It can be seen that there are two conditions for combustion and explosion in the air: (1) the concentration of flammable gas or vapor, that is, the explosion limit. One way to avoid an explosion is to control the limits of the explosion, such as ventilation in engineering to reduce the concentration of combustible materials in the air. (2) The ignition source, ie the ignition temperature or open flame. In order to prevent the surface temperature from reaching the ignition temperature during the operation of the equipment in the combustible gas, the ignition temperature of the combustible gas must be paid attention to when designing and selecting the equipment, as shown. Several common combustible gases or vapors, ignition temperature, gas name, ignition temperature, gas name, ignition temperature, methane, 537, carbon disulfide, 102 propane, 466 ammonia, 630, ether, 170, ethylene, 425, hydrogen, 560, acetaldehyde, 140, acetylene, 305, methylamine 430, for the convenience of designers. And specifications, explosion-proof standards will be divided into six groups of ignition temperatures, as shown. For example, in the presence of ether in an explosive atmosphere, the explosion-proof electrical product of the T4 group is selected because the ignition temperature of the ether is 170. In the design of the air conditioner, it is necessary to select different temperature groups for different flammable gas or air 21 explosion-proof regulators, such as motors, electric heaters, condensing fans, etc., different loads in an explosion-proof air conditioner ( The temperature groups of compressors, electric heating pipes, blowers, etc. are different. The temperature group of the whole machine is the temperature group of the whole machine with the lowest temperature group in the load. Temperature group, equipment surface temperature flammable gas or vapor ignition temperature relationship Temperature group T1T2T3T4T5T6 The highest surface temperature of electrical equipment 45030020013510085 ignition temperature of gas or steam>450>300>200>135>100>85 The gas can be classified according to the explosive capacity according to the maximum experimental safety clearance (MESG) value of the flammable gas. As shown. The degree of explosion protection is directly related to the nature of the flammable substance. It is not directly related to the ignition temperature of the flammable gas due to the pressure, temperature, humidity and position of the ignition source. Combustible gas or steam according to the classification of explosive capacity, class MESGmmMICR explosion-proof electrical equipment according to the explosive environment (place of use) used Classes (for coal mines) and classes (for factories), explosion-proof air conditioners for factories are classified as products. The explosion-proof type %d and intrinsically safe %i electrical equipment are further classified into categories A, B and C according to the explosive gas characteristics according to the maximum experimental safety clearance (MESG) and minimum ignition current (MIC). Explosion-proof air conditioners for industrial use are according to GB3836.12000 Electrical equipment for explosive gas atmospheres Part 1: General requirements, GB3836.22000 Electrical equipment for explosive gas atmospheres Part 2: Explosion-proof type %d, GB3836.42000 for explosive atmospheres Electrical equipment - Part 4: Intrinsically safe type %i, GB3836.990 Explosion-proof electrical equipment for explosion-proof electrical installations - Electrical equipment - Part 3: Electrical equipment for explosive atmospheres - Part 15: Electrical installation in hazardous areas (except for coal mines) The regulations are made into an explosion-proof structure. According to the above conditions of combustion and explosion, different explosion-proof measures can be taken. The common types of explosion-proof are as follows: (1) Explosion-proof enclosure %d Most of the explosion-proof air conditioner units are equipped with such explosion-proof types, such as air conditioners. The electric control box of the machine, the wiring device of the air conditioner equipment, the motor of the air supply motor, and the motor of the condensation fan. (2) Positive pressure shell type %p. (3) Oil-filled casing %o. (4) Sand-filled casing %p. (5) The encapsulation type %m is convenient to operate by this method, and is also easy to achieve in the design of the explosion-proof air conditioner. Therefore, most of the electrical parts of the air conditioner that cannot be used with explosion-proof equipment use this method, such as the compressor junction box part and Other solenoid valves or pressure controllers are potted with materials such as epoxy. (6) Intrinsically safe type %i This method is used in the design of electrical equipment for explosion-proof air conditioners, and limits the voltage and current of electrical equipment in explosive mixtures as much as possible. Explosion-proof temperature and humidity sensors, high and low pressure controllers, air pressure switches, user fault input points, etc. are used for explosion-proof treatment. Intrinsically safe devices and associated devices are classified into two levels, ia and ib, depending on the area of ​​use and the degree of security. The ia grade equipment can be used in hazardous areas in zones 0, 1, and 2, and it is safer. The ib grade equipment can be used in hazardous areas in Zones 1 and 2, and its safety is lower than ia. Explosion-proof air conditioners are generally used in hazardous areas in Zone 2, and can reach ib level. (7) Increased safety type %e This method