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OL GTH2 at-a-glance

This online course provides new technicians and people desiring a better understanding of gas heating systems including theory, components and troubleshooting. Topics coved include combustion theory, gas furnaces, burners, controls, ignition systems, installation practices, ventilation and combustion air and troubleshooting. This program consists of 10 modules and is available as each module or as a complete course. To receive FAD credit you must pass the final exam.

duration cost format register*
2 hrs per module $25/module
online Complete course

*To register for individual modules, select the module from the list below and click 'Register'.


Course Overview

The most popular form of heating in North America is gas. Servicing gas heating systems requires understanding the theory of operation and how the system components function to provide safe, economical comfort heating. This online training series provides the background to understand both the theory and function of components used in gas heating systems. These modules are presented in simple language and concentrate on presenting the concepts in ways that can be easily understood by people new to the industry. After completing these modules, a student should possess the understanding of the concepts behind systems which use gas heating, the types of systems and components, and basic troubleshooting techniques. Each module is self-paced and contains a quiz and final exam for the section, each with reference to the appropriate section of the module, allowing students to evaluate their understanding of the concepts presented. To receive FAD credit you must pass the module or final exam.

HVAC Training Requirements

Who Should Take this Training

This course is new technicians or others in the industry who wants to better understand air conditioning theory, components and troubleshooting of HVAC systems.

Learning Methods Used

This course is a narrated online PowerPoint lecture with animations. Student’s achievement of the learning objectives is determined by successful completion of the module skill check and / or final online exam.

Course Details

Module 1 – Introduction to Gas Heating

Course Overview

This first module introduces students to four of eight foundation blocks of heating: 1) Heat; 2) Molecules, Heat and Temperature; 3) Heat Transfer; 4) Pressure.

HVAC Training Objectives
  • Identify the main components of all gas furnaces
  • Select the definition for heat
  • Define terms Btu, specific heat, and change of state
  • Describe latent heat and how it applies to the change from solid to liquid and liquid to solid
  • Select definitions for conduction, convection and radiant heat transfer
  • Define pressure and the ways that pressure influences heat flow
  • Name two instruments used to measure pressure in heating systems
Topics Covered*
  • Heat (9)
  • Molecules, Heat and Temperature (14)
  • Heat transfer (20)
  • Pressure (20)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 2 – Principles of Gas Combustion

Course Overview

This second module introduces the remaining four foundation blocks of heating: 5) Gas Properties; 6) Combustion Theory; 7) Practical Combustion; and 8) Efficiency.

HVAC Training Objectives
  • Name the common fuel gases, how they were formed and their chemical makeup
  • Define combustion and list the three conditions necessary for combustion to take place
  • Explain what is meant by controlled combustion
  • Select what is meant by burn speed, flame stability and complete combustion
  • Pick definitions for excess air, stoichiometric combustion and NOx
  • Identify the products of incomplete combustion
  • Identify the three types of gas furnaces and their efficiency level
Topics Covered*
  • Gas Properties (20)
  • Combustion theory (20)
  • Practical Combustion (10)
  • Heating efficiency (18)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 3 – Gas Furnaces

Course Overview

In this module students learn basic furnace design, gas system components, furnace controls, and system controls and components.

HVAC Training Objectives
  • Describe the heat exchangers used in the three types of furnaces and how they differ in achieving the efficiency levels
  • Identify the relationship between CFM and temperature rise
  • Identify the types of blowers used in furnaces and how the airflow is changed
  • Name the basic gas controls found on a typical furnace and their function
  • Name the types of ignition controls and how they work
  • Identify the safety controls found on a typical gas furnace and the function of each
  • Select from a list the operating controls used on typical gas furnaces
Topics Covered*
  • Furnace design (47)
  • Gas system components (30)
  • System controls and components (10)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 4 – Gas Burners

Course Overview

Module 4 expands on basic concepts from the first three modules and includes: theoretical flame characteristics; burner design; actual flame characteristics; combustion systems; and pilot burners.

HVAC Training Objectives
  • Name the three color zones in a burner and what is happing in each zone
  • Select the definition of primary air and secondary air in a burner
  • Name the two factors of gas combustion which affect flame stability
  • Name the two functions of the gas orifice and the cautions to observe when changing orifices
  • Explain the function of the venturi, burner head, primary air shutters and carryover ports
  • Name three types of pilot burners and how they function
Topics Covered*
  • Theoretical flame characteristics (24)
  • Burner design (14)
  • Actual flame characteristics (15)
  • Combustion systems (5)
  • Pilot burners (5)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 5 – Gas Controls

Course Overview

This module focuses on the controlled combustion process: gas controls; manual and automatic valves; and gas regulators.

