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San Joaquin Valley College Blog

HVAC-R 101 – What You Need to Know

August 3, 2023

Heating and cooling systems are found in every building in the country. These systems are highly complex, with moving parts and components that require precise care. They need qualified technicians and installers to keep them running. In order to work on heating and cooling systems, technicians need the right training and certification, which starts with the right education. Studying HVAC-R will  prepare you for the different demands in this career.

What Does HVAC-R Stand For?

HVAC-R stands for heating, ventilation, air conditioning and refrigeration. This acronym refers to the various comfort systems that keep homes and businesses comfortable no matter the season, such as furnaces, heat pumps, central air conditioners, boilers and refrigeration systems. Within the world of HVAC-R, there are numerous job opportunities, including:

  • Residential HVAC-R technician
  • Commercial HVAC-R technician
  • HVAC-Rinstaller
  • HVAC-Rsales representative


While each of these jobs covers a slightly different area of HVAC-R, all of them start with understanding the basics of these systems to provide services to customers.

What Are the Different Components of HVAC-R

The “H” in HVAC-R stands for heating. Here is a breakdown of the important parts of a heating system.


Heating refers to the system that keeps your home warm in the winter. There are three basic types of heating systems:


Furnaces can run on either gas or electricity, but they heat your home or business by heating the air using a combustion process, then blowing it through your ductwork to disperse throughout your home.

Heat Pumps

Heat pumps transfer heat from areas where there is more heat energy to areas where there is less. They move this heat energy from inside your home to the outdoors, and vice versa, depending on the season. They can both heat and cool the home with the same unit.


Boilers use steam to heat a home or business. This is a common heating option for larger, older or commercial spaces. Boiler heat is quite energy-efficient but is not always easy to fix when problems arise.


As building envelopes get tighter, the need for improved ventilation increases. Fresh air is necessary to reduce indoor air quality problems. Some components of ventilation systems include:


Ventilation fans mount to the ceiling or wall of a home to help circulate fresh air through the property. They bring air from outside the home inside to help ventilate the space.


Ductwork allows air to move from one area of a home to the next, often passing through the heating or cooling system. Proper duct sealing helps reduce the risk of contaminants getting into the property. Sealed ducts also reduce energy loss.

Air Conditioning

Air conditioning systems are responsible for cooling the home. They also reduce humidity to help the home feel more comfortable when temperatures are high. Their main components include:


Refrigerant is the material that removes heat from the air. Through the function of the air conditioner, it changes from a liquid to a gas and back again, and this process removes heat from the air. The two main types of refrigerant are R-22, which goes by the brand name Freon, and R410a, or Puron. Few systems use Freon today, as it has been phased out by the more eco-friendly Puron and is no longer manufactured.


The compressor is the heart of the air conditioner. It takes the refrigerant and changes it back and forth from a cool liquid at low pressure to a hot gas under high pressure. This process pulls heat from the air to cool your home. The compressor pulls air toward the refrigerant. The refrigerant absorbs heat from that air and turns it into a vapor. The cooled air is sent through your home, while the heat is expelled to the outdoors through fans and ductwork. Eventually, the refrigerant vapor cools down and condenses, and the process starts over.

Evaporator Coils

The evaporator coils are full of liquid refrigerant that the compressor sends to them. Air from your home is sent through the coil by the blower fan, and the refrigerant absorbs the heat and evaporates, converting it to gas. The coils then move the gas back into the system to cool and condense, The evaporator coils also allow water vapor from your home’s indoor air to condensate into a drip pan, helping reduce your home’s humidity.

Know the Basic Principles of HVAC-R

If you’re considering studying HVAC-R or getting a job in this field, knowledge of some basic scientific principles will be important. These principles fall into either thermodynamics or psychometrics.


Thermodynamics refers to the relationship between heat and other forms of energy. Because HVAC systems work by moving heat around to keep your building comfortable, the laws of thermodynamics play an integral role in these systems.

