HVAC Gas Heat Certification Practice Exam

These questions are part of the practice quiz. Start practicing

• What is the primary purpose of a flue baffle in a furnace?
• The vent system for a condensing furnace is classified as what by the National Field Gas Code?
• What is the name of the tool used to cut threads on a steel pipe?
• What safety feature is designed to shut down the furnace during unsafe conditions?
• What type of repairs might indicate that it's time for a furnace replacement?
• What age is recommended for considering a gas furnace replacement?
• Which method is used to ensure safe ignition in gas systems?
• How does a two-stage gas valve differ from a single-stage valve?
• What effect does a dirty air filter have on a gas furnace?
• What should you do if a furnace won't ignite?
• How can low manifold pressure affect a gas burner?
• How can gas flow volume to a natural gas furnace be checked?
• What is the purpose of a crossover on a gas burner?
• What should a technician check when a gas valve fails to open but other conditions are met?
• In a natural gas furnace with perfect combustion, what is the expected percentage of CO2 content in the flue gases?
• A good thermocouple should read approximately how many millivolts on a D.C. meter?
• What is one primary component necessary for achieving combustion efficiency?
• Which instrument is commonly used to measure return airflow to a gas furnace?
• What is an indication of a clogged air filter in a gas furnace?
• Which component allows a furnace to maintain temperature until the desired level is reached?
• What is a potential risk of a cracked heat exchanger in a furnace?
• What does the term "flame rollout" refer to?
• What type of solder should be used for a copper elbow on an LP gas line?
• Why is a condensate drain essential in a high-efficiency furnace?
• When running thermostat wire for 75 feet, which wire gauge should a technician use to avoid voltage drop?
• Under what condition should a thermopile be replaced?
• What is a primary advantage of using a sealed combustion furnace?
• What type of solder should a technician use when soldering spade connectors to a wire?
• Which of the following is a safety hazard associated with gas heating systems?
• A category 1 natural gas furnace typically has an air temperature rise of what range?
• What CO2 content in exhaust gases is expected in a Category IV LP unit with 50% excess air?
• What is the minimum chimney height for proper venting of a furnace?
• In a natural draft furnace, what is the typical vent stack temperature?
• What is the minimum number of installed gas furnace required for safe operation?
• How does a bi-metal fan switch operate the blower motor on a gas furnace?
• What may cause a furnace to emit yellow or orange flames?
• A spark igniter operates at what voltage?
• If a technician reads 0 Ohms between the common and low speed wires on a 120 VAC furnace motor, what does this indicate?
• When using an extension ladder to work on a rooftop unit, how far should the top of the ladder extend beyond the support point?
• What type of connectors are used to secure sections of the trunk line in a duct installation?
• What is a potential consequence of improper venting in a gas furnace?
• What should the LP gas pressure be at the appliance gas valve?
• What is the common material used for gas supply lines?
• For proper furnace operation, what should the manifold gas pressure typically be?
• When is it advisable to replace an old gas furnace?
• Gas furnaces installed at altitudes above what height require adjustments to operate properly?
• What should a technician use to clean a completely clogged pilot assembly orifice of a spark ignition furnace?
• What is the purpose of a "spud" or burner orifice in a gas furnace?
• What service is typically needed for older gas furnaces?
• What does a GFCI circuit breaker detect?
• The primary purpose of an anticipated heating thermostat is to accomplish what?
• What is a key indicator that a gas furnace may need replacement?
• A natural gas furnace usually requires what gas pressure at the manifold and burners?
• Generally, what is a sign of a furnace that should be replaced?
• Why is it important to check the AFUE rating of a furnace?
• What component is likely faulty if the spark ignition continues to spark, but the burner goes out after 60 seconds?
• When might an LP gas furnace exhibit yellow flames instead of blue?
• What happens if voltage is applied across two speed terminals on a fan motor?
• What is the purpose of fan time/temperature delay switches in gas furnaces?
• Which of the following is essential for the proper combustion of gas in a furnace?
• What happens if gas piping is not properly sized according to standards?
• What is the term used for air that is mixed with natural gas in the burner?
• What is the typical temperature rise through a gas furnace?
• What is the volume of flue gas produced by a 60,000 BTU/h Category I fan assisted natural gas furnace operating with 50% excess air?
• What is a significant safety concern when working on gas heating systems?
• A gas furnace is to be installed in a garage. The national standards require that the burners and ignition sources must be located ______ above the floor.
• To change the speed of a belt driven blower, what should the technician adjust?
• What must a technician consider when sizing a gas furnace?
• What is the function of a cut-off plate in a gas furnace?
• What is a common effect of improper duct sealing in gas heating systems?
• Which gases are classified as liquefied petroleum (LP) gases?
• Why is it important to check for gas leaks after installation?
• What might indicate that a gas valve in the furnace needs attention?
