RETA CIRO REFRIGERATION SYSTEM
FAILURE DIAGNOSIS PRACTICE EXAM
WITH QUESTIONS AND VERIFIED
ANSWERS, PLUS DETAILED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
Question 1
An ammonia refrigeration system serving a large cold-storage facility
experiences a gradual increase in suction pressure. Operators report that
the refrigerated rooms are no longer reaching their normal design
temperature. Compressor suction temperature is higher than usual, while
discharge pressure remains relatively stable. Inspection shows that the
evaporator fans and motors are operating normally, and there is no
obvious accumulation of ice on the evaporator coil. Which condition is
the MOST likely initial suspect?
A. Excessive liquid ammonia entering the compressor
B. Restricted condenser water flow
C. Reduced evaporator heat transfer caused by an inadequate refrigerant
feed
D. Excessively high compressor discharge temperature
Answer: C. Reduced evaporator heat transfer caused by an
inadequate refrigerant feed
Rationale: A poorly fed evaporator can produce inadequate cooling
capacity while causing suction pressure and suction temperature
behavior to deviate from normal operating conditions. The evaporator
may not have enough liquid refrigerant available to absorb the
intended heat load. The operator should investigate the liquid feed
1
,device, upstream valves, strainers, differential pressure, and liquid
supply conditions. Excessive liquid carryover would instead raise
concern for compressor damage from liquid slugging or oil dilution,
while restricted condenser flow would more directly affect condensing
pressure.
Question 2
During diagnosis of an ammonia refrigeration system, an operator
observes that the compressor discharge pressure is significantly higher
than normal. The suction pressure is also somewhat elevated, and the
condenser appears clean externally. Ambient temperature has not
changed significantly. Which condition should receive the highest
diagnostic priority?
A. Non-condensable gases accumulated in the condenser
B. Excessively low evaporator pressure
C. Compressor suction strainer restriction
D. Insufficient refrigerant charge
Answer: A. Non-condensable gases accumulated in the condenser
Rationale: Non-condensable gases such as air occupy condenser
volume without condensing like ammonia. This reduces effective
condenser capacity and can force the system to operate at an
abnormally high condensing pressure. Elevated head pressure without
a corresponding environmental explanation is a classic reason to
investigate non-condensables, although dirty condenser surfaces,
inadequate cooling-water flow, excessive ambient temperature, and
overcharge must also be considered.
Question 3
2
,A reciprocating ammonia compressor begins making a sharp metallic
knocking sound immediately after a sudden change in suction
conditions. The suction pressure has risen rapidly, and the compressor
suction line is unusually cold with evidence of liquid accumulation.
Which failure mechanism is MOST concerning?
A. Bearing overheating caused by excessive discharge pressure
B. Liquid slugging caused by liquid ammonia entering the compressor
cylinder
C. Condenser fouling caused by scale
D. Excessive non-condensable concentration
Answer: B. Liquid slugging caused by liquid ammonia entering the
compressor cylinder
Rationale: Compressors are designed to compress vapor, not
incompressible liquid. Liquid ammonia entering a reciprocating
compressor cylinder can cause severe mechanical damage to valves,
pistons, connecting rods, and other components. A rapid suction-
pressure change combined with unusually cold suction piping and
evidence of liquid migration should prompt immediate protective
action according to the facility's operating procedures.
Question 4
A system's evaporator pressure is substantially lower than normal while
the compressor is operating continuously. The refrigerated space is
warmer than its setpoint. The liquid receiver contains an adequate
quantity of ammonia, and the condenser is operating normally. Which
problem is MOST consistent with these observations?
A. Excessive refrigerant migration to the receiver
B. Overfeeding of the evaporator
3
, C. Restricted refrigerant flow to the evaporator
D. Excessive condenser capacity
Answer: C. Restricted refrigerant flow to the evaporator
Rationale: A restriction in the liquid feed path can starve the
evaporator. The compressor continues removing vapor, causing
evaporator pressure to fall while insufficient refrigerant is available to
absorb the room's heat load. Possible causes include a partially closed
valve, plugged strainer, restricted control valve, insufficient pressure
differential, or another obstruction in the liquid supply path.
Question 5
An ammonia refrigeration system has progressively increasing discharge
temperature. Discharge pressure is moderately elevated, while suction
superheat is also higher than normal. Which combination could
contribute significantly to the elevated discharge temperature?
A. Excessively wet suction gas
B. Low compression ratio with abundant liquid feed
C. High suction superheat combined with high compression ratio
D. Excessive evaporator flooding
Answer: C. High suction superheat combined with high
compression ratio
Rationale: High suction superheat means the compressor receives
hotter vapor, increasing the temperature of the gas entering
compression. A high compression ratio further raises discharge
temperature. Excessive discharge temperature can threaten
compressor lubrication, valve integrity, and oil quality. Operators
should investigate suction conditions, condensing pressure, evaporator
feeding, compressor loading, and system restrictions.