depends on the requirements of the air conditioner user for the explosion-proof grade. Explosion-proof electric heating pipes used in explosion-proof air conditioners use this type of explosion-proof. The explosion-proof mark is ExeT3. Some people often mistakenly write the explosion-proof mark of explosion-proof electric heating pipe as ExdBT3, which should be noted. (8)%n type China's explosion-proof electrical equipment must be inspected by the state-approved explosion-proof inspection agency, and the corresponding product is awarded the unique explosion-proof certificate number, the main explosion-proof inspection agency has the national explosion-proof electrical product quality supervision and inspection center. The meaning of the explosion-proof mark code is as follows: the explosion-proof mark of the explosion-proof type, category and temperature group should be marked on the product. Different types of explosion-proof air conditioners have different explosion-proof types, and the explosion-proof marks are written differently. If more than one type of explosion-proof type is used, the main body explosion-proof type shall be marked first, and other explosion-proof types shall be marked. Such as explosion-proof heat pump type cabinet machine, because the unit increases the explosion-proof electric heating tube, the explosion-proof mark is: ExeT3, so the explosion-proof mark of the explosion-proof heat pump type cabinet machine is: ExdmeibBT3. The various types of explosion protection mentioned above should be considered in terms of the process and the environmental protection requirements of the environment. Points to be noted and problems (1) For compressors with electronic motor protectors above 15 hp, the wiring of the electronic motor protector should be very careful. The cable connecting the power supply of the electronic motor protector and the cable connecting the contacts should be Separate routing, can not be connected to the power supply and contacts with a 4-core cable, use two two-core cable to connect to the power supply and contacts, the electronic motor protector contacts are connected to the control line without adding a safety barrier, Since the compressor junction box must be potted, some people often mistakenly increase the safety barrier, which should be noted. (2) For explosion-proof electronic electric actuators, the power supply is AC220V, the control signal is 420mA, and the shielded cable is required for connection. (3) Since the working voltage of the compressor heating belt is 220V, it is better to use the built-in heater for the explosion-proof type air conditioner. If the heating belt is installed outside the compressor, the heating belt should be removed or the explosion-proof type should be used. Electric heating. Related equipment (such as safety barriers) involving intrinsically safe type shall ensure that the distance between the intrinsically safe end and other electrical components is greater than 50 mm, and the intrinsically safe line is separated from the non-intrinsically safe line. For the safety barrier components used in explosion-proof air conditioners, There is no need to increase the terminal block. The intrinsically safe components such as the air pressure switch, high and low pressure switch, temperature and humidity sensor are directly connected to the intrinsically safe end of the safety barrier component. The intrinsically safe end and the non-intrinsically safe end of the safety barrier component should be separated when wiring. One of the non-intrinsic end of the gate element should be connected to DC24V in the line. The safety barrier should be grounded reliably. The grounding pin is connected by brass piece, and then grounded to the grounding screw in the electric control box for grounding. The connection is firm. The grounding wire is larger than 2.5mm2. The grounding connection of the electrical equipment should be at least with the cross-sectional area. For the 4mm2 grounding wire to be effectively connected, the external grounding of the explosion-proof TD200 controller should be connected to the grounding of the whole machine. When designing an explosion-proof air conditioning unit, the size of the explosion-proof electrical control box should be limited as much as possible. For example, most of the compressors used in the cabinet air conditioners are Copland compressors, and the Kaplan compressors below 12 hp and below 12 hp have built-in overload. Protector and exhaust temperature protection device eliminate the need for an external overcurrent protector and exhaust temperature protector. At the same time, the unit removes the three-phase power monitor, and the power supply such as the air supply motor and compressor is directly taken out from the AC contactor, eliminating the corresponding terminals of the air supply motor and the compressor. In this way, the size of the electric control box can be reduced, and the size of the whole machine is correspondingly reduced, which not only reduces the unit footprint but also saves the unit design cost. In the design of explosion-proof air conditioning units, for electrical control drawings, it is best to indicate those electrical components (such as: temperature and humidity sensors, high and low pressure controllers, solenoid valves, explosion-proof water regulating valves, etc.) outside the explosion-proof electrical control box, and Identify those electrical components (eg, temperature and humidity sensors, high and low pressure controllers, etc.) as intrinsic components. 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