Electrical design of household cloth and wire_Anhui Honglin Instrument Cable Co., Ltd.

Electrical design of household cloth and wire

Author：hlyb Add Time：2016-05-25 08:24:26

Since its invention in the 19th century, electrical design has had an extremely extensive and profound impact on the development of human society. In recent years, with the improvement of living standards of urban and rural residents and the expansion of residential area of each family, especially household appliances with high power consumption, such as air conditioners, microwave ovens, electric kettles, electric rice cookers, electric heating showers, electric heaters, and even electric ovens for cooking, have been rapidly popularized to every family in cities and towns with the release of power consumption restrictions, The power load of many families has reached 4kw and above. In the past, the design standard of mixed power supply with one TV, one refrigerator, one washing machine, one lamp in each room and one 5A watt hour meter in each household can no longer meet the requirements. It is necessary to improve the design requirements and grade. At present, according to the new household grade standard, ordinary residence 4kw / household; Medium residential 6kW / household; The power supply design shall be carried out according to the load requirements of 10kW / household of higher residence. This paper discusses some views on the electrical design of general family houses, which can be used as a reference for the electrical installation of new houses or the electrical transformation of old houses. When the power load of higher houses reaches 10kW and above, three-phase five wire system should be used for power supply, which is not involved here.

1. Electrical selection of incoming power circuit

The general household power supply load is calculated as 4 ~ 6kW. The single-phase three wire system can still be used for household power supply, and the electric energy meter is 10 (40) a. The code for residential design requires: "the electrical lines shall be laid in a way that meets the safety and waterproof requirements, and the wires shall be copper wires. The section of each residential incoming line shall not be less than 10mm2, and the section of branch circuit shall not be less than 2.5mm2." Therefore, bv-105 heat-resistant PVC insulated copper core wire should be selected for household power supply and house wiring, and laid in concealed pipe. The incoming power line is led from the floor main line to the household electric energy meter box, and then to the household distribution box in the house. Its section is selected as 3 according to the regulations × 10mm2, or 2 × 10mm２+1 × 6mm2. This selection has fully taken into account the increase and development of household power load, and can carry 57A current. It should not be lower than this standard in design and installation.

Hy122-63a / 2p modular bipolar disconnector should be selected as the main switch of household power supply in household distribution box. It has obvious disconnection point, which is convenient for maintenance. Outlet switches of other circuits in the box, such as lighting and socket circuit of wall GUI air conditioner, shall select bipolar automatic air switch with overload tripping function; Leakage switches with overload tripping function shall also be used for other ordinary socket circuits and cabinet air conditioner circuits.

2 separate circuit power supply for household appliances

The specification requires: "each residential air conditioning power socket, other power sockets and lighting shall be set separately; the kitchen power socket and toilet power socket should be set with * * * vertical circuit." The purpose of requiring shunt setting here is to avoid affecting the normal operation of lighting fixtures and other electrical equipment in case of failure of electrical equipment in a socket circuit. With the advent of the information age, many home computers have been connected to the Internet. In order to prevent other household appliances from affecting the computer power supply, it is necessary to set up another circuit for the computer. In this way, the general family residence shall have at least 6 circuits such as lighting, computer, air conditioning, kitchen, toilet and other ordinary sockets, or 1 ~ 2 circuits can be added. For example, two circuits can also be set for lighting. When one circuit fails, it will not cause all darkness in the house, which can bring convenience to maintenance. In hot weather areas, some families use two air conditioners, one cabinet air conditioner with large cooling capacity is placed in the living room and one wall mounted air conditioner is placed in the bedroom. If used at the same time, the load can exceed 4kw, so two circuit power supply can also be used. There are many household appliances in the kitchen and bathroom, which can send a main power supply respectively and install a socket box locally. For outgoing circuit conductor, except for lighting computer circuit, 2.5mm2 can be selected, and 4mm2 can be selected for other circuits. If a 2500W electric stove is used in the kitchen for cooking, 6mm2 should be selected as the power line, because the line is used frequently and the section is larger, which can prevent the wire from aging in advance and reduce the potential fire hazard. In short, although some sections are increased, and some have more than one circuit, the wires used are not too long, and the increase of one-time investment is not much. But the benefits of safety and convenience are great. The household appliance socket in the house shall be installed in a concealed manner along with the concealed laying of the pipeline. The installation position shall first consider the safety and convenience during use, and be close to the position when the household appliance is used. The installation height of kitchen socket is 1.6m, which is convenient to use; The installation height of toilet socket should be 1.6m or slightly higher, and water should not be splashed when using shower; For all kinds of sockets in the living room and bedroom, in order not to affect the indoor beauty, it is appropriate to be 0.3m away from the ground. When not in use, the sockets shall be covered to prevent children from electric shock. The installation position of wall mounted air conditioner sockets shall adapt to the air conditioner.

