HVAC UNIT 31 GAS HEAT FINAL
EXAM 2026 WITH 115 QUESTIONS
AND VERIFIED ACCURATE
ANSWERS | ALREADY GRADED A+ |
GUARANTEED SUCCESS | HVAC GAS
HEAT LATEST EXAM 2026
What gases is liquefied petroleum made of? - ANSWER-It can be liquified
propane, butane or a combination of both.
Why is butane not a popular fuel source? - 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? -
ANSWER-2500 Btu of heat energy.
What is the specific gravity of propane? - ANSWER-1.52 which means it is
heavier than air and will sink if released to the air.
,How many Btu of heat energy do you get from 1 cubic foot of butane? -
ANSWER-3200 Btu of heat energy.
Why is specific gravity of a gas important? - ANSWER-It affects the gas flow
through the piping and through the orifice of the furnace.
What is an orifice and a spud? - ANSWER-An orifice is a precisely sized hole in a
gas fitting which gas flows from the manifold to the burners.
A spud is another name for a gas fitting.
If both a light gas and a heavy gas are at the same pressure, which will flow more
through a given orifice? - ANSWER-A light gas will flow more through an orifice.
How many inches WC is in 1 psig? - ANSWER-27.7 " WC
Why is manifold pressures expressed in inches WC instead of psig? - ANSWER-
Manifold pressures are very small, less than 1 psig. Inches WC is a much more
precise measurement for less than 1 psig.
How is inches WC calculated with a water manometer? - ANSWER-A tube is
formed into a U and filled halfway with water. Gas pressure is piped to one side of
the tube and the difference in their heights is inches WC.
What are the manifold pressures for natural gas and LP gas? - ANSWER-Natural
gas 3 to 3.5 in. WC
LP gas 9 to 11 in. WC
, T or F: both a water and digital manometer can measure positive and negative
pressures. - ANSWER-False- only a digital manometer can measure negative
pressure. A water manometer can only measure a positive pressure.
What are the three elements for combustion? - ANSWER-Fuel
Oxygen
Heat
If one of the elements are not available, can there still be combustion? - ANSWER-
No, if any of the elements are missing, no combustion is possible.
How much oxygen is in the air we breathe? - ANSWER-The air contains 21%
oxygen.
Name the four main components of a gas fired heating system. - ANSWER-
Manifold and controls
Burners
Heat exchanger
Venting system
Name the four types of furnace flow patterns. - ANSWER-Upflow
Low-boy
Downflow
Horizontal
Which type of furnace is usually found in basements that have low headroom? -
ANSWER-Low-boy
EXAM 2026 WITH 115 QUESTIONS
AND VERIFIED ACCURATE
ANSWERS | ALREADY GRADED A+ |
GUARANTEED SUCCESS | HVAC GAS
HEAT LATEST EXAM 2026
What gases is liquefied petroleum made of? - ANSWER-It can be liquified
propane, butane or a combination of both.
Why is butane not a popular fuel source? - 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? -
ANSWER-2500 Btu of heat energy.
What is the specific gravity of propane? - ANSWER-1.52 which means it is
heavier than air and will sink if released to the air.
,How many Btu of heat energy do you get from 1 cubic foot of butane? -
ANSWER-3200 Btu of heat energy.
Why is specific gravity of a gas important? - ANSWER-It affects the gas flow
through the piping and through the orifice of the furnace.
What is an orifice and a spud? - ANSWER-An orifice is a precisely sized hole in a
gas fitting which gas flows from the manifold to the burners.
A spud is another name for a gas fitting.
If both a light gas and a heavy gas are at the same pressure, which will flow more
through a given orifice? - ANSWER-A light gas will flow more through an orifice.
How many inches WC is in 1 psig? - ANSWER-27.7 " WC
Why is manifold pressures expressed in inches WC instead of psig? - ANSWER-
Manifold pressures are very small, less than 1 psig. Inches WC is a much more
precise measurement for less than 1 psig.
How is inches WC calculated with a water manometer? - ANSWER-A tube is
formed into a U and filled halfway with water. Gas pressure is piped to one side of
the tube and the difference in their heights is inches WC.
What are the manifold pressures for natural gas and LP gas? - ANSWER-Natural
gas 3 to 3.5 in. WC
LP gas 9 to 11 in. WC
, T or F: both a water and digital manometer can measure positive and negative
pressures. - ANSWER-False- only a digital manometer can measure negative
pressure. A water manometer can only measure a positive pressure.
What are the three elements for combustion? - ANSWER-Fuel
Oxygen
Heat
If one of the elements are not available, can there still be combustion? - ANSWER-
No, if any of the elements are missing, no combustion is possible.
How much oxygen is in the air we breathe? - ANSWER-The air contains 21%
oxygen.
Name the four main components of a gas fired heating system. - ANSWER-
Manifold and controls
Burners
Heat exchanger
Venting system
Name the four types of furnace flow patterns. - ANSWER-Upflow
Low-boy
Downflow
Horizontal
Which type of furnace is usually found in basements that have low headroom? -
ANSWER-Low-boy
