Consumer unit (split load)


Postby denboy09 » Thu Aug 05, 2010 8:37 pm

I changed out an upstairs wall light fitting. I switched off the MCB and took off the old fitting all was ok. I started to connect up new fitting and my earth wire touched the neutral wire. Straight away my radio went off downstairs meaning the downstairs ring main had failed. Went back to the consumer unit and found that the RCD had tripped. My question is " is this normal?" bit worrying as that RCD feeds my freezers. So any earth to neutral fault on that RCD trips it, and every thing else it protects.
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Postby ericmark » Fri Aug 06, 2010 10:37 pm

Yes it is normal. With a TN-C-S supply it will depend on the current being drawn. The RCD measures the power out on the Line live wire and the power back on the Neutral live wire and if the two are within 15ma then all is OK. If current leaks there will be an unbalance and some where between 15ma and 30ma the 30ma RCD will trip. Some RCD's do give pre-trip warning.
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Postby kbrownie » Sat Aug 07, 2010 2:16 am

Yes this is quite normal, whilst doing remedial work on circuits protected by RCDs or RCBOs even though the circuit is not live it will trip the RCD/RCBO.
A way I prevent this from happening whilst working on a circuit, is to tape the end of the neutral up.
Last edited by kbrownie on Sat Aug 07, 2010 8:54 pm, edited 1 time in total.
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Postby denboy09 » Sat Aug 07, 2010 8:20 pm

Thanks guys
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