FDNY Z-51 / RSOE Fundamentals 450 Original Practice Questions & Answers | 2026–2027 Study Edition

450 Original Practice Questions & Answers | 2026–2027 Study
Edition

1. Math & Refrigeration Theory
1. A refrigeration system absorbs 120,000 Btu/h and receives 20,000 Btu/h of compressor input. Approximately
howmuch heat must be rejected at the condenser?
A. 100,000 Btu/h
B. 140,000 Btu/h
C. 20,000 Btu/h
D. 120,000 Btu/h
Answer: B. 140,000 Btu/h

2. A chiller is rated at 1 tons of refrigeration. Approximately how much heat does it remove per hour?
A. 12,000 Btu/h
B. 1,000 Btu/h
C. 6,000 Btu/h
D. 14,400 Btu/h
Answer: A. 12,000 Btu/h

3. Water enters a heat exchanger at 55°F and leaves at 40°F. What is the temperature difference?
A. 15°F
B. 95°F
C. 40°F
D. 55°F
Answer: A. 15°F

4. Water enters a heat exchanger at 50°F and leaves at 32°F. What is the temperature difference?
A. 50°F
B. 18°F
C. 82°F
D. 32°F
Answer: B. 18°F

5. A refrigeration system absorbs 120,000 Btu/h in the evaporator and rejects 150,000 Btu/h at the condenser.
Assuming steady operation, what is the approximate compressor input?
A. 30,000 Btu/h
B. 270,000 Btu/h
C. 90,000 Btu/h
D. 150,000 Btu/h
Answer: A. 30,000 Btu/h

6. Water enters a heat exchanger at 42°F and leaves at 30°F. What is the temperature difference?
A. 30°F
B. 42°F
C. 12°F



FDNY Z-51 / RSOE Fundamentals • Original Practice • Page 1

, D. 72°F
Answer: C. 12°F

7. A chiller is rated at 10 tons of refrigeration. Approximately how much heat does it remove per hour?
A. 120,000 Btu/h
B. 10,000 Btu/h
C. 60,000 Btu/h
D. 144,000 Btu/h
Answer: A. 120,000 Btu/h

8. A refrigeration system absorbs 170,000 Btu/h and receives 45,000 Btu/h of compressor input. Approximately
howmuch heat must be rejected at the condenser?
A. 125,000 Btu/h
B. 170,000 Btu/h
C. 215,000 Btu/h
D. 45,000 Btu/h
Answer: C. 215,000 Btu/h

9. A pressure gauge reads 15 psig at sea level. Approximately what is the absolute pressure?
A. 44.4 psia
B. 0.3 psia
C. 29.7 psia
D. 15 psia
Answer: C. 29.7 psia

10. A refrigeration system absorbs 60,000 Btu/h in the evaporator and rejects 85,000 Btu/h at the condenser.
Assuming steady operation, what is the approximate compressor input?
A. 145,000 Btu/h
B. 25,000 Btu/h
C. 85,000 Btu/h
D. 35,000 Btu/h
Answer: B. 25,000 Btu/h

11. Water enters a heat exchanger at 90°F and leaves at 70°F. What is the temperature difference?
A. 70°F
B. 90°F
C. 160°F
D. 20°F
Answer: D. 20°F

12. A refrigeration system absorbs 220,000 Btu/h and receives 40,000 Btu/h of compressor input. Approximatelyhow
much heat must be rejected at the condenser?
A. 40,000 Btu/h
B. 260,000 Btu/h
C. 220,000 Btu/h
D. 180,000 Btu/h
Answer: B. 260,000 Btu/h

13. A refrigeration system absorbs 80,000 Btu/h and receives 30,000 Btu/h of compressor input. Approximately
howmuch heat must be rejected at the condenser?



