Earth problem in lighting circuit?

[gbrown100]

Noticed the other night that our energy saving bulb was lightly flickering every so often when switched off so decided to change the rose. When I thought about it more wondered how it could pulse when switched off...

Checked the circuit and found 12v on both the earth and neutral when nothing was switched on (power was on at board though). Started checking switches & roses on other lights and found the earth (inc screws on switches) were carrying 12v also.

Finally, in one room found that if I switched the light on, the earth in a lot of the other rooms rose to 36V.

I assume this is one of two things...

1. The earth is not going anywhere so picking up a current from the other cables
2. There is an incorrectly wired or damaged component / wire somewhere.

Anyone got any ideas where I go from here or why this may be happening?

Thanks

Graham

 

[Adam_151]

The flickering of the CFL will be due to cable capacitance on the switch drop: a small current trickles through the capacatance, the voltage on the caps in the CFL rise, when they hit a certain level, the lamp tries to strike, the caps discharge and the process starts over...

Its entirely possible that

The earth is not going anywhere so picking up a current from the other cables

and you should check that the earth is connected to earth (a wander lead from the MET and a multimeter is one way of doing this) (voltages appearing on the CPC happen through the same cable capacatnace pheonominom), in a lot of cases where there is only one way switching involved, the fact that the two current carrying conductors are separated by an earthed core serves to eliminate the flickering CFL problem

 

[Softus]

Adam, as a non-electrician, I'm intrigued by the "cable capacitance on the switch drop" - can you explain a little more about this, so satisfy my insatiable curiosity?

 

[plugwash]

whenever two conductors are close together you have a (fairly poor) capacitor.

not much current can travel this way but it seems its sometimes enough to trickle charge the starter unit in a flourescent until it triggers and fires the lamp.

but then because its only connected to mains through a low value capacitor the voltage collapses very quickly and the bulb goes off again

repeat ad-infinitum

 

[Steve]

gbrown100, it is normal for energy saving lamps to flicker occasionally, especially on 2-way swith circuits. Dont waste money and time replacing light fittings!

 

[Hightowermark]

I got energy saving light blubs and the only one that flickers are the landing ones (2 way)

 

[arctic]

Is that the same as induced current that you can get from flouro starters?

Kev

 

[gbrown100]

Ok - flickering when on yes.. Flickering when off, I wouldn't expect that. We are talking about once every 15 - 20 seconds.

Although I don;t notice it it drives my wife mad.

Now - to the wander lead thing. I have a multimeter, you are suggesting I test whether the earth upstairs is connected back to the main earth at the fuse box? Is a wander lead a very long piece of twin & earth?

Graham

 

[gbrown100]

Wow - finally got round to replying! I kind of did several things at once:

1. Some fool had left a live lighting cable running from a junction box feeding the downstairs lights running up conduit alongside the ringmain in my bedroom upstairs , it was cut and taped and left behind a socket. I removed that...

2. I replaced the old Wylex fusebox with a new consumer unit.

I think it was the consumer unit that fixed it so not sure what the problem was there, I had been known to get the occasional mild shock from the case of the consuer unit (just enough to not feel like static) so maybe it had an issue.