The distribution box is the central hub of the home circuit and the general control of our daily power consumption. It is an indispensable electrical equipment. If there are some potential safety hazards, we can deal with them in time. However, many electrical beginners don't know how to install and connect the distribution box. Next, let's introduce the wiring mode, installation method and size determination of the distribution box, For your reference.

(1) Wiring method of distribution box

1) Generally, the incoming line of power distribution box adopts five wire system, i.e. three phase lines a, B and C (generally yellow, green and red), one zero line (light blue) and one ground line (yellow with green stripes). Outgoing line as required.

① 220V load generally takes one phase line, one zero line and one ground line.

② 380V load, (such as 380V AC motor) three-phase full extraction, plus grounding wire. (zero line is also required if the load is locally controlled.)

③ There is a special two-phase 380V AC welding machine, which can draw two-phase lines arbitrarily. Add grounding wire. The grounding wire is generally required to be connected, but it is not connected on many occasions (such as construction site). Generally, the incoming line is the air switch, circuit breaker, knife switch or other circuit breaker of three-phase incoming and one-way 3pin; The zero line is pressed to the neutral terminal block, and the ground line is pressed to the grounding terminal block. There are also incoming lines that directly use 4Pin circuit breaker, three-way phase lines and zero lines enter together, and the grounding wire is pressed to the of the grounding terminal block.

2) According to the load, one phase line + one zero line + one grounding wire can be used for lighting distribution; Or the above power distribution 220V.

(2) Installation mode of distribution box

1) Open mounted distribution box. When the distribution box is installed on the wall, it shall be fixed with split bolts (expansion bolts). The bolt length is generally the sum of the buried depth (75 ~ 150mm), the thickness of the box bottom plate, the thickness of nuts and washers, plus about 5mm "head allowance". For smaller distribution boxes, wood bricks can also be embedded at the installation position (embedded according to the installation holes at the four corners of the distribution box or distribution board), and then wood screws can be used to fix the distribution box or distribution board at the wood bricks.

2) Concealed distribution box shall be installed. The distribution box shall be embedded in the wall. During wall construction, the reserved hole shall 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 plastering on the inner wall of the hole. When embedding the distribution box, the box can be fixed by filling concrete between the box and the wall.

3) The distribution box shall be installed firmly, horizontally and vertically, and the vertical deviation shall not be greater than 3mm; During concealed installation, there shall be no gap around the distribution box, the edges around the panel shall be close to the wall, and the contact part between the box and buildings and structures shall be coated with anti-corrosion paint.

4) For the spiral fuse installed in the distribution box, its power line shall be connected to the terminal of the intermediate contact, and the load line shall be connected to the threaded terminal. In this way, there will be no electric shock when loading and unloading the molten core. Porcelain plug-in fuses shall be installed vertically.

5) The AC, DC or power supplies with different voltage levels in the distribution box shall have obvious signs. The lighting distribution box shall be provided with zero line (N line) and protective zero line (PE line) bus bars respectively. The zero line and protective zero line shall be connected on the bus bar without splicing and shall be numbered.

6) When the conductor leads out of the panel, the panel wire hole shall be smooth without burr, and the metal panel shall be equipped with insulating protective sleeve. The shell of metal shell distribution box must be reliably grounded (connected to neutral).

(3) Classification of distribution box

1) Fixed panel switchgear, often called switch board or distribution panel. It is an open switch cabinet with panel blocking. The front has protective effect, and the back and side can still touch the live parts. The protection level is low. It can only be used for centralized power supply in the substation in industrial and mining enterprises with low requirements for power supply continuity and reliability.

2) Protective (i.e. closed) switchgear refers to a low-voltage switchgear whose sides are closed except the mounting surface. The switch, protection, monitoring and control and other electrical components of the cabinet are installed in a closed shell made of steel or insulating materials, which can be reliably installed on or off the wall. No isolation measures can be taken between each circuit in the cabinet, or grounded metal plate or insulating plate can be used for isolation. Generally, the door is mechanically interlocked with the main switch. In addition, there is a protective platform type switch cabinet (i.e. console), which is equipped with control, measurement, signal and other electrical appliances. The protective switch cabinet is mainly used as the power distribution device on the process site.

