distribution box is the central hub of the circuit in the home and the overall control of our daily electricity use. It is a very indispensable electrical equipment. If some safety hazards occur, we can deal with it in time. However, many electrical beginners do not know much about how to install and wire the distribution box. Next, let me introduce the wiring method, installation method and size determination of the distribution box for your reference.
(1) Wiring method of distribution box
1) The general power distribution box inlet is a five-wire system, namely, A, B, and C three-way phase line (usually yellow, green, red), one-way neutral line (light blue color), and one-way ground line (color yellow with green stripes). Quit as needed.
① 220V load is generally taken with one phase line, one neutral line, and one ground line.
② 380V load, (such as 380V AC motor ) full three-phase acquisition and grounding wire is added. (Nether wire is also required if the load is controlled on site.)
③ There is a special two-phase 380V AC welding machine, and any two-phase phase wire is produced. Add ground wire. grounding wire is generally required to be connected, but it is not connected in many occasions (such as construction sites). Generally, the inlet line is a three-phase inlet 3PIN empty opening, circuit breaker, knife switch or other circuit breaker; the neutral line is pressed to the zero terminal strip, and the ground line is pressed to the ground terminal strip. There are also 4PIN circuit breakers that directly use three phase lines and neutral lines to enter the incoming wires, and the grounding wire is pressed to the grounding terminal strip.
2) Depending on the load size, lighting distribution can use one phase line + one neutral line + one grounding line; or the above power distribution 220V.
(2) Installation method of distribution box
1) When installing the distribution box on the wall, it should be fixed with open foot bolts (expanding pipe bolts). The length of the bolt is generally the buried depth (75~150mm), the thickness of the box bottom plate, the sum of the thickness of the nut and washer, plus the "outlet margin" of about 5mm. For smaller distribution boxes, wooden bricks can also be buried at the installation site (buried according to the location of the four corners of the distribution box or distribution board), and then use wooden screws to fix the distribution box or distribution board at the wooden brick.
2) Concealed assembly power box, the distribution box is embedded in the wall to install. When building the wall, the reserved hole should be about 20mm larger than the length and width of the distribution box. The reserved depth is the thickness of the distribution box plus the thickness of the plastering in the hole. When burying the distribution box, concrete is filled between the box and the wall to fix the box.
3) The distribution box should be firmly installed, horizontally and vertically, and the vertical deviation should not be greater than 3mm; when concealed, there should be no gaps around the distribution box, and the edges of the panels should be close to the wall, and the parts in contact with the building and structure should be coated with anticorrosion paint.
4) The power cord of the spiral fuse installed in the distribution box should be connected to the terminal of the intermediate contact, and the load cord should be connected to the terminal of the thread. In this way, there will be no electric shock when loading and unloading the melt core. The porcelain plug-in fuse should be installed vertically.
5) The AC, DC or power supplies in the distribution box with different voltage levels should have obvious signs. In the lighting distribution box , the bus bars of neutral wire (N wire) and protective neutral wire (PE wire) should be set separately. The neutral wire and protective neutral wire should be connected on the bus bar and must not be twisted and should be numbered.
6) When the wire leads out of the panel, the panel wire holes should be smooth and burrs free, and an insulating protective sleeve should be installed on the metal panel. The metal shell distribution box housing must be reliably grounded (zeroed).
(3) Classification of distribution box
1) Fixed panel switch cabinet , often called switch board or distribution screen . It is an open switch cabinet with panel blocking. The front has a protective effect, and the live parts can still be touched on the back and sides. The protection level is low. It can only be used for industrial and mining enterprises with low requirements for power supply continuity and reliability, for centralized power supply in substations.
2) protective (i.e. closed) switch cabinet refers to an low-voltage switch cabinet that is closed on all other sides except the installation surface. The electrical components of this cabinet, such as switching, protection and monitoring control, are installed in a closed shell made of steel or insulating material, and can be installed against or off-wall. There can be no isolation measures between each circuit in the cabinet, or grounded metal plates or insulating plates can be used for isolation. Usually the door and the main switch are mechanically interlocked. There is also a protective table type switch cabinet (i.e., console), and the panel is equipped with control, measurement, signal and other electrical appliances. The protective switch cabinet is mainly used as the power distribution device at the process site.
3) drawer switch cabinet . This type of switch cabinet is made of steel plates to enclose the outer shell, and the electrical components of the inlet and outlet circuits are installed in drawable drawers, forming a functional unit that can complete a certain type of power supply task. The functional unit is separated from the busbar or cable by grounded metal plates or functional plates, forming three areas: busbar, functional unit and cable. There are also isolation measures between each functional unit. Drawer switch cabinets have high reliability, safety and interchangeability, and are relatively advanced switch cabinets. Most of the switch cabinets currently produced are drawer switch cabinets. They are suitable for industrial and mining enterprises and high-rise buildings that require high power supply reliability, and serve as centralized control distribution centers.
