Issue where a time delayed RCCB supplying DB which has single pole rcbos tripping the time delay under fault conditions.
where as if you have double pole rcbos disconnects the rcbos under fault conditions. Why is not stated that the use of Double pole in IET on these conditions.
Raymond,
What is the time delay that is built into your "Time delayed" RCCB? Could it be that that device is still operating faster than the final circuit single pole RCBO's? What is the earth leakage setting of the "Time delayed" RCCB compared to the final circuit RCBO's?
Does one of the final circuit single pole RCBO's actually "Trip" same time as the "Time delayed" RCCB? If there is no sign of that could the "Time delayed" RCCB just be tripping due to summation of earth leakage on all of the final circuits?
I have worked in the world of TT earthing systems and flammable atmospheres for many years, and we utilise at least three diffrent levels of time/earth leakage current cascading, and yes 30mA instantanous final circuit RCBO's are all pole isolation. So we very very seldom hav a main or submain earth leakage device operating on a final circuit "Fault".
I would also think the original "Designer" also needs to take into account 314.1 (i) where you do not want numerous or all healthy circuits being disconnected by one faulty one.
Other reason we have all pole devices on our protection items is due to the requirement for hazardous area circuits for all "Live" conductors to be disconnected in event of a fault so that includes the neutral.
Maybe a few things for you still to look at perhaps.
Cheers GTB
Raymond,
What is the time delay that is built into your "Time delayed" RCCB? Could it be that that device is still operating faster than the final circuit single pole RCBO's? What is the earth leakage setting of the "Time delayed" RCCB compared to the final circuit RCBO's?
Does one of the final circuit single pole RCBO's actually "Trip" same time as the "Time delayed" RCCB? If there is no sign of that could the "Time delayed" RCCB just be tripping due to summation of earth leakage on all of the final circuits?
I have worked in the world of TT earthing systems and flammable atmospheres for many years, and we utilise at least three diffrent levels of time/earth leakage current cascading, and yes 30mA instantanous final circuit RCBO's are all pole isolation. So we very very seldom hav a main or submain earth leakage device operating on a final circuit "Fault".
I would also think the original "Designer" also needs to take into account 314.1 (i) where you do not want numerous or all healthy circuits being disconnected by one faulty one.
Other reason we have all pole devices on our protection items is due to the requirement for hazardous area circuits for all "Live" conductors to be disconnected in event of a fault so that includes the neutral.
Maybe a few things for you still to look at perhaps.
Cheers GTB
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