DIY Doctor UK DIY Forums

Hi everyone,
about 10 years ago i had an extension built to my property,this led to having a larger landing. So i decided to convert my 2 way lighting and fitted an intermediate switch, this has worked fine for the past 10 years until now. Tonight i replaced a blown 100w lamp for a low energy lamp which seemed to work okay,but later in the evening i went up the stairs with the lights off and noticed a flash,which i thought was a firework but heard no bang.All of a sudden another flash, this is when i noticed it was the lamp, i have gone back to using a filament lamp for the time being. I was wondering if any of you good guys could shed any light as to why this would happen (pardon the pun).
I have put the low energy lamp into another 2 way circuit and it seems to work fine. Am thinking of fault finding with a coil meter,just want to see what some of you guys think.
Kind Regards
Remelad[/u]

Are any of the switches electronic? Dimmers, touch control etc. Not seen this with standard switches but I have with electronic.
Eric

Hi ericmark,
thanks for taking the time to try and help.
the light works on normal switches. to add a little more info, the intermediate switch is on the end of the switching circuit rather than in the middle. How ever as i said earlier this works okay with a filament lamp. The low energy lamp has been in another 2 way circuit for at least 24 hrs now and has been okay. I will do a test at the lamp holder in the near future but can not at present as i have a broken arm which is re-strickting me. If you come up with anything it will be much appreciated.
Regards
Remelad

Suspect this is caused by capacitance between the 2 way cabling. Some low energy lamps can illuminate (for a short time) on a low voltage. This voltage comes from capacitance coupling between conductors. Longer cabling between your 2 way switches = more capacitane = higher voltage.
That's why the bulb might be OK on another circuit.
Try another make of low energy bulb?
Another solution is to wire a resistor in parallel with the low energy bulb's terminals. We'd need to work out a value.
Hope this helps
TE

Hi T.E i can see what you are saying, but would you not think that after a couple of bright flashes this would of exhausted any capacitance. The flashes were as bright as a kitchen type flourecent light just being turned on. You know the type, the ones that use a starter. The light had been switched off for some time.
Regards
Remelad[/list]

Although TE may not be spot on it is somewhere near. Normal tungsten bulbs present a load at all voltages but discharge lamps often present no load until a critical voltage is reached. So any leakage, capacitance, or inductance.
In the electronic lamp often the AC is converted to DC then charges a capacitor then is converted back to AC at high frequency which feeds the tube.
It is the ability to store power in the capacitor is what causes the flash.
But what needs to be found is how the small amount of power gets into the circuit in first place.
Electronic switches is the norm. Old switches with carbon tracks could also cause it.
For many years the practice of borrowed lives on two way switches has been stopped but in early wiring two core rather than three core cable was used between two way switches this causes current to flow in one direction only and as a result is more likely to cause EMC problems.
Eric

Hi T.E and ericmark and anyone who read this post,
today (Tuesday) i put the low energy lamp back into original lamp holder on the 3 way circuit. So far so good,the lamp has been working fine,can only assume the circuitry within the lamp had a gremlin.
Many thanks for the input
Remelad