Ring main question


Postby robdib » Fri May 24, 2013 3:54 pm

I have three ring mains in my house. I have found that there is continuity(as tested with a multimeter) between earth and neutral on all three circuits.
Is this a problem?
If so, how do I fix it?
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Postby ericmark » Sat May 25, 2013 10:06 am

This is normal. The earth and neutral are bonded at some point. However this is always before the main isolator in the consumer unit. With main isolator off there should be no connection between earth and neutral, but the MCB's only switch the line, not neutral, so would need to be main isolator not individual MCB's. I have found it where the main isolator is faulty, but changing these is not really a DIY job.

So question is where did you isolate?

If correctly isolated then yes it is a problem in that any RCD's may trip, and under fault conditions the bonded surfaces could have a raised voltage from true ground, which could be dangerous.
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Postby robdib » Sat May 25, 2013 6:02 pm

Thanks for your reply Ericmark. My consumer unit is an old style fuse wire type - no MCB's. how should I proceed with this system? Regards, Robdib.
p.s. is the main isolator the on/off switch on the consumer unit?
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Postby ericmark » Mon May 27, 2013 8:09 am

Yes main isolator is the on/off switch on consumer unit. If that is off the neutral and earth should not be connected. In the main isolators are red switches but some old ones are not. A good example of an isolator is the cooker switch which is normally red.

If you just remove fuses then neutral and earth should show as being connected together.

Today earth neutral faults would open the RCD.
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Postby robdib » Mon May 27, 2013 10:53 am

I'll re test with the main isolator off, and take it from there. Thanks.
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