3 telephone and television system of family residence

(1) Telephone communication: telephone has become an indispensable communication tool in people's life. With the popularization of computers, the number of computers accessing the Internet in families is also increasing. Generally, families should set up two incoming telephone lines, one for credit, and the telephone terminal box should be set in the living room or master bedroom; Another computer can be used for Internet access, which can be set in the study or the room where the computer is installed. The telephone line shall also be buried in the house. The telephone junction box or floor public junction box shall be set in the corridor and other public places for maintenance.

(2) TV signal: watching TV has developed from one for each household to two or more for each household. Therefore, at least one TV signal terminal socket shall be set in the living room and the master bedroom. The equipment location shall be suitable for the TV cabinet, and a power socket shall be set nearby. When cable TV enters the unit building, amplifiers, distributors, branches, etc. shall be set. These equipment shall be placed in the common box and distribution box in the public part of the residence at the front end of the TV, and the line shall also be laid in the way of concealed pipe threading.

4 problems needing attention in the reconstruction of old houses

During the construction of old houses in the past, due to the limitations of the development of the times, most of the power supply capacity and layout can not meet the needs of today. Therefore, in the renovation and home decoration of old houses, the power supply capacity of the line shall be checked according to the current load standard, and the conductor shall be checked for aging and damage. If it cannot be used, it can be replaced with a new line or another open line. Don't just increase the number of sockets and change the layout of lights. If we do not increase the conductor section and the number of power supply circuits, but also use the mixed power supply mode, it is bound to cause potential fire accidents. Once an accident occurs, the consequences will be unimaginable, so we must not be careless.

People with a little electrical knowledge know that short circuit, overload operation and excessive contact resistance of wires may produce electric sparks and arcs, causing overheating of wires and leading to fire. Therefore, pay attention to the following matters when wiring:

1. Select the model of wire correctly. According to the power of existing electrical equipment and electrical appliances that may be added in the future, the conductor with appropriate section shall be selected to avoid fire risk due to exceeding the safe carrying capacity of the conductor. At the same time, different wires should be selected according to different environments. For example, in bathrooms, kitchens and other places, moisture-proof wires should be selected due to contact with water.

2. Pay attention to the reasonable direction of wires. That is, the line shall be short and straight as far as possible to avoid twists and turns and reduce cross connection. In particular, a certain safe distance must be maintained between lines, between conductor fixing points, between lines and pipelines and the ground.

3. Pay attention to strict construction. Protective measures for threading shall be taken, and the conductor connection shall be firm. When the copper core conductor is hinged, tin welding shall be carried out as far as possible to prevent loosening and oxidation. The insulation problem shall be handled well at the wire joint.

4. Strict protective measures should be taken. That is, fuse and automatic switch are used for short-circuit protection and overload protection.

Here is a brief overview of electrical wiring in home decoration:

1. Selection of conductor section is very important in household cross-section. Code for design of residential buildings (gb50096-1999) clearly stipulates that the section of incoming line of each residence shall not be less than 10mm2, and the section of fenwen circuit shall not be less than 2.5mm2. Article 2.2.8 of gb50054-95 code for design of low voltage power distribution stipulates that when the single core conductor is used as the main line of pen line, when it is copper, the section shall not be less than 10mm2; When it is aluminum, it shall not be less than 16mm2; When the core wire of multi-core cable is adopted, it shall not be less than 4mm2.

Similarly, in the home installation, the phase line section should be the same as the N line. It should be noted that two circuits cannot share one N line. For example, in a cross section installation project, five branch circuits are separated from the household distribution box, of which two circuits share an N line, which is equivalent to that the N line section is L / 2 of the phase line section, which is not allowed.

2. Regulations on conductor color in household horizontal installation project, the selection of conductor color is easy to be ignored. For convenience, some people often use the remaining conductor that does not meet the color regulations in the project, such as using the red conductor originally used as phase conductor as grounding wire, which is not allowed.

The purpose of specifying the conductor color is not only to facilitate identification during installation and construction, but also to provide convenience for future maintenance and reduce accidents caused by misjudgment.

Relevant national standards have clearly stipulated that the phase line (L) is yellow, green and red; Neutral line (n) is light * * *; The protective wire (PE) is green / yellow.

If a household supplies three-phase power, the phase line from the household switch box must be * * * the same color as the incoming line.

The three phase wires of the three-phase socket use the same color wire, which is also not allowed. Because it is difficult to judge which phase is missing when the socket is out of phase. In three-phase power supply system, the phase line of single-phase socket shall also be the same color as the incoming line of power supply.

The color code of the power line of fixed three-phase equipment shall be consistent with that of the power supply. In some projects, the power line of the equipment has been connected before the power supply is finally connected. When the phase sequence is found to be wrong during the test run, the phase line at the equipment end cannot be adjusted, so it is adjusted at the power end, resulting in the inconsistency between the phase line color and the phase line color of the distribution line. At this time, the negative method of wrapping the color band can only be adopted.

