① small circuit breaker 1P, 1P + N, 2p in the end what is the difference?
answer:
For micro-circuit breakers, 1P + N, 1P, 2P are generally used as single-phase electrical appliances on-off control, but the effect is different.
1P ------ single pole circuit breaker, with thermal magnetic trip function, only control the fire line (phase line), modulus 18mm;
1P + N ---- unipolar + N circuit breaker, while controlling the line of fire, zero line, but only the FireWire with thermal magnetic trip function; modulus of the same 18mm;
2P ------ single-phase 2-pole circuit breaker, while controlling FireWire, zero line, and have a thermal magnetic trip function, modulus 2 * 18mm = 36mm.
 So, you can draw the following conclusions:
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.
② on the circuit breaker 1P, 1P + N, 2P, 3P, 3P + N, 4P a detailed explanation!
A: 1P, 2P, 3P, 4P is the number of poles, that can be divided into several lines. Now + N, are N-line break, but the N line does not set the trip device. Only when the phase line breaking the N line along the cut off. For example, if the 4P 16A circuit breaker, N-line current is greater than 16A, or greater than 20A, theoretically, the circuit breaker will trip. But 3P + N of the circuit breaker, N line current 160A, will not jump. Provided that the phase current does not exceed the rated value.
③ 1P, 2P, 3P have what electrical appliances in use? What is the difference between them?
A: 1P, 2P single-phase equipment, lighting can be used 1P, socket to 2P; 3P used in three-phase equipment, there is a three-phase power into the home.
④ lighting circuit is 1P or 1P + N?
answer: 
1. lighting with 1P, the traditional practice, but also nothing bad. There are 1P + N, feel no need. Lighting without leakage.
2. In fact, with 1P + N good, like DPN this switch, and 1P switch module the same!
3. Lighting generally use 1P, residential standard refers to the residential toilet lighting should be with leakage protection, so the toilet lighting circuit can be used 1P + N with leakage. But the trial does not mention, we generally use all the 1P lighting.
⑤ residential single-phase distribution box into the line should be 1P or 2P?
 (Residential residential construction, from the meter box outlet to the indoor distribution box for single-phase outlet, why the distribution box into the line with 2P instead of 1P? Switch without leakage?)
answer:
1. 2P, easy maintenance, safe!
2. Design of electrical design for civil buildings 25.3 / 11 When a single-phase power supply is used in each household, the micro-circuit breaker of the household shall be bipolar. When the three-phase power supply is used, the miniature circuit breaker of the household shall adopt three poles. And should be set from the complex over, under voltage protection.
⑥ on home decoration with 1P or 2P empty open question?
(Home decoration branch open with 1P only cut off the line of fire, and the common zero line, so cut off one of the loop, and this cut off the circuit of the terminal socket, the zero line or voltage, 2P does not exist. And if you do not understand is the use of 1P or 2P people certainly mistakenly believe that there will be no electricity, so would not it be very safe?)
answer:
 According to the "Residential Design Code" GB50096-1999 6.5.2 residential power supply system design, should meet the following basic safety requirements:
  1. TT, TN-C-S or TN-S grounding should be used and the total equipotential bonding should be carried out.
  2. Electrical lines should be used to meet the safety and fire protection requirements of the laying of wiring, wire should be used copper, each house into the household line section should not be less than 10 square millimeters, branch circuit section should not be less than 2.5 square millimeters.
  3. Each residential air-conditioning power outlet, power outlet and lighting, should be divided design; kitchen power outlet and toilet outlet should be set up an independent circuit;
  4. In addition to air conditioning power outlet, the other power outlet circuit should be set leakage protection device;
  5. Each house should be set to the total power circuit breaker, and should be used to disconnect the phase line and the neutral line of switching appliances;
  6. Bath should be equipped with bathroom should be equipotential bonding;
  7. The total power supply line breaker of each house should have leakage protection function.