4
FAILURE DIAGNOSIS PRACTICE EXAM
WITH QUESTIONS AND VERIFIED
ANSWERS, PLUS DETAILED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
Question 1
An ammonia refrigeration system serving a large cold-storage facility
experiences a gradual increase in suction pressure. Operators report that
the refrigerated rooms are no longer reaching their normal design
temperature. Compressor suction temperature is higher than usual, while
discharge pressure remains relatively stable. Inspection shows that the
evaporator fans and motors are operating normally, and there is no
obvious accumulation of ice on the evaporator coil. Which condition is
the MOST likely initial suspect?
A. Excessive liquid ammonia entering the compressor
B. Restricted condenser water flow
C. Reduced evaporator heat transfer caused by an inadequate refrigerant
feed
D. Excessively high compressor discharge temperature
Answer: C. Reduced evaporator heat transfer caused by an
inadequate refrigerant feed
Rationale: A poorly fed evaporator can produce inadequate cooling
capacity while causing suction pressure and suction temperature
behavior to deviate from normal operating conditions. The evaporator
may not have enough liquid refrigerant available to absorb the
intended heat load. The operator should investigate the liquid feed
1
,device, upstream valves, strainers, differential pressure, and liquid
supply conditions. Excessive liquid carryover would instead raise
concern for compressor damage from liquid slugging or oil dilution,
while restricted condenser flow would more directly affect condensing
pressure.
Question 2
During diagnosis of an ammonia refrigeration system, an operator
observes that the compressor discharge pressure is significantly higher
than normal. The suction pressure is also somewhat elevated, and the
condenser appears clean externally. Ambient temperature has not
changed significantly. Which condition should receive the highest
diagnostic priority?
A. Non-condensable gases accumulated in the condenser
B. Excessively low evaporator pressure
C. Compressor suction strainer restriction
D. Insufficient refrigerant charge
Answer: A. Non-condensable gases accumulated in the condenser
Rationale: Non-condensable gases such as air occupy condenser
volume without condensing like ammonia. This reduces effective
condenser capacity and can force the system to operate at an
abnormally high condensing pressure. Elevated head pressure without
a corresponding environmental explanation is a classic reason to
investigate non-condensables, although dirty condenser surfaces,
inadequate cooling-water flow, excessive ambient temperature, and
overcharge must also be considered.
Question 3
2
,A reciprocating ammonia compressor begins making a sharp metallic
knocking sound immediately after a sudden change in suction
conditions. The suction pressure has risen rapidly, and the compressor
suction line is unusually cold with evidence of liquid accumulation.
Which failure mechanism is MOST concerning?
A. Bearing overheating caused by excessive discharge pressure
B. Liquid slugging caused by liquid ammonia entering the compressor
cylinder
C. Condenser fouling caused by scale
D. Excessive non-condensable concentration
Answer: B. Liquid slugging caused by liquid ammonia entering the
compressor cylinder
Rationale: Compressors are designed to compress vapor, not
incompressible liquid. Liquid ammonia entering a reciprocating
compressor cylinder can cause severe mechanical damage to valves,
pistons, connecting rods, and other components. A rapid suction-
pressure change combined with unusually cold suction piping and
evidence of liquid migration should prompt immediate protective
action according to the facility's operating procedures.
Question 4
A system's evaporator pressure is substantially lower than normal while
the compressor is operating continuously. The refrigerated space is
warmer than its setpoint. The liquid receiver contains an adequate
quantity of ammonia, and the condenser is operating normally. Which
problem is MOST consistent with these observations?
A. Excessive refrigerant migration to the receiver
B. Overfeeding of the evaporator
3
, C. Restricted refrigerant flow to the evaporator
D. Excessive condenser capacity
Answer: C. Restricted refrigerant flow to the evaporator
Rationale: A restriction in the liquid feed path can starve the
evaporator. The compressor continues removing vapor, causing
evaporator pressure to fall while insufficient refrigerant is available to
absorb the room's heat load. Possible causes include a partially closed
valve, plugged strainer, restricted control valve, insufficient pressure
differential, or another obstruction in the liquid supply path.
Question 5
An ammonia refrigeration system has progressively increasing discharge
temperature. Discharge pressure is moderately elevated, while suction
superheat is also higher than normal. Which combination could
contribute significantly to the elevated discharge temperature?
A. Excessively wet suction gas
B. Low compression ratio with abundant liquid feed
C. High suction superheat combined with high compression ratio
D. Excessive evaporator flooding
Answer: C. High suction superheat combined with high
compression ratio
Rationale: High suction superheat means the compressor receives
hotter vapor, increasing the temperature of the gas entering
compression. A high compression ratio further raises discharge
temperature. Excessive discharge temperature can threaten
compressor lubrication, valve integrity, and oil quality. Operators
should investigate suction conditions, condensing pressure, evaporator
feeding, compressor loading, and system restrictions.
4
