Objectives

• After studying this unit, you should be able to
• describe each of the major components of a gas furnace.
• list two fuels burned in gas furnaces and describe characteristics of each.
• discuss a multi-poise furnace and its safety devices.
• discuss flame roll-out switches, auxiliary limit switches, and draft safeguard switches.
• discuss gas pressure measurement in inches of water column and describe how a manometer is used to make this measurement.
• discuss gas combustion.
• describe a solenoid, diaphragm, and heat motor gas valve.
• list the functions of an automatic combination gas valve.
• describe the function of a servo-operated gas pressure regulator.
• discuss the meaning of a redundant gas valve.
• discuss different gas burners and heat exchangers.
• describe the difference between induced-draft and forced-draft systems.
• describe and discuss different ways of controlling the warm-air fan.
• state the function of an off-delay timing device for a warm-air fan control.
• describe the standing pilot, intermittent pilot, direct-spark, and hot surface ignition systems.
• list three flame-proving devices and describe the operation of each.
• discuss reasons and the systems used for the delay in starting and stopping the furnace fan.
• state the purpose of a limit switch.
• describe flue-gas venting systems.
• discuss flame rectification and how it pertains to local and remote flame sensing.
• apply flame rectification troubleshooting and maintenance procedures.
• discuss the components of a high-efficiency gas furnace.
• describe direct-vented, non-direct-vented, and positive pressure systems.
• explain dew point temperature as it applies to a high-efficiency condensing furnace.
• discuss excess air, dilution air, combustion air, primary air, and secondary air.
• describe the condensate disposal system of a high-efficiency condensing gas furnace.
• identify furnace efficiency ratings.
• discuss electronic ignition modules and integrated furnace controllers.
• describe a two-stage furnace, a modulating gas furnace, and a variable-output thermostat.
• explain gas piping as it applies to gas furnaces.
• interpret gas furnace wiring diagrams and troubleshoot flowcharts or guides.
• compare the designs of a high-efficiency gas furnace and a conventional furnace.
• describe procedures for taking flue-gas carbon dioxide and temperature readings.
• describe typical preventive maintenance procedures.

Next: Advance to the Learning Center Dashboard and complete the lessons.