FDNY Z-51 / RSOE Fundamentals • Original Practice • Page 2

, A. 80,000 Btu/h
B. 110,000 Btu/h
C. 50,000 Btu/h
D. 30,000 Btu/h
Answer: B. 110,000 Btu/h

14. A refrigeration system absorbs 140,000 Btu/h and receives 30,000 Btu/h of compressor input. Approximatelyhow
much heat must be rejected at the condenser?
A. 170,000 Btu/h
B. 140,000 Btu/h
C. 30,000 Btu/h
D. 110,000 Btu/h
Answer: A. 170,000 Btu/h

15. A chiller is rated at 8 tons of refrigeration. Approximately how much heat does it remove per hour?
A. 96,000 Btu/h
B. 8,000 Btu/h
C. 115,200 Btu/h
D. 48,000 Btu/h
Answer: A. 96,000 Btu/h

16. Water enters a heat exchanger at 68°F and leaves at 48°F. What is the temperature difference?
A. 68°F
B. 116°F
C. 20°F
D. 48°F
Answer: C. 20°F

17. A refrigeration system absorbs 200,000 Btu/h and receives 30,000 Btu/h of compressor input. Approximatelyhow
much heat must be rejected at the condenser?
A. 230,000 Btu/h
B. 170,000 Btu/h
C. 30,000 Btu/h
D. 200,000 Btu/h
Answer: A. 230,000 Btu/h

18. A refrigeration system absorbs 140,000 Btu/h in the evaporator and rejects 175,000 Btu/h at the condenser.
Assuming steady operation, what is the approximate compressor input?
A. 35,000 Btu/h
B. 175,000 Btu/h
C. 315,000 Btu/h
D. 105,000 Btu/h
Answer: A. 35,000 Btu/h

19. A pressure gauge reads 25 psig at sea level. Approximately what is the absolute pressure?
A. 39.7 psia
B. 10.3 psia
C. 54.4 psia
D. 25 psia
Answer: A. 39.7 psia


FDNY Z-51 / RSOE Fundamentals • Original Practice • Page 3

, 20. Water enters a heat exchanger at 80°F and leaves at 62°F. What is the temperature difference?
A. 80°F
B. 142°F
C. 62°F
D. 18°F
Answer: D. 18°F

21. Water enters a heat exchanger at 72°F and leaves at 60°F. What is the temperature difference?
A. 72°F
B. 132°F
C. 60°F
D. 12°F
Answer: D. 12°F

22. A refrigeration system absorbs 100,000 Btu/h and receives 40,000 Btu/h of compressor input. Approximatelyhow
much heat must be rejected at the condenser?
A. 60,000 Btu/h
B. 100,000 Btu/h
C. 140,000 Btu/h
D. 40,000 Btu/h
Answer: C. 140,000 Btu/h

23. A chiller is rated at 15 tons of refrigeration. Approximately how much heat does it remove per hour?
A. 216,000 Btu/h
B. 15,000 Btu/h
C. 180,000 Btu/h
D. 90,000 Btu/h
Answer: C. 180,000 Btu/h

24. A pressure gauge reads 75 psig at sea level. Approximately what is the absolute pressure?
A. 89.7 psia
B. 60.3 psia
C. 104.4 psia
D. 75 psia
Answer: A. 89.7 psia

25. A refrigeration system absorbs 60,000 Btu/h and receives 20,000 Btu/h of compressor input. Approximately
howmuch heat must be rejected at the condenser?
A. 80,000 Btu/h
B. 20,000 Btu/h
C. 60,000 Btu/h
D. 40,000 Btu/h
Answer: A. 80,000 Btu/h

26. A refrigeration system absorbs 190,000 Btu/h and receives 25,000 Btu/h of compressor input. Approximatelyhow
much heat must be rejected at the condenser?
A. 25,000 Btu/h
B. 215,000 Btu/h
C. 190,000 Btu/h
D. 165,000 Btu/h



FDNY Z-51 / RSOE Fundamentals • Original Practice • Page 4