• What is the material used for the inner pipe of a Type B vent pipe?
• What are the factory settings for a standing pilot furnace equipped with a bi-metal fan/limit control?
• Why is proper venting important in gas heating systems?
• If a furnace nameplate specifies a temperature rise of 40 to 70 degrees and measurements indicate a rise of 80 degrees, what is the most appropriate action?
• Why is proper application of pipe joint compound important?
• What instrument is commonly used to monitor combustion efficiency?
• What tools are essential for troubleshooting gas heating systems?
• How can you detect a gas leak in a furnace?
• What is the function of a flame sensor in a gas furnace?
• What role does the integrated circuit board play in a gas furnace system?
• How should fan speed be set in an HVAC system?
• What condition is indicated by frequent furnace cycling?
• Which component is essential for detecting excess gas pressure in an HVAC system?
• If a furnace makes a loud bang upon ignition, what is the technician likely to check first?
• What role does the blower motor play in a gas heating system?
• Which maintenance task is critical for maintaining proper airflow in a gas furnace?
• How can the efficiency of an existing gas furnace be improved?
• How much combustion air is required to burn one cubic foot of natural gas completely?
• What is the typical current produced by a flame sensor?
• What should a technician check before replacing a hot surface igniter that is not lighting?
• What is the most common type of burner found in an induced draft furnace?
• Burning one cubic foot of liquefied petroleum gas completely will produce approximately how many BTUs?
• Natural gas primarily consists of which component?
• What does flashback indicate?
• When testing for gas leaks, what substance is commonly used?
• What does an inclined manometer measure?
• If a two-year-old gas furnace locks out while attempting to light, what has the technician determined when reading 19 VAC at the gas valve?
• What is the function of the heat exchanger in a gas furnace?
• What type of connectors are specified to control noise and vibrations in metal ductwork?
• What component regulates the flow of gas to ensure proper burner operation in gas furnaces?
• Which component is typically responsible for fan motor operation in a gas furnace setup?
• What is a common issue if a furnace has an incorrect heat anticipatory setting?
• Typical condensing furnaces have an AFUE rating of at least what percentage?
• What does the AFUE rating in gas furnaces measure?
• What is the role of combustion air in gas heating systems?
• What does a low AFUE rating indicate?
• A BTU is defined as the amount of heat required to raise the temperature of how much water?
• Burning one cubic foot of natural gas will produce approximately how many BTUs?
• During installation, which clearance is required from the gas furnace to combustible materials?
• What is the consequence of using inappropriate solder on gas lines?
• Which component is critical for the operation of a gas furnace's fan cycling during heating?
• What safety device is used to prevent overheating in a gas furnace?
• What instrument is proper for measuring carbon dioxide in flue gas?
• What is the primary purpose of a gas furnace?
• Building pressure diagnostic testing compares which of the following?
• If a furnace is over 15 years old and efficient, what should you do?
• What is the role of a thermostatic expansion valve in gas heating systems?
• What is a common cause of short cycling in gas furnaces?
• Where is a fire stop support plate typically located in a dedicated vent system?
• In a Category IV two-pipe vent system that terminates through the roof, the elbow for the combustion air intake should be pointed in which direction?
• What type of combustion occurs when there is sufficient air for natural gas to burn completely?
• What is a benefit of replacing an old furnace?
• What is the acceptable percentage of carbon monoxide in a sample of flue gas?
• What is a primary cause of "flashback" in a burner?
• During heating, how is the fan cycled in a gas furnace with an electronic control board?
• Which condition can lead to the temperature limit safety switch shutting off the burner?
• What could be the result of neglecting the cleaning of air filters in a gas furnace?
• Which maintenance action can help prevent carbon monoxide issues in gas heating systems?
• When venting Category I furnaces, where should the vent pipe size be adapted to a larger size?
• What could likely cause a blockage in the gas line of a heating system?
• Type B vent pipe must be kept at least how far from combustible materials?
• The pressure inside an induced draft heat exchanger for a mid-efficiency furnace is approximately how much?
• What preventative maintenance is recommended for gas furnaces?
• Which factor is crucial in evaluating furnace efficiency?
• What does an elevated CO2 reading in flue gases typically indicate?
• What is the first action to take with the gas line before servicing a gas furnace?
• What is the typical flue gas temperature range of a Category III furnace?
• What is the expected amperage reading for a thermostat anticipator in a standard operation?
• What type of gas is primarily used in residential heating applications?
• What is a common symptom of insufficient combustion air in gas appliances?
• What is the typical design pressure for residential natural gas systems?
• What feature do redundant gas valves provide on gas furnaces?
• When a technician observes "roll out" flames during the main ignition of a standing pilot furnace, what condition is suspected?
• What pitch should gas piping be installed with for proper drainage?
• Where should pipe joint compound be applied on threaded connections?
• How do high-efficiency gas furnaces achieve better energy savings?
