1, in order to reduce costs, with 1P can, but the higher circuit breaker must have leakage tripping function, maintenance to prevent fire, zero disorder caused by accidents, must cut off the power supply;
2, for maintenance to avoid a problem, available 1P + N (ie DPN);
3, with the 2P reason: the same is 18mm modulus circuit breaker shell, the internal installation of 1P and installed 1P + N is different, the former in the short-circuit accident state of the "limit breaking capacity" is certainly higher than after After all, space is an important factor affecting the breaking capacity. Therefore, for the more important, overhaul and operation frequently, prone to failure of the electricity circuit, it is best to use 2P (higher cost).
4, with 1P premise is the lighting distribution box must have leakage tripping function, at least into the line (or outlet of the upper level) to use leakage circuit breakers.