Introduction to Commercial Systems: Chapter 2
Residential vs Commercial: Refrigeration Cycle
In this module, we will learn about the refrigeration cycle for a commercial system.
We will also discuss components used in the refrigeration cycle of a commercial system. Skip to quiz!
Refrigeration Cycle
In our daily life, we live in rooms having a comfortable temperature. This is made possible by the refrigeration cycle — especially during the hot summer months. The refrigeration cycle is the basis of our air conditioning unit and our refrigerator.
Recall that the four main components of the basic refrigeration cycle are:
Compressor,
Condenser,
A metering device, and
Evaporator
Recall that air conditioning works by absorbing heat from your indoor air and ejecting it outdoors. It uses a refrigerant to do this. A refrigerant is a fluid used in refrigeration systems to transfer heat.
The refrigeration cycle for commercial HVAC systems works in the same way as in residential systems. Commercial systems use the same principle for cooling as residential systems.
Residential vs Commercial System Components
We use the same components in the commercial refrigeration cycle as the residential refrigeration cycle. However, the size of components used in the commercial system is large.
We also use different types of components that suit specific purposes for commercial HVAC applications.
For example, in a chiller system, we use a shell and tube evaporator. Recall that a finned-tube evaporator is used in residential air conditioners.
The number of control components used in the commercial refrigeration cycle is more than the residential cycle. This is because we need more precise temperature control in commercial HVAC systems.
For example, commercial refrigerators and freezers are used to store more stuff than residential systems. They may contain perishable products such as milk, vegetables, meat, etc. If we don't control the temperature precisely, it may spoil them.
Along with the main components of a refrigeration cycle, there are many secondary components present in the commercial system.
Some of them include:
Liquid line receiver tank,
Oil Separator,
Filter drier, and
Accumulator tank.
The receiver tank stores all the excess refrigerant present in the refrigeration system. Recall that the commercial system has a higher cooling load that fluctuates as per surrounding conditions and the number of occupants. We need this refrigerant whenever the load fluctuates.
The receiver tank stores all the excess refrigerant present in the refrigeration system. Recall that the commercial system has a higher cooling load that fluctuates as per surrounding conditions and the number of occupants. We need this refrigerant whenever the load fluctuates.
Recall that components of the commercial system are larger. We require excessive oil for the lubricating compressor of the commercial system.
If this oil enters the evaporator coil, it reduces the heat transfer and cooling. We use an oil separator to remove the oil from the refrigerant.
Recall that we use a filter drier to remove moisture from the refrigerant and filter the refrigerant. They are used in both residential as well as commercial HVAC systems. However, they are a necessity in commercial systems. We can sometimes find multiple filter driers in commercial HVAC appliances.
Recall that an accumulator is used in the residential system to prevent liquid from entering the compressor. As the commercial system works on the same cycle, we use an accumulator tank to protect the commercial system from damage.
Component Difference
Recall that commercial refrigeration systems differ from residential refrigeration systems in size, energy consumption, and equipment location. Similarly, commercial and residential components also vary in size, energy consumed, and equipment location.
Recall that the residential system uses a capillary tube or thermostatic expansion valve (TXV) for the metering device. Recall that thermostatic valves rely on the sensing bulb to operate. These devices cannot control refrigerant flow precisely.
For example, if the temperature of the refrigerant in the evaporator is increased or decreased slightly, TXV’s cannot precisely control refrigerant flow. Electronic Expansion Valve (EEV) controls refrigerant flow electronically in commercial systems. EEV’s are extremely precise and offer great control.
As discussed earlier, multi-stage or multiple compressors are used in commercial refrigeration systems. The most commonly used compressors in residential refrigeration are reciprocating, scroll, and rotary types. Commercial refrigeration systems consist of centrifugal or screw-type compressors.
The commonly used condenser for residential refrigeration systems is the fin and tube condenser. A microchannel condenser and spine fin condenser are preferred for commercial systems.
The refrigeration cycle for commercial systems works in the same way as residential HVAC systems in our home. Many secondary components are present in the commercial system for precise operation. We use an electronic expansion valve instead of TXV’s in a commercial unit for better control.
Residential vs Commercial: Air Conditioning System
In this module, we will introduce you to components used for the commercial air conditioning system. We will also compare components of commercial air conditioning systems with the residential system.
Air Conditioning Components
Recall that the refrigeration cycle runs the air conditioning system. The residential air conditioners are used to serve the needs of smaller areas, and we use them at home. The commercial air conditioners are used in large spaces such as office buildings.
Commercial systems differ from residential systems in terms of components used for air conditioning.
Recall that some components seen in residential air conditioning are:
Compressor,
Condenser,
Metering device,
Evaporator,
Blower fans,
Dampers, and
Ductwork.
Apart from these, the commercial system has additional components.
The additional components used in commercial air conditioning systems are:
Cooling towers,
Water Pumps,
Air handling units,
Solenoid switches, and
Economizers.
