Modern Refrigeration and

1
Modern Refrigeration and Air Conditioning
Althouse Turnquist Bracciano
PowerPoint Presentation by Associated
Technical Authors
PublisherThe Goodheart-Willcox Company,
Inc.Tinley Park, Illinois
2
Chapter 22
Cooling and Dehumidifying Systems
3
Learning Objectives

• Explain the principles of air conditioning.
• Classify types of comfort cooling systems and
  recognize variations between them.
• Properly install and service window air
  conditioners.
• Properly install and service console air
  conditioners.
• Follow approved safety procedures.

4
Principles ofAtmosphere Cooling
22.1

• Comfort depends on temperature and relative
  humidity.
• Certain industrial operations depend on
  temperature and relative humidity. Examples
  include
• Manufacturing of medicines and biological
  products.
• Operations dealing with hygroscopic
  (water-absorbing) materials.

5
Principles ofAtmosphere Cooling continued
22.1

• The operation of a typical cooling unit return
  air is mixed with some fresh air, the air mixture
  is filtered and cooled, moisture is removed, and
  air is redistributed.

6
Principles ofAtmosphere Cooling continued
22.1

• Cool air leaving the evaporator is at 100
  relative humidity.
• Saturated air warms up somewhat while mixing with
  air in the conditioned space. This brings the
  relative humidity down to a comfortable level.

7
Principles ofAtmosphere Cooling continued
22.1

• This system controls relative humidity by
  bypassing some of the return air into the air
  conditioner outlet. This warms up the cooled air
  prior to it leaving the duct system.

8
Cooling Cycle
22.1.1

• In a cooling cycle, the dry bulb temperature of
  air is lowered. When this occurs, relative
  humidity increases. Note A to B. Some moisture
  should be removed to make the air comfortable.

9
Cooling Cycle continued
22.1.1

• The first method is to dehydrate the air with
  chemicals. The second method is to cool the air
  down and remove moisture by condensing it on a
  cool surface. Note the drop in vapor pressure or
  grains of moisture removed. Note the curve C to D.

10
Cooling Cycle continued
22.1.1

• Reheating along a horizontal line (D to E)
  decreases humidity. Air leaving at D is mixed
  with room air, which is between 81ºF and 100ºF
  (27ºC and 38ºC). The mixture meets on a line
  between point D and point A. If a third of air,
  by weight, is passed through the evaporator, the
  mixed air temperatures will be a third of the way
  from A to D (point F).

11
Evaporative Cooling
22.1.2

• Desirable and practical in dry climates.
• If air at 105ºF (41ºC) and 20 relative humidity
  is moved rapidly over water at the same
  temperature, some water will evaporate. The
  remaining water can cool as low as 55ºF (13ºC),
  but normally cools to about 65ºF to 70ºF (18ºC to
  21ºC).
• Other air forced around the water container can
  be distributed into the space to be cooled.
• Cool air leaving the unit is approximately
  75ºFto 80ºF (24ºC to 27ºC) at about 40 relative
  humidity.

12
Evaporative Cooling
22.1.2
13
Comfort Cooling Systems
22.2

• Several types are in use.
• Classified by the arrangement of the mechanism
• Self-contained coolers.
• Window units.
• Package terminal units.
• Console units.
• Multizone ductless split systems.
• Remote (controlled from a distance).
• Condensing unit is remote.
• Central air conditioning plant.

14
Self-Contained Comfort Coolers
22.3

• All self-contained comfort conditioners provide
  cooling during the hot season.
• Some provide heating during the cold season.
• Contain a complete refrigeration system,
  including
• Condensing unit.
• Refrigerant controls.
• Evaporator.
• Filters.
• Individual room thermostats provide control.

15
Self-Contained Comfort Coolers continued
22.3

• Window units are air-cooled and operate from 120V
  or 240V single-phase circuits. Capacities vary
  from 4000 Btu/hr. to 40,000 Btu/hr.
• Console units may be air- or water-cooled. May be
  installed in the room to be conditioned or an
  adjacent room. If in an adjacent room, short
  ducts deliver and return air.

16
Window Units
22.3.1

• Inexpensive and simple method for providing
  comfort cooling to a portion of a building or
  residence.
• Mount on the windowsill. Installation is
  relatively easy.
• The condenser is located in the section of the
  cabinet that is outside the building.
• Operation
• Outside air is forced over the condenser by a
  fan.
• Inside the room, another fan draws air in through
  a filter and forces it over the evaporator.
• The two airflow fans may be driven by the same
  motor or each may have its own motor.

