Ontario Refrigeration Operator Class B
Exam (TSSA) Questions & Correct
Answers Verified Plus Rationales 2026 |
Instant Download Pdf
1. What is the minimum required operating experience in a Class A or B
refrigeration plant to challenge the TSSA Refrigeration Operator Class B exam?
A) 720 hours
B) 1,440 hours
C) 2,160 hours
D) 3,000 hours
Correct Answer: B
Explanation: TSSA guidelines require 1,440 hours of practical training in a Class A or B
refrigeration plant to qualify for the Class B certification exam .
2. Which code governs the mechanical safety requirements for the design,
construction, installation, and inspection of refrigeration systems in Ontario?
A) CSA B51
B) CSA B52
C) ASHRAE 15
D) CSA B149.1
Correct Answer: B
Explanation: CSA B52: Mechanical Refrigeration Code sets the standards for safety in
refrigeration systems. CSA B51 covers boilers and pressure vessels .
3. A refrigeration system uses R-717. What safety property is most critical for the
operator to monitor?
A) Its high global warming potential
,B) Its toxicity and flammability
C) Its low odor detection threshold
D) Its high miscibility with oil
Correct Answer: B
Explanation: R-717 (Ammonia) is classified as a B2L refrigerant, meaning it has high
toxicity and moderate flammability, requiring specific safety protocols .
4. What is the primary purpose of a purge unit on a low-pressure chiller?
A) To remove non-condensable gases from the condenser
B) To lubricate the compressor bearings during startup
C) To prevent the evaporator from freezing
D) To recover refrigerant for recharging
Correct Answer: A
Explanation: Non-condensable gases such as air and water vapor can enter the system
and accumulate in the condenser, raising the head pressure. A purge unit removes
them .
5. What is the primary effect of non-condensable gases (air) in the condenser?
A) Lowered discharge pressure
B) Increased subcooling
C) Increased condensing pressure and temperature
D) Decreased compressor amp draw
Correct Answer: C
Explanation: Non-condensables occupy volume in the condenser, raising the head
pressure and requiring the compressor to work harder, reducing efficiency .
6. What is the primary function of a thermal expansion valve (TXV)?
A) To maintain constant condenser pressure
B) To meter refrigerant flow based on evaporator superheat
C) To pump down the system for maintenance
D) To separate oil from the refrigerant discharge gas
Correct Answer: B
,Explanation: The TXV modulates refrigerant flow into the evaporator to maintain a
consistent superheat at the evaporator outlet, preventing liquid slugging .
7. What force acts to open a standard thermostatic expansion valve (TXV)?
A) Evaporator pressure
B) Spring pressure
C) Sensing bulb pressure
D) Oil pump pressure
Correct Answer: C
Explanation: A TXV operates on a balance of forces. Sensing bulb pressure acts on top of
the diaphragm trying to open the valve, while evaporator pressure and internal spring
pressure act underneath trying to close it .
8. Which compressor type is most suitable for very low temperature applications
requiring high pressure ratios?
A) Centrifugal
B) Two-stage reciprocating or screw
C) Rotary vane
D) Single-stage scroll
Correct Answer: B
Explanation: Two-stage compression reduces the pressure ratio per stage, keeping
discharge temperatures manageable and improving volumetric efficiency at low
evaporator temperatures .
9. What is the primary benefit of installing an intercooler between stages in a two-
stage compression system?
A) It desuperheats the booster discharge gas, reducing final stage temperatures
B) It allows oil to return faster to the evaporator
C) It eliminates the need for an expansion valve
D) It decreases the overall mass flow rate of the plant
Correct Answer: A
Explanation: Intercooling cools down the hot superheated discharge vapor coming out
, of the low-stage compressor before it enters the high-stage compressor, keeping the
final discharge temperature within safe limits .
10. In a cooling tower, what is "blowdown"?
A) The intentional draining of water to control dissolved solids
B) The evaporation of water droplets into the atmosphere
C) The process of cleaning the fill media
D) The sound of water falling into the basin
Correct Answer: A
Explanation: Blowdown (or bleed-off) removes a portion of the highly concentrated
recirculating water to prevent scale formation due to mineral buildup .
