G2 Gas Technician Module 12
Questions with 100% Correct Answers
| Verified | Latest Update 2026
What does an Aquastat do? - CORRECT ANSWERS 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 ANSWERS 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 ANSWERS Automatic
safety control (normally open). Senses water flow and switch closes
What does a Pressure Control Switch (pressuretrol) do in a steam boiler? - CORRECT ANSWERS
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
ANSWERS Automatic safety control that is normally closed. It senses high pressure in the
steam boiler and opens the switch. This is at 15 psi when it opens.
How does a Thermocouple work? - CORRECT ANSWERS 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 ANSWERS 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 ANSWERS The thermocouple is screwed into the pilostat coil
What are Thermopiles? - CORRECT ANSWERS Thermopiles are a collection of thermocouples
connected in series.
How many milivolts can a Thermopile generate? What is unique about this system? - CORRECT
ANSWERS 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 ANSWERS 20-30
milivolts
Thermocouple milivolts in a closed circuit what is a good range? - CORRECT ANSWERS 10-15
milivolts
What milivolts indicates a good thermopile in an open circuit? - CORRECT ANSWERS 700-800
milivolts
What is the purpose of the pilot drop out test? - CORRECT ANSWERS To find the minimum
voltage produced by the thermocouple that will still energize the pilot stat. Usually between 2-4
milivolts
What is the flame failure response test time for a thermocouple/thermopile residential system. -
CORRECT ANSWERS 90 seconds
Closed circuit test(thermostat OPEN) on a thermopile system. - CORRECT ANSWERS 600
milivolts
Questions with 100% Correct Answers
| Verified | Latest Update 2026
What does an Aquastat do? - CORRECT ANSWERS 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 ANSWERS 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 ANSWERS Automatic
safety control (normally open). Senses water flow and switch closes
What does a Pressure Control Switch (pressuretrol) do in a steam boiler? - CORRECT ANSWERS
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
ANSWERS Automatic safety control that is normally closed. It senses high pressure in the
steam boiler and opens the switch. This is at 15 psi when it opens.
How does a Thermocouple work? - CORRECT ANSWERS 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 ANSWERS 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 ANSWERS The thermocouple is screwed into the pilostat coil
What are Thermopiles? - CORRECT ANSWERS Thermopiles are a collection of thermocouples
connected in series.
How many milivolts can a Thermopile generate? What is unique about this system? - CORRECT
ANSWERS 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 ANSWERS 20-30
milivolts
Thermocouple milivolts in a closed circuit what is a good range? - CORRECT ANSWERS 10-15
milivolts
What milivolts indicates a good thermopile in an open circuit? - CORRECT ANSWERS 700-800
milivolts
What is the purpose of the pilot drop out test? - CORRECT ANSWERS To find the minimum
voltage produced by the thermocouple that will still energize the pilot stat. Usually between 2-4
milivolts
What is the flame failure response test time for a thermocouple/thermopile residential system. -
CORRECT ANSWERS 90 seconds
Closed circuit test(thermostat OPEN) on a thermopile system. - CORRECT ANSWERS 600
milivolts
