David Gardiner asks about strange MCCB tripping in a horticultural premises installation. His question has been answered by Schneider Electric (Theme – Distribution Equipment):
Question: In a horticultural premises, six panels (A - F), each have three Merlin-Gerin NS160 N three-pole MCCBs. Each MCCB supplies 14 x three-pole D16A MCBs, which protect nine x 600W 400V SON lights per MCB.
After eight hours of running, an MCCB trips in three of the panels, at the same time. They all reset straight away and will run for another three hours until the system is switched off.
It is the same MCCB tripping every time - and why always after eight hours? Do you have any ideas?
Answer: The rating may be too low. Depending on lamp running current and cable length, we also tend to recommend a circuit breaker in the order of 25A rating for this type of load.
Note that the ambient temperature and other effects may also affect the choice of circuit breaker rating.
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