Weak current College】 【air supply unit control.

<br> Air supply unit control including: air temperature control, air relative humidity control, Frost control, CO2 concentration control and interlocking. If the air supply unit to consider responsible indoor load (such as DC units), you also control the indoor temperature .(or indoor relative humidity). <br> 1. air temperature control <br> Air temperature control is specified outlet temperature control, the applicable conditions are usually the air supply unit is to meet the requirements of the indoor health rather than a burden to .the use of the indoor load. Therefore, the entire control of time, the air temperature to maintain constant value principle. Because of the winter and summer on request, so winter and summer air temperature should have different requirements. Also means that the air supply .unit for supply air temperature control, throughout the year there are two control values - winter control values and summer control values, so you must consider the controller winter and summer conditions of conversion issues. <br> Air temperature control, usually the summer water control .cold dishes, winter control tube heat water or steam coil steam flow. For administrative convenience, the temperature sensor is generally located in the unit is located in the engine air supply pipe. <br> 2. indoor temperature control <br> For some DC .system, the fresh air can not only meet the health standards for the environment, but also to undertake all indoor load. As indoor load is changing, then take control of the supply air temperature way certainly does not meet the requirements for Interior (possible overheating .or too cold). It is necessary to use the location of the temperature control. It can be seen, then you must put the temperature sensors located in the typical accused room. Because the DC system is usually equipped with exhaust system, temperature sensors located .in the exhaust pipe and considering certain correction is also a feasible solution. <br> In addition to the DC system, the fresh air handling units are usually used with fan coil. In some works, consider the various reasons (such as fan coil of .dehumidifying capacity restrictions, etc.), air supply unit at design time to assume part of the Interior-load, this approach for design, air supply unit as supply air temperature control is not the problem. But when outdoor climate change makes indoor thermal equilibrium .is reached (such as transition quarter some time), if you continue to control the air temperature will cause the room is too cold (for cold water conditions) or thermal (heat and water condition), you should use the indoor temperature control. Therefore ., in this case, from year-round operation, should adopt the supply air temperature and room temperature of joint control. <br> 3. relative humidity control <br> Relative humidity-controlled air supply unit is mainly choose humidity sensor settings location or .control parameters, in view of its humidification source and control. <br> (1) steam humidification <br> For higher places, should be charged with humidity, automatically adjust the amount of steam humidification. This approach requires steam humidifier with room should be .adjustable valve (linear characteristic), the regulator should use PI-controller. Due to the stability of this approach is better, humidity sensors can be located in the engine room air distribution pipes. <br> For General requirements for the purposes of tall buildings ., or you can use old-style control. This can be bit-type humidifier (with quick closure type valve) and bit-regulator, is in the interest of reducing investment. <br> Dual-control, because only humidifiers full open full .off functionality, humidity sensor if or supposes the air pipe, once the humidifier full open, the sensor immediately detect the humidity is higher than the set value and closing valve (because usually choose humidifier maximum humidifying capacity necessarily higher than the design value); but .once off, makes the sensor immediately detect the humidity is lower than the set value and requirements, so open humidifier necessarily lead humidifier valve oscillation run, action, service life is reduced. Obviously, this phenomenon is due from the humidifier to produce wind pipe range .wet capacity is too small. Therefore, the steam humidifier with old-style control, humidity sensors should be located in a typical room (regional) or relative humidity change relatively flat location, to increase the moisture capacity, to prevent the humidifier valve switch action .too often. <br> (2) high pressure spray, ultrasonic humidification and electro wetting <br> These three are bit-for humidification. Therefore, their control and sensor settings should be using bit-mode control of steam humidification. The controller uses .the old style, the control of humidifier stops (or switch), humidity sensors should be located in a typical room area. <br> (3) circulating water spraying humidification <br> Circulating water spraying humidification and high-pressure spray humidification process is .distinct. In theory, the former belong to, Pui humidification and the latter belongs to no dew point wetting. If you use old-style controller control spray pump when starting and stopping, setting the principles and similar high pressure spray. But in some works ., the Jet pump itself does not do control but only with the air conditioning unit interlock start and stop, in order to control the humidity, you should set the warm-up before the humidifier coil, by controlling the preheating heating coil, guarantee the machine .after humidifier "dew point" tL (L point to dN line and φ = 80% to 85% of the intersection), control purpose of relative humidity. <br> (4) carbon dioxide (CO2) concentration control <br> Typically air .supply unit maximum air flow is meet health requirements (considering the commitment of the indoor unit load DC), then the number of rooms by full consideration. In actual use, the room size was not always full, when the staff number, you can reduce .the new amount of wind to energy savings, this method is particularly suitable for use in some fresh air and fan groups-coil system of office buildings in use in small conference rooms space, etc. <br> In order to guarantee the basic indoor air .quality, usually measuring indoor CO2 concentration measured by the method. All rooms are equipped with CO2 concentration controllers, control its fresh air pipes on electric air valve to open degree, at the same time, in order to prevent the system pressure is too high, .the total air tube set static pressure controller controls the fan speed. Therefore, do not only fresh air cooling load reduction and fan energy consumption will decrease. <br> Obviously, this control is part of variable air volume control (on VAV control, please .refer to the latter), this control is currently not many applications, an important reason is the CO2 concentration of the controller products andNot universal (only a few manufacturers), at the same time, this control method of investment considerably, its overall economic efficiency .requires specific analysis. <br> (5) antifreeze and interlock <br> In the winter outdoor design temperatures lower than 0 ℃, consideration should be given to the coil of antifreeze. In addition to the air conditioning system design itself should adopt preventive measures ., from electrical and control unit, it should adopt certain means. <br> 1) limit the heat coil electric valve for most small opening <br> In coil selection to meet certain requirements, to limit heat coil electric valve minimum opening. Especially the .two control system for cold and hot-spare tube, the smallest aperture setting should guarantee that the water tubes not icy water Wmin minimum; <br> 2) set the antifreeze temperature control <br> This is to prevent running pattern coils of measures. .Usually available in hot water coil outlet (or coil backwater even box) set a temperature sensor (Controller), temperature measurement backwater. When the measured value is lower than 5 ¡ .æ, antifreeze controller action to stop the air conditioning unit, while large hot water valve. <br> 3) interlocking fresh air valve <br> To prevent excessive infiltration due to wind coil-crack should stop the unit runs, interlocking off fresh air .valve. When the crew starting, open air supply valve (typically the first open air valve, after fans, prevent the air valve pressure differential is too large to open). Regardless of the outdoor air valve is open or closed, the aforementioned antifreeze controller .always work properly. <br> In addition, wind-electric water valve, humidifier and spray pump and fan should be electrical interlock. In winter, hot water valve should give priority to all units within the start and turn on the device. <br .> <br> <br> <br> <br>.