RETA CIRO REFRIGERATION PLANT
TROUBLESHOOTING PRACTICE EXAM WITH
QUESTIONS AND VERIFIED ANSWERS,
PLUS DETAILED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1. A reciprocating ammonia compressor is operating with a suction
pressure substantially lower than normal. The compressor is
running continuously, but the refrigerated space is not reaching its
normal temperature. The liquid level in the high-pressure receiver is
normal, while the evaporator outlet superheat is considerably higher
than normal. Which condition is the MOST likely primary cause?
A. Excessive liquid refrigerant entering the compressor
B. Restricted liquid supply to the evaporator
C. Excessive condenser flooding
D. Excessive refrigerant charge in the high-pressure receiver
Answer: B. Restricted liquid supply to the evaporator
Rationale: A restricted liquid supply starves the evaporator, causing
insufficient refrigerant to boil throughout the coil. The evaporator
outlet becomes highly superheated, suction pressure falls, and
refrigeration capacity decreases. Possible causes include a restricted
hand valve, plugged strainer, malfunctioning liquid-feed valve,
inadequate pressure differential across the feed device, or an
improperly adjusted control valve.
1
,2. An operator notices that a screw compressor's discharge
temperature has increased significantly while discharge pressure
has remained approximately normal. Suction pressure is also
normal. Which troubleshooting observation should receive the
HIGHEST priority?
A. Whether the condenser fan motors are drawing excessive current
B. Whether the compressor oil temperature and oil injection system are
functioning correctly
C. Whether the high-pressure receiver contains too much liquid
D. Whether the evaporator room temperature is slightly above setpoint
Answer: B. Whether the compressor oil temperature and oil
injection system are functioning correctly
Rationale: Screw compressors rely heavily on oil for lubrication,
sealing, and—in many designs—discharge-temperature control
through oil injection. Insufficient, excessively hot, or improperly
circulated oil can allow discharge temperature to rise even when
suction and discharge pressures appear reasonable. Oil injection
temperature, oil pressure differential, oil separator condition, and oil
cooler performance should therefore be investigated promptly.
3. A flooded evaporator system is experiencing progressively poorer
refrigeration performance. Operators report that the liquid level in
the surge drum is unusually low, although the receiver contains an
adequate quantity of ammonia. What is the BEST initial
troubleshooting approach?
A. Increase compressor discharge pressure
B. Investigate the liquid-feed path between the receiver and surge drum
C. Reduce condenser capacity
D. Immediately add more refrigerant to the system
2
,Answer: B. Investigate the liquid-feed path between the receiver and
surge drum
Rationale: An adequate receiver inventory does not guarantee that
liquid is reaching the evaporator system. A closed or partially closed
valve, plugged strainer, inadequate pressure differential, failed level-
control valve, or control malfunction can prevent proper liquid
transfer. Adding refrigerant before identifying the restriction could
worsen system conditions and obscure the actual problem.
4. A compressor's suction pressure suddenly rises above its normal
operating range while the refrigerated space is warming. Which
condition is MOST consistent with these symptoms?
A. The evaporator is receiving excessive refrigerant load relative to
compressor capacity
B. The compressor suction isolation valve is completely closed
C. The condenser is operating at exceptionally low pressure
D. The oil separator is completely empty
Answer: A. The evaporator is receiving excessive refrigerant load
relative to compressor capacity
Rationale: When evaporator load increases or compressor capacity
decreases, more vapor can accumulate on the suction side than the
compressor can remove. Suction pressure therefore rises while
refrigeration performance deteriorates. Troubleshooting should
distinguish between increased load, compressor capacity-control
problems, unloading mechanisms, compressor mechanical problems,
and excessive liquid feed.
5. A condenser's approach temperature has gradually increased
over several weeks. Head pressure has also increased despite similar
3
, ambient conditions and refrigeration load. Which condition should
be investigated FIRST?
A. Fouling or reduced heat-transfer performance in the condenser
B. Excessive evaporator superheat
C. Low compressor oil level
D. A partially closed compressor suction valve
Answer: A. Fouling or reduced heat-transfer performance in the
condenser
Rationale: Increasing condenser approach temperature indicates that
the condensing temperature is becoming higher relative to the heat-
rejection medium. Fouling, scale, blocked tubes, inadequate water
flow, air accumulation, or inadequate airflow can reduce condenser
heat transfer. The trend is particularly important because gradual
degradation often indicates a maintenance-related problem rather
than a sudden control failure.
6. A high-pressure ammonia system develops unusually high
condensing pressure while the condenser fans and pumps appear to
be operating normally. Noncondensable gases are suspected. Why
can noncondensables produce high head pressure?
