard

I too have met this problem and wasted a lot of time changing switches and ceiling rose to try to reassure a client. I then experimented with a long length of flex with a Philips 20w lamp at one end and a switch at the other and found the lamp flashes when switched off. Philips ought to publicise this phenomenon and avoid widespread anxiety and electricians' time wasting

i am sorry but
why should a low energy light bulb flicker interminably if the circuit is interrupted/off.
I have low energy bulbs at top and bottom of my domestic staircase, controlled by conventional three-way switching.
no low energy bulb fails to flicker

where does its energy come from

It comes from the mains. Two parallel conductors separated by insulation forms a capacitor. A capacitor will block DC current, but with AC power, some current can "leak" through. In a two or three-way switched system, there will be two switched live conductors running in the same cable, and this cable run can be several metres.

The leakage current is far too small to light a normal lamp, but the electronics driving the fluorescent lamp stores this power up until there's enough to strike the lamp.

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S P Barker BSc PhD MIET

I had this problem with my landing light, which is 2-way switched. When fitted with a Philips low-energy fluorescent bulb it flashed weakly and intermittently when switched off.

After checking the wiring and reading around on the web, I concluded it must be capacitive coupling in the 2-way switch wiring, possibly due to the light-to-switch1 and switch1-to-switch2 wires running alongside each other for part of their run.

I understand this is safe and does not need to be fixed. But I just fancied fixing it anyway.

A suggested solution is to fit a "snubber". I bought one from Maplin (product code RG22Y) for £2.37. I wired this in parallel with the light, inside the ceiling rose.

It seems to have fixed the problem.

Hello

I just have same problem, so I ask, is this not reducing the expected lifetime of the bulbs?
I feel that using 12 V tasters (relays)instead of regular switches would prevent it.

kind regards
AK

Hello

I just have same problem, so I ask, is this not reducing the expected lifetime of the bulbs?
I think that using 12 V tasters (relays) instead of regular switches would prevent it.

kind regards
AK

Edited: 21 January 2009 at 10:58 AM by antoniskyriazis

Why not just change one of them for a GLS lamp and see if the problem goes away? If it does then capacitive linking is certainly to be the cause and the resistor route could be considered.

switch to LED's. They are more efficient and other low efficiency bulbs are actually bad for the environment. Most contain a ton of mercury

But only if by "ton" you mean about 5 milligrams.

Health Protection Agency factsheet

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S P Barker BSc PhD MIET

You may well be correct about LED however most people still let their dentist fit amalgam fillings which contain far more mercury.....not only that in the filling but the bits that go down the throat when they fit/remove them.

Regards.

Edited to remove the quoted spam link

Edited: 31 August 2009 at 07:45 PM by IET Moderator