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Topic Title: 50v fault on a lighting circuit
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Created On: 18 February 2013 09:06 PM
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 18 February 2013 09:06 PM
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Fins729

Posts: 3
Joined: 18 February 2013

Hi has anybody had a fault where there is about 50v on a 2 way lighting circuit ? With the switch 'open' position there is 50v between the two strappers and e/n close the switch and u get 230 on one , I suspect a partial breakdown in cable insulation? Any other suggestions? there are no dimmer switches on the circuit .

Thanks
Dave
 18 February 2013 09:19 PM
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Martynduerden

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Joined: 13 July 2008

Sounds like a neutral fault, you get all sorts of voltages on faulty lighting circuits.

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 18 February 2013 09:53 PM
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Fins729

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Got the same voltage to earth as well though and 230v to the same reference from other side of switch????
 18 February 2013 09:55 PM
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slittle

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What are you measuring it with ??

You could just be measuring capacitive coupling between the strappers depending on the length of run.

Try measuring with an old fashioned AVO or a drummond lamp across it and see what you've got.


Stu
 18 February 2013 09:55 PM
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daveparry1

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Sounds like induced voltage to me, are you testing with a digital meter? Is the circuit working ok? if so why are you testing it? If not working normally what are the symptoms? Sorry for all the questions but you need to tell us more!

Dave.
 18 February 2013 11:09 PM
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impvan

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Pop a 40W bulb across the two wires you're measuring, and take your readings again.
 19 February 2013 03:19 PM
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oshta

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Depending on everything else, nail through a phoneline....
 19 February 2013 04:35 PM
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daveparry1

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Will that cure his problem then Oshta? !!

Dave.
 19 February 2013 04:39 PM
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ebee

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Of course it will Dave

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Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 19 February 2013 04:48 PM
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daveparry1

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I thought it might Ebee!
 19 February 2013 05:01 PM
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Fins729

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Hmm not that common a problem then it seems, I'll need to go back for further investigation thanks for the help
Dave
 19 February 2013 05:11 PM
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daveparry1

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You still haven't told us what the symptoms are and why you're taking these measurements Dave?
 19 February 2013 05:22 PM
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AJJewsbury

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Hmm not that common a problem then it seems

It's a common potential problem - but most people are aware of it these days and work around it (see above posts).

Basic problem is using a high-impedance voltmeter (e.g. electronic meter) to test an unconnected (floating) conductor that's lying close, but not connected to, other live conductors. The two conductors and their insulation form a long thin capacitor - so a tiny amount of current can flow when connected to an a.c. supply - that's more than likely what you're measuring. The actual voltage registered depends on the capacitance (which is proportional to the length of the cables) and the impedance of your meter.

It's generally more reliable - and usually safer - to use an insulation or continuity tester on a dead circuit to trace problems.

There are lots of related problems with low-energy (i.e. high impedance) lamps flickering or occasionally flashing when switched off, if you care to search for them - it's the same underlying cause.

- Andy.
 19 February 2013 05:28 PM
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penrynrugby

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Swap the strappers around that should cure this
 19 February 2013 05:31 PM
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penrynrugby

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sorry to continue swap l2 and l3 on both two way switches I think it's induced voltages
 19 February 2013 05:38 PM
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ebee

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Originally posted by: oshta

Depending on everything else, nail through a phoneline....


I`m glad you never mentioned knotted cables.
Knotted cables causes Lumpy Lectric and we all know how bad Lumpy Lectric can be

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Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 19 February 2013 06:00 PM
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OMS

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Originally posted by: ebee

Originally posted by: oshta

Depending on everything else, nail through a phoneline....


I`m glad you never mentioned knotted cables.

Knotted cables causes Lumpy Lectric and we all know how bad Lumpy Lectric can be


I've not heard that in ages Ebee - made my day

The old chap I was apprenticed to used to mutter than when he was unimpressed with my surface clipping of 3 or more cables together with buckle clips - if he could get a rizzla paper between them then it was dog rough in his view - he never used to have a problem until this new fangled capathene appeared - when you clipped lead sheath cables, they stayed clipped -

OMS

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