A. They reduce compressor suction temperature directly
B. They accumulate in the condenser and occupy heat-transfer volume
without condensing
C. They increase ammonia solubility in lubricating oil
D. They cause the evaporator to flood automatically
Answer: B. They accumulate in the condenser and occupy heat-
transfer volume without condensing
Rationale: Air and other noncondensable gases do not condense at
normal ammonia condensing conditions. Their presence increases the
4
TROUBLESHOOTING PRACTICE EXAM WITH
QUESTIONS AND VERIFIED ANSWERS,
PLUS DETAILED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1. A reciprocating ammonia compressor is operating with a suction
pressure substantially lower than normal. The compressor is
running continuously, but the refrigerated space is not reaching its
normal temperature. The liquid level in the high-pressure receiver is
normal, while the evaporator outlet superheat is considerably higher
than normal. Which condition is the MOST likely primary cause?
A. Excessive liquid refrigerant entering the compressor
B. Restricted liquid supply to the evaporator
C. Excessive condenser flooding
D. Excessive refrigerant charge in the high-pressure receiver
Answer: B. Restricted liquid supply to the evaporator
Rationale: A restricted liquid supply starves the evaporator, causing
insufficient refrigerant to boil throughout the coil. The evaporator
outlet becomes highly superheated, suction pressure falls, and
refrigeration capacity decreases. Possible causes include a restricted
hand valve, plugged strainer, malfunctioning liquid-feed valve,
inadequate pressure differential across the feed device, or an
improperly adjusted control valve.
1
,2. An operator notices that a screw compressor's discharge
temperature has increased significantly while discharge pressure
has remained approximately normal. Suction pressure is also
normal. Which troubleshooting observation should receive the
HIGHEST priority?
A. Whether the condenser fan motors are drawing excessive current
B. Whether the compressor oil temperature and oil injection system are
functioning correctly
C. Whether the high-pressure receiver contains too much liquid
D. Whether the evaporator room temperature is slightly above setpoint
Answer: B. Whether the compressor oil temperature and oil
injection system are functioning correctly
Rationale: Screw compressors rely heavily on oil for lubrication,
sealing, and—in many designs—discharge-temperature control
through oil injection. Insufficient, excessively hot, or improperly
circulated oil can allow discharge temperature to rise even when
suction and discharge pressures appear reasonable. Oil injection
temperature, oil pressure differential, oil separator condition, and oil
cooler performance should therefore be investigated promptly.
3. A flooded evaporator system is experiencing progressively poorer
refrigeration performance. Operators report that the liquid level in
the surge drum is unusually low, although the receiver contains an
adequate quantity of ammonia. What is the BEST initial
troubleshooting approach?
A. Increase compressor discharge pressure
B. Investigate the liquid-feed path between the receiver and surge drum
C. Reduce condenser capacity
D. Immediately add more refrigerant to the system
2
,Answer: B. Investigate the liquid-feed path between the receiver and
surge drum
Rationale: An adequate receiver inventory does not guarantee that
liquid is reaching the evaporator system. A closed or partially closed
valve, plugged strainer, inadequate pressure differential, failed level-
control valve, or control malfunction can prevent proper liquid
transfer. Adding refrigerant before identifying the restriction could
worsen system conditions and obscure the actual problem.
4. A compressor's suction pressure suddenly rises above its normal
operating range while the refrigerated space is warming. Which
condition is MOST consistent with these symptoms?
A. The evaporator is receiving excessive refrigerant load relative to
compressor capacity
B. The compressor suction isolation valve is completely closed
C. The condenser is operating at exceptionally low pressure
D. The oil separator is completely empty
Answer: A. The evaporator is receiving excessive refrigerant load
relative to compressor capacity
Rationale: When evaporator load increases or compressor capacity
decreases, more vapor can accumulate on the suction side than the
compressor can remove. Suction pressure therefore rises while
refrigeration performance deteriorates. Troubleshooting should
distinguish between increased load, compressor capacity-control
problems, unloading mechanisms, compressor mechanical problems,
and excessive liquid feed.
5. A condenser's approach temperature has gradually increased
over several weeks. Head pressure has also increased despite similar
3
, ambient conditions and refrigeration load. Which condition should
be investigated FIRST?
A. Fouling or reduced heat-transfer performance in the condenser
B. Excessive evaporator superheat
C. Low compressor oil level
D. A partially closed compressor suction valve
Answer: A. Fouling or reduced heat-transfer performance in the
condenser
Rationale: Increasing condenser approach temperature indicates that
the condensing temperature is becoming higher relative to the heat-
rejection medium. Fouling, scale, blocked tubes, inadequate water
flow, air accumulation, or inadequate airflow can reduce condenser
heat transfer. The trend is particularly important because gradual
degradation often indicates a maintenance-related problem rather
than a sudden control failure.
6. A high-pressure ammonia system develops unusually high
condensing pressure while the condenser fans and pumps appear to
be operating normally. Noncondensable gases are suspected. Why
can noncondensables produce high head pressure?
A. They reduce compressor suction temperature directly
B. They accumulate in the condenser and occupy heat-transfer volume
without condensing
C. They increase ammonia solubility in lubricating oil
D. They cause the evaporator to flood automatically
Answer: B. They accumulate in the condenser and occupy heat-
transfer volume without condensing
Rationale: Air and other noncondensable gases do not condense at
normal ammonia condensing conditions. Their presence increases the
4
