Ontario Refrigeration Operator
Class B (TSSA) Exam
Questions with Answers & Rationales
,Question 1. What is the primary purpose of the compressor in a
mechanical refrigeration system?
A. To cool the refrigerant liquid before it enters the evaporator
B. To raise the pressure and temperature of refrigerant vapour so it can be
condensed
C. To meter refrigerant into the evaporator
D. To remove moisture from the refrigerant
Answer: B
Rationale: The compressor draws low-pressure vapour from the evaporator
and compresses it, raising its pressure and temperature so the vapour can
reject heat and condense in the condenser.
Question 2. In the basic refrigeration cycle, where does the refrigerant
absorb heat from the space being cooled?
A. Condenser
B. Compressor
C. Evaporator
D. Receiver
Answer: C
Rationale: The evaporator is the low-pressure, low-temperature component
where liquid refrigerant boils and absorbs heat from the surrounding air or
product, producing the cooling effect.
Question 3. What happens to refrigerant pressure and temperature as it
passes through the expansion (metering) device?
A. Both increase
B. Both decrease
C. Pressure decreases and temperature drops as liquid partially flashes to
vapour
D. Pressure increases while temperature stays constant
Answer: C
Rationale: The expansion device drops the high-side liquid pressure to the
low-side pressure; some liquid flashes to vapour, absorbing heat from the
,remaining liquid and lowering its temperature.
Question 4. Which component of the refrigeration system rejects heat
absorbed in the evaporator plus the heat of compression to the outside
air or water?
A. Evaporator
B. Receiver
C. Condenser
D. Accumulator
Answer: C
Rationale: The condenser is the high-side heat exchanger where hot,
high-pressure refrigerant vapour gives up heat to air or water and condenses
into a liquid.
Question 5. What is 'superheat' in a refrigeration system?
A. The temperature difference between the condensing temperature and
ambient temperature
B. The amount a vapour's temperature is above its corresponding
saturation temperature at that pressure
C. The temperature of oil in the compressor crankcase
D. The pressure drop across the expansion valve
Answer: B
Rationale: Superheat is the number of degrees a vapour has been heated
above the saturation (boiling) temperature corresponding to its pressure; it
confirms all liquid has vaporized before reaching the compressor.
Question 6. What is 'subcooling'?
A. Cooling a liquid refrigerant below its saturation temperature at the
existing pressure
B. Cooling the compressor motor windings
C. Reducing suction pressure below atmospheric
D. The process of removing non-condensable gases
Answer: A
, Rationale: Subcooling is lowering the temperature of liquid refrigerant below
its saturation temperature for the pressure it is under, ensuring solid liquid
reaches the expansion device.
Question 7. Why is some superheat at the compressor suction
important?
A. It increases the refrigerating effect
B. It prevents liquid refrigerant from entering and damaging the
compressor (slugging)
C. It reduces discharge pressure
D. It lowers oil temperature
Answer: B
Rationale: Superheated vapour at the suction confirms no liquid droplets
remain; liquid entering the compressor can cause slugging, washing oil from
bearings and damaging valves or pistons.
Question 8. Which refrigerant property describes its tendency to
vaporize, expressed as the pressure exerted by the vapour in
equilibrium with its liquid at a given temperature?
A. Latent heat
B. Vapour pressure
C. Specific volume
D. Critical temperature
Answer: B
Rationale: Vapour pressure is the pressure at which a liquid and its vapour
are in equilibrium at a given temperature; it determines operating pressures
for a given refrigerant.
Question 9. What is the 'critical temperature' of a refrigerant?
A. The temperature at which the refrigerant freezes
B. The lowest temperature the refrigerant can reach in the evaporator
C. The temperature above which the refrigerant cannot be liquefied
regardless of pressure
D. The temperature at which oil breaks down
Class B (TSSA) Exam
Questions with Answers & Rationales
,Question 1. What is the primary purpose of the compressor in a
mechanical refrigeration system?
A. To cool the refrigerant liquid before it enters the evaporator
B. To raise the pressure and temperature of refrigerant vapour so it can be
condensed
C. To meter refrigerant into the evaporator
D. To remove moisture from the refrigerant
Answer: B
Rationale: The compressor draws low-pressure vapour from the evaporator
and compresses it, raising its pressure and temperature so the vapour can
reject heat and condense in the condenser.
Question 2. In the basic refrigeration cycle, where does the refrigerant
absorb heat from the space being cooled?
A. Condenser
B. Compressor
C. Evaporator
D. Receiver
Answer: C
Rationale: The evaporator is the low-pressure, low-temperature component
where liquid refrigerant boils and absorbs heat from the surrounding air or
product, producing the cooling effect.
Question 3. What happens to refrigerant pressure and temperature as it
passes through the expansion (metering) device?
A. Both increase
B. Both decrease
C. Pressure decreases and temperature drops as liquid partially flashes to
vapour
D. Pressure increases while temperature stays constant
Answer: C
Rationale: The expansion device drops the high-side liquid pressure to the
low-side pressure; some liquid flashes to vapour, absorbing heat from the
,remaining liquid and lowering its temperature.
Question 4. Which component of the refrigeration system rejects heat
absorbed in the evaporator plus the heat of compression to the outside
air or water?
A. Evaporator
B. Receiver
C. Condenser
D. Accumulator
Answer: C
Rationale: The condenser is the high-side heat exchanger where hot,
high-pressure refrigerant vapour gives up heat to air or water and condenses
into a liquid.
Question 5. What is 'superheat' in a refrigeration system?
A. The temperature difference between the condensing temperature and
ambient temperature
B. The amount a vapour's temperature is above its corresponding
saturation temperature at that pressure
C. The temperature of oil in the compressor crankcase
D. The pressure drop across the expansion valve
Answer: B
Rationale: Superheat is the number of degrees a vapour has been heated
above the saturation (boiling) temperature corresponding to its pressure; it
confirms all liquid has vaporized before reaching the compressor.
Question 6. What is 'subcooling'?
A. Cooling a liquid refrigerant below its saturation temperature at the
existing pressure
B. Cooling the compressor motor windings
C. Reducing suction pressure below atmospheric
D. The process of removing non-condensable gases
Answer: A
, Rationale: Subcooling is lowering the temperature of liquid refrigerant below
its saturation temperature for the pressure it is under, ensuring solid liquid
reaches the expansion device.
Question 7. Why is some superheat at the compressor suction
important?
A. It increases the refrigerating effect
B. It prevents liquid refrigerant from entering and damaging the
compressor (slugging)
C. It reduces discharge pressure
D. It lowers oil temperature
Answer: B
Rationale: Superheated vapour at the suction confirms no liquid droplets
remain; liquid entering the compressor can cause slugging, washing oil from
bearings and damaging valves or pistons.
Question 8. Which refrigerant property describes its tendency to
vaporize, expressed as the pressure exerted by the vapour in
equilibrium with its liquid at a given temperature?
A. Latent heat
B. Vapour pressure
C. Specific volume
D. Critical temperature
Answer: B
Rationale: Vapour pressure is the pressure at which a liquid and its vapour
are in equilibrium at a given temperature; it determines operating pressures
for a given refrigerant.
Question 9. What is the 'critical temperature' of a refrigerant?
A. The temperature at which the refrigerant freezes
B. The lowest temperature the refrigerant can reach in the evaporator
C. The temperature above which the refrigerant cannot be liquefied
regardless of pressure
D. The temperature at which oil breaks down
