• SkillCat Team

Commercial HVAC Systems: Complete Overview

Updated: Aug 11

Introduction to Commercial Systems: Chapter 1


Residential vs Commercial: Overview


In this module, we will go over brief overview of residential and commercial systems. We will introduce you to types of commercial HVAC systems. Skip to quiz!


Overview


Recall that residential systems deal with the heating and cooling of homes and small businesses. Residential systems are installed inside the 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 the residential system. Commercial systems are used to heat or cool larger spaces such as 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 will discuss each of them in detail in later courses.


Residential Vs Commercial System


The commercial system differs from the 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 the backyard or rest against the side of the house. Commercial systems are usually installed on rooftops or in the locked areas of buildings. This saves space inside and around the building and allows easy maintenance of the system.


The drainage system is used to collect condensed liquid. As the commercial systems are much larger in size, they drain more liquid than residential systems. The drainage system for commercial systems 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 the system. 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 do such customization in a residential system.


The maintenance cost of commercial HVAC systems is more than that for residential units. The reason for the high cost is the complexity of components, the size of the units, and the frequency of maintenance. The commercial system is usually serviced every 3 to 6 months, whereas a residential unit is serviced annually.


The 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 compared to a residential. It is 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 for providing heating and cooling.

Recall that a compressor compresses the refrigerant used in an air conditioner. This refrigerant is then circulated throughout the cycle to cool the air inside the 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 to maintain the temperature in an acceptable range. The HVAC system is not always required to run on full load. The load on the system changes as per the demand.


The load on heating or cooling equipment depends on the:

  • Number of occupants in the conditioned space, and

  • Surrounding conditions

As the number of occupants in the conditioned space increase, 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 the equipment.


Another example is, during winters, when the surrounding temperature is lower, so the heating load increases. When the conditions are reversed, the equipment load decreases.


Depending on the condition, we need to control the system for full load and partial load. Recall that compressor compresses the refrigerant. We can control the equipment load by the number of stages used for compressing the refrigerant.


Single-stage compression means compressing the 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 the system ON and OFF continuously.


In a single-stage system, we control the compressor using a thermostat. Recall that a thermostat is a device that senses the temperature of the room and gives feedback to the control system. If we set the thermostat to 68 ℉, the compressor will start anytime when the temperature reaches 69 ℉.


The traditional method of using a thermostat to control the compressor draws more electricity during each cycle. Single-stage systems are relatively inefficient than multi-stage systems.


Multi-staging is compressing the 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 as per the requirement.


A zoned system for residential use is only effective for a multi-story or big home and not preferred for small 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 need to keep a cloth store at one temperature and a meat store at a lower temperature.


Commercial systems deal with the heating and cooling of larger spaces, while the residential system is used for heating and cooling smaller spaces. Commercial systems are much larger in size compared to residential systems. The maintenance cost of commercial HVAC systems is more than that for residential units.


A commercial system can have a much higher capacity compared to a residential. The commercial system design differs from residential by the number of compression stages and the number of zones for cooling.



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.

Let us look at a short video that would recall the basic refrigeration cycle!



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:

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.



Question #1: Which of the following is a type of residential HVAC system?

  1. Mixer

  2. Window AC

  3. Ceiling fan

  4. Electric oven

Scroll down for the answer...








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)

  1. Rooftop packaged units

  2. Chillers

  3. Window AC

  4. Split AC

Scroll down for the answer...








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: The commercial system is different from residential in terms of _____________. (select all that apply)

  1. Material

  2. Size

  3. Complexity

  4. Capacity

Scroll down for the answer...







Answer: Size

Complexity

Capacity

The commercial system differs from the residential system in size, drainage system, complexity, customization, maintenance, and capacity.


Question #4: Design of commercial HVAC system differs from residential system by _________. (select all that apply)

  1. Refrigeration cycle

  2. Number of zones

  3. Number of refrigerant compression stages

  4. Main components used in system

Scroll down for the answer...








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)

  1. Number of occupants

  2. Number of zones

  3. Surrounding conditions

  4. Main components used in system

Scroll down for the answer...













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.

  1. False

  2. True

Scroll down for the answer...












Answer: False

False.

Single-stage compression means compressing the refrigerant inside a single cylinder.


Question #7: A residential system controls heating or cooling load by using ______. (select all that apply)

  1. Refrigerant lines

  2. Multi-stage compression

  3. Thermostat

  4. Condenser

Scroll down for the answer...