Gas Furnace Certification Practice Exam

These questions are part of the practice quiz. Start practicing

• At what temperature is natural gas considered highly flammable?
• What does CO2 percentage indicate in the context of gas combustion?
• The vent system for a condensing furnace is classified as _______ by the National Field Gas Code.
• What routine check should be performed on a gas furnace during maintenance?
• What maintenance can improve furnace efficiency over time?
• Which agency provides safety standards for gas appliances?
• What is the required height for burners and ignition sources above the floor when installing a gas furnace in a garage?
• What is the main gas used in most residential gas furnaces?
• What regular maintenance activity extends the lifespan of a gas furnace?
• What component is wired in series with the anticipator on a mid-efficiency induced draft furnace?
• Burning one cubic foot of natural gas will produce approximately ________ BTUs.
• When should you consider upgrading an old gas furnace?
• When testing a gas furnace, what indicates a potential issue with the furnace's electrical circuit?
• What is a primary cause of burner "flashback"?
• What does a two-stage gas valve provide in a furnace?
• How can homeowners increase the efficiency of their gas furnace?
• What is the purpose of a crossover on a gas burner?
• What type of furnace utilizes a downstream venting system?
• What are the hazards of improper venting in a gas furnace?
• What is the function of the limit switch in a gas furnace?
• What should be your next step if the furnace fails to reset after an emergency?
• What is the typical vent stack temperature on a natural draft furnace?
• What should be done if a gas furnace produces strange smells?
• What role does a spark ignition play in a gas furnace?
• At what temperature should the vent safety switch in induced draft furnaces open?
• What is a hot surface ignitor?
• How many BTUs are produced by burning one cubic foot of Liquefied Petroleum?
• What is the purpose of a spoiler screw or adjustable shutters on a burner?
• While evaluating a gas valve that failed to open, if continuity is present and proper voltage is at the terminal, what should be checked next?
• Which component of a gas furnace is responsible for igniting the gas?
• What is the main function of the fan/limit control in a standing pilot furnace?
• What is the maximum pressure drop allowance for natural gas piping?
• If a technician finds that the burner flames waver in one corner after starting a 5-year-old natural gas furnace, what could be the likely issue?
• Thermostat wire typically comes in which two standard gauges?
• For an 80,000 BTU gas furnace with a 3-ton cooling system, what size copper conductor is normally used?
• What type of filter should be used for optimal gas furnace performance?
• What is the required gas pressure at the manifold and burners for a natural gas furnace?
• What does an inclined manometer measure?
• What are the two types of gas utilized by residential furnaces?
• What connectors are specified to control noise and vibrations in metal ductwork?
• What safety device is typically used to prevent overheating in gas furnaces?
• Which of the following is NOT a component needed for combustion?
• What should you avoid doing during a gas furnace emergency?
• What importance does proper ventilation have for a gas furnace?
• What is the approximate R-value for one inch of duct wrap insulation used on round metal ducts?
• What is the consequence of failing to wire a replacement low voltage transformer in an electronic ignition furnace correctly?
• What is the LP gas pressure supplied to the appliance gas valve?
• The cut-off plate is a component of which part of the furnace?
• What can happen if a gas furnace operates with a clogged filter?
• What instrument would a technician use to measure the return airflow to a furnace?
• Which component is essential for safe operation of a gas furnace during ignition sequence?
• Typical condensing furnaces have an AFUE rating of at least:
• How much combustion air is required to burn one cubic foot of natural gas completely?
• What type of solder is recommended when soldering spade connectors to a wire?
• What is the purpose of an anticipator in a thermostat?
• Which component is essential for the ignition process in a gas furnace?
• Where should pipe joint compound be applied?
• What must a technician check before replacing a gas furnace?
• In a Category IV LP unit, what is the expected CO2 content when properly installed and operating with 50% excess air?
• What is the primary function of the flame sensor in a gas furnace?
• An installed gas furnace should have a minimum of how many inches for service access?
• Natural gas primarily consists of:
• What issue might arise from using the wrong size gas furnace?
• What is a potential cause of excessive soot accumulation in the heat exchanger of an LP gas furnace that was converted from natural gas?
• What is the significance of venting in gas furnaces?
• A GFCI circuit breaker is designed to detect what?
• How is the fan cycled during heating in a gas furnace with an electronic control board?
• What is a characteristic of a dedicated vent system in a gas furnace?
• What is one of the safety measures used in gas line installation to prevent leakage?
• How can you tell if a gas furnace blower motor is failing?
• What component in a furnace is typically assessed when diagnosing lighting issues?
• What causes carbon monoxide to be produced in gas furnaces?
• Which of the following describes the primary purpose of a combustion air intake in a furnace?
• Why is it essential to have a carbon monoxide detector near a gas furnace?
