Cfl lamps flickering

[Stork75]

Hi new to this forum stuff, have a issue with me hallway light: it's on a 1way switch that switches 2 pendants (bc caps), when I was putting in some cfl lamps one at a time, when I put the second one in that one started flickering when switch was closed, so I put a filament lamp in it and it was fine but reintroducing the cfl introduced the flickering, so to recap: one cfl on circuit=no flickering 2 cfl on circuit= flickering on pendant furthest from switch, am I right in believing there is nothing wrong with the wiring and coupling is causing problem as the cfl lamps work fine on circuits with one pendant per switch? My fingers hurt from writing this essay cheers for the time to read this

 

[Marvo]

Yeah, it sounds like capacitive coupling causing a slight voltage that can cause flickering, it's usually down to a capacitor in the ballast power circuit that charges slowly and discharges quickly with enough current to strike or partially strike the lamp.

When you say it was happening with the switch 'closed' do you mean the switch was in the off position or the on position.

If the switch was off and the lamps were flickering you can either leave one incandescent lamp somewhere in the circuit or you can install a snubber resistor somewhere like in the switch box for example.

You may find that certain brands of CFL are more or less prone to flickering so you could try a different make of lamp as well.

If you want to try a resistor then I'd suggest maybe a 400ohm would be a place to start and maybe drop to 200ohm if the problem persists. We made up an r-c snubbers recently for LED lamps with a similar problem and we used a 320ohm resistor and a 0.1uF cap in parallel. The snubber is wired in parallel with the lamps (between switched live and neutral), you can locate it in one of the fittings or in the back-box of the switch.

There's also a final option I can think of where you can replace the switch with a 2-way switch, wire perm live on the Nc terminal, switched live to the common and neutral to the No contact. This will short the switched live and neutral when the light is switched off. I'm not a big fan of this option because it can cause confusion in future for other electricians who might not be so wide awake plus you need a neutral in the switch which tends to open a whole other can of worms on this forum. I suppose you could use the CPC for this function as well, it is a functional earth after all *runs for cover*

 

[Stork75]

Thank marvo, in reply to switch being closed, yes switch 'on'. Have solved the problem by using a different make of cfl lamp, tho still baffled why this would happen with full mains voltage through lamp!? As the lamp was flickering when energised and not off.

The idea of a 2way switch seems like a solution, tho not particular to mine as no neutral at switch, but am I correct in understanding you mentioned switching the earth??

 

[Wiresandthings]

I had one flickering recently, checked all the connections at the switch and pendant, all ok, checked the voltage, all ok, turns out it was a loose neutral in a joint box under the floor, sorted that out and no more flicker!!

 

[Richard Burns]

I would have said that you just happened to have a faulty lamp. If replacing the lamp solves it then it may just have been that the lamp was not firing up properly.
Though the loose connection idea is also valid since a low voltage on start up could cause flickering. In that case with your results so far I would be looking at the ceiling rose as it may have been moving the fitting as you change the lamp that has reconnected things.

 

[Marvo]

...but am I correct in understanding you mentioned switching the earth??

Forget the using the CPC suggestion, it was tongue in cheek. I didn't fully understand your problem, all the advice I gave was assuming the CFL's were flickering when they were switched off. Glad you got it sorted out, if there were no loose connections and the lamp holder was in good condition I guess it was just poor quality lamps.