Set my mind at ease - flickering light

[spooky_b329]

Hi,

A few days ago I replaced the ceiling roses and light switches in one bedroom and the landing. Everything seemed fine, the following day I replaced the remaining rose and switch in the second bedroom. Appeared fine until we went to bed, when we discovered that when we turned the landing light off from either switch it flickered. I assume an incandescent bulb would just dim...anyway I flicked the breaker off for upstairs lights and went to sleep.

Landing light is energy saving bulb, 2 way switching. Wiring is feed from bed1 rose to landing rose then on to bed2 rose. From landing rose we have a 3w+E to switch1, and then from switch1 another 3w+E to switch2.

Problem has disappeared today but obviously somethings not right so began to investigate. Suspected the rose in bed2 but checked everything and all seems correct. Then when I removed the first landing switch I could hear the common moving in its terminal, found it was pretty loose so tightened it up. Obviously as I couldn't replicate the fault I can't be sure I've found the cause, though I'm 99% sure that was it. So just to set my mind at rest, would the loose common cause the light to flicker? Anything else I should check?

Hmmmm...bit long winded but better to get all the info in rather than being asked later

Thanks

 

[Steve]

Hi,

A few days ago I replaced the ceiling roses and light switches in one bedroom and the landing. Everything seemed fine, the following day I replaced the remaining rose and switch in the second bedroom. Appeared fine until we went to bed, when we discovered that when we turned the landing light off from either switch it flickered. I assume an incandescent bulb would just dim...anyway I flicked the breaker off for upstairs lights and went to sleep.

Landing light is energy saving bulb, 2 way switching.

Perfectly normal. Ours does it. No ill effects. And its NOT incandescent - there is no filament.

I shall explain. You have a long run of cable between the 2 switches, with 3 cores. At all times, one of these is live and one is dead. When the light is off, the dead core is connected to the light of course. Now, something happens when you put a live wire alongside a dead wire for some distance. Charge builds up on the dead wire. This is not dissimilar to a capacitor. If you have a filament lamp connected to it, this means the dead wire is connected straight to neutral through the lamp's filament. The charge disappears to neutral as it builds up. However, with a CFL lamp there is no filament, the lamp requires a certain amount of energy to strike an "arc" across its gas tube. The flickering you see is the lamp dissipating the charge from the dead core, through the tube. In effect it is trying to start up, but there isn't enough energy to start it, and of course, run it.

Its quite cool, in my opinion

 

[daytona]

its a loose connection mate for sure check switches and lights

 

[Steve]

its a loose connection mate for sure

No its not.

Many CFLs flicker a little their entire life. Does them no harm.

 

[daytona]

i take your point mate but i beg to differ.he already said the common was loose and when tightened it cured the problem.had the problem persisted then i would have gone down your route

 

[spooky_b329]

Thanks Daytona.

Steve, it wasn't just a little flicker, it was flashing on and off rapidly, to full brightness. But thanks for the input anyway, all appreciated Also, when I mentioned incandescent I was making a guess at what an incandescent would have done in the same situation...it would have dimmed rather than flashed would it not?

Thanks again

 

[Spark123]

Maybe both the switches were switched one way yesterday and they are both the other way today??
If it was a capacitive effect of the cable then a normal filament lamp will have a low enough resistance to remove the potential caused by the capacitance of the cable.