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Topic Title: Strange Fault
Topic Summary: Tripping
Created On: 29 October 2013 06:58 PM
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 29 October 2013 06:58 PM
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Ampman

Posts: 1004
Joined: 06 February 2006

Evening ,

Had a call out to investigate downstairs lights tripping , rcbo goes off when lights turned on .

This happens from anywhere on the circuit so when a load is put on circuit it trips ?

I meggar tested circuit live neutral joined together to earth , that shows dead short , Why does the rcbo stay on but only trip when load is on ?

There are dimmers on circuit ?

I put wiring into another rcbo to prove i didnt have a faulty one .

Weird ?

anybody had similar .

I explained to customer that i will have to strip everything down to find fault

cheers
 29 October 2013 07:04 PM
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daveparry1

Posts: 6151
Joined: 04 July 2007

You did remove the neutral from the neutral bar when you tested I suppose?
 29 October 2013 07:11 PM
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Ampman

Posts: 1004
Joined: 06 February 2006

Yes removed from rcbo completely

strange one
 29 October 2013 07:18 PM
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daveparry1

Posts: 6151
Joined: 04 July 2007

Not teaching you to suck eggs Ampman but was it really a dead short or something like 0.01 meg? It's easy to think there's a dead short and confuse yourself when on the ins. range of the meter!

Dave.
 29 October 2013 07:30 PM
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Ampman

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0

it read on meter
 29 October 2013 07:33 PM
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daveparry1

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0 megohms maybe!
 29 October 2013 07:37 PM
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Ampman

Posts: 1004
Joined: 06 February 2006

yes megohms ,

tested at 250 volts to avoid damage
 29 October 2013 07:44 PM
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daveparry1

Posts: 6151
Joined: 04 July 2007

All i'm trying to say Ampman is that 0 megohms isn't necessarily a dead short, it could still be quite a few hundred k-ohms.

Have you tried measuring N-E and L-E? I find that testing L+N-E doesn't always give helpful results.

Edited: 29 October 2013 at 07:55 PM by daveparry1
 29 October 2013 08:19 PM
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Banners

Posts: 115
Joined: 06 October 2013

Has to be a neutral to earth fault - current returning to RCBO = trip perhaps earth tied to a copper pipe etc. so (sufficient) fault current not coming down earth to trip RCBO.
 29 October 2013 09:02 PM
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Ampman

Posts: 1004
Joined: 06 February 2006

Dave ,

I will test L-E , N-E , when i return , to be honest it was 6 ish when i left too late to start stripping it all down .

Banners cheers

See it being a ball ache ,
 29 October 2013 09:21 PM
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leckie

Posts: 1759
Joined: 21 November 2008

Ampman, as banners says, it a neutral to earth fault. The imbalance is only detected by the rcd when a load is applied.
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