light flashes when OFF

[ljarrald]

in our ground floor hallway the lights flash when the switch is OFF.
we have replaced the switch and stuff and the only reason i can think of that it's doing this is that either:

mice have chewed through the cable and its shorting slightly (we did have mice about 4 years ago)

electrical interference from other cables running close to it.

switched neutral rather than live and its earthing or something.

i have attatched a video.

 

[elrobbo82]

not sure about this one. could be inducing a voltage from another cable i suppose thus making the lamps try to start. try replacing with normal incandescent bulbs.

sure i'll get shot down on this one but hey ho.

 

[Space cat]

The hidden capacitor strikes again!

It's a problem that didn't exist until CFLs became popular.

electrical interference from other cables running close to it.

That's not a bad guess but the 'interference' is within the switch cable itself. It usually happens in two-way lighting circuits where permanent live and switched live cores lie side by side in the cable with no intervening earth core. The capacitive coupling between these two cores is enough to make a CFL flicker.

What happens is that the trickle of AC current gets rectified inside the lamp's electronics and, slowly, charges up a bigger capacitor that's in there. When the voltage reaches a critical level, the lamp strikes briefly and discharges the capacitor, ready for another cycle.

There's no easy solution to this (other than going back to a filament bulb) but you should check that your earths are all properly connected. A floating earth wire greatly increases the capacitive coupling between the other cores.

 

[Alarm]

If you have a little search there is a fix for this.

 

[ban-all-sheds]

the only reason i can think of that it's doing this is that either:

mice have chewed through the cable and its shorting slightly (we did have mice about 4 years ago)

electrical interference from other cables running close to it.

switched neutral rather than live and its earthing or something.

Could "we've just replaced the bulbs with low-energy ones" be added to the list?

//search.diynot.com/forum_sear...0&author=&search=Search+Forum&stype=0[/QUOTE]

I've now watched the video, and aren't they flashing a lot faster than is usually (always?) reported?

ljarrald - when you had traditional light bulbs did they work OK? Didn't appear to glow very slightly when they should have been off?

 

[ljarrald]

i don't remember what normal bulbs were like. i'll swap them out with normal ones when i find a shop that sells them.

i would not be surprised if there was no earth in the lighting circuit at all. our house should probably be rewired but at the moment we can not afford it.

 

[JohnW2]

I've now watched the video, and aren't they flashing a lot faster than is usually (always?) reported?

I would have guessed that (assuming the usual reason) the frequency of flashing would be dependent upon the degree of capacitive coupling - enough capacitance and they would be on permanently! If, as the OP now suggests may be the case, the lighting wiring has no CPCs, the degree of coupling could be quite high.

Kinde Regards, John.

 

[ljarrald]

the strange thing is that it does not always do it

 

[Space cat]

the strange thing is that it does not always do it

Does this light have two-way switches? If so, there are two ways that the light can be off. I wouldn't be surprized if only one switch combination causes the problem.

 

[JohnW2]

Does this light have two-way switches? If so, there are two ways that the light can be off. I wouldn't be surprized if only one switch combination causes the problem.

Good suggestion.

Kind Regards, John.

 

[flameport]

The speed and brightness of the flashing suggests a fault either in the switch or the cables, most likely causing arcing between the line and switched line.

 

[ljarrald]

we replaced the switches and it still happens (making me think mice could be the cause)

i will try the different switch combinations tomorrow.