3) Drawer type switch cabinet. This kind of switch cabinet is made of closed shell made of steel plate, and the electrical components of incoming and outgoing circuit are installed in withdrawable drawers to form a functional unit that can complete a certain type of power supply task. The functional unit is separated from the bus or cable by a grounded metal plate or a functional plate made of plastic to form three areas of bus, functional unit and cable. Isolation measures are also taken between each functional unit. Drawer type switch cabinet has high reliability, safety and interchangeability. It is a switch cabinet. At present, most of the switch cabinets produced are drawer type switch cabinets. They are suitable for industrial and mining enterprises and high-rise buildings that require high power supply reliability as centralized control distribution centers.

4) Power and lighting distribution control box. Mostly closed vertical installation. Due to different use occasions, the enclosure protection grade is also different. They are mainly used as power distribution devices at the production site of industrial and mining enterprises.

(4) Precautions for distribution box setting

1) The distribution system shall be equipped with indoor general distribution box and outdoor distribution box or outdoor general distribution box and each distribution box to implement hierarchical distribution.

2) The power distribution box and lighting distribution box should be set separately. If they are combined in the same distribution box, the power and lighting lines should be set separately.

3) The main distribution box shall be located near the power supply area. The distribution box shall be installed in the area with relatively concentrated electrical equipment or load. 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 controlled by it shall not exceed 3M.

4) The distribution box that needs to be installed on the ground shall be installed 50 ~ 100mm away from the ground, and within the range of 0.8 ~ 1.2m in front of the distribution box, there shall be no sundries that hinder the power supply, and the surrounding environment shall be ventilated and dry.

5) The wiring bus bar in the box shall be set with zero line, protective grounding wire and phase line respectively to ensure that all components, instruments and lines in the distribution box are firmly installed and arranged in order for easy maintenance and maintenance. After installation, the sundries and dust in the box shall be removed in time.

6) The electrical appliances in the distribution box shall be first installed on the non-metallic or wooden insulated electrical installation board, and then fastened in the distribution box as a whole. The metal plate and the iron distribution board box shall be electrically connected.

7) Each electric equipment shall have its own special switch box. The system of "one machine, one switch and one protection" must be implemented. It is strictly prohibited to use the same switch to directly control more than two electric equipment.

8) The rated leakage action current and rated leakage action time of the two-stage leakage protector in the distribution box and switch box shall be reasonably matched to make it have the function of hierarchical and sectional protection.

9) The wooden bricks and iron parts required for the installation of the distribution board shall be buried in advance, and the exposed distribution box shall be fixed with metal expansion bolts. The wiring shall be neatly arranged and bound into bundles, and the moving parts shall be fixed.

10) The rated value of various switching appliances shall adapt to the rated position of their control electrical equipment.

11) When the operation on the construction site is stopped for more than one hour, the power switch box shall be powered off and locked.

12) During the inspection and maintenance of the distribution box and switch box, the corresponding power switch at the previous level must be switched off and powered off, and the power-off signboard shall be hung. Live work is strictly prohibited.

(5) Sizing of distribution box

1) When the electric box is only a lighting electric box or small power, and the incoming line is less than 10 square meters, if the number of switches is less than 20, the switch width plus 20mm on each side is the width of the electric box, the height is the switch height plus 40mm, and the depth is the switch depth plus 10mm.

2) When the electric box is only a lighting electric box or a small power, and the incoming line is less than 10 square meters, if the number of switches is greater than 20, the electric box needs to be arranged as two rows of switches. The switch width plus 40mm on each side is the width of the electric box, the height is the switch height plus 40mm, and the depth is the switch height

Depth plus 10mm.

3) When the electric box is only a lighting electric box or small power, and the incoming line is less than 10 square meters, if the incoming line switch needs a separate row, the switch width plus 20mm on each side is the width of the electric box, the height is the switch height plus the incoming line switch height plus 40mm, and the depth is the switch depth plus 10mm.

4) When the power box is a power box or a power lighting box, the algorithm is basically the same as above. However, when the incoming line is greater than 10 square meters, the bending radius of the incoming line shall be considered, and sufficient space shall be reserved for the incoming line at the primary wiring terminal. When the switches are arranged in two rows, the wiring route of the switches shall be considered.

Of course, there is no final conclusion on the size of the electric box. The actual installation should be considered. It depends on the actual wiring diagram and how to arrange the switch and arrange the routing of the primary switch. If all miniature circuit breakers are determined according to the number of bits (18mm for each), PZ series distribution box has a fixed size. If the circuit exceeds 80, it can be identified by Party A in the drawing (words). The equipment control box identifies that the equipment is brought with it. The incoming line is greater than 185mm2 and the output is greater than 2. Cabinet type shall be selected as far as possible.