HVAC Unit 31 Gas Heat Exam Questions Correctly Answered 2024.
Name the four main components of a gas fired heating system. - CORRECT ANSWER Manifold and controls
Burners
Heat exchanger
Venting system
Name the four types of furnace flow patterns. - CORRECT ANSWER Upflow
Low-boy
Downflow
Horizontal
Which type of furnace is usually found in basements that have low headroom? - CORRECT ANSWER Low-
boy
What is another name for a downflow furnace? - CORRECT ANSWER Counterflow
Where do you usually find horizontal furnaces? - CORRECT ANSWER In crawl spaces, attics and suspended from floor joists in basements.
What is so special about multipoise furnaces? - CORRECT ANSWER They can be installed in any position. They are very versatile and give installers the option of upflow, downflow, horizontal right or horizontal left discharge.
Why do multipoise furnaces have extra safety controls? - CORRECT ANSWER Because these furnaces can
be placed in four different configurations, they must multiple safety controls designed into the furnace. Where are flame rollout switches usually installed? - CORRECT ANSWER They are installed near the top of the burner box, where the flame is most likely to roll out.
How do auxiliary limit switches work? - CORRECT ANSWER They are used for counterflow and horizontal furnaces. They are usually bimetallic and are mounted on the warm air blower housing to they can monitor room return air temperature and interrupt the burners when the temperature gets too hot.
Are vent limit / draft safeguard switches NC or NO and what do they do? - CORRECT ANSWER They are NC switches and monitor the draft hood temperature and open when there is any spillage of flue gas.
What are the three commonly used gas fuels? - CORRECT ANSWER Natural gas
Manufactured gas
Liquified petroleum or LP gas
What is the specific gravity of natural gas and is it lighter than air? - CORRECT ANSWER The specific gravity is .60 and it is lighter than air so it rises.
How many Btu of heat energy do you get from 1 cubic foot of natural gas? - CORRECT ANSWER 1050 Btu
of heat energy.
T or F: Natural gas is poisonous to breath and has a distinctive smell. - CORRECT ANSWER False. It is not poisonous and has no odor. In fact, an odorant is added to it to make leak detection easier.
What gases is liquified petroleum made of? - CORRECT ANSWER It can be liquified propane, butane or a combination of both.
Why is butane not a popular fuel source? - CORRECT ANSWER It has a high boiling point of 31° and is difficult to keep the pressure high enough to move the gas to the main burner.
How many Btu of heat energy do you get from 1 cubic foot of propane ? - CORRECT ANSWER 2500 Btu of heat energy.
Name the four main components of a gas fired heating system. - CORRECT ANSWER Manifold and controls
Burners
Heat exchanger
Venting system
Name the four types of furnace flow patterns. - CORRECT ANSWER Upflow
Low-boy
Downflow
Horizontal
Which type of furnace is usually found in basements that have low headroom? - CORRECT ANSWER Low-
boy
What is another name for a downflow furnace? - CORRECT ANSWER Counterflow
Where do you usually find horizontal furnaces? - CORRECT ANSWER In crawl spaces, attics and suspended from floor joists in basements.
What is so special about multipoise furnaces? - CORRECT ANSWER They can be installed in any position. They are very versatile and give installers the option of upflow, downflow, horizontal right or horizontal left discharge.
Why do multipoise furnaces have extra safety controls? - CORRECT ANSWER Because these furnaces can
be placed in four different configurations, they must multiple safety controls designed into the furnace. Where are flame rollout switches usually installed? - CORRECT ANSWER They are installed near the top of the burner box, where the flame is most likely to roll out.
How do auxiliary limit switches work? - CORRECT ANSWER They are used for counterflow and horizontal furnaces. They are usually bimetallic and are mounted on the warm air blower housing to they can monitor room return air temperature and interrupt the burners when the temperature gets too hot.
Are vent limit / draft safeguard switches NC or NO and what do they do? - CORRECT ANSWER They are NC switches and monitor the draft hood temperature and open when there is any spillage of flue gas.
What are the three commonly used gas fuels? - CORRECT ANSWER Natural gas
Manufactured gas
Liquified petroleum or LP gas
What is the specific gravity of natural gas and is it lighter than air? - CORRECT ANSWER The specific gravity is .60 and it is lighter than air so it rises.
How many Btu of heat energy do you get from 1 cubic foot of natural gas? - CORRECT ANSWER 1050 Btu
of heat energy.
T or F: Natural gas is poisonous to breath and has a distinctive smell. - CORRECT ANSWER False. It is not poisonous and has no odor. In fact, an odorant is added to it to make leak detection easier.
What gases is liquified petroleum made of? - CORRECT ANSWER It can be liquified propane, butane or a combination of both.
Why is butane not a popular fuel source? - CORRECT ANSWER It has a high boiling point of 31° and is difficult to keep the pressure high enough to move the gas to the main burner.
How many Btu of heat energy do you get from 1 cubic foot of propane ? - CORRECT ANSWER 2500 Btu of heat energy.
