Introduction to Commercial Systems: Chapter 1
Residential vs Commercial: Overview
In this module, we will go over residential and commercial systems. We’ll introduce you to the different types of commercial HVAC systems. Skip to quiz!
Overview
Recall that residential systems work with the heating and cooling of homes and small businesses. Residential systems are installed inside a house and designed for human comfort.
The types of residential HVAC systems are:
A window air conditioner,
Split air conditioner,
Centralized HVAC systems, and
Evaporative coolers.
Commercial systems are also used for heating and cooling, similar to residential systems. Commercial systems are used to heat or cool larger spaces like supermarkets, office buildings, and restaurants. Commercial HVAC equipment comes in large, self-contained, pre-packaged cabinets.
Some of the types of commercial HVAC systems are:
Rooftop packaged units,
Chillers,
Computer Room Air Conditioning, and
Supermarket refrigerators.
We’ll discuss each of them in detail in later courses.
Residential Vs Commercial System
A commercial system differs from a residential system in the following ways:
Size and Placement of components,
Drainage system,
Complexity,
Customization,
Maintenance, and
Capacity.
Recall that commercial systems are used to cool or heat a much larger space compared to residential systems. Commercial systems are much larger in size compared to residential systems.
Residential systems are placed in backyards or rest against the side of a house. Commercial systems are usually installed on rooftops or in the locked areas of buildings. This saves space inside and around a building and allows easy maintenance of a system.
A drainage system is used to collect condensed liquid. As commercial systems are much larger in size, they drain more liquid than residential systems. The drainage system for a commercial system consists of multiple pipes and pans. In comparison, a single pan is used in a residential system.
A residential system has fewer controls compared to a commercial system. This is because we need precise control in commercial systems.
A commercial system is modular. This allows series of separate units to be added or removed from these systems. If our business grows and we need more cooling or heating capacity, we can add another modular unit instead of replacing the whole unit. We cannot perform such customization in a residential system.
The maintenance cost of commercial HVAC systems is higher than that of residential units. The reason for higher costs is the complexity of components, size of the units, and frequency of maintenance. A commercial system is usually serviced every 3 to 6 months, whereas a residential unit is serviced annually.
Residential systems are available with a cooling capacity of 0.5 tons to 7 tons of refrigeration. A commercial system can have a much higher capacity than residential. It’s in the range of 2.8 tons to 28 tons of refrigeration. Furthermore, commercial packaged units can be built to higher capacities than standard units.
Comparison Based on Design
Depending on the space to be cooled, the design of residential and commercial systems varies. The two most common differences between residential and commercial systems are:
Number of refrigerant compression stages, and
Number of zones used to heat and cool.
Recall that a compressor compresses refrigerant used in an air conditioner. This refrigerant is then circulated throughout the cycle to cool the air inside a room. We can split the conditioned space into zones for precise control of temperature.
Recall that the cooling or heating load is the amount of energy used to maintain temperature in an acceptable range. An HVAC system is not always required to run on a full load. The load on a system changes with the demand.
The load for heating or cooling equipment depends on the:
Number of occupants in the conditioned space, and
Surrounding conditions.
As the number of occupants in a conditioned space increases, the load on equipment increases. For example, when guests visit our home, we need to set the temperature lower than usual. This increases the cooling load on our equipment.
Another example would be during winters. When the surrounding temperature is lower, the heating load increases. When conditions are reversed, the equipment load decreases.
Depending on the conditions, we need to control a system for full load and partial load. Recall that compressors compress refrigerant. We can control an equipment load by the number of stages used for compressing refrigerant.
Single-stage compression refers to compressing refrigerant inside a single cylinder. This type of compression is used in residential systems. Single-stage compressors always operate on full load capacity. They turn a system ON and OFF continuously.
In single-stage systems, we control the compressor using a thermostat. Recall that a thermostat is a device that senses the temperature of a room and gives feedback to the control system. If we set a thermostat to 68 ℉, the compressor will start any time the temperature reaches 69 ℉.
The traditional method of using a thermostat to control a compressor draws more electricity during each cycle. Single-stage systems are relatively more inefficient than multi-stage systems.
Multi-staging is compressing refrigerant in two or more cylinders instead of using a single cylinder. This type of compression is used in commercial systems. Multi-stage offers part load and full load operation with fewer ON and OFF cycles. This reduces power consumption and improves efficiency.
A zoned system is a single HVAC system used to provide heating and cooling for two or more zones. A zoned system can heat or cool zones of a room at different temperatures based on the requirement.
A zoned system for residential use is only effective for multi-story or large homes, and is not suggested for smaller rooms. Zoning allows us to maintain different temperatures at different locations of your house.
Zoning is often helpful when different areas within one commercial space have different heating or cooling needs. For example, in a mall we should keep a clothing store at one temperature and a meat store at a lower temperature.
Commercial systems heat and cool larger spaces, while residential systems are used to heat and cool smaller spaces. Commercial systems are much larger in size compared to residential systems. The maintenance cost of commercial HVAC systems is more than that of residential units.
A commercial system can have a much higher capacity compared to a residential system. Commercial system design differs from residential systems by the number of compression stages and zones for cooling.
