faulty two way switch ?

[izzy eckerslike]

Just fitted a new low energy bulb on the top landing -the newer ones that light faster & we noticed that even when it's off there is a slight flicker every now & again.
I tested the bulbholder with my mainstester screwdriver & when it's off it still gives a faint glow off the live pin.
It's connected by two way switches & I wonder if there is a fault or incorrect wiring on one or the other that might cause this ?

 

[Spark123]

More likely the capacitance of the cabling - try doing a search for capacitive coupling

 

[starspark]

its the type of lamp. on two way switching etc u somwtimes get flickering when u put in energy saving bulbs think because of the electronic starter in it and as spark says capacitance in the cabling although im sure someone may correct me!! a normal 60watt lamp will stop this.

 

[ban-all-sheds]

mainstester screwdriver

Throw that away and get some proper test equipment.

 

[izzy eckerslike]

mainstester screwdriver

Throw that away and get some proper test equipment.

Why would I do that ? it's a perfectly handy tool for for a quick check on live wires with the amount of testing I would be likely to do, I do have a multimeter also

 

[Johnmelad502]

Why would I do that ? it's a perfectly handy tool for for a quick check on live wires with the amount of testing I would be likely to do, I do have a multimeter also

Unreliable, use your MM.

 

[Steve]

A side note, I have a 20 watt low energy lamp on my landing, that has flickered like this when off, for over 5 years now. Its done it no harm. It isnt a bad thing.

Here's the science:

A 2-way switching scenario presents long runs of cable, whereby there will usually by a live cable running a distance alonside a "dead" live cable - ie. one is live, one is dead. They swap when either switch is operated.

This creates a large capacitor (though its capacity as a capacitor is actually quite small). Charge "leaks" from the live cable to the dead cable (which is connected to the light when the light is off). This you have a small voltage present at the light.

A filament lamp deals with this small voltage by passing it over the filament to neutral. However, in an energy saving lamp, there is no filament. For the charge to get to neutral, it has to build up on one side of the fluorescent tube, until the charge is great enough to jump across the tube. You see this as a brief, dim flicker.

 

[electronicsuk]

A 2-way switching scenario presents long runs of cable, whereby there will usually by a live cable running a distance alonside a "dead" live cable - ie. one is live, one is dead. They swap when either switch is operated.

This creates a large capacitor (though its capacity as a capacitor is actually quite small). Charge "leaks" from the live cable to the dead cable (which is connected to the light when the light is off). This you have a small voltage present at the light.

And the best way to fix this without replacing any fixed wiring is to convert your entire house and appliances to run on DC, which capacitors are excellent at blocking

 

[RF Lighting]

An even easier fix is to ditch the dreaded CFL and put in a good old fashioned proper lamp

 

[flameport]

Problem can also be fixed by fitting a small neon lamp and a suitable resistor somewhere - and if you need to ask what resistor or where to fit, you shouldn't be doing it.

 

[Taylortwocities]

There are a lot of posts on this. Quite often the problem can be fixed by using another make of CFL. Also the prob can occur if there is no earth (CPC) on the 2-way switch cables.

The presence of the earth can "sink" the capacitive effect.

While the addition of a hidden neon might fix the problem, it sure plays merry hell with IR tests when doing a PIR!