17
Window Units
22.3.1
18
Window Units continued
22.3.1

• Available in three types
• Only cools and filters air has a fresh air
  intake.
• With an electrical resistance heating unit to
  furnish heat as well as cool.
• Using a reverse cycle system (heat pump). This
  type operates for both comfort cooling and
  heating.

19
Window Units continued
22.3.1
Schematic of window or in the wall comfort
cooling unit.
20
Window Units continued
22.3.1

• Evaporator condensate may be drained through a
  tube to the outside of the building or to the
  base of the condensing unit to assist in cooling
  the compressor and condenser.
• A capillary tube or bypass AEV refrigerant
  control is typically used.
• Some units move the cooled airflow from side to
  side as the unit runs by using deflector plates,
  which are turned by an air-operated rotor in the
  exhaust air.

21
Window Units
22.3.1
22
Window Units continued
22.3.1

• Window units contain a built-in thermostat to
  operate the unit. The thermostat sensing bulb is
  usually mounted at the inlet of the evaporator. A
  differential of about 5ºF (3ºC) normal.
• It is best to insulate the part of the bulb
  farthest from the evaporator so it responds
  accurately to evaporator temperatures. It will
  cool sooner and stop prior to overcooling or
  evaporator ice up. On ice up, the unit will not
  start until the ice melts.

23
Window Units continued
22.3.1

• Some units have a hand-held infrared controller
  with which the user can program the clock,
  operating mode, fan speed, temperature control,
  and start/stop times.

24
Window Units continued
22.3.1

• Caution As with all capillary tube refrigerant
  systems, if the unit is shut off and immediately
  turned on, it may stall. The compressor high-side
  pressure will not have equalized with the
  low-side pressure. Allow time for the system to
  equalize after shutdown to prevent compressor
  damage.

25
Installing Window Units
22.3.1

• Must be installed with the outside tilted down
  for condensate drain.
• Must be securely fastened in place to prevent the
  unit from falling out of the window.
• All edges should be sealed to minimize air
  infiltration.
• The window must be secured in the proper
  position.
• Installed into the opening using metal plates,
  rubber gaskets, and sealing compounds.

26
Installing Window Units continued
22.3.1

• The parts needed to install the unit safely and
  seal the opening.

27
Installing Window Units continued
22.3.1

• A leveling and security bracket are mounted to
  the windowsill.

28
Installing Window Units continued
22.3.1

• Another method of bracing and leveling the
  comfort cooling unit.

29
Installing Window Units continued
22.3.1

• The unit housing should be adjusted to tilt
  downward about 1/4" on the outside for condensate
  drainage.
• A sponge rubber or plastic strip is usually
  placed between the housing and windowsill for a
  leak-proof joint. The sill bracket and unit
  housing are then installed.

30
Installing Window Units continued
22.3.1

• Rubber seal strips and filler boards are put in
  place.

31
Installing Window Units continued
22.3.1

• Filler boards are held in place with sheet metal
  screws and spring clips.

32
Installing Window Units continued
22.3.1

• Where the lower sash is raised, an air gap will
  exist between the two sashes. Seal the opening
  with a sponge rubber or foam strip. Notches can
  help the strip fit.

33
Installing Window Units continued
22.3.1

• A typical window unit installation in a casement
  window.

34
Installing Window Units continued
22.3.1

• The inside mechanism is heavy. Move it using a
  dolly or special carrier. Avoid moving or lifting
  the unit using tubing or coils as handgrips.
  Carry the unit by holding onto the bottom pan.
• Avoid forcing the unit into the casing. While
  placing the unit, check that refrigerant lines
  and wiring are free and clear.
• Check all joints for tightness. Caulk seams where
  light shows through.
• Use a separate circuit for electrical hookup. A
  polarized plug with ground wire is required.

35
Installing Window Units continued
22.3.1

• Thermostats are used with most window units. They
  are adjustable to cut out between 56ºF and 60ºF
  (13ºC and 16ºC). The cut-in adjustment is between
  77ºF and 80ºF (25ºC and 27ºC). Differentials vary
  between 3ºF and 8º F (2ºC and 4º C).
• If thermostat fails, the unit will not start. To
  test the thermostat, cover the air outlet and
  inlet with cloth. Air will now recirculate into
  the unit. The temperature will quickly drop to
  the cutout temperature. Use a thermometer to
  determine the temperature.

36
Installing Window Units continued
22.3.1

• Units that mount through a wall are popular in
  apartments because there is no interference with
  windows.