Heat Transfer

According to the laws of thermodynamics, heat always wants to move from an area of high concentration to a low concentration, and HVAC systems capitalize on this through the principle of heat transfer. This principle involves three processes:

  • Radiation – When heat transfers through light energy, radiation occurs. In buildings, sunlight coming in through windows and heating a building is a common type of radiation.
  • Conduction – Conduction occurs when heat travels through solid materials, like the burner on a stove touching a pan and heating it up. In buildings with boiler heat, conduction is a common way to heat the home.
  • Convection – Hot air naturally rises, and this process is known as convection.

HVAC-R systems utilize all three of these processes to heat homes.

Refrigeration Cycle

The refrigeration cycle is the cycle within an air conditioner that sends coolant through a compressor, condenser and evaporator to change it from liquid to gas and back again in order to remove heat from the home. Refrigeration is a vital part of the cooling process.


Psychometrics is the study of the properties of air, and it is essential to understanding HVAC-R systems since these systems heat and cool the air. The key aspects of psychometrics include:

Air Properties

Air properties include the temperature and humidity of the air. Sometimes understanding these properties also involves measuring air pressure.

Humidity and Moisture

HVAC-R systems impact the humidity and moisture content of the air inside a home. Air conditioning systems remove humidity, while sometimes heating systems make the air too dry and require the addition of humidity.

Electrical Principles

Finally, HVAC-R systems require an understanding of electrical principles because these systems all require electricity to operate. Though HVAC-R professionals are not electricians, they must know how to safely work with electricity and the basic principles of electricity. The main principles included in an HVAC-R program include these three factors:


Voltage is the pressure that sends an electrical current through a wire. In North America, both 240 and 120-voltage delivery is possible. Large appliances need more voltage to operate, and so air conditioning systems use 240 volts.


Amperage measures the current’s rate as it flows through the circuit. Problems with amperage will prevent the system from running. If the amperage is too high, it can overload and damage the system. Air conditioning systems need 30 to 50 amps to operate properly.


Resistance, measured in ohms, is a measure of how much a wire resists the flow of electricity. Every wire material has some form of resistance, though the goal is for this to be low in HVAC-R systems.

What Are the Different Types of HVAC-R Systems?

Finally, to work in HVAC, you will need to know the different types of HVAC-R systems, which include:

Split Systems

Any system with an indoor and outdoor unit connected with copper tubing is a split system. Heat pumps and most home HVAC systems are examples of split systems.

Package Systems

Package systems are all-in-one systems that are not split between the home’s interior and exterior. They save space and can provide both heating and cooling. In commercial properties, these systems often get mounted to the roof of the building, but in residential properties, they can be on the ground outside of the home.

Ductless Mini-Split Systems

Ductless mini-splits are miniature heat pumps that mount to an exterior wall of your home. They provide cooling and heating to one room or area through a hole in the wall. These systems are commonly used in homes with boilers (so they don’t have ductwork for an AC unit) or for additions and non-heated rooms in a home not connected to the ductwork. They can also be installed in spaces that need a little boost in heating and cooling, like second-floor bedrooms or rooms that have a lot of electronics in them.

Variable Refrigerant Flow (VRF) Systems

VRF systems heat and cool a homes or commercial building with one unit that operates like a heat pump or heat recovery system. These are ductless, high-capacity systems often appearing in commercial applications.


The  HVAC-R tech is a great place to start your career for  both commercial and residential property owners need knowledgeable professionals to help them maintain and repair their systems. To enter this field, you should have the right training to understand electricity, air properties, the various systems and the basic principles of heating and cooling. If you’re interested in becoming an HVAC-R technician, the Heating, Ventilation, Air Conditioning and Refrigeration program at SJVC could be a good fit. This hands-on program will prepare you for a fulfilling career working with heating and cooling systems. In as few as ten months, you could be ready for a career in this exciting field. Reach out to our team today to learn more.


What Are Evaporator and Condenser Coils and How Do They Help Cool Your Home?,roof%2C%20walls%2C%20and%20windows.

The Refrigeration Cycle


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