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Mark1982 · Oct 4, 2009, 05:52 AM

I am a fully qualified electrician and I am currently doing a small wiring job in a 3phase farm house in France. I have wired a lighting and power circuit in a bedroom and when I I turned it live it all works fine,the sockets the 2-way switching etc. However when I put my volt tester on the ceiling pendant I had 130v when the switch was off, same on the wall lights there was a 50v reading. If I put the bulbs in it then works fine switching on and off, and when off no voltage but take out the bulb I have voltage there again. I thought it could be a problem with the neutrals but found none , I checked the rest of the house and the problem is the same all over 150v in one place. I'm on a hourly basis so don't want to spend hours investigated if anyone else could help me who might have encountered this problem before?Thanks in advance!
Mark

Perito · Oct 4, 2009, 06:15 AM

I suspect you have an induced voltage (induction) from a nearby live wire. Without a bulb in the socket, the voltage is present. With a bulb there, the voltage is dissipated through the bulb. If you had a lower-impedance voltmeter, you probably wouldn't see the voltage at all.

Mark1982 · Oct 4, 2009, 08:37 AM

Thanks I did think induced voltage but its on every lighting circuit in the house and 150v seems higher than any induced voltage I've come across.I picked up a voltage on my volt stick so tested on my tester and found the voltage.

KISS · Oct 4, 2009, 04:12 PM

Could this be related to High leg delta distribution? High leg delta - Wikipedia, the free encyclopedia

KISS · Oct 4, 2009, 05:05 PM

Try replacing the switch too.

InfoJunkie4Life · Oct 5, 2009, 06:17 AM

I'm not sure what you mean by testing the ceiling pendant. I've never heard that term before.

However with 2 way switching you will get some strange readings. Let me try to explain. Within a 2 way switch there are three connections. I always break the positive. You have the one input and then two outputs which the switch selects. If you connect your voltage meter to the negative wire and then to the input of the 3 way switch you should get 120v or whatever is standard for your area. One of the two remaining wires (red and white) should be 0 and the other 120. However if you were to move you meter to be between the red and the white, then you would be getting feedback from the black wire through the bulb (Negative) and a positive connection through the other one. That would be a low reading.

InfoJunkie4Life · Oct 5, 2009, 06:59 AM

Do any of the switches light up or have timers on them, digital?

Mark1982 · Oct 5, 2009, 01:10 PM

Thanks for your help, they are standard switches no, dimmers or light etc. By the ceiling pendant its just the light.And I'm only getting a voltage present when the bulb is not in the light.

KISS · Oct 5, 2009, 01:18 PM

I still say try replacing the switch. I don't know the input Z od your multimeter, but if it's 10 meg ohms all it takes is is another 10 m Ohms and you have a voltage divider giving 1/2 the voltage.

Basically, do this test. Remove the switch. Go measure the voltage at the lamp. Connect the two wires together where the switch was (no switch) and test again.

You could even have leakage to ground.

Nonetheless, that's where I would start.

Mark1982 · Oct 7, 2009, 08:39 AM

Thanks a lot I'll try that and let you know

Mark1982 · Oct 11, 2009, 09:08 AM

Right I tried that test and when it was just a one way switch it worked fine with no high voltage when the switch was off, the other single switch and light newly wired in the on suite bathroom also seems to work fine. However when I put the two way switches back on the problem returns also I'm getting voltages at lights all around the house on single and two way switches.It seems to be a problem throughout the house .It is a very old 3 phase french farm house and I wired the bedroom and bathroom that's been newly built upstairs.I think It may be to do with the earthing but don't no where to start?

Mark1982 · Oct 12, 2009, 08:59 AM

Right I tried that test and when it was just a one way switch it worked fine with no high voltage when the switch was off, the other single switch and light newly wired in the on suite bathroom also seems to work fine. However when I put the two way switches back on the problem returns also I'm getting voltages at lights all around the house on single and two way switches.It seems to be a problem throughout the house .It is a very old 3 phase french farm house and I wired the bedroom and bathroom that's been newly built upstairs.I think It may be to do with the earthing but don't no where to start?