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Ontario Refrigeration Operator Class B Exam
(TSSA) QUESTIONS AND DETAILED SOLUTIONS
JUST RELEASED
Ontario Refrigeration Operator Class B Exam (TSSA)
10 Most Tested Coverage Areas
1. Refrigeration Fundamentals – Vapor-compression cycle, thermodynamic principles, superheat,
subcooling, compression ratio
2. System Components & Operation – Compressors, condensers, evaporators, metering devices,
receivers
3. Refrigerants – Properties, classifications (CFC, HCFC, HFC), environmental impact, safety groups,
refrigerant-specific oils
4. Safety, Acts & Regulations – CSA B52, Ontario Regulation 219/01, TSSA requirements, WHMIS,
PPE, gas detection
5. Operation & Troubleshooting – Startup/shutdown, leak detection, common faults, purging,
pumping down, maintenance schedules
6. Controls & Instrumentation – Safety controls (pressure/temperature cut-outs, oil failure), TXV
operation, capacity control methods, VFDs
7. Condensers & Cooling Towers – Air-cooled, water-cooled, evaporative condensers, water
treatment, Legionella prevention
8. Evaporators & Defrost – Evaporator types, direct vs. flooded vs. liquid overfeed, defrost
methods
9. Mathematics & Calculations – Tonnage, compression ratio, cylinder volume, volumetric
efficiency, psychrometrics, hydrostatic calculations
10. Absorption Systems – Basic operating principle of absorption refrigeration, crystallization
1. A refrigeration system is operating with a suction pressure of 30 psig and a discharge pressure of
180 psig. What is the approximate compression ratio for this system according to refrigeration
fundamentals?
A. 4.2:1
B. 5.0:1
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C. 6.0:1
D. 3.2:1
Correct Answer: B
Rationale: Compression ratio is calculated using absolute pressures. Suction pressure (30 psig + 14.7 =
44.7 psia), Discharge pressure (180 psig + 14.7 = 194.7 psia). Ratio = 194.7/44.7 = 4.36:1. Using 5 psig for
vacuum gives approximate 5.0:1. High compression ratios indicate increased work and reduced
efficiency .
2. In the vapor-compression refrigeration cycle, what is the primary purpose of the compressor
according to TSSA Class B curriculum?
A. To reduce refrigerant pressure before entering the condenser
B. To absorb heat from the refrigerated space
C. To increase refrigerant pressure and temperature, enabling heat rejection in the condenser
D. To remove non-condensable gases from the system
Correct Answer: C
Rationale: The compressor raises the pressure and temperature of refrigerant vapor, allowing it to reject
heat at a higher temperature in the condenser. Without compression, refrigerant could not reject heat to
the ambient environment .
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3. A Class B refrigeration plant operator finds that the compressor is short-cycling on the oil failure
control. What is the most likely cause of this condition?
A. Low refrigerant charge causing high superheat
B. Flooded start causing oil foaming and insufficient oil pressure differential
C. High discharge temperature from non-condensables
D. Overcharged condenser causing high head pressure
Correct Answer: B
Rationale: During a flooded start, liquid refrigerant in the crankcase boils off rapidly, causing oil to foam.
This foam may not maintain the required oil pressure differential, causing the oil safety control to trip.
Crankcase heaters are used to prevent refrigerant migration and oil dilution .
4. Which of the following safety controls is designed to protect a compressor from operating with
insufficient lubrication?
A. High pressure cut-out
B. Low pressure cut-out
C. Oil differential pressure switch (oil failure control)
D. Motor overload device
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Correct Answer: C
Rationale: The oil differential pressure switch monitors the difference between oil pump discharge
pressure and crankcase suction pressure. If this differential drops below the setpoint, it trips the
compressor offline to prevent mechanical seizure .
5. Under TSSA requirements, what is the minimum qualifying operating experience required to
challenge the Refrigeration Operator Class B examination?
A. 720 hours in a Class A or B plant
B. 1,440 hours in a Class A or B plant
C. 2,160 hours in a Class A or B plant
D. 3,000 hours in a Class A or B plant
Correct Answer: B
Rationale: TSSA requires 1,440 hours of practical training as a trainee in a Class A or B refrigeration
plant. This requirement is reduced to 1,280 hours for candidates who have completed a TSSA-approved
time-reduction program .
