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Hey so just been to see a dad from the little daughters school class who asked me to have a look at his upstairs landing light pendant as his mrs said it's flickering the lamp when on a few mins and then goes right out altogether ! She then needs to switch off and on to get it on again, sounded strange so had a few mins to take a look.

New build estate, and just at top of stairs single pendant with a GU10 lamp holder and a CFL GLS lamp in place. Tested with T5-1000 Fluke at rose and had L-N 25V ac, then 23V L-E and nothing at all N-E, switched any one of the 2 way and inter switches and got 241V tightened all rose terminals and checked secure & not clamped onto insulation and then checked at inter sw and top of stairs 2 way switch, had 1 x 3 core as expected plus conn block with 3 x lines and 3 x Neutrals in and tested at 241V between and 242V to metal backbox / cpc's all ok then test one strapper to cpc and / or N and got 19V which then rose to 25V ac like a second hand ticking up ? but all switching operating lamp fine and 240V across to other strapper and back and forth always leaving 22-25V ac on the strapper not in use to cpc or N and same after at ceiling rose ! 19V slowly rising up to 23V which then brought on red light on meter then 25V stopped again ! Also picked up 41V or so between Com and L1 strapper think it was while lamp was off.

Wondering if barely connected N in connection somewhere or other loose wire causing capacitance or inducing a voltage etc.. or wondering what third line and N are for tapping off the connector block and whether they are supplying something else which is causing the kind of ghost voltage and then if this residual voltage is the cause of the cfl lamp problem ?

Have said if he wants it sorted will need to go back and start going through things more while isolated etc.. and make sure no borrowed neutral or anything loose.

Any more experienced thoughts welcome, Thanks.
 
Sticking in a snubber normally sorts it out.
 
Really ? thought there may be a weird connection in there somewhere, found same kind of weird voltages before on really old junction box wired houses with also borrowed neutrals.

Thought snubbers only for contractors and underfloor heating kind of situations ?
 
Apparently huge snagging list involved ! think it's always happened and only on that one fitting / pendant, nowhere else. They've not tried any other lamp, I did say maybe we could try wiring in a standard gls bc lamp to the rose and see if that stops the hassle, but limited time today. I expected my super excitable fluke volt sticks to pick up on the juice but they didn't ! well the newer LVD2 or whatever it is did light up blue which is normally when close to juice but that was only one. I'm thinking along the lines of my digi T5 being high impedance rather than a basic analogue meter but thought would be much better kit ? as last time I used analogue was at college with AVO 8's many years ago.
 
Sounds like confusion here. The OP says the lamp is flickering and going OFF when it should be ON. That's not caused by capacitance or leakage, it's either a faulty lamp or a poor contact / loose connection in the switch or holder that's heating up and going open-circuit.

The various voltage readings may well be caused by capacitance, e.g. the first readings mentioned at 25V are due to capacitive leakage when the switch is off, combined with the O/C voltage of the lamp. These would have been zero with a filament lamp, and do not indicate a fault.

With 2-way or 3-way switching, if L & SL go to the commons of the 2-ways, one strapper floats when the light is on, and could be at any random voltage. When off, one will be at 230V and one at lamp volts (again will only be truly zero with a filament lamp). OTOH, if L & SL go to L1 & L2, one strapper will always be at 230V, one at lamp volts. The coms will be at 230V when on and either 230V or zero when off depending on which position both switches are in. So with a CFL you might read various voltages at various times, with a filament lamp the only time you'll see other than 230V or zero is on the floating strapper with the first scheme.
 
Am I missing something here? Why are people recommended snubbers / loads when the problem is that the lamp goes off when it should be on, not the other way round??
 
Thanks to you all & Lucien for teaching me a load that I've never known or ever been taught before ! Only started seeing the whole capacitive issue by trying to locate other people who've come across these weird problems. I get the snubber thing and have already come across LED's recessed into ceiling downlights which of old type with many seperate heads ( maybe 7 of 15 ) inside main lens akin to water droplets were randomly glowing at night on bedroom ceiling and driving the girl mad. Like absorbing a small current of enough to glow a little.

So what I'm thinking is if with the CFL lamp if this capacitive voltage floats there, then why does it not always appear in houses 2 way circuits etc.. ? As never had one like that before ? All replies have been helpful.
 

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