Voltage flowing even when breaker is off.


Postby uglytotempole » Thu Apr 10, 2008 5:48 pm

Today i was fitting new lighting in the shed, so turned off breaker and began removing old lights. this was fine. When fitting the new light, i stripped back the negative wire and touched the earth wire with the strippers, this caused the wires to spark. When i checked with a volt meter, it read 9v's across the negative and earth wire, not across the positive wire. i have read in other posts that over loading the breaker can cause it to not switch off properly could this be the problem as we run some very powerful tools and lots of lights in there.
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Postby ericmark » Thu Apr 10, 2008 11:28 pm

Earth and Neutral are not the same. Although at some point they may be connected together because current flows in the neutral and not in the earth so over distance the difference increases.

Neutral earth faults with earth leakage trips becomes quite a problems as when no current is drawn they will hold in but current drawn on a completely different circuit it trips earth leakage trip.
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Postby uglytotempole » Fri Apr 11, 2008 8:43 am

so is it same to continue working on it, or is there something i should do to stop it?
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Postby ericmark » Fri Apr 11, 2008 3:43 pm

Although the voltage is unlikely to do you personally any harm due to shocks it could cause wires to get far too hot is wrong ones touch and turning off the power with the twin pole main breaker rather than single pole MCB should remove any chance of injury due to burns while working on the lights. Read what I have said under "Electrics to feed new shed?" this may also help you if you can find document by IET
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