37
Servicing Window Units
22.3.1

• Similar to servicing hermetic refrigerating
  units.
• External service operations
• Place a tarp or newspapers on the floor.
• Remove or tie back curtains.
• Use a vacuum cleaner with a brush nozzle to clean
  the inside of the cabinet.

38
Servicing Window Units continued
22.3.1

• Semiannual cleaning or replacement of filter.

39
Servicing Window Units continued
22.3.1

• Clean the unit annually. Inspect and lubricate
  the fan motor (hermetic bearings require no
  additional lubrication).

40
Servicing Window Units continued
22.3.1

• Finned evaporators and condensers are difficult
  to clean. Never use metal blades for cleaning.
• Service the unit outdoors, if possible. If fins
  are bent, they should be straightened.
• Check that fans are tight and balanced on their
  shaft.
• Inspect and clean the drain.
• Check bolts, nuts, and screws for tightness.
• Run the unit and check for noise before putting
  it in the cabinet.
• Place a cloth over the air conditioner outlet
  when first starting the unit after cleaning.

41
Servicing Window Units continued
22.3.1

• Wiring of a window unit.

42
Servicing Window Units continued
22.3.1

• Wiring is similar to domestic and commercial
  units except
• Fan motors usually have two or three speeds.
• Some systems have three capacitors starting,
  running, and fan motor.
• Prior to doing internal service, test for power.
  Check the thermostat, relay, capacitors, and
  electrical and temperature overload protectors.

43
Servicing Window Units continued
22.3.1

• A unit with starting and running capacitors.

44
Servicing Window Units continued
22.3.1

• Location of the fan control switch, thermostat,
  capacitors, and wiring.

45
Servicing Window Units continued
22.3.1

• This is a wiring diagram for a three-speed fan
  motor system with a 21,000 Btu/hr (6.15 kW)
  capacity using a 240V circuit.

46
Troubleshooting Window Units
22.3.1

• Potential internal problems
• Lack of refrigerant.
• Stuck compressor.
• Inefficient compressor.
• Clogged refrigerant circuit.
• Short circuit, open circuit, or grounded motor
  windings.

47
Troubleshooting Window Units continued
22.3.1

• Check the motor condition using a continuity
  light or ohmmeter.
• Check for lack of refrigerant or clogged
  refrigerant lines. Installation of service valves
  may be necessary. Then, install a gauge manifold.

48
Troubleshooting Window Units
22.3.1
49
Troubleshooting Window Units continued
22.3.1

• Move the unit to the shop if the compressor needs
  repair or replace the compressor on-site.
• If the unit lacks refrigerant, locate and repair
  the leak prior to recharging.
• Many window air conditioners use permanent split
  capacitor (PSC) compressor motors, which do not
  use a relay for starting. If the supplied voltage
  is low (by 10 or more), they will start with
  difficulty. Installation of a correctly sized
  capacitor and relay may solve the problem.

50
Troubleshooting Window Units continued
22.3.1

• Follow manufacturers recommendation for sizing
  of capacitors or use this chart.

51
Troubleshooting Window Units continued
22.3.1

• This is a hard start capacitor designed to be
  used with permanent split capacitor motors.

52
Troubleshooting Window Units continued
22.3.1

• If the unit drips water into the room, check the
  slope of the unit. Level the unit on its other
  dimensions. Make certain the drain hole is open.
  Recheck the installation for an airtight seal.
• If the unit is not removed for winter, it may be
  winterized
• Block the air inlet and outlet grilles with
  cardboard or flexible plastic sheeting.
• A storm sash may be custom built to fit around
  the unit. Plywood held in place with caulking or
  rubber grommets may be used.
• Replacement capillary tubes for window unitsmust
  be accurately selected by size.

53
Troubleshooting Window Units
22.3.1
54
Packaged TerminalAir Conditioners
22.3.2

• This is a combined heating and cooling system
  designed to service an individual room or zone.

55
Packaged TerminalAir Conditioners continued
22.3.2

• This packaged terminal air conditioner is a
  heating and cooling system.

56
Packaged TerminalAir Conditioners continued
22.3.2

• Heating is provided by a gas-fired heat
  exchanger.
• Units normally operated with natural or LP gas.
• The refrigeration system has a hermetically
  sealedrotary compressor.
• Airflow system includes an airflow and combustion
  fanfor evaporator and condensing units.
• Basic controls include heating and cooling
  thermostat.
• System uses capillary tube metering device.
• Normally operated with R-22 or R-134a.
• For servicing, the entire unit slides out of the
  wall cabinet.

