1. Heating, Ventilating, A ir-C onditioning
&
Refrigeration Technology

2. SECTION 5
COMMERCIAL REFRIGERATION
UNIT 26
APPLICATION OF
REFRIGERATION SYSTEMS

3. UNIT OBJECTIVES
After studying this unit, the reader should
be able to
• Describe the different types of display equipment
• Discuss heat reclaim
• Describe package versus remote condensing unit applications
• Describe mullion heat
• Discuss walk-in refrigeration applications
• Describe basic vending machine operation
• Describe basic refrigerated air-dry unit operation

4. REACH-IN REFRIGERATION
MERCHANDISING
• Available in high-, medium-, and low-
temperature ranges
• Open cases – Less efficient but are
more appealing to the customer
• Closes cases – More efficient but are
less appealing to the customer

5. Reach-in refrigerators
with doors
Open display case

6. SELF-CONTAINED REACH-IN
FIXTURES
• Heat is rejected back into the store (good in the
winter, bad in the summer)
• Equipment can be moved around easily
• Since each unit is separate, if one system breaks
down the others are not affected
• Condenser cleaning and condensate removal need
to be addressed
• Condensate can be used to help cool the
compressor

7. Self-contained boxes have their own
condensing unit

8. INDIVIDUAL CONDENSING
UNITS
• Only one system is affected when a breakdown
occurs
• Condensing units can be located outside or in an
equipment room
• Air temperature in the equipment room can be
controlled with dampers
• Rejected heat can be reused to heat the store
in the winter

9. MULTIPLE EVAPORATORS AND SINGLE-
COMPRESSOR APPLICATIONS
(ADVANTAGES)
• Compressor motors are more efficient
• System heat can be captured for use in
heating the store (heat reclaim)
• First-stage heat controls the three-way
heat reclaim valve
• Parallel and series heat reclaim systems

10. Multiple
evaporators
connected to a
single
compressor

11. Rooftop air cooled condenser
Duct mounted coil
Receiver
3-way heat reclaim
valve
Liquid line Compressor

12. Rooftop air cooled condenser
Receiver Heat
exchanger
Pump
Liquid line Compressor
Water tank

13. Return air from the
structure
Dampers
Cooling coil Supply air to
structure
Mixed
air
Filters Blower
Outside air Heat reclaim coil Primary heat source

14. MULTIPLE EVAPORATORS AND SINGLE-
COMPRESSOR APPLICATIONS
(DISADVANTAGES)
• Refrigeration load cannot be easily matched
• Starting of large compressors draws higher
locked rotor amperage
• Short cycling of large compressors
• Increases power consumption
• Small increases in load may cause large
compressor to cycle on

15. PARALLEL COMPRESSOR SYSTEMS
• Often referred to as rack systems
• Uses two or more compressors
• Connected with common suction and discharge
headers and receiver
• Compressors cycle on an off to satisfy the load
of the system
• If there are three compressors connected in
parallel, only one compressor will operate during
the lowest load period

16. Vent line
Oil strainers Oil
reservoir
Oil
separator
Suction to
compressors
Discharge
from
Oil level regulators compressors

17. ADVANTAGES OF PARALLEL
COMPRESSORS
• Load matching
• Diversification
• Flexibility
• Higher efficiencies
• Lower operating costs
• Less compressor cycling

18. DISADVANTAGES OF PARALLEL
COMPRESSORS
• Leaks affect the entire rack
– Large leaks will result in the failure of
multiple remote units
• Compressor burnouts affect the
entire rack
– One motor burnout can result in the
formation of acid in the entire system
– Extensive cleanup procedure required

19. LOAD MATCHING
• As the load changes, the common suction
pressure entering the compressor will vary
• Actual load is sensed by a pressure transducer
• Compressors will cycle on, cycle off, load, or
unload depending on the load on the system
• Systems can be even (same size compressors)
or uneven (different size compressors)

20. SYSTEM PRESSURE REGULATORS
(SPR)
• Located between the condenser and the receiver
• Utilizes a parallel receiver instead of a series
receiver
• Controls the amount of liquid in the active
refrigeration system
• On hot days, the SPR causes refrigerant to enter
the receiver to maximize the condenser’s
effective surface area

21. SECONDARY FLUID
REFRIGERATION SYSTEMS
• Primary HFC or HCFC refrigerant used to cool
a secondary refrigerant
• Secondary fluid is usually an antifreeze solution
and is always a liquid
• Secondary fluid is circulated to individual
fixtures to absorb box heat
• Heat exchange process then takes place
between primary and secondary fluids

22. Condenser
Secondary refrigerant (water)
circuit
Evaporator
Pump
Heat
exchanger
Primary refrigerant
circuit
SECONDAY FLUID REFRIGERATION SYSTEM
(SIMPLIFIED)

