A: for miniature circuit breakers, 1p + N and 2p are generally controlled by two lines, but the effect is different.

1p + n ---- single pole + n circuit breaker, which controls live line and zero line at the same time, but only live line has thermal magnetic tripping function; The modulus is also 18mm;

2p ----- single phase 2-pole circuit breaker, which controls live line and zero line at the same time, and has thermal magnetic tripping function, with modulus of 2 * 18mm = 36mm.

Therefore, the following conclusions can be drawn:

1. In order to reduce the cost, 1p can be used, but the superior circuit breaker must have leakage tripping function. In order to prevent accidents caused by fire and zero disorder during maintenance, the superior power supply must be cut off;

2. In order to avoid one problem during maintenance, 1p + n (i.e. DPN) can be used;

3. Reason for using 2p: for the circuit breaker shell with the same 18mm module, there is a difference between installing 1p inside and installing 1p + n. The "ultimate breaking capacity" of the former in the state of short-circuit accident must be higher than that of the latter. After all, space is an important factor affecting the breaking capacity. Therefore, it is better to use 2p (higher cost) for power circuits that are important, frequently overhauled and operated, and prone to failure.

4. The premise of using 1p is that the lighting distribution box must have leakage tripping function, and at least the incoming line (or the upper level of outgoing line) should use leakage circuit breaker.