FDNY Z51 WRITTEN EXAM 2026/2027 NEWEST
EXAM PREPARATION WITH COMPLETE
QUESTIONS AND CORRECT ANSWERS WITH
RATIONALES | ALREADY GRADED A+| |BRAND
NEW VERSION!!
1. The efficiency of the refrigerant cycle is affected by the operation of the
condenser. A more efficient centrifugal compressor operation results from:
A) Lowering the condensing pressure
B) Raising the condensing pressure
C) Lowering the evaporator pressure
D) Increasing the compressor speed
Answer A: Lowering the condensing pressure
Rationale: Lowering condensing pressure reduces the compression ratio,
improving compressor efficiency and reducing energy consumption .
2. The heat removed from the refrigerant in a condenser is:
A) Sensible heat only
B) Sensible and latent heat
C) Latent heat only
D) Radiant heat only
Answer B: Sensible and latent heat
,Rationale: The condenser removes both sensible heat (temperature change) and
latent heat (phase change from vapor to liquid) .
3. An automatic expansion valve maintains a constant:
A) Superheat
B) Evaporator pressure
C) Condenser pressure
D) Liquid level
Answer B: Evaporator pressure
Rationale: An automatic expansion valve (AXV) maintains constant evaporator
pressure by regulating refrigerant flow .
4. Refrigerant leaves the compressor as a:
A) Subcooled liquid
B) Superheated vapor
C) Saturated vapor
D) Saturated liquid
Answer B: Superheated vapor
Rationale: Compression raises the refrigerant temperature above the saturation
point, producing superheated vapor .
,5. The amount of refrigerant that passes through an orifice plate is
determined by the:
A) Orifice diameter only
B) Difference between high side and low side pressure
C) Refrigerant temperature
D) Compressor speed
Answer B: Difference between high side and low side pressure
Rationale: Flow through an orifice is driven by the pressure differential across it .
6. Water, oil, and refrigerant would settle in a container in what order from
top to bottom?
A) Refrigerant, oil, water
B) Oil, water, refrigerant
C) Water, oil, refrigerant
D) Oil, refrigerant, water
Answer B: Oil, water, refrigerant
Rationale: Oil is lighter than water but heavier than refrigerant; refrigerant sinks to
the bottom .
7. What is the heat transfer rate of a 30-ton system?
A) 240,000 BTU/hr
B) 360,000 BTU/hr
C) 480,000 BTU/hr
, D) 300,000 BTU/hr
Answer B: 360,000 BTU/hr
Rationale: One ton of refrigeration = 12,000 BTU/hr; 30 tons = 360,000 BTU/hr .
8. What device is used to control the speed of a steam turbine?
A) Throttle valve
B) Governor valve
C) Hand valve
D) Bypass valve
Answer B: Governor valve
Rationale: A governor valve controls steam flow to the turbine, regulating its
speed .
9. The pressure graduation rate on a gauge should be at least:
A) 1.0 times the design pressure
B) 1.2 times the design pressure
C) 1.5 times the design pressure
D) 2.0 times the design pressure
Answer B: 1.2 times the design pressure
Rationale: Safety standards require gauges to be graduated to at least 1.2 times
the maximum working pressure .
EXAM PREPARATION WITH COMPLETE
QUESTIONS AND CORRECT ANSWERS WITH
RATIONALES | ALREADY GRADED A+| |BRAND
NEW VERSION!!
1. The efficiency of the refrigerant cycle is affected by the operation of the
condenser. A more efficient centrifugal compressor operation results from:
A) Lowering the condensing pressure
B) Raising the condensing pressure
C) Lowering the evaporator pressure
D) Increasing the compressor speed
Answer A: Lowering the condensing pressure
Rationale: Lowering condensing pressure reduces the compression ratio,
improving compressor efficiency and reducing energy consumption .
2. The heat removed from the refrigerant in a condenser is:
A) Sensible heat only
B) Sensible and latent heat
C) Latent heat only
D) Radiant heat only
Answer B: Sensible and latent heat
,Rationale: The condenser removes both sensible heat (temperature change) and
latent heat (phase change from vapor to liquid) .
3. An automatic expansion valve maintains a constant:
A) Superheat
B) Evaporator pressure
C) Condenser pressure
D) Liquid level
Answer B: Evaporator pressure
Rationale: An automatic expansion valve (AXV) maintains constant evaporator
pressure by regulating refrigerant flow .
4. Refrigerant leaves the compressor as a:
A) Subcooled liquid
B) Superheated vapor
C) Saturated vapor
D) Saturated liquid
Answer B: Superheated vapor
Rationale: Compression raises the refrigerant temperature above the saturation
point, producing superheated vapor .
,5. The amount of refrigerant that passes through an orifice plate is
determined by the:
A) Orifice diameter only
B) Difference between high side and low side pressure
C) Refrigerant temperature
D) Compressor speed
Answer B: Difference between high side and low side pressure
Rationale: Flow through an orifice is driven by the pressure differential across it .
6. Water, oil, and refrigerant would settle in a container in what order from
top to bottom?
A) Refrigerant, oil, water
B) Oil, water, refrigerant
C) Water, oil, refrigerant
D) Oil, refrigerant, water
Answer B: Oil, water, refrigerant
Rationale: Oil is lighter than water but heavier than refrigerant; refrigerant sinks to
the bottom .
7. What is the heat transfer rate of a 30-ton system?
A) 240,000 BTU/hr
B) 360,000 BTU/hr
C) 480,000 BTU/hr
, D) 300,000 BTU/hr
Answer B: 360,000 BTU/hr
Rationale: One ton of refrigeration = 12,000 BTU/hr; 30 tons = 360,000 BTU/hr .
8. What device is used to control the speed of a steam turbine?
A) Throttle valve
B) Governor valve
C) Hand valve
D) Bypass valve
Answer B: Governor valve
Rationale: A governor valve controls steam flow to the turbine, regulating its
speed .
9. The pressure graduation rate on a gauge should be at least:
A) 1.0 times the design pressure
B) 1.2 times the design pressure
C) 1.5 times the design pressure
D) 2.0 times the design pressure
Answer B: 1.2 times the design pressure
Rationale: Safety standards require gauges to be graduated to at least 1.2 times
the maximum working pressure .