Recall that condenser is a type of heat exchanger that cools the refrigerant. In a commercial chiller system, we use a cooling tower as a heat exchanger in addition to the condenser. This equipment helps cool the condenser by supplying cold water.
We use water pumps to carry water from the condenser to the cooling tower in a commercial system. There are commercial systems that use the refrigeration cycle to provide cold water instead of cold air. Large water pumps are used in such systems to pump the water throughout the building.
An air handling unit (AHU) is a box-type structure that contains cooling coils, fans, and filters.
We use a single air handling unit to move the air throughout our home. In a commercial unit, we use more than one AHU. The image to the right shows AHU located on each floor of a commercial building.
Recall that a solenoid valve is used in residential air conditioners to turn the refrigerant flow on and off. In commercial systems, we use many solenoid valves to control the higher flow rate of refrigerant in the system. Multiple solenoid valves can help provide separate cooling for different office spaces.
Recall that one commercial system usually cools a complete building. However, the residents of different floors will have different temperature requirements. So the refrigerant flow is controlled by the solenoid valves to control temperatures.
In a commercial system, as the cooling or heating load is high, we use an economizer. It uses the wind blowing at the top of the building to cool the air inside. This reduces electricity consumption.We will learn about how this equipment is used in commercial systems in later courses.
Residential Vs Commercial Air Conditioner
Commercial and residential air conditioning systems both aim to provide human comfort. However, commercial air conditioning systems do it on a much larger scale.
Recall that the cooling capacity of air conditioners is expressed in tonnage. Residential air conditioners are available in 1.5 to 5-ton units. The average commercial AC size ranges from 2 tons for small buildings to more than 30 tons for large buildings.
The temperature for the residential system is maintained between 67°F and 82°F. The average temperature range for most commercial building spaces is 60°F to 76°F.
Recall that finned-tube evaporators are commonly used in most residential air conditioning systems. A commercial air conditioning system uses a spine fin type evaporator. Chilled water systems use shell and tube type of evaporators. We also use finned tube evaporators in some commercial HVAC systems.
We use a finned-tube type of condenser for residential air conditioning systems. Earlier, commercial systems were also equipped with fin and tube condensers. Microchannel types of condensers are replacing these condensers as they are more efficient and smaller in size.
Recall that in a commercial system, multi-stage compressors compress the refrigerant to high pressure and high temperature. We use a centrifugal or screw-type compressor for commercial air conditioners. Recall that a piston-type or scroll-type of compressor is often used in residential systems.
A commercial air conditioning system has additional components for providing cooling to large spaces. These additional components help provide large-scale cooling, efficient air conditioning, and better control over temperatures.
Question #1: Which of the following components are used in the basic refrigeration cycle? (Select all that apply)
Thermostat
Compressor
Metering Device
Radiator
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Answer: Compressor
The four main components of the basic refrigeration cycle are:
Compressor,
Condenser,
A metering device, and
Evaporator
Question #2: After the evaporator, which component does the refrigerant go to next?
Condenser
Compressor
Metering Device
Your AC Unit
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Answer: Compressor
After the evaporator, refrigerant goes to the compressor.
Question #3: The refrigeration cycle used for the commercial system is different from the residential system.
True
False
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Answer: False.
The refrigeration cycle for commercial systems works in the same way as residential refrigeration systems.
Question #4: Which of the following are secondary components always found in commercial HVAC systems but only sometimes in residential HVAC systems? (Select all that apply)
Oil Separator
Liquid line receiver tank
Metering device
Compressor
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Answer: Oil Separator, Liquid line receiver tank
There are many secondary components present in the commercial system, including:
Liquid line receiver tank,
Oil Separator,
Filter drier, and
Accumulator tank
Question #5: A filter drier is used in both residential and commercial refrigeration systems.
True
False
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Answer: True
We use a filter drier to remove these foreign materials in both commercial and residential systems.
Question #6: Which of the following characteristics of commercial systems differ from the residential ones? (select all that apply)
Energy consumption
Size
Material
Power supplied for operation
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Answer: Energy consumption, Size, Power supplied for operation
Commercial and residential systems’ components vary in size, energy consumed, and power supply for operation.
Question #7: Which components are generally not found in residential air conditioning systems? (select all that apply)
Evaporator
Chilled water pumps
Compressor guide vanes
Ductwork
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Answer: Chilled water pumps, Compressor guide vanes
Recall that some components seen in residential air conditioning are:
Compressor,
Condenser,
Metering device,
Evaporator,
Blower fans,
Dampers, and
Ductwork.
Question #8: Economizers and air handling units are used in commercial air conditioning systems only.
True
False
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Answer: True
The components used in commercial air conditioning systems are:
Cooling tower
Water Pumps
Air handling units
Fan cycling unit
Solenoid switch
Economizers