Energy saving bulb flashing faintly when switched off

dinsdale · Jul 27, 2012

Firstly I am am a DIY'er not an electrician.

Last night I noticed that the energy saving bulb in my landing light was flashing faintly even tough it was witched off..

It is two way switched, one switch on the landing and one in the hall, power feeds the switch on the landing, wiring is done using ceiling roses.

I checked the voltage across live and neutral to the bulb in the ceiling rose with the light switched off, voltage is 30V.

I removed the positive switch wire from the ceiling rose and again check the voltage to the bulb, it was now 3V.

The house was rewired in stages between 1986 and 1988.

I have never come across this before. Has anyone any idea what could be the cause and how best to progress.

I do not wish to call in an electrician until I have investigated the simple possibilities.

Taylortwocities · Jul 27, 2012

This is caused by voltages induced into the wiring from adjacent circuits.

Some low energy bulbs are susceptible to this.
This can be fixed in a number of ways
1. Get a lamp from a different manufacturer and try that
2. Check that the lighting circuit has an earth conductor (cpc) and that is( and all the earths) are properly earthed. You can use your multimeter on ohms to test continuity, but please turn off all the power first. That stray voltage could just be a fault..
3. Put an R/C network across the lamp contacts. One of these works pretty good Buy RC Network Contact Suppressor PCB mount 100nF 120R Roxburgh EMC XE1201 online from RS for next day delivery.
4. Stop messing about with low energy lamps and put in a standard GLS lamp.

dinsdale · Jul 27, 2012

Taylortwocities - Many thanks, I had not thought of induction.
The bulb is a cheap B&Q one, so I will find another make.
The circuit is earthed and test OK on installation . I might have to get an electrician to re-test it.
If the change of bulb does not work I will try the capacitor.

KevinS · Jul 27, 2012

You will find the problem to be worse with Philips bulbs
at some of the sheltered accommodations that I work at they have banned Philips bulbs
you will also notice the more energy saving bulbs you have in the house the worse/more noticeable it is
what we advise is to put 1 normal bulb in each circuit (ie 1 upstairs & 1 downstairs in a normal house) this quite often solves the problem - but not always.
it depends on the induced voltage from other circuits.
Hope this is some help