PowerPoint Presentation

							Chapter 18

Heat Pumps
                     Objectives
• After completing the material in this chapter, the
  student should be able to:
   – Explain the cooling and heating cycles of a heat pump
     system.
   – Trace refrigerant as it flows through a heat pump
     system in the heating and cooling modes.
   – Identify the state and condition of the refrigerant as it
     passes through the heat pump system.
   – Describe the operation of the four-way reversing
     valve.


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                    Objectives
• After completing the material in this chapter, the
  student should be able to:
   – Explain the difference between a direct-acting
     reversing valve and a pilot-operated reversing valve.
   – Explain the purpose of check valves in a heat pump
     system.
   – Explain the importance of the suction line
     accumulator.
   – Describe various types and classifications of heat
     pump systems.


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                    Objectives
• After completing the material in this chapter, the
  student should be able to:
   – Explain how temperature, pressure, and time are
     used to defrost heat pump systems.
   – Describe the operation of a geothermal heat pump
     system.
   – Explain the difference between open- and closed-loop
     geothermal systems.
   – Describe the various types of well configurations
     found on a geothermal system.
   – Troubleshoot heat pump systems.

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          Heat Pump Theory
• By adding additional components to the
  basic air conditioning system, we will be
  able to create a piece of equipment that
  performs both heating and cooling
  functions.




                                              5
            Heat Pump Theory
• Heat pump system operating in the cooling mode.




• Heat pump system operating in the heating mode.




                                                    6
               Heat Pump Theory
• Four-way reversing
  valve.
  (Photo by Bill Johnson)




                                  7
              Suction Line
              Accumulators
• Installed in the suction line leading back to
  the compressor.
• Prevents liquid refrigerant from entering
  the compressor.
• Allows liquid refrigerant to boil into a vapor
  before returning to the compressor.




                                              8
      Suction Line Accumulators
• Accumulators are located in the suction line
  between the compressor and the reversing
  valve.




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       Conditions that Allow
Refrigerant Back to the Compressor
•   Dirty or blocked evaporator coil
•   Dirty or blocked air filters
•   Defective evaporator fan motor
•   Defective or dirty evaporator blower or fan
•   Broken evaporator blower belt




                                             10
Bidirectional Filter Driers




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       Heat Pump Configurations
•   Air-to-air heat pumps
•   Air-to-liquid heat pumps
•   Liquid-to-air heat pumps
•   Liquid-to-liquid heat pumps




                                  12
        Heat Pump Configurations




Piping diagram showing the direction of refrigerant flow in the cooling
                              mode.
                       (Courtesy of Carrier)

                                                                    13
       Heat Pump Configurations
• Liquid-to-air piping
  diagram.
• Heating mode
  (Courtesy of ClimateMasters,
  Inc.)




                                  14
            Defrost Methods
• When operating in the heating mode, the
  outdoor coil (the evaporator) often freezes
  up.
• Ice can form on the outdoor coil when
  temperatures are as high as 50˚ F.
• Removing the ice must be accomplished
  with a defrost cycle.
  – Defrost is accomplished by placing the heat
    pump into a cooling mode for a short period of
    time.
                                               15
           Defrost Initiation
      and/or Termination Methods
•   Time
•   Temperature
•   Time and temperature
•   Pressure




                                   16
        Defrost Cycle Operation
• The reversing valve switches over to the cooling
  mode of operation.
• The outdoor fan motor is de-energized (most of
  the time).
• The air supplied to the occupied space is heated
  slightly to prevent cold air from entering the
  space during defrost.
• The cycle is long enough to ensure proper
  defrosting of the outdoor coil.
• The cycle is short enough so as not to have a
  large effect on the normal system operation.
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         Geothermal Heat Pump
                Theory
• When an adequate source of water is available, a
  geothermal heat-pump system may provide a viable
  alternative to air-or liquid-source heat pumps.
• The geothermal heat pump uses a liquid-to-liquid
  heat exchanger as the source of heat during the
  winter months and a heat sink during the warmer
  summer months.
• The main difference between the liquid-to-air heat
  pump and the geothermal system is that the
  temperature of the liquid flowing through the heat
  exchanger is maintained at a relatively constant
  temperature by the earth itself.
                                                 18
          SEER (Seasonal
       Energy Efficiency Ratio)
• It is calculated by dividing the Btu output of
  the system by the power input in watts.
• The higher the SEER rating, the higher the
  efficiency of the heat pump.




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        Geothermal Heat Pump
         System Configuration
• Open-loop:
  – Utilize wells to supply water to the heat
    exchanger
     • Water can be discharged to another well, the same
       well, or to a lake or pond.
• Closed-loop:
  – Utilize sealed loops
     • Loops can contain water or a mixture of water and
       antifreeze.


                                                     20
     Geothermal Heat Pump
      System Configuration




Closed-loop, water source heat pump in the heating mode.
         (Courtesy of Oklahoma State University)
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    Closed-Loop Configurations
• Vertical
• Horizontal
• Parallel




                                 22
     Closed-Loop Configurations
• Single-layer, horizontal ground loop.




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    Closed-Loop Configurations
• Two-layer, horizontal ground loop in the
  cooling mode.




                                             24
     Closed-Loop Configurations
• Vertical, parallel ground loop configuration
  in the cooling mode.




                                            25
    Closed-Loop Configurations
• Four-pipe, horizontal ground loop
  configuration.




                                      26
      Spiral Loop Configuration
• Spiral-type ground loop.




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                  Summary
• The four-way reversing valve permits the
  automatic changeover from heating to cooling
  and vice versa.
• Reversing valves can be either direct-acting or
  pilot-operated.
• The outdoor coil functions as the evaporator in
  the cooling mode and as the condenser in the
  heating mode.
• Heat pump systems can be either air-source or
  liquid-source systems.

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                  Summary
• Suction line accumulators reduce the chance of
  liquid refrigerant flooding back to the
  compressor.
• Air-source heat pumps utilize air as the heat
  source while operating in the heating mode.
• Liquid-source heat pumps utilize liquid as the
  heat source while operating in the heating mode.
• Heat pump defrost is accomplished by putting
  the system into the cooling mode temporarily
  and is controlled by a combination of time,
  temperature, and pressure.
                                               29
                  Summary
• Geothermal heat pump systems provide
  relatively constant performance year-round.
• Geothermal systems can be open-loop or
  closed-loop systems.
• Closed-loop systems can be configured in either
  series or parallel patterns.
• Open-loop systems often require the use of a
  well to provide water to the heat exchanger.



                                              30
                  Summary
• Geothermal wells have the supply and return
  water piped within the same well.
• Geothermal water circuit problems can be in the
  form of water leaks, air restrictions, defective
  water pumps and motors, or mineral deposits.
• A Pete’s port can be used to obtain pressure
  and temperature readings to aid in the
  troubleshooting process.
• Airflow problems can result in system conditions
  that resemble water flow problems.

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