G2 Gas Technician Module 20 Revised
Questions with 100% Correct Answers
| Verified | Latest Update 2026
What prevents the water in a hydronic heating system from boiling into steam when the system is
operating above the atmospheric temperature? - CORRECT ANSWERS Pressurization of the
system
List the four subsystems of a hydronic space heating system? - CORRECT ANSWERS Heat
Source, Circulation system, Heat Emitters, Control system
What must be done to protect the potable water supply to a hot water boiler? - CORRECT ANSWERS
Approved backflow preventer installed in the water supply
Above what input is a low water cut-off a required component of a hot water boiler? - CORRECT
ANSWERS 400,000 BTU
Why are cast-iron sectional boilers used only in closed loop hydronic system? - CORRECT ANSWERS
Purge itself of Air and reduces corrosion
Why does a copper fin-tube boiler require less surface area to transfer heat than a steel fire tube boiler?
- CORRECT ANSWERS Copper Tube has a higher thermal conductivity than steel tube
What happens to the water vapour in the combustion products if the flue gases are cooled below the
dew point? - CORRECT ANSWERS The water vapour condenses into liquid state
How is an automatic vent damper interlocked to ensure it is in the open position before the burner can
fire? - CORRECT ANSWERS The damper actuator has a proving switch that is interlocked with
the thermostat controlling the burner
, Which is the simplest hydronic distribution system? - CORRECT ANSWERS Single Series
Circuit
What two purposes are served when a combination system is used? - CORRECT ANSWERS
Space Heating and Domestic Water
May chemical additives be introduced into a combustion system? - CORRECT ANSWERS No
What device within a closed hydronic system is required to provide provision for the volumetric
expansion of the system fluid under normal operating condition? - CORRECT ANSWERS
Expansion Tank
List four common air elimination devices used on hydronic heating system. - CORRECT ANSWERS
Manual Air Vent, Automatic Air vent, Air purgers, and Microbubblers
Which device within a hydronic heating system is required to release water during an unsafe condition
caused by excessive pressures? - CORRECT ANSWERS ASME Pressure Relief Valve
Which type of valve is best suited for throttling flow? - CORRECT ANSWERS Globe Valve or
Gate Valve
What two types of drive heads can be used on a thermostatic radiator valve? - CORRECT ANSWERS
Mechanical and electrical
On three and four-way mixing valves, where does the mixing take place? - CORRECT ANSWERS
Within the valve body
Questions with 100% Correct Answers
| Verified | Latest Update 2026
What prevents the water in a hydronic heating system from boiling into steam when the system is
operating above the atmospheric temperature? - CORRECT ANSWERS Pressurization of the
system
List the four subsystems of a hydronic space heating system? - CORRECT ANSWERS Heat
Source, Circulation system, Heat Emitters, Control system
What must be done to protect the potable water supply to a hot water boiler? - CORRECT ANSWERS
Approved backflow preventer installed in the water supply
Above what input is a low water cut-off a required component of a hot water boiler? - CORRECT
ANSWERS 400,000 BTU
Why are cast-iron sectional boilers used only in closed loop hydronic system? - CORRECT ANSWERS
Purge itself of Air and reduces corrosion
Why does a copper fin-tube boiler require less surface area to transfer heat than a steel fire tube boiler?
- CORRECT ANSWERS Copper Tube has a higher thermal conductivity than steel tube
What happens to the water vapour in the combustion products if the flue gases are cooled below the
dew point? - CORRECT ANSWERS The water vapour condenses into liquid state
How is an automatic vent damper interlocked to ensure it is in the open position before the burner can
fire? - CORRECT ANSWERS The damper actuator has a proving switch that is interlocked with
the thermostat controlling the burner
, Which is the simplest hydronic distribution system? - CORRECT ANSWERS Single Series
Circuit
What two purposes are served when a combination system is used? - CORRECT ANSWERS
Space Heating and Domestic Water
May chemical additives be introduced into a combustion system? - CORRECT ANSWERS No
What device within a closed hydronic system is required to provide provision for the volumetric
expansion of the system fluid under normal operating condition? - CORRECT ANSWERS
Expansion Tank
List four common air elimination devices used on hydronic heating system. - CORRECT ANSWERS
Manual Air Vent, Automatic Air vent, Air purgers, and Microbubblers
Which device within a hydronic heating system is required to release water during an unsafe condition
caused by excessive pressures? - CORRECT ANSWERS ASME Pressure Relief Valve
Which type of valve is best suited for throttling flow? - CORRECT ANSWERS Globe Valve or
Gate Valve
What two types of drive heads can be used on a thermostatic radiator valve? - CORRECT ANSWERS
Mechanical and electrical
On three and four-way mixing valves, where does the mixing take place? - CORRECT ANSWERS
Within the valve body