23. ADVANTAGES OF SECONDARY
REFRIGERANT SYSTEMS
• Uses less refrigerant
• Easier to install with less critical piping
• Lower superheat in primary refrigerant
circuit
• Less complicated defrost cycles
• Less maintenance
• Only low-pressure fluid is located in the
customer area of store

24. DISADVANTAGES OF SECONDARY
REFRIGERANT SYSTEMS
• Higher initial equipment costs
• Added cost of secondary refrigerant
pumping
• Thicker and better insulation
required on secondary loop
• Higher cost for low-temperature
secondary fluids

25. PRESSURIZED LIQUID SYSTEMS
• Uses a small centrifugal pump to pressurize
the liquid in the liquid line
• Saturation temperature is raised while liquid
temperature remains the same
• Liquid will not flash into a vapor if it
experiences a pressure drop in the line
• Leads to lower condensing temperatures, head
pressures, and compression ratios which
increase efficiency

26. Condenser
Centrifugal pump
Compressor
Evaporator

27. UNITARY STAND-ALONE
REFRIGERATION SYSTEMS
• Multiple compressor modules located close to
display cases
• Condensers are cooled by a closed loop fluid
cooler
• Can be used as to reclaim heat for heating the
space or hot water
• Refrigerant usage is reduced
• Less piping required, fewer solder joints,
reduced leak potential

28. EVAPORATOR TEMPERATURE
CONTROL
• Multiple evaporators may not operate
at the same temperature
• Evaporator pressure regulators can
be used to maintain different
pressures
• EPR valves are located on all of the
higher temperature evaporator
circuits

29. INTERCONNECTING PIPING IN MULTIPLE
EVAPORATOR INSTALLATIONS
• Liquid and suction lines need to be run
to remote condensing units
• Suction lines need to be insulated
• Lines can be run in a pipe chase
• Lines can be run through individual
plastic pipes for ease in replacement in
case of a leak

30. Refrigerated case
Condensate System piping
piping
Piping chase

31. TEMPERATURE CONTROL OF THE FIXTURE
– MEDIUM TEMPERATURE
• Can be accomplished without
interconnecting wiring between box and
condensing unit
• Planned off cycle defrost can be
controlled from equipment room
• Defrost for the boxes can be staggered
so each box is defrosted at a different
time

32. TEMPERATURE CONTROL OF THE
FIXTURE – LOW TEMPERATURE
• Heat must be furnished to each evaporator
(either electric or hot gas)
• Defrost cycles can be staggered
• Heat from other boxes is used for hot gas
defrost
• Electric heat defrost is easier to
troubleshoot

33. HOT GAS DEFROST
• Discharge gas from the compressor is
directed to the evaporator being defrosted
• The other evaporators can remain in the
cooling mode while one evaporator is being
defrosted
• Three-way valves are used to direct the hot
gas to the defrosting evaporator
• The evaporator in defrost is piped in parallel
to the condenser

34. Cooling
Cooling
Cooling Solenoid open
Receiver
Accumulator

35. Cooling
Cooling
Defrost Solenoid
closed
Receiver
Accumulator

36. CHEST-TYPE DISPLAY FIXTURES
• Reach-in equipment can have lids or be open
type
• Fresh vegetables and meat are usually in
open-type cases
• Evaporators are usually mechanical draft
and are at the bottom of the display
• Chest-type cases can have remote
condensing units or be self-contained units

37. BACK-TO-BACK CHEST-TYPE DISPLAY CASES
Evaporator
coils Plenum
Plenum

38. CLOSED-TYPE CHEST FIXTURES
• Normally low-temperature boxes for ice
cream and frozen foods
• Lids are a barrier to the customer and are
not popular
• Upright, closed display with glass doors
allow customer to see the product
• Upright displays can often be loaded from
inside the walk-in cooler

39. DISPLAY CASE/WALK-IN COOLER (PLAN VIEW)
Merchandising
displays
Product
Storage
Walk-in cooler
Customer
access to
product

40. CONTROLLING SWEATING ON THE
CABINET OF FIXTURES
• Sweating forms when the cabinet is below
dew point temperature
• Small (mullion) heaters prevent moisture
from forming
• Heaters can be controlled based on the
humidity level in the store
• Stores are kept cool to reduce load on
the refrigeration equipment

41. MAINTAINING STORE
AMBIENT CONDITIONS
• In warm weather, the air-conditioning
systems remove moisture
• Less humidity in the store means less
moisture on the evaporator coils
• Reduced defrost time since less ice will
form on the coils

42. WALK-IN REFRIGERATION
• Permanently erected
– Not intended to be moved
– Larger walk-in boxes are permanently installed
• Knock-down type
– Constructed of insulated metal panels
– Can be disassembled and moved if necessary
– Equipped with interior safety catches to
prevent someone from becoming locked inside

