Flashing Energy Saving Light with the light switch OFF

[blindpew]

Help.

One of my energy saving bulbs on a 2 bulb, 3 way switched lighting circuit just blew. I turned off the switch to replace the bulb and found that the good bulb was flashing very weakly at about 10 flashes/minute. Further investigation revealed that there was a stray 40v on all the red wires of both ceiling roses and all 3 switches. This voltage had been insufficient to indicate on a normal 100w bulb and presumably has been like this for some time as no changes have been made to the electrical system. I measured the voltage on the other hallway 2 bulb 2 way switched circuit and this indicated 15v which makes me wonder now whether or not this kind of behaviour is normal for 2 or 3 way switching. Can anyone out there tell me what's going on please?
Cheers

Pete

 

[Adam_151]

Capacative coupleing between the switch feed and the switch wire becuase the two way strappers connected to them which probably run together for a fair few metres without a cpc between them.

A cfl at the lamp holder will flash a bit as the capacitors inside it trickle charge through the cableing, the lamp will try and strike, it will then go out and the cycle starts over, connect a high impedance voltmeter there instead and you'll get some voltage between 0 and 230, which will vanish as soon as any sort of real resistive load is connected

 

[bernardgreen]

Once lit and the gas ionised low energy lamps will continue to "work" on traces of voltage. Capacitive coupling between adjacent wires is enough to produce this effect.

A snubber can be fitted ( skilled job ) into the lamp holder to stop the effect.

 

[blindpew]

2 replies in 9 minutes, that's quicker than using the phone! I just measured the voltage with 1 Energy bulb in a holder and the other socket empty and it was down to 10v. With a standard 100w bulb in one socket the volts read zero so it looks like Capacitive coupling between adjacent wires is the culprit. The lights don't flash when both sockets have bulbs in them so I don't think I need a snubber; but can you confirm that this phenomena is normal and no cause for alarm or the services of an electrician?

Thanks a lot.

Pete

 

[bernardgreen]

2 replies in 9 minutes, that's quicker than using the phone! I just measured the voltage with 1 Energy bulb in a holder and the other socket empty and it was down to 10v. With a standard 100w bulb in one socket the volts read zero so it looks like Capacitive coupling between adjacent wires is the culprit. The lights don't flash when both sockets have bulbs in them so I don't think I need a snubber; but can you confirm that this phenomena is normal and no cause for alarm or the services of an electrician?

Thanks a lot.

Pete

Yes normal.... not wanted though. Solid state switches are the worse for this as they have a capacitor across the switch "ensuring" there is enough stray to keep the lamp almost continuously alight.

 

[blindpew]

Thanks again bernardgreen. My switches are as mechanical as they come circa 1990. Do you think I should revert to normal bulbs (as per the last 15 years) or have these snubbers fitted?

 

[Steve]

Thanks again bernardgreen. My switches are as mechanical as they come circa 1990. Do you think I should revert to normal bulbs (as per the last 15 years) or have these snubbers fitted?

no. dont go back to normal bulbs. you're doing your bit to sve the planet. and unless the flickering is really peeing you off, leave it. its not dangerous or unusual. I have 2 fittings that do this.

 

[JohnD]

It doesn't seem to happen when you use T&E with the earth connected. Have you got any two-core, for example the flex drop to the lampholder, that you could change to 3-core with earth connected?

 

[blindpew]

The flashing occurs when only one ES bulb of the Philips type that has 3 U shaped tubes is fitted with the other socket empty. If I have 2 ES bulbs fitted there's no flashing and I now find, experimenting further based on the knowledge gained from your information, that the voltage with 2 ES bulbs fitted is virtually zero. So I'm happy with that. It's been fine for 2 years and I would have continued in blissful ignorance had not one of the bulbs blown. Now I know what caused the flashing and the stray voltage I can get some sleep! Thank you all for your help. This really is an excellent site.

Pete

 

[Steve]

I'm guessing both lamps absorb the induced voltage, so theres not enough for both to strike? just a guess.

 

[Adam_151]

It doesn't seem to happen when you use T&E with the earth connected. Have you got any two-core, for example the flex drop to the lampholder, that you could change to 3-core with earth connected?

Capactive coupling in parralel with the lamp doesn't really matter, its when its bridgeing the switch drop that it matters, you could however cancel that out by adding more in parrallel with the lamp

 

[Lanfire]

Thanks for the info guys, my house has this problem in the hallway and the master bedroom and both the celing roses have Philips ES bulbs fitted.

 

[Taylortwocities]

If you look at the 'similar topics' panel, below,
or use the search feature
search for "flashing low energy"

you'll find that this subject has been done over and over and over andover (thats in Hampshire)

 

[ban-all-sheds]

I keep thinking that there should be another sticky or wiki - "Common Problems".

But then I think "What would be the point - nobody would look there".

 

[Taylortwocities]

True, true..