G2 EXAM PREP 550 QUESTIONS & CORRECT
ANSWERS LATEST 2025
1. What is the most effective way to prevent lime deposits in the water heater?
a. Install a charcoal filter upstream of the water heater
b. Install a water softening system
c. Install a cartridge filter upstream of the water heater
d. Install an aluminum anode - ANSWER-b
2. A gurgling sound due to firing a water heater may be a symptom of:
a. Low gas pressure
b. Over firing
c. Too low water temperature, erratic temperature control
d. The need for de-liming - ANSWER-d
3. A low limit is provided on a hot water tank which provides both space heating
and
domestic hot water to
a. Prevent rusting in the system
b. Prevent freeze-up
c. Reduce oil consumption
d. Assure a constant supply of domestic hot water - ANSWER-d
,4. A customer complains that the hot water runs out in the middle of one shower.
The
water temperature coming out of the tap is 140 ºF and begins falling within 1
minute.
After drawing water for 5 minutes, the water temperature at the bottom of the
tank
is measured at 130ºF and the burner has not come on. What is the most likely
cause?
a. The temperature control is out of calibration
b. The shower head passes too much water
c. The dip tube is cracked or broken
d. The temperature sensor is in the wrong location - ANSWER-c
5. The most likely cause of a puddle of water at the side of a water heater where
the
drain cock and relief valve are located is that:
a. The drain cock is opening intermittently
b. The relief valve is opening periodically
c. It is caused by condensation when cold water enters the heater
d. The Unitrol fitting is leaking and resealing itself - ANSWER-b
6. The high limit switch on a water heater
a. Sets the temperature of the outlet water
b. Sets the temperature for the storage tank heater
c. Limits the temperature of the water entering the heater
d. Limits the temperature in the heater - ANSWER-d
,7. Scenario: There is a storage type of system. The boiler is hot, the circulating
pump
motor is running, the thermostat is calling for heat and the upstairs is cold. The
most
likely problem is:
a. A faulty limit control
b. A faulty operator
c. An open relief valve
d. A broken pump coupling - ANSWER-d
8. What action should be taken when testing the control system on a water
heater
which is not working, and the following results are obtained?
Open circuit test—27 millivolts
Closed circuit test—13 millivolts
Drop out test—10 millivolts
a. Replace the thermocouple
b. Replace the control valve
c. Replace the pilot
d. Replace the high limit control - ANSWER-b
9. If a water heater has black scorch marks on the front above the burner access
opening, what should be done?
a. Decrease the amount of primary air and decrease the manifold pressure
, b. Adjust the pilot flame and increase the manifold pressure
c. Adjust the burner flame and decrease the draft
d. Adjust the burner flame and check the flue baffle for soot or scale - ANSWER-d
10. The purpose of a mixing valve on a combination system employing a water
heater to
provide hot water for potable use and provide space heating is to:
a. Mix hot water with cold water in the heating loop
b. Mix cold water with the hot water supply to the domestic plumbing system to
maintain a consistent temperature of domestic hot water
c. Mix cold water with the hot water supply to the heating loop to maintain a
consistent temperature of water in the heating loop
d. Return some of the hot water to the tank so that it does not run out of water -
ANSWER-b
11. The vent on a power-vented water heater requires what slope?
a. ½" per foot away from the heater
b. ½' per foot toward the heater
c. ¼" per foot away from the heater
d. ¼' per foot toward the heater - ANSWER-c
12. An aquastat responds to changes in:
a. Water pressure
b. Water temperature
c. Water flow
ANSWERS LATEST 2025
1. What is the most effective way to prevent lime deposits in the water heater?
a. Install a charcoal filter upstream of the water heater
b. Install a water softening system
c. Install a cartridge filter upstream of the water heater
d. Install an aluminum anode - ANSWER-b
2. A gurgling sound due to firing a water heater may be a symptom of:
a. Low gas pressure
b. Over firing
c. Too low water temperature, erratic temperature control
d. The need for de-liming - ANSWER-d
3. A low limit is provided on a hot water tank which provides both space heating
and
domestic hot water to
a. Prevent rusting in the system
b. Prevent freeze-up
c. Reduce oil consumption
d. Assure a constant supply of domestic hot water - ANSWER-d
,4. A customer complains that the hot water runs out in the middle of one shower.
The
water temperature coming out of the tap is 140 ºF and begins falling within 1
minute.
After drawing water for 5 minutes, the water temperature at the bottom of the
tank
is measured at 130ºF and the burner has not come on. What is the most likely
cause?
a. The temperature control is out of calibration
b. The shower head passes too much water
c. The dip tube is cracked or broken
d. The temperature sensor is in the wrong location - ANSWER-c
5. The most likely cause of a puddle of water at the side of a water heater where
the
drain cock and relief valve are located is that:
a. The drain cock is opening intermittently
b. The relief valve is opening periodically
c. It is caused by condensation when cold water enters the heater
d. The Unitrol fitting is leaking and resealing itself - ANSWER-b
6. The high limit switch on a water heater
a. Sets the temperature of the outlet water
b. Sets the temperature for the storage tank heater
c. Limits the temperature of the water entering the heater
d. Limits the temperature in the heater - ANSWER-d
,7. Scenario: There is a storage type of system. The boiler is hot, the circulating
pump
motor is running, the thermostat is calling for heat and the upstairs is cold. The
most
likely problem is:
a. A faulty limit control
b. A faulty operator
c. An open relief valve
d. A broken pump coupling - ANSWER-d
8. What action should be taken when testing the control system on a water
heater
which is not working, and the following results are obtained?
Open circuit test—27 millivolts
Closed circuit test—13 millivolts
Drop out test—10 millivolts
a. Replace the thermocouple
b. Replace the control valve
c. Replace the pilot
d. Replace the high limit control - ANSWER-b
9. If a water heater has black scorch marks on the front above the burner access
opening, what should be done?
a. Decrease the amount of primary air and decrease the manifold pressure
, b. Adjust the pilot flame and increase the manifold pressure
c. Adjust the burner flame and decrease the draft
d. Adjust the burner flame and check the flue baffle for soot or scale - ANSWER-d
10. The purpose of a mixing valve on a combination system employing a water
heater to
provide hot water for potable use and provide space heating is to:
a. Mix hot water with cold water in the heating loop
b. Mix cold water with the hot water supply to the domestic plumbing system to
maintain a consistent temperature of domestic hot water
c. Mix cold water with the hot water supply to the heating loop to maintain a
consistent temperature of water in the heating loop
d. Return some of the hot water to the tank so that it does not run out of water -
ANSWER-b
11. The vent on a power-vented water heater requires what slope?
a. ½" per foot away from the heater
b. ½' per foot toward the heater
c. ¼" per foot away from the heater
d. ¼' per foot toward the heater - ANSWER-c
12. An aquastat responds to changes in:
a. Water pressure
b. Water temperature
c. Water flow