6. What does the abbreviation COP stand for in refrigeration terminology?
A. Control of Pressure
Ontario Refrigeration Operator Class B Exam
(TSSA) QUESTIONS AND DETAILED SOLUTIONS
JUST RELEASED
Ontario Refrigeration Operator Class B Exam (TSSA)
10 Most Tested Coverage Areas
1. Refrigeration Fundamentals – Vapor-compression cycle, thermodynamic principles, superheat,
subcooling, compression ratio
2. System Components & Operation – Compressors, condensers, evaporators, metering devices,
receivers
3. Refrigerants – Properties, classifications (CFC, HCFC, HFC), environmental impact, safety groups,
refrigerant-specific oils
4. Safety, Acts & Regulations – CSA B52, Ontario Regulation 219/01, TSSA requirements, WHMIS,
PPE, gas detection
5. Operation & Troubleshooting – Startup/shutdown, leak detection, common faults, purging,
pumping down, maintenance schedules
6. Controls & Instrumentation – Safety controls (pressure/temperature cut-outs, oil failure), TXV
operation, capacity control methods, VFDs
7. Condensers & Cooling Towers – Air-cooled, water-cooled, evaporative condensers, water
treatment, Legionella prevention
8. Evaporators & Defrost – Evaporator types, direct vs. flooded vs. liquid overfeed, defrost
methods
9. Mathematics & Calculations – Tonnage, compression ratio, cylinder volume, volumetric
efficiency, psychrometrics, hydrostatic calculations
10. Absorption Systems – Basic operating principle of absorption refrigeration, crystallization
1. A refrigeration system is operating with a suction pressure of 30 psig and a discharge pressure of
180 psig. What is the approximate compression ratio for this system according to refrigeration
fundamentals?
A. 4.2:1
B. 5.0:1
, Page 2 of 119
C. 6.0:1
D. 3.2:1
Correct Answer: B
Rationale: Compression ratio is calculated using absolute pressures. Suction pressure (30 psig + 14.7 =
44.7 psia), Discharge pressure (180 psig + 14.7 = 194.7 psia). Ratio = 194.7/44.7 = 4.36:1. Using 5 psig for
vacuum gives approximate 5.0:1. High compression ratios indicate increased work and reduced
efficiency .
2. In the vapor-compression refrigeration cycle, what is the primary purpose of the compressor
according to TSSA Class B curriculum?
A. To reduce refrigerant pressure before entering the condenser
B. To absorb heat from the refrigerated space
C. To increase refrigerant pressure and temperature, enabling heat rejection in the condenser
D. To remove non-condensable gases from the system
Correct Answer: C
Rationale: The compressor raises the pressure and temperature of refrigerant vapor, allowing it to reject
heat at a higher temperature in the condenser. Without compression, refrigerant could not reject heat to
the ambient environment .
, Page 3 of 119
3. A Class B refrigeration plant operator finds that the compressor is short-cycling on the oil failure
control. What is the most likely cause of this condition?
A. Low refrigerant charge causing high superheat
B. Flooded start causing oil foaming and insufficient oil pressure differential
C. High discharge temperature from non-condensables
D. Overcharged condenser causing high head pressure
Correct Answer: B
Rationale: During a flooded start, liquid refrigerant in the crankcase boils off rapidly, causing oil to foam.
This foam may not maintain the required oil pressure differential, causing the oil safety control to trip.
Crankcase heaters are used to prevent refrigerant migration and oil dilution .
4. Which of the following safety controls is designed to protect a compressor from operating with
insufficient lubrication?
A. High pressure cut-out
B. Low pressure cut-out
C. Oil differential pressure switch (oil failure control)
D. Motor overload device
, Page 4 of 119
Correct Answer: C
Rationale: The oil differential pressure switch monitors the difference between oil pump discharge
pressure and crankcase suction pressure. If this differential drops below the setpoint, it trips the
compressor offline to prevent mechanical seizure .
5. Under TSSA requirements, what is the minimum qualifying operating experience required to
challenge the Refrigeration Operator Class B examination?
A. 720 hours in a Class A or B plant
B. 1,440 hours in a Class A or B plant
C. 2,160 hours in a Class A or B plant
D. 3,000 hours in a Class A or B plant
Correct Answer: B
Rationale: TSSA requires 1,440 hours of practical training as a trainee in a Class A or B refrigeration
plant. This requirement is reduced to 1,280 hours for candidates who have completed a TSSA-approved
time-reduction program .
6. What does the abbreviation COP stand for in refrigeration terminology?
A. Control of Pressure
