G2 / Gas Technician G2 Exams (Latest 2024/ 2025
Updates STUDY BUNDLE WITH COMPLETE SOLUTIONS)
Questions and Verified Answers| 100% Correct| Grade
A
What does an Aquastat do? - ANSWERIts 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? - ANSWERAutomatic 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? - ANSWERAutomatic
safety control (normally open). Senses water flow and switch closes
What does a Pressure Control Switch (pressuretrol) do in a steam boiler? -
ANSWERAutomatic 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?
- ANSWERAutomatic 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? - ANSWERTwo 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? - ANSWERIt 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? - ANSWERThe thermocouple is screwed
into the pilostat coil
What are Thermopiles? - ANSWERThermopiles are a collection of thermocouples
connected in series.
How many milivolts can a Thermopile generate? What is unique about this system? -
ANSWERIt 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? - ANSWER20-30
milivolts
, Thermocouple milivolts in a closed circuit what is a good range? - ANSWER10-15
milivolts
What milivolts indicates a good thermopile in an open circuit? - ANSWER700-800
milivolts
What is the purpose of the pilot drop out test? - ANSWERTo 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. - ANSWER90 seconds
Closed circuit test(thermostat OPEN) on a thermopile system. - ANSWER600 milivolts
away from drafts and within the pilot flame about 3/8" to 1/2",Pilot flame
installation rules. - ANSWERMust no impinge on main burner or heat exchanger
What is flame ionization? - ANSWERThe process of heating air molecules to allow for
separation of electrons allowing a flame to conduct an electrical current. When an
AC signal is directed through the flame it will conduct an electrical charge across the
flame to the ground.
What is flame rectification? - ANSWERWhen you over size your ground to prevent a
flame detector from getting a false positive and thinking there is still flame present
due to carbon build up.
Closed circuit test(thermostat CLOSED) on a thermopile system. - ANSWER400-450
milivolts
What does a flame rod do? - ANSWERSenses a pulsating dc current that signals flame
is present.
How should you size a flame rod? Why? - ANSWERMust have 4 times less surface
area then the ground. Normal practice is 10 times smaller. This causes the signal to
flow easier from the flame rod to ground.
- ANSWERFlame failure response 0.8 seconds
- ANSWERTotal for ignition lockout between 15 & 90s
- ANSWERSpark gap 1/8 to 3/16"
Pilot flame rectification- - ANSWERPre purge up to 45 seconds
- ANSWERWhat is flame failure response time?
Updates STUDY BUNDLE WITH COMPLETE SOLUTIONS)
Questions and Verified Answers| 100% Correct| Grade
A
What does an Aquastat do? - ANSWERIts 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? - ANSWERAutomatic 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? - ANSWERAutomatic
safety control (normally open). Senses water flow and switch closes
What does a Pressure Control Switch (pressuretrol) do in a steam boiler? -
ANSWERAutomatic 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?
- ANSWERAutomatic 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? - ANSWERTwo 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? - ANSWERIt 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? - ANSWERThe thermocouple is screwed
into the pilostat coil
What are Thermopiles? - ANSWERThermopiles are a collection of thermocouples
connected in series.
How many milivolts can a Thermopile generate? What is unique about this system? -
ANSWERIt 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? - ANSWER20-30
milivolts
, Thermocouple milivolts in a closed circuit what is a good range? - ANSWER10-15
milivolts
What milivolts indicates a good thermopile in an open circuit? - ANSWER700-800
milivolts
What is the purpose of the pilot drop out test? - ANSWERTo 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. - ANSWER90 seconds
Closed circuit test(thermostat OPEN) on a thermopile system. - ANSWER600 milivolts
away from drafts and within the pilot flame about 3/8" to 1/2",Pilot flame
installation rules. - ANSWERMust no impinge on main burner or heat exchanger
What is flame ionization? - ANSWERThe process of heating air molecules to allow for
separation of electrons allowing a flame to conduct an electrical current. When an
AC signal is directed through the flame it will conduct an electrical charge across the
flame to the ground.
What is flame rectification? - ANSWERWhen you over size your ground to prevent a
flame detector from getting a false positive and thinking there is still flame present
due to carbon build up.
Closed circuit test(thermostat CLOSED) on a thermopile system. - ANSWER400-450
milivolts
What does a flame rod do? - ANSWERSenses a pulsating dc current that signals flame
is present.
How should you size a flame rod? Why? - ANSWERMust have 4 times less surface
area then the ground. Normal practice is 10 times smaller. This causes the signal to
flow easier from the flame rod to ground.
- ANSWERFlame failure response 0.8 seconds
- ANSWERTotal for ignition lockout between 15 & 90s
- ANSWERSpark gap 1/8 to 3/16"
Pilot flame rectification- - ANSWERPre purge up to 45 seconds
- ANSWERWhat is flame failure response time?