43. EVAPORATOR LOCATION IN A WALK-
IN COOLER
• Can be piped to remote condensers or
can be package units
• Located in the box so the cold air does
not blow out when the door is opened
• Some have a fan switch to turn the fan
off when the door is opened
• Some systems pump down when the door
is opened

44. CONDENSATE REMOVAL
• Drain pan should be piped to the outside
of the cooler
• On low-temperature applications, the
drain line needs to be heated
• Drain lines should be pitched downward to
prevent trapping condensate

45. Heat tape
keeps the line
warm
Condensate line
Condensate line pitched
run to the downward
outside of the
cooler

46. REFRIGERATION PIPING
• Standard installations require fittings,
soldering, leak checking, evacuating
• Line sets are pre-charged flexible lines with
quick-connect fittings
• Condensing unit and evaporator are also pre-
charged and have quick-connect fittings
• No soldering or evacuation is required
• Long line sets can be coiled horizontally to aid
in oil return

47. Quick-connect fitting on
unit
Pre-charged tubing line
with quick-connect
fitting

48. VENDING MACHINE REFRIGERATION
• Self-contained refrigerated dispensing machines
• Equipment is similar to domestic refrigerators
• Evaporators operate below freezing
• Usually equipped with low-ambient controls
• Some have self-contained, removable systems
• When a breakdown occurs, the entire unit can be
replaced
• Health switch – device that will disable the unit if
the temperature of the storage area is too high

49. WATER COOLERS
• Water dispensed through a bubbler
• Can use bottled or city water as a source
• Pressure-type systems use supply water pressure
to dispense water
• Water pressure regulator can be adjusted for
proper flow
• Evaporator is a small tank with the refrigeration
lines wrapped around it
• The water that goes down the drain is used to
either cool incoming water or the refrigerant in
the liquid line

50. REFRIGERATED AIR DRIERS
• Process of dehydrating air, removing moisture
• Air used in pneumatic controls must be dry
• Air is cooled down below dew point to allow the
moisture to condense
• The evaporator in the heat exchanger operates
just above freezing
• Hot gas bypass provides a false load on the
system to prevent freeze ups
• The hot gas bypass is usually controlled by the
suction pressure of the system

51. SUMMARY
• Refrigerated cases can be either open or closed
• Closed cases are more efficient than open cases
• Self-contained units have their own compressor
and are not affected if other systems fail
• Larger compressors can be used to service multiple
units and evaporators
• Heat from multiple evaporator systems can be
used to heat the store or domestic water
• Parallel compressor (rack) systems use a bank of
compressors to control multiple systems

52. SUMMARY
• Compressors cycle on an off to satisfy the load of
the system
• Rack systems are more efficient than multiple units
with individual compressors
• Leaks in a rack system affects the entire system
• Rack systems have the advantage of load matching
• System pressure regulators utilize parallel
receivers to adjust the amount of refrigerant in
the active circuit
• Secondary refrigerant systems use an HFC or
HCFC refrigerant to cool a secondary liquid (usually
a water/antifreeze mixture)

53. SUMMARY
• Secondary fluid is circulated to the remote units
• Heat exchanges take place between the remote unit
and the secondary refrigerant as well as between
the primary and secondary refrigerants
• Secondary refrigerant systems require less
maintenance than conventional refrigeration systems
• Pressurized liquid systems use small centrifugal
pumps to pressurize the liquid in the liquid line
• Pressurized liquid systems operate with lower
condensing temperatures, head pressures, and
compression ratios which increase efficiency

54. SUMMARY
• Evaporator pressure regulators can be used to
maintain different pressures in multiple evaporator
systems
• Suction and liquid lines need to be field installed to
connect the evaporator to the condensing units
• Refrigerant lines can be run in pipe chases to
provide access for servicing and repair
• Medium temperature systems can be defrosted by
random, planned or off cycle methods
• Low temperature systems can be defrosted by hot
gas or by external electric heaters

55. SUMMARY
• Cabinet sweating can be reduced by mullion heaters
• Evaporators should be located so that cool air is not
blown from the box when the door is opened
• Walk-in refrigeration systems can be permanently
erected or knock-down units
• Condensate must be removed from the box
• Drain lines on low temperature systems should be
heated to keep them warm
• Condensate lines should be pitched to aid in the
condensate removal

56. SUMMARY
• Refrigerant piping can be accomplished with
pre-charged line sets
• Refrigerated vending machines are self-
contained units
• Evaporators on water coolers are small tanks
with refrigeration lines wrapped around it
• Refrigerated air driers are used to remove
moisture from air used in pneumatic controls
systems