HVAC Training Objectives
  • Identify the basic components, function and principle of operation of a gas pressure regulator
  • Identify the main components and the operating principle of a typical automatic gas valve
  • Explain the term redundant as it applies to automatic combination gas valves
  • Explain what is meant by “pick” and “hold” coils used in automatic gas valve
  • Describe the steps you would take to troubleshoot a gas valve
Topics Covered*
  • Pressure regulators (15)
  • Gas valves (16)
  • Combination gas valves (14)
  • Troubleshooting gas valves (6)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 6 – Gas Ignition Systems

Course Overview

Module 6 explains the three types of ignition systems commonly used: standing pilot; re-ignition pilot; and direct burner ignition.

HVAC Training Objectives
  • Indicate the function of a standing pilot and name the two functional components
  • Explain the major steps to troubleshoot a thermocouple pilot
  • Explain the function and operation of a flame rectification ignition system
  • Explain the function and operation of a spark re-ignition system
  • Describe the steps to follow in troubleshooting a spark re-ignition system
  • Describe the operation of a glow coil re-ignition system
  • Explain the steps to troubleshoot a glow coil re-ignition system
Topics Covered*
  • Standing pilots (17)
  • Pilot re-ignition systems (21)
  • Direct burner ignition (8)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 7 – Gas Safety & Operating Controls

Course Overview

Module 7 covers the overall concept of the heat pump, its operation, benefits and disadvantages, operating economics, servicing concerns and how water-source heat pumps are used for heat reclaim in commercial buildings.

HVAC Training Objectives
  • Identify six safety controls found on various types of gas furnaces
  • Explain how to check the operation of a limit switch
  • Identify three safety controls used in conjunction with induced draft combustion systems
  • Identify and explain the main differences in safety controls between natural draft and condensing furnaces
  • Identify six operating controls found on various gas furnaces
  • Identify seven situations that should be considered when locating a thermostat
  • Explain the function and operation of a heat anticipator in a room thermostat
Topics Covered*
  • Safety Controls (24)
  • Operating Controls (16)
  • System controls (19)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 8 – Furnace Installation Practices

Course Overview

In Module 8 students learn application principles: planning; designing; and selecting equipment, as well as proper gas-piping techniques and installation practices.

HVAC Training Objectives
  • State the three concepts that apply to a good furnace installation
  • Explain the relationship between building heating load and furnace capacity
  • Describe what openings need to be provided in the building for combustion air
  • State the factors involved in determining the size of the gas supply pipe
  • Describe two leak dedication methods to be used with gas pipe
  • State how minimum clearances impact location of a gas furnace
  • State the startup steps to be taken with all gas furnaces
Topics Covered*
  • Application principles (24)
  • Gas piping (18)
  • Installation principles (12)
  • Start-up Procedures (19)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 9 – Ventilation & Combustion Air

Course Overview

This module introduces terminology of Category I vent design basics, vent design and combustion air, as well as Category IV venting and combustion air.

HVAC Training Objectives
  • Explain the differences between a condensing furnace vent system and a natural-draft vent system
  • Explain why a vent must be large enough for a furnace and what factors must be considered in selecting the proper vent size diameter
  • State the characteristics of a vent that are needed for best performance
  • Define the term common vent and state the five design rules
  • Be able to select a vent pipe diameter from the vent pipe sizing tables given the furnace input, the vertical height, and the lateral length of the vent
  • Explain the requirements of a Category IV venting system
Topics Covered*
  • Category 1 venting basics (28)
  • Category 2 vent design (17)
  • Category 1 combustion air (20)
  • Category IV venting and combustion (8)
*All times are approximate and shown as (time in minutes).
Register for this Module

Module 10 – Gas Troubleshooting

Course Overview

Module 10 covers basic troubleshooting practices. Covers: basic adjustments; gas input; primary air; efficiency checks; furnace problems; how to identify and correct the operation and function of basic switches and loads.

HVAC Training Objectives
  • Use a gas orifice calculator to determine the proper manifold pressure for a given furnace, orifice and gas
  • Describe how to clock a gas meter
  • Explain how to measure temperature rise and how to use it to calculate the CFM of air being circulated
  • Define what is meant by lifting flames, what causes it and how to correct it
  • Identify two methods that can be used to determine if a heat exchanger is cracked
  • Define what is meant by delayed ignition, what causes it and how it can be corrected
  • Explain flame rollout, what causes it and how it can be corrected
Topics Covered*
  • Checking gas flow (25)
  • Other system checks (13)
  • Troubleshooting combustion (27)
*All times are approximate and shown as (time in minutes).
Register for this Module

Course Requirements

Completion Requirements

To receive a certificate for any module or for the complete course a student must receive a grade of 70% on the module skill check or final exam. Once you complete the exam you will be able to print a certificate.

Prerequisite requirements

Basic math skills are required to calculate electrical values in skill check problems.


This program is appropriate for anyone interested in a better understanding of the fundamentals of air conditioning systems.


This program uses a software program that uses flash animations and will run on most PC based computers. Some Apple and mobile devices may need a plugin / app to be able to run these programs.




Not applicable.


Class can be accessed 24/7 and is available for completion for 2 weeks after first login.


This program is located on the Carrier University Learning Management System. Access information and enrollment key are provided after registration.