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cbw

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There are low energy bulbs installed on a standard lighting circuit, there is 3 or 4 way switching using standard intermediate and 2 way switches, all tests ok with no deviation to regs.

WHY do the low energy bulbs constantly pulse at about 40 pulses per minuite, it looks like they are trying to start up even though switched off?

It does not happen with standard bulbs.

How can I get around this, they want to use low energy bulbs?

CBW
 
This comes up fairly regularly,so out of interest I have copied some information about the reasons and possible solutions
I was aware that 2-way switching wired via 2 strappers could cause this problem
below is some info I found,as yet i cant find a supplier

A CFL may flash occasionally when off if the switch wire run is especially long.

In exceptional cases a CFL will flash occasionally when switched off. This is due to wiring capacitance passing a tiny current, which gradually charges the CFL's reservoir capacitor, and after a while it attmpts to start, giving a momentary flicker.
2 conditions tend to cause this:


an especially long switch run
supply switched on the neutral instead of live pole

If a filament lamp is on the the same switch (or PIR/ timer) as the flickering CFL, the problem will not occur. The filament lamp can be a low power type, such as 15w.
Resistor

It is also possible to stop the problem by fitting a suitable resistor in parallel with the bulbholder. Use either:

  • A 270k to 470k 400v rated resistor, or
  • 2x 150k to 220k 200v rated resistors in series, with both the same resistance value.
Resistor choice explained:

A capacitor can be used in the same way as a resistor. These should not be fitted inside the lampholder itself for temperature reasons. Capacitors consume no power.
A 10nF 275vac capacitor with X2 dielectric is suitable.
Note that capacitors marked as 250v rated are totally unsuitable for mains use. Before the advent of X & Y capacitor classifications, 600vdc caps were often used on unfiltered mains, but this is no longer compliant.
A 270k resistor will dissipate 0.2w on 240v mains.
2 way switch
R1
o---/\/\--- Neutral
switched live line to lamp ----o---
o------ Live

No-flash variation
R1 is a single 270k resistor rated to 400v, or 2 identical 150k 1/4w resistors in series.
 
Thanks Des, thing is it goes on and on, nothing momentary, it is only on the circuits with intermediate switches.

Got me stummped, plan to go and have a long play with this in the new year!

CBW
 
Hi cbw

I had a fluorescent fitting flicker like this when the switch was off and it turned out to be a reverse polarity coming in from supply authority
 

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