• What represents a crucial design factor for forced air systems in HVAC?
• What is a characteristic of a modulating gas furnace?
• Which of the following are common types of gas furnaces?
• Which type of gas furnace uses a venting system that requires two pipes, one for exhaust and one for intake?
• What could cause a furnace to fail to stay lit after ignition?
• In a gas furnace, what does the term 'static pressure' refer to?
• A gas valve with 100% shut-off ensures which of the following?
• What does a dedicated vent system signify?
• In what scenario would a furnace require a direct vent intake?
• Which of the following symptoms may indicate a cracked heat exchanger?
• What will happen if a low voltage transformer is wired incorrectly in an electronic ignition furnace?
• What is the maximum pressure drop allowance for natural gas piping to prevent excessive pressure drops?
• What is the purpose of a spoiler screw located on a burner or adjustable shutters?
• Which component is typically responsible for the ignition process in gas furnaces?
• What type of thermocouple is commonly used in gas heating applications?
• Condensing furnaces primarily operate at what efficiency level?
• What is the typical pressure for natural gas entering a furnace?
• When a technician measures 5.5 amps on the thermostat sub-base, what should he set the heat anticipator to?
• What is the approximate number of threads for a 1/2" and 3/4" black iron pipe used in a natural gas furnace?
• What precaution should be taken during furnace installation in a home?
• What can nitrogen combine with to form NOx?
• Which component is primarily responsible for igniting the gas in a gas heating system?
• What is likely to occur if a technician attempts to run a combustion analyzer without proper calibration?
• Why is a furnace's blower CFM rating important?
• What does the term "heat pump backup" imply in gas heating systems?
• Which aspect is not typically assessed when considering furnace replacement?
• Inshot burners are known for which primary characteristic?
• What is a likely result of using an oversized mid-efficiency furnace?
• Additionally, which kind of filter is considered beneficial for indoor air quality in gas furnaces?
• What is the ignition temperature range of natural gas?
• What is the purpose of a limit switch in a furnace?
• Which factor is not typically a reason to replace a gas furnace?
• What are the two standard gauges of thermostat wire?
• At what temperature should a vent safety switch on induce draft furnaces open?
• What is the purpose of a draft inducer motor in a gas furnace?
• What is a common material used for duct insulation?
• What is the maximum external static pressure for a typical gas furnace blower system?
• What is the role of a gas pressure regulator in a furnace?
• In the formula for sensible heat calculations, what does "Cfm" represent?
• Which component is NOT essential in a gas heating system?
• A furnace requiring replacement may lead to what financial impact?
• Which safety feature is commonly integrated into modern gas furnaces?
• When a customer's furnace stops heating on very cold nights, what is a likely issue according to the technician's assessment?
• Which of the following must be present for combustion to occur?
• What should always be checked if a furnace is cycling on and off too frequently?
• What must be regularly checked to ensure safe operation of gas heating systems?
• What does AFUE stand for?
• What essential feature does a modern gas furnace often include for safety?
• What component is wired in series with the anticipator on a mid-efficiency induced draft furnace?
• What is the normal voltage for a hot surface or glow coil igniter in a furnace?
• What action should be taken if gas leaks are detected in a heating system?
• How often should a gas furnace be serviced for optimal performance?
• What is the approximate R-value for one inch of duct wrap insulation?
• What is the main purpose of the gas valve in a gas furnace?
• What type of burner is most efficient in gas combustion?
• How is the combustion process initiated in a gas furnace?
• What device is commonly used to indicate a gas leak?
• If temperature measurements on a furnace indicate a temperature rise of 80 degrees while the nameplate specifies 40 to 70 degrees, what should be done?
• What is the purpose of a gas regulator in a heating system?
• What does "bonnet capacity" refer to in a furnace?
• What could be a sign that a gas furnace is not operating efficiently?
• An infinity reading on an ohmmeter between high and low speed wires on a 120 VAC furnace motor indicates what?
• If a technician determines that a natural gas furnace has a defective heat exchanger, what should the technician do?
• What does the purging process in gas systems involve?
• What is the highest temperature a typical gas furnace vent stack should reach?
• For an 80,000 BTU gas furnace with a 3-ton cooling system, what size copper conductor is normally used?
• How does a high limit switch protect the gas furnace?
• What is the most likely cause of soot accumulation in an LP gas furnace that has been converted from natural gas?
• Furnace limit switches are typically wired in series with what component?
• If a 5-year-old natural gas furnace has wavering burner flames, what is the technician likely to suspect?
• What must operate properly for the ignition sequence to start in a gas furnace with an induced draft fan?
• Costly repairs and low efficiency ratings often indicate what?
• What is the purpose of a blower in a gas furnace?
• What type of filter is advised for gas furnace maintenance?
• What should a technician verify if a gas furnace is cycling too frequently?
• What is the specific gravity range of LP gas?