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1 BASIC REFRIGERATION & CHARGING PROCEDURES

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2 REFRIGERANT PRESSURES, STATES & CONDITIONS SECTION ONE

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3 Load in from house Load out to ambient

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4 Heat flows from hot to cold.

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5 Evaporator Side Terms Evaporating Pressure Low Side Pressure Suction Pressure Back Pressure

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6 Condensing Pressure High side pressure Discharge pressure Head pressure Condenser Side Terms

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7 Compressor Pumps refrigerant vapor only! Divides low and high side.

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8 Discharge Line Connects the compressor to the condenser.

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9 Condenser Rejects heat from the refrigerant.

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10 Liquid Line Supplies liquid refrigerant from the condenser to the metering device.

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11 Metering Device Controls the flow of refrigerant. Divides low and high side.

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12 Evaporator Absorbs heat into the refrigerant. Removes moisture from the air

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13 Suction Line Returns superheated vapor from the evaporator to the compressor

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14 Receiver An accessory added in the liquid line to store refrigerant for different loads placed on the system.

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15CONDENSER Temperatures Pressures States

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16 High Pressure High Temperature Superheated Vapor Saturation Point (vapor changing to a liquid as heat is removed) Near Ambient Temperature High Pressure Subcooled Liquid CONDENSER INLET OUTLET

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17EVAPORATOR Temperatures Pressures States

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18 Evaporator inlet Low Pressure Low Temperature About 80% Liquid, 20% Vapor Saturated vapor (Temperature in which liquid is changing to a vapor) Low Pressure Low Temperature Superheated Vapor Evaporator Outlet

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19 SUBCOOLING & SUPERHEAT SECTION TWO

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20 The concepts of subcooling and superheating are the two most important principles that the service technician must understand before attempting to systematically troubleshoot hvac/r systems. Subcooling and Superheating

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21 R-22 210 psig = 105 F -100 F Subcooling 5 F Condenser Subcooling

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22 TOTAL SUBCOOLING 210 psig = 105 F -95 F Subcooling 10 F

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23Superheat Superheat is any heat added to completely saturated vapor that results in a rise in temperature (sensible heat change) of the gas.

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24 60 F 76 psig = 45 F 15 F superheat Evaporator Superheat

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25 Total or System Superheat Suction line Temperature 60F 76 psig = 45F 76 psig = 45F Superheat 15F

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26 METERING DEVICES SECTION THREE

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27 Capillary Tube Thermostatic Expansion Valve Automatic Expansion Valve Fixed Bore Piston

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28 Capillary Tubes Low Cost device Have no moving parts Can be used on a wide range of applications

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29 Thermostatic Expansion Valve Most efficient Maintains a constant evaporator superheat Helps prevent compressor flooding

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30 TXV Types Pressure Limiting Balance Port Externally equalized Internally Equalized Electric operated

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31 TXV Bulb Placement

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32 TXV External Equalizer Tap Location

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33 Automatic Expansion Valves Maintain a constant evaporator pressure Used on small systems which have constant loads

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34 Fixed-Bore Metering Devices Most common today on Residential systems Dual purpose device Works as metering a device Works as a check valve Critical charge

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35 System CHARGE SECTION FOUR

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36 Is The Refrigerant Charge Correct? All refrigeration systems differ in the amount of charge they hold. There are guidelines, charts, and techniques to follow. System design & layout must be known

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37 How long & what size is the line set? Whats the volume of the filter drier?

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38 TXV CHARGING RULES 1. Charge system under a high load 2. Charge as a liquid when possible 3. Throttle liquid blends into low side 4. Record evaporator & compressor superheat & Condenser subcooling

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39 Capillary Tube or Fixed Orifice #1 Weigh in the correct charge #3 Use system superheat method AIRCONDITIONING SYSTEMS #2 Manufacture's charging charts

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40 Requirements for system superheat charging Proper evaporator air flow Accurate remote bulb temperature tester Accurate gauge manifold set

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41 What should the Superheat be?

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42 System Superheat Suction line Temperature 60 F 76 psig = 45 F 76 psig = 45 F Superheat 15 F

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43 AIR FLOW Can be measured in many ways 1. Equipment data charts 2. Air flow meters 3. Combination of meter readings and formulas

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44 Sensible Heat Formula CFM = Sensible heat BTUs 1.08 X temperature difference

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45 Sensible Heat Formula Electric Heat Heater amps X volts X 3.41BTUs = CFM = Sensible heat BTUs 1.08 X temperature difference

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46 Sensible Heat Formula 3 Phase Electric Heat Heater amps X volts X 3.41 X 1.73BTUs = CFM = Sensible heat BTUs 1.08 X temperature difference

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47 Sensible Heat Formula Fossil Fuel Heat CFM = Sensible heat BTUs 1.08 X temperature difference BTUs = Heater input X Efficiency or Bonnet capacity

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48 Measuring Duct Velocity CFM = Velocity X Area in square feet

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49 SAMPLE QUESTIONS

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50 The high and low pressures in a refrigeration system are separated by: a. The compressor. b. The evaporator. c. The metering device. d. The filter drier. The metering device.

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51 Subcooling can be defined as: a.The cooling effect of an evaporator. b.Any sensible heat removed from 100% saturated liquid. c.The superheat that is removed at the top of the condenser. d.The cooling of the compressor motor by returning refrigerants. Any sensible heat removed from 100% saturated liquid.

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52 Always charge a TXV with a receiver and sightglass under a: a.No load condition. b.Low load condition. c.High load condition. d.None of the above. High load condition.

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53 Superheat is defined as: a.The heat added the the saturated liquid. b.Heat removed from the saturated liquid in the condenser. c.The heat added to the saturated vapor exiting the evaporator. d.The heat removed from the saturated vapor exiting the evaporator. The heat added to the saturated vapor exiting the evaporator.