G2 Gas Technician Module 12 Exam 2026
Questions and Answers
What does an Aquastat do? - Correct Answer -Its an automatic operating switch
(normally open). Sense water temperature of a boiler and closes when temperature
drops.
What does a low water cut off do? - Correct Answer -Automatic safety control
(normally closed). Senses water level in the boiler. If level drops the switch opens
and shuts off the gas valve.
in series with gas valve.,What does a water flow switch do? - Correct Answer -
Automatic safety control (normally open). Senses water flow and switch closes
What does a Pressure Control Switch (pressuretrol) do in a steam boiler? - Correct
Answer -Automatic control that senses high and low steam pressure in a boiler. It
closes to start burner on low pressure and opens at high temperature to stop the
burner. Controls steam pressure in the boiler.
What does a high pressure control do in a steam boiler and at what psi does it
open? - Correct Answer -Automatic safety control that is normally closed. It senses
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, high pressure in the steam boiler and opens the switch. This is at 15 psi when it
opens.
How does a Thermocouple work? - Correct Answer -Two dissimilar metals that are
joined at two junctions. Heating one of the junctions produces a DC voltage. The
temp difference between the hot and cold metals determines the quantity of the DC
voltage.
sufficient to hold a solenoid like a pilot stat energized.,How much voltage will a
thermocouple produce? - Correct Answer -It produces 25 - 30 millivolts
it should be tightened a 1/4 turn past finger tight.,Where do you screw in a
thermocouple and how tight should it be? - Correct Answer -The thermocouple is
screwed into the pilostat coil
What are Thermopiles? - Correct Answer -Thermopiles are a collection of
thermocouples connected in series.
How many milivolts can a Thermopile generate? What is unique about this
system? - Correct Answer -It can generate 750 milivolts and it is sufficient to
operate a milivolt gas valve system. This system does not require power.
Thermocouple milivolts in a open circuit what is a good range? - Correct Answer -
20-30 milivolts
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Questions and Answers
What does an Aquastat do? - Correct Answer -Its an automatic operating switch
(normally open). Sense water temperature of a boiler and closes when temperature
drops.
What does a low water cut off do? - Correct Answer -Automatic safety control
(normally closed). Senses water level in the boiler. If level drops the switch opens
and shuts off the gas valve.
in series with gas valve.,What does a water flow switch do? - Correct Answer -
Automatic safety control (normally open). Senses water flow and switch closes
What does a Pressure Control Switch (pressuretrol) do in a steam boiler? - Correct
Answer -Automatic control that senses high and low steam pressure in a boiler. It
closes to start burner on low pressure and opens at high temperature to stop the
burner. Controls steam pressure in the boiler.
What does a high pressure control do in a steam boiler and at what psi does it
open? - Correct Answer -Automatic safety control that is normally closed. It senses
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, high pressure in the steam boiler and opens the switch. This is at 15 psi when it
opens.
How does a Thermocouple work? - Correct Answer -Two dissimilar metals that are
joined at two junctions. Heating one of the junctions produces a DC voltage. The
temp difference between the hot and cold metals determines the quantity of the DC
voltage.
sufficient to hold a solenoid like a pilot stat energized.,How much voltage will a
thermocouple produce? - Correct Answer -It produces 25 - 30 millivolts
it should be tightened a 1/4 turn past finger tight.,Where do you screw in a
thermocouple and how tight should it be? - Correct Answer -The thermocouple is
screwed into the pilostat coil
What are Thermopiles? - Correct Answer -Thermopiles are a collection of
thermocouples connected in series.
How many milivolts can a Thermopile generate? What is unique about this
system? - Correct Answer -It can generate 750 milivolts and it is sufficient to
operate a milivolt gas valve system. This system does not require power.
Thermocouple milivolts in a open circuit what is a good range? - Correct Answer -
20-30 milivolts
©COPYRIGHT 2025 ALL RIGHTS RESERVED 2
