Furnace Types
This type of furnace takes in return air from the bottom and forces it upward.
Upflow
This is the chemical process of rapid oxidation that requires fuel, heat, and oxygen
Combustion
This type of valve controls the supply of gas to the manifold and burners.
Gas Valve
This chamber transfers heat from combustion gases to the circulating air.
Heat exchanger
This type of ignition system uses a continuously burning pilot light.
Standing Pilot
This device prevents overheating of the heat exchanger.
What is a high-limit switch?
This type of furnace is commonly used if the ductwork runs below the level of the furnace.
Downflow
This term refers to the perfect combustion of fuel with the exact amount of oxygen
What is stoichiometric combustion
This type of gas valve combines multiple functions into one unit.
Combination gas valve
This type of heat exchanger is connected directly to the combustion chamber.
Primary heat exchanger
This ignition system lights the pilot only when needed.
What is an intermittent-pilot ignition system?
This switch monitors for flame rollout.
Rollout switch
This furnace can operate at two different heat levels.
Two stage
This type of air is mixed with fuel prior to ignition.
Primary air
This component ensures the gas valve does not open unless the pilot is lit.
Thermocouple
This type of heat exchanger extracts both sensible and latent heat.
Secondary heat exchanger
This system uses an electric spark to ignite the gas burners.
What is a direct-spark ignition system?
This component ensures the combustion blower is operating before ignition.
What is a pressure switch?
This type of furnace can vary its heat output from 40% to 100%.
Modulating
This type of air surrounds the flame after ignition to maintain combustion.
Secondary air
This device monitors the gas pressure in the furnace.
Pressure regulator
This type of furnace has an AFUE rating above 90%.
High efficiency
This ignition system uses a high-resistance heating element to ignite gas.
What is a hot-surface ignition system?
This type of control prevents the system from operating under unsafe conditions.
What are electric interlocks?
This type of furnace uses both primary and secondary heat exchangers to extract additional heat.
Condensing furnace
This is the measure of a furnace's combustion quality.
Combustion efficiency
This type of valve is used for controlling gas flow to the pilot.
Pilot Valve
This type of heat exchanger is often made of stainless steel to handle condensate.
What is a secondary heat exchanger in a condensing furnace?
This type of ignition system is controlled by an ignition control module.
What is an ignition control system?
This control monitors the temperature in the plenum.
What is a thermostatic control?