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Confused - lighting circuit.
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<blockquote data-quote="Geoff1946" data-source="post: 559671" data-attributes="member: 28452"><p>You did say it tripped a few minutes after switch on. If it goes immediately then it's more likely where the fault lies, but still not 100%. </p><p>I'll try to explain; When you switch on a load the current drawn slightly raises the potential on the neutral, due to the resistance of the cable. That small potential is applied to all the neutrals which share that RCD. Note that neutrals are not switched by normal MCBs. </p><p>Now if one of those dormant circuits has a short, or partial short, to earth, some current will flow and that may be enough to cause the RCD to trip. </p><p>An electrician has equipment which can measure for any such short circuit and will quite likely disconnect individual circuits at your consumer unit in order to test them.</p></blockquote><p></p>
[QUOTE="Geoff1946, post: 559671, member: 28452"] You did say it tripped a few minutes after switch on. If it goes immediately then it's more likely where the fault lies, but still not 100%. I'll try to explain; When you switch on a load the current drawn slightly raises the potential on the neutral, due to the resistance of the cable. That small potential is applied to all the neutrals which share that RCD. Note that neutrals are not switched by normal MCBs. Now if one of those dormant circuits has a short, or partial short, to earth, some current will flow and that may be enough to cause the RCD to trip. An electrician has equipment which can measure for any such short circuit and will quite likely disconnect individual circuits at your consumer unit in order to test them. [/QUOTE]
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