Safe isolation when cutting cable

ADCG22 · 9 Mar 2020

Hello all

I understand that when an RCD protected circuit has only the MCB switched off and thus only the live isolated that when cutting cable a N-E fault would trip the RCD

What if the circuit was only protected by an MCB and not an RCD? Isolate the live then if you were to cut the cable and create a N-E fault......what would happen?

JohnW2 · 9 Mar 2020

ADCG22 said:
What if the circuit was only protected by an MCB and not an RCD? Isolate the live then if you were to cut the cable and create a N-E fault......what would happen?

Nothing would (should) happen. ... but if you are going to 'cut a cable', I would urge/advise you to switch everything off, using the Main Switch in your CU, rather that just switching off the MCB in question.

Kind Regards, John

muffking · 9 Mar 2020

Agreed. That's the basic principle of what an RCD would do, although apprentices still forget this. That said, I get many a builder having a moan when I catch the two after locking off the MCB

plugwash · 9 Mar 2020

Current would flow through the tool doing the cutting.

In most cases the voltages and currents involved would be too small to produce any noticable effects, but it can't be absoloutely gauranteed.

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Safe isolation when cutting cable

ADCG22

JohnW2

muffking

plugwash

DIYnot Local

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