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same fashion as crankcase pressure regulators sincethey are responsive to outlet pressure, modulate fromfully open to fully closed, and open in response to adecrease in downstream pressure. The constructionmust be suitable to withstand the high temperaturedischarge gas from the compressor.Hot gas valves are set to maintain a desired minimumpressure by spring tension, and may be either director pilot operated. They are normally equipped with anexternal equalizer connection, which operates in thesame fashion as an external equalizer on an expansionvalve to compensate for pressure drops in the lines. Theexternal equalizer should be attached to the suction lineat the point where it is desired to control the suctionpressure.REVERSING VALVESIn recent years, usage of the “heat pump” principle toenable an air conditioning unit to supply both cooling andheating has become increasingly popular. Basically thisinvolves switching the functions of the evaporator andcondenser by a change in refrigerant flow as desired, sothat the indoor coil becomes the evaporator for coolingpurposes, and the condenser for heating usage. Theoutdoor coil in turn is a condenser during the coolingcycle, and an evaporator during the heating cycle.To conveniently reverse the system operation, four-wayreversing valves have been developed. By means ofa slide action actuated by a solenoid, the connectionsfrom the compressor suction and discharge ports to theevaporator and condenser can be reversed at will.Three-way valves are being increasingly used for hotgas defrosting. This valve enables the flow of hot gasfrom the compressor discharge valve to be shunted fromthe condenser to the evaporator for defrosting purposes,and then conveniently returned to the condenser whennormal cooling is resumed.CHECK VALVESIt is often desirable to prevent refrigerant from reversingits direction of flow during an off cycle, or during achange in the operating cycle. A simple spring loadedvalve such as shown in Figure 34 allows flow in onedirection only, and closes if pressures are such thatreverse flow could occur. Check valves may be usedin either liquid or gas lines, and are frequently used toprevent backflow of liquid refrigerant or hot gas in lowambient condenser controls, and in reverse cycle heatpumps. Check valves used in refrigeration systemsshould be spring loaded to prevent noise and chattering© 1967 Emerson Climate Technologies, Inc.All rights reserved.7-10
which may be caused by pulsations in refrigerant floworiginating in the compressor.MANUAL SHUT-OFF VALVESManual shut-off valves are often used so that portionsof the refrigeration system can be isolated for service orrepairs. Special valves designed for refrigeration usageare required to avoid leakage.COMPRESSOR SERVICE VALVESCompressor suction and discharge service valves areshut-off valves with a manual operated stem. Mostservice valves are equipped with a gauge port so thatthe refrigerant operating pressure may be observed.When the valve is back-seated (the stem turned all theway out) the gauge port is closed and the valve is open.If the valve is front-seated (the stem turned all the wayin) the gauge port is open to the compressor and theline connection is closed. In order to read the pressurewhile the compressor is in operation, the valve shouldbe back-seated, and then turned in one or two turnsin order to slightly open the connection to the gaugeport. The compressor is always open to either the lineor the gauge port, or both if the valve is neither frontnor back-seated.SCHRADER TYPE VALVEThe Schrader type valve is a recent developmentfor convenient checking of system pressures whereit is not economical, convenient, or possible to usethe compressor service valves with gauge ports. TheSchrader type valve is similar in appearance andprinciple to the air valve used on automobile or bicycletires, and must have a cap for the fitting to insure leakproofoperation.7-11© 1967 Emerson Climate Technologies, Inc.All rights reserved.
Page 3 and 4: Part IIREFRIGERATION SYSTEM COMPONE
Page 5 and 6: Section 4COMPRESSORSThe compressor
Page 7 and 8: CROSS-SECTIONAL VIEW OF COPELAMETIC
Page 9 and 10: When the piston starts down on the
Page 11 and 12: COMPRESSORS WITH UNLOADERSIn order
Page 13 and 14: flow by means of louvers is also an
Page 15 and 16: Figure No.20 shows parallel circuit
Page 17 and 18: and the total pressure existing in
Page 19 and 20: if the evaporator temperature is to
Page 21 and 22: In modern refrigeration practice, a
Page 23 and 24: CAPILLARY TUBE SELECTION R-22HIGH T
Page 25 and 26: CAPILLARY TUBE SELECTION R-12MEDIUM
Page 27 and 28: CAPILLARY TUBE SELECTION R-502LOW T
Page 29: multiple evaporators are used. On l
Page 33 and 34: WATER REGULATING VALVESOn water coo
Page 35 and 36: CONDENSER FAN CYCLING CONTROLIn ord
Page 37 and 38: 1. The continuous VA (volt-amperes)
Page 39 and 40: A. Continuous VA requirement2 Conta
Page 41 and 42: The desired pulley size or the resu
Page 43 and 44: un winding is wound with relatively
Page 45 and 46: TWO PHASE MOTORSTwo phase power is
Page 47 and 48: 1 = 1 + 1MFD total MFD1 MFD2For exa
Page 49 and 50: voltage torque, and star-delta star
Page 51 and 52: 10-6© 1967 Emerson Climate Technol
Page 53 and 54: Regular Copeland® brand motor prot
Page 55 and 56: contact prematurely due to shock or
Page 57 and 58: The effect of an open phase in the
Page 59 and 60: vulnerable to liquid damage such as
Page 61 and 62: REFRIGERATION GAUGESPressure gauges
Page 63 and 64: © 1967 Emerson Climate Technologie

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