Neutral and earth

eletricaz · May 14, 2012

Was asked by a colleague at work earlier in the week what is the danger of having the neutral connected to earth?

He is a domestic spark and whilst carrying out 1 of his installs to a bathroom he had to upgrade the mcb for a rcbo for additional protection, upon completion he turned the rcbo on but to no avail it kept tripping, the lighting circuit in question done the whole house so in effect the whole house had no lighting, whilst carrying out his fault finding he found in one of them fancy 'orange shed' lights whoever had installed it had connected the earth together with the neutral so was causing the tripping.

I have no answer to him at the moment hoping you wonderful people on here can help.

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Knobhead · May 14, 2012

What do you want, the “dangers” or the “problems”?
Two separate sets of questions.

eletricaz · May 14, 2012

Dangers and problems please ;-)

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telectrix · May 14, 2012

hoover???? water spills???

soz. wrong thread.

Darkwood · May 14, 2012

1 of many reasons... the neutral is a seperate path to safely carry the current of the circuit when it breaks the circuit stops working and highlights the possible fault, if the earth was connected at any point on the consumer side a broken neutral would just return down the earth path, this would have current going through the earthing and wouldn't give any indication of the broken neutral. The issues here are potentially a shock risk or fire hazard. As an example if the main switch burnt out on the neutral effectively breaking its connection and a N/E fault existed on any circuit the loading of all the board would travel up to the N/E fault and back down the Earthing system effectively overloading the circuit where the fault is and burning it out.
Modern rcd boards will limit this kind of fault though but just 1 example.