FDNY Z-51 / RSOE FUNDAMENTALS NEW FORMAT |
ACTUAL QUESTIONS,ANSWERS & DETAILED
EXPLANATIONS|BRAND NEW 2026-2027 UPDATE
1. Math and Theory
Question 1
A refrigeration system removes 120,000 Btu/h from a space and rejects 150,000 Btu/h at the
condenser.
What is the compressor input, assuming steady operation?
A. 20,000 Btu/h
B. 30,000 Btu/h
C. 120,000 Btu/h
D. 270,000 Btu/h
CORRECT ANSWER
B. 30,000 Btu/h
EXPLANATION
Energy balance requires heat rejected = heat absorbed + compressor work. Therefore compressor
input is 150,000 − 120,000 = 30,000 Btu/h.
Question 2
A pressure gauge reads 20 psig. Approximately what is the absolute pressure at sea level?
A. 5.3 psia
B. 14.7 psia
C. 20 psia
D. 34.7 psia
CORRECT ANSWER
D. 34.7 psia
EXPLANATION
1 @THE STUDY VAULT
,Absolute pressure is gauge pressure plus atmospheric pressure. At sea level, 20 + 14.7 = 34.7 psia.
Question 3
A chiller removes 240 tons of refrigeration. Approximately how much heat is being removed per
hour?
A. 24,000 Btu/h
B. 240,000 Btu/h
C. 2,880,000 Btu/h
D. 8,640,000 Btu/h
CORRECT ANSWER
C. 2,880,000 Btu/h
EXPLANATION
One refrigeration ton is 12,000 Btu/h. Thus 240 × 12,000 = 2,880,000 Btu/h.
Question 4
Water enters a heat exchanger at 60°F and leaves at 50°F. What is the water temperature
difference?
A. 5°F
B. 10°F
C. 50°F
D. 110°F
CORRECT ANSWER
B. 10°F
EXPLANATION
The temperature difference is the entering temperature minus the leaving temperature: 60 − 50 =
10°F.
Question 5
If a pump moves 600 gallons per minute for 2 minutes, approximately how many gallons are
moved?
A. 300 gal
2 @THE STUDY VAULT
,B. 600 gal
C. 1,200 gal
D. 1,800 gal
CORRECT ANSWER
C. 1,200 gal
EXPLANATION
Volume equals flow rate multiplied by time: 600 gpm × 2 min = 1,200 gallons.
Question 6
A compressor operates at 3,600 rpm. How many revolutions does it make in 10 seconds?
A. 360
B. 600
C. 1,800
D. 36,000
CORRECT ANSWER
B. 600
EXPLANATION
3,600 revolutions per minute equals 60 revolutions per second. In 10 seconds, it makes 60 × 10 = 600
revolutions.
Question 7
A 50-ton chiller is operating at 80% of its rated cooling capacity. What is its approximate present
load?
A. 10 tons
B. 20 tons
C. 40 tons
D. 62.5 tons
3 @THE STUDY VAULT
, CORRECT ANSWER
C. 40 tons
EXPLANATION
80% of 50 tons is 0.80 × 50 = 40 tons.
Question 8
Which statement best describes sensible heat?
A. Heat that changes a substance from liquid to vapor
B. Heat that changes temperature without changing phase
C. Heat stored only in refrigerant oil
D. Heat that exists only below freezing
CORRECT ANSWER
B. Heat that changes temperature without changing phase
EXPLANATION
Sensible heat changes temperature while the substance remains in the same phase.
Question 9
Which statement best describes latent heat?
A. Heat associated with a phase change
B. Heat measured only by a pressure gauge
C. Heat that cannot be transferred
D. Heat produced only by an electric motor
CORRECT ANSWER
A. Heat associated with a phase change
EXPLANATION
Latent heat is associated with a phase change, such as liquid refrigerant boiling into vapor.
