John K Posted August 28, 2014 Share Posted August 28, 2014 Ok this is totally a non car post but I am wondering about my house electrics. I was finalising the cabling to a light fitting before boarding over. I had a temporary chocolate block in place until I was ready to fit the permanent junction box. I like to make my connections in a junction box rather than in the fitting so each JB has circuit has four cables, circuit in and out, switch and fitting. I was looking at the supply to the fitting, I tested knowing I had the power on and got 239 volts. Then I switched off at the wall socket (circuit breaker still on) and got 10 volts, which did surprise me a bit. And there are no surprises to hear with the circuit breaker off, I got 0 volts. Why the 10 volts? Is something leaking back somewhere, is this anything to worry about? Cheers Quote Link to comment Share on other sites More sharing options...
ACW Posted August 28, 2014 Share Posted August 28, 2014 what sort of light switch? Fancy touch one or electronic dimmer or remote controlled on? Quote Link to comment Share on other sites More sharing options...
John K Posted August 28, 2014 Author Share Posted August 28, 2014 Bog std mechanical switch Quote Link to comment Share on other sites More sharing options...
DerekJ Posted August 28, 2014 Share Posted August 28, 2014 Could be just EMI pickup from an adjacent cable. Try testing the current to ground / neutral it should ne next to naff all. If so then nothing to worry about. Quote Link to comment Share on other sites More sharing options...
John K Posted August 28, 2014 Author Share Posted August 28, 2014 EMI... Electromagnetic Induction..? Never thought to check the current. Like Dad used to say, "it's the volts that jolts, but it's the mills that kills" I'll check tomorrow, I've had a few sherbets so I think I will leave the lecy alone for tonight... Quote Link to comment Share on other sites More sharing options...
alexander72 Posted August 28, 2014 Share Posted August 28, 2014 have you got your volt meter thingy set to the right setting? I was up a tree once and thought the pole said 110V but it was 11Kv - bad mistaka to make :-) Quote Link to comment Share on other sites More sharing options...
Lawrie Posted August 28, 2014 Share Posted August 28, 2014 I'm not insured to give advice on lethal electricity voltages, but if you can't smell burning, you should be OK, for a while anyway. I thought high voltage resistance checks were normal for new wiring. Have you removed the switch to see if it makes a difference. Its in the club rules somewhere - just because its new doesn't mean it works Quote Link to comment Share on other sites More sharing options...
John K Posted August 28, 2014 Author Share Posted August 28, 2014 LOL, that's the difference between tingly and crispy... It's quite a good meter (thanks work) and it auto ranges by default. I would swear blind it was 10v but I will double check tomorrow. Quote Link to comment Share on other sites More sharing options...
Darrell O'Neill Posted August 28, 2014 Share Posted August 28, 2014 Quote Link to comment Share on other sites More sharing options...
Lyonspride Posted August 28, 2014 Share Posted August 28, 2014 Remember your talking about AC voltage, live and neutral are actually both giving you a sine wave, they're just 90 degrees (IIRC) out of phase with each other, neutral is connected to earth/ground away from your house. So ground actually carries a voltage, you just never see it because you always measure in relation to ground (so it would appear as zero volts). If you measure a conductor that's not grounded or connected to a supply (ie floating), then given the above and due to the extremely high resistance in a digital multimeter you will most likely see a voltage. If you use classic analogue meter, you'd probably not see anything at all. Also if you'd got say a CFL bulb connected, that would hold a small voltage when turned off (a bit like a capacitor) and with no route to ground you would see a voltage when using a DMM. I would advise checking all your wiring again though. I have a pocket DMM with me right now, if I let the leads hang freely it reads 7v and then starts to creep up to about 60v, if I then stroke the leads with my free hand, I can get it to read 600v. If you have a poor connection somewhere, then your effectively doing the same. Quote Link to comment Share on other sites More sharing options...
John K Posted August 28, 2014 Author Share Posted August 28, 2014 Ah... The bulb is a fluorescent one in the utility room. And it was on seconds before I took the reading as I was testing with it on and off. Thanks to all for the comments and replies. Quote Link to comment Share on other sites More sharing options...
corsechris Posted August 29, 2014 Share Posted August 29, 2014 Even a cheap crappy DMM has an input impedance in the megohms on a voltage range, so a 10V reading in that situation is almost certainly going to be induced voltage and nowt to fret about. No substitute for a 500v leakage test though, as Darrell quite rightly says. ...and don't forget, you need to provide inspection access for those JBs..... Quote Link to comment Share on other sites More sharing options...
John K Posted August 29, 2014 Author Share Posted August 29, 2014 'Most' of the JBs for the downstairs circuit are under a liftable chip board panel in the upstairs hall way. If I know I will need access in the future I cut the T&G of the chipboard in that area. The upstairs circuit are all in the attic space and again all the chip board there has no T&G There are two under the box room floor for kitchen and utility room. Again the board can be lifted but it will be a bit more agg. Cos I came from a line diagram background I have actually drawn circuit diagrams with JB positions on it. And I've even labelled every cable in and out to each JB. And flipping glad I did as when I go back to a job 6 months later I have no idea what goes where until I look at the diagram / labels... Truth be told, knowing what I know now, I would have used those 'maintenance free' connectors as I am a little worried about the screw down terminals working free over time. Not sure if this is an actual or theoretical risk designed to keep manufacturers (and Sparks, sorry Chaps ) in business... It is a very simple setup so hopefully not saving up too many problems for the future. Quote Link to comment Share on other sites More sharing options...
Yanto Posted August 29, 2014 Share Posted August 29, 2014 Could be your meter. I'm sure UK adopted EU voltage sometime ago and therefore supply voltage should be 230v +/- 3%. If your meter is showing 240 and 10 then that would indicate meter problem. BTW is it an analogue or digital meter? Quote Link to comment Share on other sites More sharing options...
Dave Eastwood (Gadgetman) - Club Chairman Posted August 29, 2014 Share Posted August 29, 2014 No, it's 230 Volt +10/-6% However, that was pretty much a paper exercise only, as note how the upper tolerance conveniently means we could leave the AC distribution at 240 Volts without being in breach! Quote Link to comment Share on other sites More sharing options...
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