Assessments - 2, GPA: 5
(
)
)
|
por este dispositivo também tem outras instruções :
Facilidade de uso
R410a Overview R410a is a non-chlorine based (HFC) refrigerant, that with R407c and R134a, is seen as the future of all refrigerants used worldwide. R410a characteristics compared to R22 are: • Binary and near azeotropic mixture of R32-50% and R125-50% • Higher effi ciencies • Higher operating pressures • Requires POE oil in compressors • In some systems can result in smaller heat exchangers with the same performance • Low global warming potential and zero ozone depletion (0.39/0.0) • Temperature glide of 0.2°F • Containers are “ROSE” colored R407c Overview R407a is a non-chlorine based (HFC) refrigerant. R407c characteristics compared to R22 are: • Ternary and near azeotropic mixture of R32-23%, R125-25%, R134a-52% • Slightly lower effi ciencies • Nearly equal operating pressures • Requires POE oil in compressors • Considered a near drop-in replacement for R22 • Low global warming potential and zero ozone depletion (0.34/0.0) • Temperature glide of 10°F • Containers are “MEDIUM BROWN” colored What is “Glide”? Pure compounds like CFC-R12 boil and condense at exactly the same temperature for a given pressure. Nearazeotropic blends are not pure compounds but a blend of compounds. These compounds will have a temperature glide or range of temperatures in which the blend will boil or condense. In these situations, for example R407c, a chart listing a bubble and dew point must be used as the pressure/temperature chart since it has a glide of 10°F. The bubble point is used for subcooling calculations. The dew point is used for superheat calculations. See Table 1. R410a has a very small glide (0.2°F) and acts as a single component refrigerant. Therefore R410a can utilize a more traditional table with only one pressure column as shown in Table 2. What is “Fractionation”? Many of the newer refrigerants are a blend of two or more other refrigerants. At various conditions these components can separate and change the ratio of the original mixture and in effect change the total performance of the remaining blend. Therefore it is recommended to use the refrigerant in liquid form, insuring that all of the components are handled together in the proper blend. R407c Temperature Bubble Dew Pressure Pressure (for subcooling) for (superheat) °F psig psig -15 17.2 9.2 -10 21.0 12.3 -5 25.1 15.7 0 29.5 19.4 5 34.4 23.4 10 39.6 27.8 15 45.2 32.6 20 51.3 37.8 25 57.8 43.4 30 64.8 49.4 35 72.4 56.0 40 80.4 63.0 45 89.0 70.6 50 98.1 78.7 55 107.9 87.4 60 118.2 96.7 65 129.2 106.6 70 140.9 117.1 75 153.2 128.4 80 166.2 140.4 85 180.0 153.1 90 194.6 166.5 95 209.9 180.8 100 226.0 195.9 105 243.0 211.9 110 260.8 228.7 115 279.5 246.5 120 299.0 265.3 125 319.6 285.0 130 341.0 305.8 135 363.4 327.6 140 386.9 350.5 145 411.3 374.6 150 436.8 399.8 Page 3 R410a Application and Service Guide Component Considerations for R410a Compressor Wall thickness has increased with the increase of operating pressures of R410a. The internal pressure relief valve setting has been increased from 375-450 psig for R22 to 550-625 psig for R410a. Although the discharge pressure is higher in R410a the discharge temperature should be lower due its higher vapor heat capacity. Desuperheating hot water generators must be designed around this lower hot gas temperatures as well. High pressure switches will now open at 600 psig ±10 psig and reset at 450 ±10 psig. The compressor oil must be polyolester (POE) based. Mineral oils should never be used. POE oils absorb moisture VERY easily. For this reason any compressor using POE oil should only be exposed to ambient air for short periods of time during manufacture or service. See the service section of this manual for more information. Condenser/Evaporator Heat Exchangers The heat exchangers must be designed to have a working pressure above the 600 psig level. In some cases this can mean a thicker wall. Filter Driers Liquid fi lter driers must have working pressure of no less than 600 psig and be approved for use with R410a. A 100% molecular sieve with no activated Alumina is recommended for maximum moisture removal. It is always required to install a new fi lter drier whenever the system is opened. Suction line fi lter driers should only be used after a burn out and should be removed after an appropriate clean-up time. Thermostatic Expansion Valves R410a metering devices are about 15% smaller than R22 devices. The selective charge used in the bulb must be matched for R410a operation, therefore a TXV must be designed for R410A use. METERING DEVICES for R22 and R410a are NOT INTERCHANGEABLE. Refrigerant Tubing There are no general changes to the tubing other than the working pressure increase to 600 psig. Generally the lower refrigerant fl ow rate of R410a versus R22 does not result in any pipe diameter changes. Polyolester Oils POE oils are VERY hygroscopic. They readily absorb moisture and hold it. For this reason POE oils should be limited in their exposure to ambient air during manufacture or service. The lubricant shou...