On Sat, 15 Sep 2007 14:44:56 +0100, LaserMark wrote:

On Sat, 15 Sep 2007 14:00:39 +0100, "Andrew Mawson"
wrote:


LaserMark wrote in message
. ..

I'm measuring 17 Vac across my bathroom light fitting when the light
switch is off. I'm also measuring 34 Vac across my landing light
fitting when the light switch is off. If I isolate the upstairs
lighting at the consumer unit then it drops to around 1.3 Vac.

What's going on?

What are you using to measure the voltage? If you are using a modern
high impedance meter such as a Fluke, then what you are measuring is
the capacitive coupling between a live wire and an isolated one, and
it is quite normal. If on the other hand you are using an older meter
based on a moving coil movement then it is time to worry!

AWEM


I'm using a Fluke 77. So why am I seeing 17 Vac on one fitting and 34
Vac on another fitting?

Beacause more or less that's the actual voltage of the wire, the wire is
neither earthed nor is it connected to a supply. Frankly a probe with a
230Vac pigmy bulb in it will tell you much more _relevant_ info about
mains wiring than a DVM.




--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html