4) Power and lighting distribution control box. Mostly closed vertical installation. The protection level of the shell is different due to different use occasions. They are mainly used as power distribution devices at the production site of industrial and mining enterprises.
(4) Precautions for setting up distribution box
1) The distribution system should set up indoor main distribution box and outdoor distribution box or set up each distribution box of outdoor main distribution box to implement hierarchical distribution.
2) The power distribution box and the lighting distribution box should be set separately. If it is placed in the same distribution box, the power and lighting lines should be set in separate channels.
3) The total distribution box should be located in an area close to the power supply. The distribution box should be installed in electrical equipment or areas with relatively concentrated loads. The distance between the distribution box and the switch box shall not exceed 30m. The horizontal distance between the switch box and the fixed electrical equipment it controls should not exceed 3m.
4) For distribution boxes that need to be installed on the ground, they should be installed 50 to 100mm from the ground, and it is required that the front side of the distribution box be within a range of 0.8 to 1.2m, without any debris hindering the supply of electricity, and the surrounding environment is ventilated and dry.
5) The wiring busbars in the box should be set up separately with neutral wires, protective ground wires, and phase wires. It is necessary to ensure that the various components, instruments and lines in the distribution box are installed firmly and arranged neatly, so as to facilitate maintenance and maintenance. After the installation is completed, the debris and dust in the box must be removed in time.
6) The electrical appliances in the distribution box should be installed first on a non-metal or wooden insulated electrical installation board, and then be tightened as a whole in the distribution box box. The metal plate and the iron distribution board box box should be electrically connected.
7) Each electrical equipment should have its own dedicated switch box, and it must be implemented with the "one machine, one gate, one protection" system. It is strictly prohibited to use the same switch appliance to directly control more than two electrical equipment.
8) The rated leakage current and rated leakage operation time of the two-stage leakage protectors in the distribution box and the switch box should be reasonably coordinated to make them have the function of hierarchical and segmented protection.
9) The wooden bricks and iron parts required to install distribution board need to be buried in advance, and the exposed distribution box should be fixed with metal expansion bolts. The wiring should be arranged neatly and tied into bundles, and the moving parts need to be fixed.
10) The ratings of various switching appliances should be adapted to the rating positioning of the electrical equipment they control.
11) When the construction site stops operation for more than one hour, the power switch box should be powered off and locked.
12) When inspecting and repairing distribution boxes and switch boxes, the corresponding power switches in the previous level must be switched off and power off, and a power outage sign is hung. It is strictly forbidden to operate with live.
(5) The size of the distribution box is determined
1) When electric box is just a lighting electric box or a small power, when the inlet line is less than 10 square meters, if the number of switch bits is less than 20 bits, the switch width dimensions are added together and 20MM is added on each side, which is the width of the box, the height is the switch height and 40MM, and the depth is the maximum depth of the switch.
2) When the electric box is just a lighting electric box or a small power, and the inlet line is less than 10 square meters, if the number of switch positions is greater than 20 bits, the electric box needs to be arranged in two rows of switches. Adding the switch width and size to add 40MM to each side is the width of the electric box, the height is the switch height and 40MM, and the depth is the maximum depth of the switch.
3) When the electric box is just a lighting electric box or a small power, and the inlet line is less than 10 square meters, if the inlet line switch needs to be a separate row, the switch width and size plus 20MM on each side is the width of the electric box. The height is the switch height and the inlet line switch height plus 40MM, and the depth is the maximum depth of the switch.
4) When the electric box is a power electric box, or a power lighting electric box, the algorithm is basically the same as above. However, when the inlet line is greater than 10 square meters, the bending radius of the inlet line should be considered. The first-level wiring terminal should reserve enough space for the inlet line. When the switch is arranged in two rows, the wiring wiring of the switch should be considered.
Of course, the size of the electric box is not determined. The actual installation must be considered, and the actual wiring diagram should be considered and how to arrange the wiring of the switch arrangement first-level switch. If all micro circuit breakers are determined according to the number of digits (18 mm per digit), the PZ series distribution box has a fixed size, and the circuit exceeds 80 digits, you can determine the design of the Party A on the drawing (words). The equipment control box is equipped with the equipment, the inlet line is greater than 185mm2, and the output is greater than 2 channels and try to choose a cabinet type.
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