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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> solve this one please https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1092172193 Message started by essox_lucius on Aug 10^th, 2004, 10:09pm

Title: solve this one please
Post by essox_lucius on Aug 10^th, 2004, 10:09pm

went to a house today,person told me when landing light was switched off the bulb would flicker every few seconds.i put my meter across the switch return and neutral it read 100v.i have meggered the cables including the strappers and they are clear.any ideas please ???

Title: Re: solve this one please
Post by plugwash on Aug 11^th, 2004, 1:19am

i would say one of the following (in decreasing order of probability)
a dodgy switch
a plateswitch locator if the load is purely flourescent
damage to the switch cable

Title: Re: solve this one please
Post by L.Spark on Aug 11^th, 2004, 2:24am

Im sure ive had this happen once before and was a mixup with Neutral + CPC..

Title: Re: solve this one please
Post by essox_lucius on Aug 11^th, 2004, 10:22pm

i have done a insulation test on the complete light circuit and between p+n,p+e,n+eand the results were +500M OHMS

Title: Re: solve this one please
Post by The_Trician on Aug 11^th, 2004, 10:29pm

Sounds to me like it could be something cross-connected.

One light in series and one in parallel?

Any other circuits hooked into the lighting circuit anywhere?

Seen L going to 'L' and N gong to 'N' on the supply side of an FCU, but L connected to the N terminal, and N connected to the L terminal on the load-side!

This gave around 100v and dim lights!
FCU was feeding a bathroom fan off the upstairs lighting circuit.

TT

Title: Re: solve this one please
Post by supersparky on Aug 12^th, 2004, 2:28pm

sounds like something electronic wired in the cct.
i had the exact same problem about....4 weeks ago now, was an alsrm panel wired onto the 2way switching- it had also bridged the upstairs and downstairs light ccts, all the upstairs lights and the 2 way switched lights flickered at 1 sec intervals when the fuse for the upstairs lights was pulled.

ss

Title: Re: solve this one please
Post by essox_lucius on Aug 12^th, 2004, 5:15pm

the property is a ist floor flat,the c/b feeds 5 standard ceiling rosesand 1 b/room extract fan,which i disconnected.with all lamps removed and the light switched off.and even with both ends of the yellow strapper sitting in free air disconnected i have close to 50v between the one end of the yellow strapper and earth ??? i am looking for the nearest canal to throw myself into.

Title: Re: solve this one please
Post by The_Trician on Aug 12^th, 2004, 7:18pm

Try disconnecting the lighting circuit cpc from the board, the switch on and turn on the lights. Measure the voltage from the disconnected cpc and the main earth termianl in the board. If you get anything above around 50v you have an earth fault between the live and the cpc.
If so, then the circuit is obviously not meeting the disconnection time and tripping out or fusing as it should under fault conditions.

Don't forget that during an IR test, you have to switch the 2 way switches over and test both ways to fully check the circuit.

TT