Question 10
If refrigerant pressure increases while temperature remains controlled, the saturation temperature
generally will:
4 @THE STUDY VAULT
ACTUAL QUESTIONS,ANSWERS & DETAILED
EXPLANATIONS|BRAND NEW 2026-2027 UPDATE
1. Math and Theory
Question 1
A refrigeration system removes 120,000 Btu/h from a space and rejects 150,000 Btu/h at the
condenser.
What is the compressor input, assuming steady operation?
A. 20,000 Btu/h
B. 30,000 Btu/h
C. 120,000 Btu/h
D. 270,000 Btu/h
CORRECT ANSWER
B. 30,000 Btu/h
EXPLANATION
Energy balance requires heat rejected = heat absorbed + compressor work. Therefore compressor
input is 150,000 − 120,000 = 30,000 Btu/h.
Question 2
A pressure gauge reads 20 psig. Approximately what is the absolute pressure at sea level?
A. 5.3 psia
B. 14.7 psia
C. 20 psia
D. 34.7 psia
CORRECT ANSWER
D. 34.7 psia
EXPLANATION
1 @THE STUDY VAULT
,Absolute pressure is gauge pressure plus atmospheric pressure. At sea level, 20 + 14.7 = 34.7 psia.
Question 3
A chiller removes 240 tons of refrigeration. Approximately how much heat is being removed per
hour?
A. 24,000 Btu/h
B. 240,000 Btu/h
C. 2,880,000 Btu/h
D. 8,640,000 Btu/h
CORRECT ANSWER
C. 2,880,000 Btu/h
EXPLANATION
One refrigeration ton is 12,000 Btu/h. Thus 240 × 12,000 = 2,880,000 Btu/h.
Question 4
Water enters a heat exchanger at 60°F and leaves at 50°F. What is the water temperature
difference?
A. 5°F
B. 10°F
C. 50°F
D. 110°F
CORRECT ANSWER
B. 10°F
EXPLANATION
The temperature difference is the entering temperature minus the leaving temperature: 60 − 50 =
10°F.
Question 5
If a pump moves 600 gallons per minute for 2 minutes, approximately how many gallons are
moved?
A. 300 gal
2 @THE STUDY VAULT
,B. 600 gal
C. 1,200 gal
D. 1,800 gal
CORRECT ANSWER
C. 1,200 gal
EXPLANATION
Volume equals flow rate multiplied by time: 600 gpm × 2 min = 1,200 gallons.
Question 6
A compressor operates at 3,600 rpm. How many revolutions does it make in 10 seconds?
A. 360
B. 600
C. 1,800
D. 36,000
CORRECT ANSWER
B. 600
EXPLANATION
3,600 revolutions per minute equals 60 revolutions per second. In 10 seconds, it makes 60 × 10 = 600
revolutions.
Question 7
A 50-ton chiller is operating at 80% of its rated cooling capacity. What is its approximate present
load?
A. 10 tons
B. 20 tons
C. 40 tons
D. 62.5 tons
3 @THE STUDY VAULT
, CORRECT ANSWER
C. 40 tons
EXPLANATION
80% of 50 tons is 0.80 × 50 = 40 tons.
Question 8
Which statement best describes sensible heat?
A. Heat that changes a substance from liquid to vapor
B. Heat that changes temperature without changing phase
C. Heat stored only in refrigerant oil
D. Heat that exists only below freezing
CORRECT ANSWER
B. Heat that changes temperature without changing phase
EXPLANATION
Sensible heat changes temperature while the substance remains in the same phase.
Question 9
Which statement best describes latent heat?
A. Heat associated with a phase change
B. Heat measured only by a pressure gauge
C. Heat that cannot be transferred
D. Heat produced only by an electric motor
CORRECT ANSWER
A. Heat associated with a phase change
EXPLANATION
Latent heat is associated with a phase change, such as liquid refrigerant boiling into vapor.
Question 10
If refrigerant pressure increases while temperature remains controlled, the saturation temperature
generally will:
4 @THE STUDY VAULT
