Guide to HVAC Design, Theory of Operation, and Primary Components

HVAC stands for Heating, Ventilation, and Air Conditioning. This is the building system that regulates the inside temperature of the building and, in some systems, the air quality as well. The principles of HVAC design include the basic theory of system operation and the factors that determine the size and capacity of the equipment installed in the system. Once you have an understanding of the basics, you’ll be given information concerning the different types of air conditioning systems. The next step is to learn about the various components that make up an HVAC system. For example, the air conditioning portion of an HVAC system requires refrigerant to cool the air inside the building, so the various refrigerants that can be found in air conditioning systems are fully discussed. Finally, you’ll learn about the details of HVAC system installation, including the placement of compressor and condenser units, as well as heat exchangers, zones, and controls.

Basic Principles of HVAC System Design, Operation and Determining Capacity Requirements

Referenced here are informational resources regarding the basics of HVAC design and operation. When upgrading a current HVAC system or getting ready to build a new system in a residential or commercial building, one of the most important design considerations is correctly calculating the heating and cooling loads that the system will support. These calculations are described in complete detail in the articles below and sample calculations are given to help you achieve the fullest understanding of how to make the calculations properly possible. After reading through this section, you will have the knowledge and tools required to make good HAVC system design decisions.

Basics of HVAC

Importance of HVAC Design

Factors Affecting HVAC Designing and Heat Load Calculations

What are Heating and Ventilating Loads?

Survey of the Residential Building for Heat Load Calculations

Residential Heat Load Estimate Form: Heat Load Calculations Made Easy

What is Psychrometric Chart? Components of Psychrometric Chart?

Psychrometric Processes: Sensible Cooling and Sensible Heating of Air

AutoCAD HVAC Design and Heat Load Calculations Software

Selecting the Correct Size Window Air Conditioner

Guide for Selecting an Independent AC Unit for Home or Office

Preliminary Heat Exchanger Design – Calculations Involved

Different Methods for Removing Heat in HVAC Systems

Air conditioners are not the only systems available in HVAC for the removal of heat from a building’s environment. A heat pump is similar to an air conditioning system, but has some significant differences, and advantages. These differences are discussed in detail so you will be able to make a decision between the two, and just so you have an understanding of what these two types of systems are. A nice variety of types of air conditioning systems can be used in overall HVAC system design. System types such as direct expansion, chilled water, split, and window air conditioners are described in detail in the resources referenced below. After reading through this section, you will have a more complete understanding of the different types of cooling systems available for HVAC systems.

Difference between the Heat Pump and the Air-Conditioner

Types of Air Conditioning Systems

Advantages and Disadvantage of Absoprtion Refrigeration over Vapor Compression Refrigeration System

Types of Air Conditioning Systems

Central Air Conditioning Plants

Direct Expansion (DX) Type of Central Air Conditioning Plant or System

Chilled Water Central Air Conditioning Systems

Split Air Conditioner System

Heat Removal Methods

Evaporative Cooler: Chiller
Industrial Air Conditioning Plant
Heat Pump

Components of an HVAC System

There are two main components of a heating, ventilation, and air conditioning system. These two parts are the air handler, heating and cooling system, and the heat exchanger. In most cases, the heat source is some type of furnace. In an air conditioning system, the cooling system is composed of a number of unique subcomponents. In the articles referenced below, the various components in an HVAC system are described and explained. You’ll also find a description of the components in a split air conditioning system.

Evaporators for Refrigerator and Air-Conditioner Systems

Introduction to Compressors

Heat Exchanger Designs

A Fin Tube Heat Exchanger Gives Good Air Heat Exchanger Efficiency

Fundamentals of Heat Exchanger Theory and Design

Heat Exchanger Types and Their Use in Everyday Life

Types of Heat Exchangers Used in HVAC Systems

Evaporators for Refrigeration and Air Conditioning Applications

Throttling Devices or the Expansion Valves Used in the Refrigeration and Air Conditioning Systems

Thermostatic Expansion Valve or TEV

Constant Pressure Expansion Valve or Automatic Expansion Valve

Capillary Tube for Refrigeration and Air Conditioning Systems

The Purpose and Types of Condensers In Air Conditioning Systems

Compressors and Capacity Control System in the Packaged Air Conditioners

Air Handling Units or Fan Coil Units

Parts of the Split Air Conditioners: Outdoor Unit

Parts of the Split Air Conditioner: Wall Mounted Indoor Unit

Packaged Air Conditioners – Types of Packaged AC

Parts of the Window Air Conditioners: Part One

Parts of the Window Air Conditioners: Part Two

Introduction to Air Furnaces

Components of an HVAC System

HVAC Ductwork
Rotary Heat Exchanger
AC Compressors

Refrigerants Explained

Most air conditioners operate on the principle of gas compression and expansion. This gas is known in the air conditioning and refrigeration industry as a refrigerant. When this refrigerant is compressed, it becomes quite cold. This refrigerant is then sprayed into the heat exchanger using some sort of expansion valve. There have been four main refrigerants used in air conditioners over the years. The refrigerant in primary use has been R-12, although this is being slowly phased out for R-34a. All of the different refrigerants are explained in detail, with special treatment for R-12, as the favored refrigerant for a number of years, being given.

What are Refrigerants? History of Refrigerants

Properties of Ideal Refrigerants used in Vapor Compression Cycle

Selection of Refrigerants

Properties of Refrigerant R11 or Freon 11 and Replacements

Refrigerant R12: Properties, Advantages and Disadvantages

Replacement for R12 Refrigerant

Alternative Refrigerants for R22

Refrigerant R134a Properties and Replacement for R12

Air Conditioner System Installation

An HVAC system with components that are incorrectly installed or installed in ways that are disadvantageous is one that is poorly designed. Maximizing airflow across the heat exchanger unit ensures maximum heat transfer and maximum system efficiency. A heating, ventilation, and air conditioning system that is improperly installed will also detract from system efficiency. Placing the thermostat too near an air outlet or return, for example, will also cause efficiency to suffer. How installation affects HVAC system design will be discussed below in some detail. Safety and longevity concerns are also briefly discussed.

Installation of the Split Air Conditioners: Deciding the Location of Indoor and Outdoor Units

Heat Exchanger Flow Patterns

HVAC System : What is a Zone? Part -1

HVAC System: Zones and Designing a Zonal System – Part 2

HVAC System : Zoning Design Considerations- Part-3

Soundproofing of Air Conditioning Ducts

How to Install UV Lights in Air Handler

Stopping Air Handler Condensation

Safety Devices in Air Conditioning and Refrigeration Plants

Controls Used in the Air Conditioning Systems: Thermostats, Humidistats and Airstats

HVAC Thermostat
Raised Floor Air Return Tile


  • HVAC Ductwork image courtesy wikimedia commons:

  • Raised Floor Air Return Tile image courtesy wikimedia commons:

  • Heat exchanger image courtesy wikimedia commons:

  • Heat pump chiller image courtesy wikimedia commons:

  • AC Compressors image courtesy wikimedia commons:

  • Industrial air conditioning image courtesy wikiemedia commons:

  • Cooling tower chiller image courtesy wikimedia commons:

  • Thermostat image courtesy wikimedia commons:

  • Mike Aguilar has more than eight years of experience as an electrician.