You cannot post a reply to this discussion. If you have a question start a new discussion
Needing to meet mcb zs with ln loop.
Former Community Member
Where an rcd is relied on for fault protection due to high zs it has been suggested to me that the loop between live Conductors needs to be less than the mcb max zs. I can't find anything on this anywhere but he said he had this confirmed by an niceic assessor. Have I got it wrong ?
It's a good job that the voltage is 16 volts above the 230 volts used for calculations to accommodate a potential 17 volts drop.
From the intake there is around 127 metres of 25mm cables then 15 metres of 4 mm cables, overall it's a long circuit.
Based on those test results installing a C32/30mA RCBO that requires a loop impedance of 0.68 ohms and a current of 320 amps to operate correctly would seem to be completely unacceptable.
The RCBO could be reduced to a B20, but that would not really alter anything.
It's a good job that the voltage is 16 volts above the 230 volts used for calculations to accommodate a potential 17 volts drop.
From the intake there is around 127 metres of 25mm cables then 15 metres of 4 mm cables, overall it's a long circuit.
Based on those test results installing a C32/30mA RCBO that requires a loop impedance of 0.68 ohms and a current of 320 amps to operate correctly would seem to be completely unacceptable.
The RCBO could be reduced to a B20, but that would not really alter anything.
