HVAC 303 FINAL EXAM QUESTIONS
AND ANSWERS 100% PASS.
What is the approximate heating value of methane? - ANS 1000 BTU per cubic foot
Is natural gas lighter or heavier than air? - ANS Lighter
What is the approximate heating value of propane? - ANS 2500 BTU per cubic foot
Is propane lighter or heavier than air? - ANS Heavier
Why is LP gas considered more hazardous than natural gas? - ANS LP gas tends to puddle in
low areas and natural gas tends to dissipate.
What are the products of complete combustion of a hydrocarbon gas? - ANS Water and
carbon dioxide
What are the three things necessary for combustion? - ANS Oxygen, fuel, and heat
When is carbon monoxide form? - ANS When the gas is not burning completely
What is Annual Fuel Utilization Efficiency (AFUE)? - ANS The efficiency of the furnace for an
entire heating season
2026 STUDY MATERIAL @COPYRIGHT RESERVED 1
, Why is carbon monoxide production undesirable in furnace operation? - ANS Carbon
monoxide is toxic.
How does venting compare on 80 percent and 90 percent efficient heating units? - ANS 80
percent furnaces use type B vent and 90 percent furnaces use PVC pipe for venting material.
A precisely drilled hole that controls the amount of gas entering a burner is called: - ANS An
orifice
The difference between 80 percent efficiency furnaces and 90 percent efficiency furnaces is that
90 percent efficiency furnaces: - ANS Have an extra recuperative heat exchanger that
condenses water out of the flue gas.
What is the purpose of the heat exchanger? - ANS To separate the combustion gas from the
circulating air while transferring heat from the combustion gas to the circulating air
The temperature rise of a furnace is: - ANS The temperature difference between the air
entering the furnace and leaving the furnace.
What type of vent is used with 90 percent Category IV furnaces? - ANS PVC
How is a concentric vent used in a high-efficiency furnace? - ANS It allows a single outdoor
exit point for the vent and combustion air pipe.
What type of vent is used with 80 percent Category I furnaces? - ANS Type B double-wall gas
vent
The two most common categories of gas-fired furnaces are: - ANS Category I and Category IV.
A Category I furnace operates with a: - ANS High-temperature, negative-pressure vent.
2026 STUDY MATERIAL @COPYRIGHT RESERVED 2
AND ANSWERS 100% PASS.
What is the approximate heating value of methane? - ANS 1000 BTU per cubic foot
Is natural gas lighter or heavier than air? - ANS Lighter
What is the approximate heating value of propane? - ANS 2500 BTU per cubic foot
Is propane lighter or heavier than air? - ANS Heavier
Why is LP gas considered more hazardous than natural gas? - ANS LP gas tends to puddle in
low areas and natural gas tends to dissipate.
What are the products of complete combustion of a hydrocarbon gas? - ANS Water and
carbon dioxide
What are the three things necessary for combustion? - ANS Oxygen, fuel, and heat
When is carbon monoxide form? - ANS When the gas is not burning completely
What is Annual Fuel Utilization Efficiency (AFUE)? - ANS The efficiency of the furnace for an
entire heating season
2026 STUDY MATERIAL @COPYRIGHT RESERVED 1
, Why is carbon monoxide production undesirable in furnace operation? - ANS Carbon
monoxide is toxic.
How does venting compare on 80 percent and 90 percent efficient heating units? - ANS 80
percent furnaces use type B vent and 90 percent furnaces use PVC pipe for venting material.
A precisely drilled hole that controls the amount of gas entering a burner is called: - ANS An
orifice
The difference between 80 percent efficiency furnaces and 90 percent efficiency furnaces is that
90 percent efficiency furnaces: - ANS Have an extra recuperative heat exchanger that
condenses water out of the flue gas.
What is the purpose of the heat exchanger? - ANS To separate the combustion gas from the
circulating air while transferring heat from the combustion gas to the circulating air
The temperature rise of a furnace is: - ANS The temperature difference between the air
entering the furnace and leaving the furnace.
What type of vent is used with 90 percent Category IV furnaces? - ANS PVC
How is a concentric vent used in a high-efficiency furnace? - ANS It allows a single outdoor
exit point for the vent and combustion air pipe.
What type of vent is used with 80 percent Category I furnaces? - ANS Type B double-wall gas
vent
The two most common categories of gas-fired furnaces are: - ANS Category I and Category IV.
A Category I furnace operates with a: - ANS High-temperature, negative-pressure vent.
2026 STUDY MATERIAL @COPYRIGHT RESERVED 2