In order to avoid the above situation, the equipment shall be temporarily connected after the power supply is connected. After the phase sequence is correct, the power line of the equipment shall be cut off, then the line shall be connected, and the equipment shall be formally connected. The power line of portable three-phase equipment is allowed to be inconsistent with the color code of distribution line. During the horizontal installation of the house, the phase sequence of the three-phase socket shall be constructed according to the design requirements. If the design does not put forward requirements, the phase sequence in the same project shall be consistent.

If the household is powered by single-phase power supply, it is recommended to use yellow, green and red for the outgoing line of household switch box in order to judge the fault. For example. In case of phase line fault of a lamp, it is necessary to check the number according to the as built drawing to know which shunt fault is. If the shunting outgoing line adopts conductors of different phase colors, i.e. phase wires of yellow, green and red, the workload of line inspection can be reduced by two-thirds

More and more high-grade residential houses for export adopt three-phase incoming. At this time, the phase line of single-phase electrical equipment must be the same color as the incoming line, and connected to the corresponding incoming line according to the design requirements; If the residence is single-phase, its shunting can use different phase color lines, but strive to be unified in the same project. For example, red is used for air conditioning circuit, * * * is used for lighting circuit, green is used for other electrical equipment, etc. The purpose of this is that once the line fails, the property management personnel can quickly find the faulty line.

The incoming and outgoing lines of single connection lighting switch shall be of the same color, and there is no need to distinguish the incoming line or outgoing line. In order to distinguish the incoming and outgoing lines of multi connected lighting switch, phase lines of two colors can be used, that is, one for incoming line and the other for outgoing line. For example, for a triple switch, when one incoming line is red, the three outgoing lines are green.

In addition, crimping wires of different colors together is not allowed.

3. Line insulation measurement line insulation measurement is the key work to ensure the normal and safe operation of the line. In case of poor line insulation, the electrical equipment can not work normally at least, or short-circuit trip, or even electrical fire.

In order to ensure good line insulation, conductors with excellent insulation performance must be * * * selected. When selecting the manufacturer, we should not only consider the price, but first ensure the conductor quality.

The conductor found in the project mainly has the following problems: the wire diameter of single strand conductor does not meet the standard, or multiple strands of conductor are missing; The insulation layer has obvious thickness or eccentricity; The conductor in the insulating layer has a joint; Length shortage.

In addition to selecting conductors with excellent insulation performance, the damage of conductor insulation layer shall be avoided during construction. Such as: no garbage in the pipe; The nozzle shall be smooth; When threading, the nozzle shall be covered with a retainer first; The conductor shall not be twisted, etc.

In order to correctly judge whether the line insulation is still good after construction, the insulation test must be carried out carefully without missing a conductor, and the test data shall be properly recorded and stored.

The megger used for measuring line insulation is a mandatory verification instrument, which can be used only after passing the verification and within the effective period of verification.

The insulation test of lighting circuit shall be carried out in two steps: the first step is after the conductor is laid (for example, after the threading in the pipe is completed); The second step is when the wiring of lamps, switches and sockets is completed and the bulb has not been installed.

(1) Insulation test after conductor laying

For pipeline laying, trunking laying and other lines, because the wires are together, they must be tested one by one without omission. When the conductor is laid in metal pipe or metal trunking, in addition to measuring the insulation between wires, it is also necessary to measure the insulation between wires and metal pipe or metal trunking. When the wire is laid in plastic pipe or plastic trunking, only the insulation of the wire needs to be measured.

During insulation measurement, 500V megger shall be selected, and the accuracy shall be grade 0.1.

Before insulation measurement, open circuit and short circuit tests shall be conducted for the megger used; To judge whether the instrument works normally. During the open circuit test, the test terminal is not connected with the conductor, shake the handle to the specified speed, and the measured value shall be infinite; During the short-circuit test, the two test terminals shall be short circuited with wires, the handle shall be shaken slowly, and the measured value shall be "0".

The insulation between wires or between wires and ground must be * * * more than 0.5m.

(2) Insulation test after wiring: the qualified insulation test after wiring does not guarantee that the insulation after wiring is still qualified, because there is the possibility of conductor insulation decline or even short circuit during wiring.

During the wiring of lamps, if the insulation layer of phase line is damaged and collides with the metal shell of lamps, it will cause short circuit between L and PE. If the n-wire insulation is damaged and collides with the metal shell of the lamp, it will cause a short circuit of N and PE. When the socket wiring is installed, it will also cause conductor insulation damage and short circuit, * * * common is: when the socket panel is fixed, when the panel screw is too long and the end of the screw is just on the conductor, the conductor insulation will be damaged. If the socket box is metal, the conductor will be short circuited with the ground; After the wires are combined, the insulation of the joint is not handled properly. For example, when the joint is wrapped directly with black wrapping cloth and the metal junction box is used, the insulation between the wire and the ground will be poor. In addition to the above conditions, there are other conditions that may reduce the insulation of the conductor or even short circuit, such as external force on the pipeline

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Electrical design of household cloth and wire