All wires should be laid horizontally and vertically, and the same applies to distribution boxes. However, in the wiring of the distribution box, although it is required to be "straight", it is also required that no 90 ° angle is allowed.
This is because when the bending angle of the wire is greater than 90 °, it will cause damage to the insulation layer of the wire - the most obvious is the whitening and discoloration of the insulation layer. The consequence is to reduce the durability of the insulation layer, which has a significant impact on both insulation and flame retardancy.
The standard practice is to fold all areas that need to be bent into circular corners, while also ensuring that the longitudinal wires are perpendicular to the transverse wires.
There are two situations where there may be intersections. The first is that the distinction between longitudinal and transverse wires has not been made as mentioned earlier, let alone ensuring that the two are perpendicular. When the wires are arranged in a disorderly manner in the distribution box, it is bound to cause poor wiring. The consequence of doing so is that the distribution box is messy, and once a malfunction occurs, it can be very troublesome to repair.
Another situation is more serious, which refers to the intersection of horizontal and vertical incoming and outgoing lines.
In the figure, the outgoing line of the main switch bypasses the left side of the switch and connects to the upper port of the right circuit breaker. In this way, it will inevitably cause the outgoing line of the main switch to cross with the incoming line of the main switch. There are two consequences of doing this: ① the incoming line of the main switch will be compressed by the outgoing line, resulting in unstable incoming wiring; ② When disconnecting the main switch for maintenance of the distribution box, maintenance personnel may come into contact with live incoming lines during the maintenance of the main switch outgoing line, resulting in electric shock.
This distribution box has a situation where the outgoing and incoming lines intersect, which belongs to the previous section and will not be further discussed. Let's just look at the outgoing lines of the main switch - there are four sub switches behind the main switch, but only two wires (one neutral wire and one live wire) are led out from the outgoing terminal of the main switch. How does it provide power for the following four sub switches? (The zero line is directly connected to the zero line, and we will no longer care about it.)
The method is to connect the outgoing line to the first sub switch, and then lead a line from the incoming terminal of the first sub switch to the second sub switch... In this way, the upper terminal of the first, second, and three separate pipes are all connected with two lines. This method of taking power from the previous circuit breaker is called "jumper". The connection of jumpers was prohibited by the national standard as early as 2010, for the following reasons.
Hazards of Jumpers
The internal wire of the box is generally 4 square millimeters or 2.5 square millimeters, with a maximum current carrying capacity of 25A or more for wires of 4 square millimeters (data sourced from GB/T 4706.1-2005). The rated current of a five hole socket is 10A, and the rated current of a three hole socket is 16A. How many sockets will there be in the entire room? Therefore, the current carrying capacity of 25A is clearly insufficient and can cause wire overload.
The entrance line is generally 6 square millimeters, with a maximum current carrying capacity of 32A or above, which can meet the requirements of household use (therefore, the rated current of the home main switch should not exceed 32A).
So, if I replace the wires inside the box, can I also replace them with 6 square millimeters? The answer is no! If the wires are too thick, they will inevitably squeeze the space inside the box and affect heat dissipation. Household PZ30 boxes require that the wires should not exceed 4 square millimeters.
The correct connection method is to lead a line from the lower port of the main switch for each branch circuit breaker.
This article is dedicated to the friendship of electrical equipment. For more relevant knowledge, please click on: http://www.tongyuhengcheng.com Sincere attitude. We will provide you with comprehensive services. We will gradually contribute more relevant knowledge to everyone. Stay tuned