• What is the primary function of a gas furnace burner's orifice?
• How does a furnace's efficiency affect energy bills?
• Which of the following materials is commonly used for venting in high-efficiency furnaces?
• What is the purpose of a flame rollout switch?
• When should routine inspections of the carbon monoxide levels in flue gas be conducted?
• What describes how a bi-metal fan switch operates a blower motor in a gas furnace?
• In a Category IV two-pipe system that terminates through the roof, the elbow for the combustion air intake should:
• What is the specific gravity range of LP gas?
• A good thermocouple should read approximately how many millivolts on a DC meter?
• What effect does high resistance in a furnace's electrical system have on operation?
• What are the factory settings for a standing pilot furnace with a bi-metal fan/limit control?
• What aspect of gas piping must be considered to avoid combustion issues?
• A technician measures 5.5 amps on the thermostat sub-base. To set the heat anticipator correctly, what should the technician set it to?
• What is the function of fresh air intake in gas furnace systems?
• In a properly functioning gas furnace, the thermocouple is responsible for:
• How much flue gas is produced from a 60,000 BTU/h Category I fan-assisted natural gas furnace operating with 50% excess air?
• What measure is essential for maintaining the efficiency of a condensing furnace?
• What can nitrogen combine with to form NOx?
• A "spud" or burner orifice is used to:
• What should a technician do if a natural gas furnace has a defective heat exchanger?
• In the formula for sensible heat, what does 'Cfm' stand for?
• What is a common method for troubleshooting a furnace that won't start?
• What is the purpose of a flue baffle?
• If temperature measurements indicate a rise of 80 degrees when a furnace nameplate specifies a rise of 40 to 70 degrees, what should be done?
• Which condition would cause the temperature safety limit switch to shut off the burner?
• How do variable speed blowers improve comfort in a gas furnace?
• What should always be done after shutting off the furnace in an emergency?
• What is the approximate pressure inside an induced draft heat exchanger for a mid-efficiency furnace?
• How does a flex connector function in a duct system?
• A category 1 natural gas furnace typically has an air temperature rise of how many degrees Fahrenheit?
• What is short cycling in a gas furnace?
• Which of the following is a sign of a limit switch malfunction?
• At what altitude must gas furnaces have adjustments to operate properly?
• How often should gas furnace filters be changed?
• What is the purpose of a gas control valve in a furnace?
• Furnace limit switches are wired in series with which component?
• What does building pressure diagnostic testing compare?
• What type of heating method does a gas furnace utilize?
• What type of solder should be used when installing a brass elbow on an LP gas line?
• What does a reading of infinity between the high and low-speed wires on a 120 VAC furnace motor indicate?
• What is a common sign of a malfunctioning gas furnace?
• A gas valve with 100% shut-off indicates what about the gas flow?
• What material is recommended for the joint between gas lines and brass fittings?
• What maintenance task can improve the efficiency of a gas furnace?
• What does an AFUE rating indicate for furnaces?
• How can gas flow volume to a natural gas furnace be checked?
• Which of the following components is essential to the functioning of an LP gas furnace?
• What is the approximate number of threads to cut when installing 1/2" and 3/4" black iron pipe to a natural gas furnace?
• What type of thermostat is often used with a gas furnace?
• The typical flue gas temperature of a Category III furnace is:
• What is the correct method for cleaning a completely clogged pilot assembly orifice in a spark ignition furnace?
• If a limit switch is functioning correctly, what should it prevent?
• What is a draft inducer's role in a gas furnace system?
• Liquefied petroleum (LP) gases primarily include which two gases?
• After stopping the furnace in an emergency, what should homeowners do next?
• Which component directly controls gas flow in a gas furnace?
• Fan speed on a gas furnace should be set based on what?
• What indicator shows a gas furnace is operating efficiently?
• The use of which type of gas is indicated by a gas color that is yellow or green?
• Which action is suggested if your furnace continually exceeds the operational temperature?
• What unit measures the heating capacity of a gas furnace?
• To avoid a voltage drop when running a thermostat wire 75 feet, which wire gauge should be used?
• What is a critical factor in ensuring effective combustion within a gas furnace?
• What is the function of an ignition board in a furnace?
• What is the recommended gas input and output for efficient furnace operation?
• At what voltage does a spark igniter typically operate?
• What is the standard for gas piping materials in residential applications?
• Which type of maintenance is crucial for ensuring the safety of a gas furnace?
• During which season is maintenance of a gas furnace most critical?
• What should be monitored to maintain safe operation of a gas furnace?
• What is the effect of too much excess air on combustion efficiency?
• Which of the following connects sections of trunk line in gas furnace installations?
• What is the purpose of fan time/temperature delay switches in gas furnaces?
• What is a common issue related to ducting in gas furnace systems?
• What might indicate a need for thermostat wire replacement?
