G2 Gas Technician Module 12 UPDATED
ACTUAL Exam Questions and CORRECT
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 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
Thermocouple milivolts in a closed circuit what is a good range? - CORRECT ANSWER -
10-15 milivolts
What milivolts indicates a good thermopile in an open circuit? - CORRECT ANSWER -
700-800 milivolts
What is the purpose of the pilot drop out test? - CORRECT ANSWER - 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 ANSWER - 90 seconds
Closed circuit test(thermostat OPEN) on a thermopile system. - CORRECT ANSWER -
600 milivolts
away from drafts and within the pilot flame about 3/8" to 1/2",Pilot flame installation rules. -
CORRECT ANSWER - Must no impinge on main burner or heat exchanger
ACTUAL Exam Questions and CORRECT
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 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
Thermocouple milivolts in a closed circuit what is a good range? - CORRECT ANSWER -
10-15 milivolts
What milivolts indicates a good thermopile in an open circuit? - CORRECT ANSWER -
700-800 milivolts
What is the purpose of the pilot drop out test? - CORRECT ANSWER - 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 ANSWER - 90 seconds
Closed circuit test(thermostat OPEN) on a thermopile system. - CORRECT ANSWER -
600 milivolts
away from drafts and within the pilot flame about 3/8" to 1/2",Pilot flame installation rules. -
CORRECT ANSWER - Must no impinge on main burner or heat exchanger
