FDNY · CERTIFICATE OF QUALIFICATION · RSOE
FDNY Z51 ACTUAL EXAM BUNDLE 2026/2027 WITH QUESTIONS AND CORRECT
ANSWERS (100% CORRECT VERIFIED ANSWERS) ACTUAL FDNY Z-51 WRITTEN
EXAM 2026/2027 (BRAND NEW!!)
2026/2027 Official Exam
A+ 5 100%
QUESTIONS EXAM DOMAINS RATIONALES
VERIFIED COVERED INCLUDED
CATEGORIES
■ Section 1: Refrigeration Fundamentals, Components & Theory (Q1–10)
■ Section 2: Refrigerants, Classifications, Recovery & Handling (Q11–20)
■ Section 3: Plant Operations, Controls & Troubleshooting (Q21–30)
■ Section 4: Codes, Machine Room Safety & Fire Protection (Q31–40)
■ Section 5: Maintenance, Recordkeeping, Cooling Towers & BOMR (Q41–50)
STUVIAACTUALEXAM
Original practice content aligned to publicly described FDNY Z-51 / RSOE knowledge areas. Not an official FDNY product.
, SECTION 1: REFRIGERATION FUNDAMENTALS, COMPONENTS & THEORY
Q1. A centrifugal chiller is running with a low refrigerant charge. The operator notices high discharge superheat and low suction
pressure. The most likely immediate effect on the compressor is:
A. Lower motor amperage with improved efficiency only.
B. Increased discharge temperature and risk of overheating due to insufficient mass flow for cooling.
C. Automatic increase in capacity with no other symptoms.
D. Complete elimination of oil circulation problems.
Correct Answer: B
Rationale: Low charge reduces mass flow; the compressor works harder on less vapor and discharge temperature rises.
Q2. In a vapor-compression cycle, the component that rejects heat from the refrigerant to the cooling medium is the:
A. Suction accumulator only.
B. Evaporator.
C. Expansion device.
D. Condenser.
Correct Answer: D
Rationale: The condenser is where high-pressure refrigerant rejects heat and condenses.
Q3. A thermostatic expansion valve (TXV) controls refrigerant flow primarily by responding to:
A. Superheat at the evaporator outlet via the sensing bulb and external equalizer (when used).
B. Cooling-tower fan speed.
C. Only the liquid-line pressure at the valve inlet.
D. Compressor discharge temperature exclusively.
Correct Answer: A
Rationale: TXVs maintain design superheat by modulating based on bulb temperature and equalizer pressure.
Q4. The purpose of a suction-line accumulator is to:
A. Increase the pressure of vapor entering the compressor.
B. Prevent liquid refrigerant from returning to the compressor during flooded or off-cycle conditions.
C. Remove all oil from the suction gas permanently.
D. Serve as the primary metering device for the system.
Correct Answer: B
Rationale: Accumulators protect compressors from liquid slug damage.
Q5. A reciprocating compressor shows high discharge pressure and normal suction pressure. One common cause is:
A. An oversized expansion valve only.
B. Excessively low evaporator load with no other factors.
C. A completely empty refrigerant receiver.
D. Fouled condenser tubes, non-condensables, or insufficient condenser water flow.
Correct Answer: D
Rationale: High head pressure is typically a condenser-side problem.
Q6. Oil pressure failure controls on a refrigeration compressor are intended to:
A. Stop the compressor if oil pressure does not develop or is lost, protecting bearings from damage.
B. Indicate only that the crankcase heater is working.
C. Bypass the oil filter automatically.
D. Increase capacity when oil pressure is high.
Correct Answer: A
Rationale: Low oil pressure can destroy the compressor; the control provides shutdown protection.
STUVIAACTUALEXAM | Page 2 of 11
FDNY Z51 ACTUAL EXAM BUNDLE 2026/2027 WITH QUESTIONS AND CORRECT
ANSWERS (100% CORRECT VERIFIED ANSWERS) ACTUAL FDNY Z-51 WRITTEN
EXAM 2026/2027 (BRAND NEW!!)
2026/2027 Official Exam
A+ 5 100%
QUESTIONS EXAM DOMAINS RATIONALES
VERIFIED COVERED INCLUDED
CATEGORIES
■ Section 1: Refrigeration Fundamentals, Components & Theory (Q1–10)
■ Section 2: Refrigerants, Classifications, Recovery & Handling (Q11–20)
■ Section 3: Plant Operations, Controls & Troubleshooting (Q21–30)
■ Section 4: Codes, Machine Room Safety & Fire Protection (Q31–40)
■ Section 5: Maintenance, Recordkeeping, Cooling Towers & BOMR (Q41–50)
STUVIAACTUALEXAM
Original practice content aligned to publicly described FDNY Z-51 / RSOE knowledge areas. Not an official FDNY product.
, SECTION 1: REFRIGERATION FUNDAMENTALS, COMPONENTS & THEORY
Q1. A centrifugal chiller is running with a low refrigerant charge. The operator notices high discharge superheat and low suction
pressure. The most likely immediate effect on the compressor is:
A. Lower motor amperage with improved efficiency only.
B. Increased discharge temperature and risk of overheating due to insufficient mass flow for cooling.
C. Automatic increase in capacity with no other symptoms.
D. Complete elimination of oil circulation problems.
Correct Answer: B
Rationale: Low charge reduces mass flow; the compressor works harder on less vapor and discharge temperature rises.
Q2. In a vapor-compression cycle, the component that rejects heat from the refrigerant to the cooling medium is the:
A. Suction accumulator only.
B. Evaporator.
C. Expansion device.
D. Condenser.
Correct Answer: D
Rationale: The condenser is where high-pressure refrigerant rejects heat and condenses.
Q3. A thermostatic expansion valve (TXV) controls refrigerant flow primarily by responding to:
A. Superheat at the evaporator outlet via the sensing bulb and external equalizer (when used).
B. Cooling-tower fan speed.
C. Only the liquid-line pressure at the valve inlet.
D. Compressor discharge temperature exclusively.
Correct Answer: A
Rationale: TXVs maintain design superheat by modulating based on bulb temperature and equalizer pressure.
Q4. The purpose of a suction-line accumulator is to:
A. Increase the pressure of vapor entering the compressor.
B. Prevent liquid refrigerant from returning to the compressor during flooded or off-cycle conditions.
C. Remove all oil from the suction gas permanently.
D. Serve as the primary metering device for the system.
Correct Answer: B
Rationale: Accumulators protect compressors from liquid slug damage.
Q5. A reciprocating compressor shows high discharge pressure and normal suction pressure. One common cause is:
A. An oversized expansion valve only.
B. Excessively low evaporator load with no other factors.
C. A completely empty refrigerant receiver.
D. Fouled condenser tubes, non-condensables, or insufficient condenser water flow.
Correct Answer: D
Rationale: High head pressure is typically a condenser-side problem.
Q6. Oil pressure failure controls on a refrigeration compressor are intended to:
A. Stop the compressor if oil pressure does not develop or is lost, protecting bearings from damage.
B. Indicate only that the crankcase heater is working.
C. Bypass the oil filter automatically.
D. Increase capacity when oil pressure is high.
Correct Answer: A
Rationale: Low oil pressure can destroy the compressor; the control provides shutdown protection.
STUVIAACTUALEXAM | Page 2 of 11