• What is the primary function of a gas line pitch?
• What is the maximum external static pressure typically found in a gas furnace blower system?
• A furnace nameplate specifies a temperature rise of 40F-70F. Temperature measurements indicate a rise of 80F. The most appropriate action is to:
• A technician notices flames "roll out" during the main ignition of a standing pilot furnace. What is the suspected issue?
• What does "bonnet capacity" refer to in a gas furnace?
• When should a technician consider replacing a fan/limit control?
• What can be a consequence of not maintaining a gas furnace?
• What type of connectors are used to secure sections of the trunk line in sheet metal duct installations?
• To change the speed of a belt-driven blower, what should a technician adjust?
• Which instrument is most appropriate for calculating carbon dioxide levels in flue gas?
• What safety device is commonly used to prevent gas leaks in a furnace?
• What is the purpose of a condensate drain in a high-efficiency gas furnace?
• What common symptom indicates a dirty filter in a gas furnace?
• What troubleshooting step should be taken if a furnace does not ignite properly?
• What does flashback indicate in a gas system?
• What is the acceptable percentage of carbon monoxide in a sample of flue gas?
• What is air mixed with natural gas in the burner called?
• When venting Category 1 furnaces, where should the vent pipe size be increased?
• Which of the following must be present for combustion to occur?
• What does the pressure switch do in a gas furnace?
• Which of the following is NOT a sign of a furnace limit switch issue?
• What is the safest route in case of gas detection in a furnace?
• Type B vent pipe is primarily constructed with which materials?
• Why is periodic inspection of gas connections vital in a furnace system?
• What is typically the major cause of furnace inefficiency on very cold nights?
• Which component is critical for ignition in a gas furnace?
• What type of gas furnace is known for its energy efficiency?
• If perfect combustion occurs in a natural gas furnace, what percentage of CO2 will be present in the flue gases?
• A BTU is the amount of heat required to raise the temperature of one pound of water:
• What immediate step should be taken if you suspect a gas leak from the furnace?
• Why is it important to contact a professional during a gas furnace emergency?
• Which switch must operate properly before the ignition sequence of a gas furnace starts?
• What type of flame can be expected when burning natural gas?
• What is the most common burner used in an induced draft furnace?
• What does a reading of 0 Ohms between the common and low-speed wires on a 120 VAC furnace motor indicate?
• What is the primary purpose of a gas meter in a gas furnace system?
• What is the typical lifespan of a gas furnace with proper maintenance?
• Why is insulation important for gas furnace ducts?
• What must be ensured when installing a gas furnace regarding air intake?
• What environmental factor can affect gas furnace performance?
• What might be a likely consequence of improperly sizing a mid-efficiency furnace?
• What is the primary purpose of a gas furnace?
• What is the ignition temperature range of natural gas?
• What indicates that a furnace's limit switch may be malfunctioning?
• A furnace that stops heating before the residence is warm on cold nights may have an issue with which setting?
• What is a common issue with metal ductwork in residential installations?
• What might be a sign of insufficient airflow in a gas furnace?
• What does AFUE stand for in relation to gas furnaces?
• What is the required pitch for installing gas piping?
• What can frequently cycling on and off indicate in a gas furnace?
• If a furnace with a hot surface igniter does not light, what should a technician check before replacing the igniter?
• What should be done if a gas furnace emits a strange odor?
• During the startup of a spark ignition furnace, if the spark continues to ignite but the burners go out after 60 seconds, what is the likely suspect?
• What is the proper name for the tool used to create threads on a steel pipe?
• What occurs if voltage is applied across two speed terminals on a fan motor?
• What component is responsible for the ignition in a direct spark ignition system?
• What could cause a fluttering flame during furnace operation?
• How much current does a typical flame sensor produce?
• If a gas furnace locks out while attempting to light and measures 19 VAC at the gas valve, what is the likely cause?
• What is the first action homeowners should take during a gas furnace emergency?
• What might indicate the need for immediate furnace troubleshooting?
• The reason heating thermostats have anticipators is to:
• What does AFUE stand for in relation to gas furnaces?
• When assessing furnace operation, what does a high temperature rise typically indicate?
• If a blower motor is running off the incorrect voltage, what is a potential outcome?
• In a dedicated vent system, where is a fire stop support plate typically located?
• Type B vent pipe must be kept at least ________ from combustible materials.
• What is a gas furnace’s role in a home’s HVAC system?
• If a furnace makes a loud bang upon ignition, what is the first action a technician should take regarding the gas pressure?
• What is a common outcome of a malfunctioning limit switch?
• In the event of a working limit switch, what is the likely system behavior?
• What is the most common voltage for a hot surface igniter designed for direct ignition?
• Why is it important to ensure proper venting of a gas furnace?
• What do redundant gas valves used in gas furnaces feature?