57
Multizone Ductless Split System
22.3.3

• Popular for new and retrofit offices, motels, and
  homes without ducts.
• Basic components of system include
• Single outdoor condenser.
• Three independent evaporators.
• Individual evaporator temperature control.
• Condensing unit located outside on a slab.

58
Multizone Ductless Split System
22.3.3
59
Multizone Ductless Split System
22.3.3

• Primary advantages
• Single condensing unit and three independent
  evaporators, which potentially provide three
  different temperatures for three different
  spaces.
• Most equipped with remote wireless temperature
  control.
• Wall or ceiling installation.

60
Console Air Conditioners
22.3.4

• Entire system is mounted in a cabinet.
• Vary in capacity from 2 hp to 10 hp.
• Often used in small commercial establishments.
• Either water- or air-cooled condensing units.
• Air-cooled models are used in areas with water
  restrictions.

61
Console Air Conditioners continued
22.3.4

• Operation of water-cooled unit
• Return air enters the lower grille.
• Cooled air discharged at the upper grilles.
• Ducts are connected to portions or all of the
  upper sections.
• The condensing unit is mounted in the bottom of
  the console.
• Air blowers are in the middle.
• The evaporator is in the top of the cabinet.

62
Console Air Conditioners continued
22.3.4

• Console units have adjustable fresh air intakes
  and evaporator bypass controls. All must have
  drains to remove condensate flowing from the
  evaporator.

63
Console Air Conditioners continued
22.3.4

• Most console models contain a complete
  refrigerating system, filtering system, and
  evaporator.

64
Console Air Conditioners continued
22.3.4

• Water-cooled units require plumbing connections
  to a water supply and drain.
• The drain also receives moisture condensed out of
  the air by the evaporator in summer.
• Such units do not usually provide heating.

65
Installing Console Air Conditioners
22.3.4

• Console units are factory-assembled.
• Move the unit into place, level it, and make
  plumbing and electrical connections per local
  code.
• Console units typically use a hermetic
  compressor.
• Refrigerant control is usually from a
  thermostatic expansion valve.
• Thoroughly check the unit including air
  temperature (inlet and outlet), electrical load,
  and opening pressures. Record the data for future
  reference.

66
Servicing ConsoleAir Conditioners
22.3.4

• Panels must be removed to work on internal
  components.
• Periodic maintenance should include
• Replacing or cleaning the filter.
• Cleaning the evaporator and fins.
• Cleaning and oiling the fan motor (sealed
  bearings do not need additional oil).
• Cleaning the drain pan and drain tube.
• Cleaning the inner lining of the cabinet by
  vacuuming.
• Checking the refrigerant charge, operation of
  thermostatic expansion valve, and water flow.

67
Servicing ConsoleAir Conditioners continued
22.3.4

• Check the following weekly
• V-belts.
• Fan speeds.
• Pump speeds.
• All standby units.
• Water leaks.
• Controls (pressure, temperature, and airflow).
• Lubrication.
• Canvas connectors on ducts.
• Cooling tower.
• Water treatments.

68
Servicing ConsoleAir Conditioners continued
22.3.4

• Check the following monthly
• Refrigerating system (charge, purge, test for
  leaks, check strainers and driers).
• Filters.
• Humidifier.
• Safety valves.
• Cooling tower pump.
• Duct dampers, registers, and diffusers.
• Piping (insulation, vibration, and wear).

69
Servicing ConsoleAir Conditioners continued
22.3.4

• Every six months
• Clean fans and casings.
• Clean duct registers and diffusers.
• Every year
• Check the efficiency of compressors.
• Check the efficiency of pumps.
• Check damper operation.
• Clean water circuits.
• Operate all hand valves.
• Every two years
• Inspect the condenser wet surfaces.

70
Remote Comfort Systems
22.4

• Refrigerating equipment is located away from the
  conditioned space.
• Units vary in capacity.
• Some units do not use long refrigerant piping
  runs.

71
Remote Comfort Systems continued
22.4

• This is a water-cooled system.
• The system has
• Service valves.
• Tube-within-a-tube condenser.
• Water valve.

72
Remote Comfort Systems continued
22.4

• Chilled water lines run to evaporator units in
  each room to be air-conditioned.
• Each room unit has thermostat.
• A solenoid valve usually controls flow to each
  unit. The valve is connected to the room
  temperature control and controls both a fan and
  solenoid coolant valve in the room unit.
• Chilled water flows to the room unit when the fan
  starts and stops flowing when the fan stops.
• Air filters may be installed in the unit.

73
Dehumidifying Equipment
22.5

• Removes moisture from the air.
• Blows air over a cold coil.
• When the coils surface temperature is below the
  dew point of the air, moisture will condense out
  of the air.
• Coil surface temperature must be kept above
  freezing. Frost or ice will block airflow.
• Useful in basements and other damp places.

