Phantom voltage?

[Gn96]

I did type this out and send it about 2hrs ago but I can’t see it on the forum so I’ll post again.

Came across a weird *fault* if you’d call it that, basically stripped out old lights in a warehouse, switch fed so perm live and neutral at the switch. Wired a 3core and earth to 18 4pin klik boxes for led panel lights. Tested the feed and neutral in the switch to confirm it was and the reasons were fine, problem started when I connected my 3 core up in the switch, black in with EM key switch with the perm and link over to the light switch common and the brown out of L1, neutral in a connector block. I tested my end of line (nothings plugged into the klik boxes yet) PL fine SL fine N fine. All readings the same IR clear. Polarity fine. The issue is when the EM key switch is on and the light switch is off I’m getting 60-120v on the SL at the end of line. I checked all the kliks connections were tight and correct. Checked my switch all correct and tight. So I disconnected the brown out of the switch and put it on a connector so no essentially it’s a single core not connected at both ends but there’s still 60-120v showing on the fluke between the brown-earth. Brown-neutral so the voltage is definitely on the brown(SL). So somewhere along this new circuit I have wired my brown is picking up voltage. Off what I don’t know because the cables all on show and there’s nothing plugged in. Someone mentioned induction voltage but it’s ran on its own near no other cables and the runs roughly 55ms total. Does anyone have ideas? Don’t want to install the LED panel lights and they stay on when the switch is off once the ceiling goes in.
Cheers lads/lasses

 

[Murdoch]

Have you re-confirmed your R1 + R2 ? as it could be your CPC isn't continuous

But yes induced voltage is very possible

 

[ProDave]

Normal capacitive coupling between a L conductor and an adjacent floating conductor measured with an over sensitive meter.

Connect a load, even a tiny load, to your "aerial wire" and he voltage will be quenched.

 

[Gn96]

Have you re-confirmed your R1 + R2 ? as it could be your CPC isn't continuous

But yes induced voltage is very possible

I have, reading was 2.10 brown-earth 2.11 black-earth, would a cpc not connected send voltage down the SL? Because nothings plugged into the kliks they’re essentially just connector blocks at the moment so no way of voltage back feeding down the SL from the PL? I thought maybe a loose neutral but the Rn R2 is the same reading as R1 R2 and I’ve checked my connections. I’ve not had much experience with induced voltage, how would you reduce that? And should it even be there? 50mtrs of 3 Core ran along metal pearlings with no other cables? I feel stupid asking this and it doesn’t sit right with me seeing voltage where there shouldn’t be, but can this be safe to leave as is? All test readings pass and visual inspection is fine, If I was following the (no live testing) that companies are pushing nowadays and carried out an R1 R2/IR/and calculated my Zs I never would have found this issue. Until I install the LEDs and they don’t turn off maybe but if it is induced then it wouldn’t power the lights. I’ve run out of ideas what to do next. Been a sparky for 8years now and testing for 2years. Never come across it before.

 

[Gn96]

Normal capacitive coupling between a L conductor and an adjacent floating conductor measured with an over sensitive meter.

Connect a load, even a tiny load, to your "aerial wire" and he voltage will be quenched.

I’ll give it a try Monday mate, just didn’t want to finish the job without an other opinion and making sure.
Nice one

 

[roys]

Test it with a moving coil meter like an old AVO 8 and I bet it would be fine, As Dave says your meter like most digital meters are over sensitive.

 

[ProDave]

I would just touch it. Let us know the result of that.

 

[Gn96]

Test it with a moving coil meter like an old AVO 8 and I bet it would be fine, As Dave says your meter like most digital meters are over sensitive.

Yeah I’ll give it another look Monday. Connect the fittings in see what happens

 

[Gn96]

I would just touch it. Let us know the result of that.

 

[Mike P]

I have had this issue before with phantom voltages in 3 core and earth.
Allot of the problems are the high impedance input on modern meters.
Fluke make a Stray Volage Eliminator (SV225) which goes across the input of your digital meter and reduces the high impedance on the input, effectively the same as Roys said earlier, Avo 8’s have a much lower input impedance. Having said that I sometimes use 3 core SY cable and earth the screen on long runs.

 

[Joules]

Back in the day when 15th Edition was in play and to mark the completion of my apprenticeship I was given a Square D Model 5008 voltage tester to use. The foreman explained that meters like an Avo 7 could give phantom readings so that's why he relied upon this tester. I would use it mainly where three phase testing was needed between phases or phase to earth. Same for single phase jobs. The probe's tip used to spark like hell and it clattered something awful. It got forgotten, stored, and was rediscovered early in the noughties. I tried using it but it tripped the RCD so it got slung - it was a final goodbye to a much simpler but well remembered era.

 

[Geoff1946]

Years ago I knew an old electrician who's most used piece of test equipment was a 15watt pygmy lamp with a couple of home made probes attached. He had a wind-up megger for problem jobs.

 

[Richard-the-Ninth]

Years ago I knew an old electrician who's most used piece of test equipment was a 15watt pygmy lamp with a couple of home made probes attached

I wonder, did it look vaguely like this? Back in the day, someone I was working with had one, and it did look like a 15w pygmy lamp in it.

 

[Geoff1946]

I wonder, did it look vaguely like this?

No, it was just what I described. A bare bulb in a standard pendant holder; it did have the luxury of a skirt. The test leads were a foot of twisted flex, half of which was untwisted, and some probes fashioned from I don't know what.

 

[UNG]

I wonder, did it look vaguely like this? Back in the day, someone I was working with had one, and it did look like a 15w pygmy lamp in it.

View attachment 14589

I still use my Drummond test lamp although it is the modern version now with the LED lamp

 

[UNG]

No, it was just what I described. A bare bulb in a standard pendant holder; it did have the luxury of a skirt. The test leads were a foot of twisted flex, half of which was untwisted, and some probes fashioned from I don't know what.

When I first started that was the standard test lamp in most electricians tool boxes

 

[Donnie76]

Yeah I’ll give it another look Monday. Connect the fittings in see what happens

Let us now how you got on?

 

[kerching]

We always used a lampholder, some transparent flex or bell wire ( the holy grail was the cotton covered stuff as it wasn't affected by the cold) 2 4" nails soldered on the end as probes. Wrap with Blakey leaving enough exposed ( about an inch ) so they would fit inside croc clips. RRough Service Pigmy lamp. Job done

This was until the Steinel Combi Check came along

 

[Geoff1946]

We always used a lampholder, some transparent flex or bell wire ( the holy grail was the cotton covered stuff as it wasn't affected by the cold) 2 4" nails soldered on the end as probes. Wrap with Blakey leaving enough exposed ( about an inch ) so they would fit inside croc clips. RRough Service Pigmy lamp. Job done

That's the type I recognise from my old friend's toolbox.

 

[kerching]

That's the type I recognise from my old friend's toolbox.

It worked!
Didn't comply with anything, but it worked
I recall putting it in place of a fuse whilst finding a fault.....probably frowned upon now