Residential vs Commercial: Refrigeration Cycle
In this module, we will learn about the refrigeration cycle for a commercial system. We’ll also discuss components used in the refrigeration cycle for a commercial system. Skip to quiz!
Refrigeration Cycle
Day to day, we live in rooms with 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.
Let’s watch a short video that recaps the basic refrigeration cycle!
Recall that air conditioning works by absorbing heat from indoor air and ejecting it outdoors. It uses refrigerant to do this. 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 in the residential refrigeration cycle. However, the size of components used in a commercial system is larger.
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 that of 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 like 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 commercial systems. Some of them include:
Liquid line receiver tank,
Oil Separator,
Filter drier, and
Accumulator tank.
A receiver tank stores all excess refrigerant present in a refrigeration system. Recall that commercial systems have 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 a commercial system are larger. We require excessive oil for the lubricating compressor of a commercial system.
If this oil enters an evaporator coil, it reduces the heat transfer and cooling. We use an oil separator to remove the oil from refrigerant.
Recall that we use a filter drier to filter and remove moisture from refrigerant. They are used in both residential and 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 a residential system to prevent liquid from entering the compressor. As commercial systems work on the same cycle, we use accumulator tanks to protect these systems 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 a residential system uses a capillary tube or thermostatic expansion valve (TXV) for the metering device. Recall that thermostatic valves rely on sensing bulbs to operate. These devices cannot control refrigerant flow precisely.
For example, if the temperature of refrigerant in an evaporator is increased or decreased slightly, TXV’s cannot precisely control refrigerant flow. Electronic Expansion Valves (EEV) control 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 a 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 a commercial system for precise operation. We use an electronic expansion valve instead of TXV’s in a commercial unit for better control.
Question #1: Which of the following is a type of residential HVAC system?
Mixer
Window AC
Ceiling fan
Electric oven
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Answer: Window AC
The types of residential HVAC systems are:
A window air conditioner,
Split air conditioner, and
Evaporative coolers.
Question #2: Which of the following is a type of commercial HVAC system? (select all that apply)
Rooftop packaged units
Chillers
Window AC
Split AC
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Answer: Rooftop packaged units
Chillers
Some of the types of commercial HVAC systems are:
Rooftop packaged units,
Chillers,
Computer Room Air Conditioning, and
Supermarket refrigerators
Question #3: A commercial system is different from residential in terms of _____________. (select all that apply)
Material
Size
Complexity
Capacity
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Answer: Size
Complexity
Capacity
Commercial systems differ from residential systems in size, drainage system, complexity, customization, maintenance, and capacity.
Question #4: The design of commercial HVAC systems differs from residential systems by _________. (select all that apply)
Refrigeration cycle
Number of zones
Number of refrigerant compression stages
Main components used in system
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Answer: Number of zones
Number of refrigerant compression stages
The two most common differences between residential and commercial systems are:
Number of refrigerant compression stages, and
Number of zones used for providing heating and cooling
Question #5: Which parameters are responsible for heating and cooling load? (select all that apply)
Number of occupants
Number of zones
Surrounding conditions
Main components used in system
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Answer: Number of occupants
Surrounding conditions
The load on heating or cooling equipment depends on the:
Number of occupants in the conditioned space, and
Surrounding conditions
Question #6: A single-stage compressor compresses the refrigerant in more than one stage.
False
True
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Answer: False
False.
Single-stage compression means compressing the refrigerant inside a single cylinder.
Question #7: Residential systems control heating or cooling loads by using a ______.
Refrigerant lines
Multi-stage compression
Thermostat
Condenser
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Answer: Thermostat
Heating or cooling loads can be controlled using a thermostat.
Question #8: A multi-stage compressor reduces power consumption and improves efficiency.
False
True
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Answer: True
True.
Multi-stage offers part load and full load operation with fewer ON and OFF cycles. This reduces power consumption and improves efficiency.
Question #9: The advantage of zoning system is _____________.
It can provide heating and cooling for two or more zones
It has low cost
It requires less space
It requires less maintenance
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Answer: It can provide heating and cooling for two or more zones
A zoned system is a single HVAC system used to provide heating and cooling for two or more zones.
Question #10: Which of the following components is used in the basic refrigeration cycle? (Select all that apply)
Thermostat
Compressor
Metering Device
Radiator
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Answer: Compressor
Metering Device
The four main components of the basic refrigeration cycle are:
Compressor,
Condenser,
A metering device, and
Evaporator
Question #11: After the evaporator, where does the refrigerant go next?
Condenser
Compressor
Metering Device
Your AC Unit
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Answer: Compressor
After the evaporator, refrigerant goes to the compressor.
Question #12: The refrigeration cycle used for commercial systems is different from that of residential systems.
True
False
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Answer: False
The refrigeration cycle for commercial systems works in the same way as residential refrigeration systems.
Question #13: 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,
Filter drier, and
Accumulator tank
Question #14: A filter drier is used in both residential and commercial refrigeration systems.
True
False
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Answer: True
True!
We use a filter drier to remove these foreign materials in both commercial and residential systems.
Question #15: 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.