74
Dehumidifying Equipment continued
22.5

• A dehumidifier is usually a small hermetic
  refrigerating system. It has a condenser and
  evaporator in a cabinet.

75
Dehumidifying Equipment continued
22.5

• Older systems use R-12 or R-500. Newer units use
  R-134a.
• Operation
• Air is drawn over the evaporator.
• As air touches the cold evaporator surface, it
  cools below its dew point.
• Water condenses out of the air and collects on
  the evaporator.
• Cooled air is moved over condenser where it is
  heated to a reasonable relative humidity.

76
Dehumidifying Equipment continued
22.5

• Units usually have a humidistat that senses
  moisture in air.

77
Dehumidifying Equipment continued
22.5

• Condensate is collected in a container or leaves
  via a drain tube.
• In some installations, chemicals are used to
  absorb moisture from air.
• Chemicals are usually cycled so moisture from air
  is first absorbed into chemical.
• The chemical is then heated and moisture is
  driven from the chemical.
• The moisture is then exhausted.

78
Questions

• Human comfort is dependent on ______________ and
  ________________.

temperature
relative humidity

• Evaporative cooling is more practical in ________
  climates.

dry

• ______ relative humidity is common for areas
  that use evaporative cooling systems.

20
79
Questions continued

• What are three types of window air conditioning
  units?

1. Only cools and filters air. 2. With an
electrical resistance heating unit to furnish
heat. 3. A reverse cycle system (heat pump) for
both comfort cooling and heating.

• What will happen to a capillary tube refrigerant
  control type system if the unit is shut off and
  immediately turned back on?

The unit will stall and not work.
80
Questions continued

• Thermostats that are used with window air
  conditioning units are adjustable their cut-out
  range is between _____________ and ____________.

56ºF (13ºC)
60ºF (16ºC)

• Thermostats that are used with window air
  conditioning units have a cut-in range between
  ___________ and ______________.

77ºF (25ºC)
80ºF (27ºC)

• A window air conditioner has a differential that
  varies between _____________ and ____________.

8ºF (4ºC)
3ºF (2ºC)
81
Questions continued

• Give two symptoms of faulty thermostat on a
  window air conditioning system.

The system operates continuously and the system
never starts.

• Cleaning of the evaporator, condenser, fan
  blades, fans motor, motor compressor, and casing
  should be done __________ on window air
  conditioning systems.

annually

• Many window air conditioners use
  ____________________ motors for both fans
  and compressor.

permanent split capacitor
82
Questions continued

• Console air conditioning systems are either
  ___________ or ________ cooled.

water-
air-

• Console air conditioning systems usually use a
  ________ type metering device for refrigerant
  control.

TXV

• Name three type of refrigerants that are used in
  dehumidifiers.

R-12, R-500, and R-134a.
83
Questions continued

• A humidistat used on a dehumidifier ___________
  on a rise in humidity.

closes
84
Safety
22.6

• Many window units are installed in upper floors.
• With double-hung windows, the upper sash is
  lowered to air conditioner keeping it in place.
  If the upper sash is accidentally opened, the air
  conditioner may fall. Therefore, it should be
  securely attached to the windowsill and braced.
• When removing mechanisms, be careful not to drop
  them.
• Safety shoes are recommended.

85
Safety continued
22.6

• Carefully follow the instructions supplied by the
  manufacturer.
• Remote systems should be sturdily mounted.
  Protect suction lines and liquid lines from
  abuse.
• Review instructions prior to performing any
  service or installation work on larger units.
• Window air conditioners are usually available in
  either 120V or 240V circuits. It is best to use a
  240V circuit (particularly with higher Btu
  ratings) because the voltage drop between the
  power panel and the unit will be less with a 240V
  motor.

86
Safety continued
22.6

• A separate air conditioner circuit should be
  provided. Be sure all systems are properly
  grounded.
• When adding refrigerant to system, be certain it
  matches the refrigerant already in the unit.
• Always wear goggles when testing for leaks and
  adding refrigerant.
• Sheet metal may have very sharp edges. Be careful
  not to cut hands or fingers.

87
Glossary

• dehumidifying equipment
• Devices used to remove moisture from the air.
• evaporative cooling
• A cooling method practical in hot, dry climates
  in which hot air is blown over hot water.
• humidistat
• Electrical control that is operated by changing
  humidity.
• packaged terminal air conditioners
• A combination heating and cooling unit designed
  for a single room or zone.