11. What is the primary cause of "flash gas" in a liquid line?
A) Excessive subcooling
B) Pressure drop due to friction or vertical lift
C) Over-sized liquid line
D) Low condenser water temperature
Correct Answer: B
Explanation: As liquid refrigerant travels through the line, pressure drops. If it drops
below the saturation pressure corresponding to the liquid temperature, some liquid
flashes to vapor .
12. Why does an evaporative condenser require less airflow than an air-cooled
condenser of identical capacity?
A) It operates at much higher baseline temperatures
B) Air density increases significantly inside the housing
C) Latent heat of vaporization removes far more heat per kilogram
D) Sensible heat transfer is completely eliminated
Correct Answer: C
Explanation: Evaporative condensers utilize the evaporation of water on the condenser
coil surfaces. Because the latent heat of vaporization of water is exceptionally high,
Exam (TSSA) Questions & Correct
Answers Verified Plus Rationales 2026 |
Instant Download Pdf
1. What is the minimum required operating experience in a Class A or B
refrigeration plant to challenge the TSSA Refrigeration Operator Class B exam?
A) 720 hours
B) 1,440 hours
C) 2,160 hours
D) 3,000 hours
Correct Answer: B
Explanation: TSSA guidelines require 1,440 hours of practical training in a Class A or B
refrigeration plant to qualify for the Class B certification exam .
2. Which code governs the mechanical safety requirements for the design,
construction, installation, and inspection of refrigeration systems in Ontario?
A) CSA B51
B) CSA B52
C) ASHRAE 15
D) CSA B149.1
Correct Answer: B
Explanation: CSA B52: Mechanical Refrigeration Code sets the standards for safety in
refrigeration systems. CSA B51 covers boilers and pressure vessels .
3. A refrigeration system uses R-717. What safety property is most critical for the
operator to monitor?
A) Its high global warming potential
,B) Its toxicity and flammability
C) Its low odor detection threshold
D) Its high miscibility with oil
Correct Answer: B
Explanation: R-717 (Ammonia) is classified as a B2L refrigerant, meaning it has high
toxicity and moderate flammability, requiring specific safety protocols .
4. What is the primary purpose of a purge unit on a low-pressure chiller?
A) To remove non-condensable gases from the condenser
B) To lubricate the compressor bearings during startup
C) To prevent the evaporator from freezing
D) To recover refrigerant for recharging
Correct Answer: A
Explanation: Non-condensable gases such as air and water vapor can enter the system
and accumulate in the condenser, raising the head pressure. A purge unit removes
them .
5. What is the primary effect of non-condensable gases (air) in the condenser?
A) Lowered discharge pressure
B) Increased subcooling
C) Increased condensing pressure and temperature
D) Decreased compressor amp draw
Correct Answer: C
Explanation: Non-condensables occupy volume in the condenser, raising the head
pressure and requiring the compressor to work harder, reducing efficiency .
6. What is the primary function of a thermal expansion valve (TXV)?
A) To maintain constant condenser pressure
B) To meter refrigerant flow based on evaporator superheat
C) To pump down the system for maintenance
D) To separate oil from the refrigerant discharge gas
Correct Answer: B
,Explanation: The TXV modulates refrigerant flow into the evaporator to maintain a
consistent superheat at the evaporator outlet, preventing liquid slugging .
7. What force acts to open a standard thermostatic expansion valve (TXV)?
A) Evaporator pressure
B) Spring pressure
C) Sensing bulb pressure
D) Oil pump pressure
Correct Answer: C
Explanation: A TXV operates on a balance of forces. Sensing bulb pressure acts on top of
the diaphragm trying to open the valve, while evaporator pressure and internal spring
pressure act underneath trying to close it .
8. Which compressor type is most suitable for very low temperature applications
requiring high pressure ratios?
A) Centrifugal
B) Two-stage reciprocating or screw
C) Rotary vane
D) Single-stage scroll
Correct Answer: B
Explanation: Two-stage compression reduces the pressure ratio per stage, keeping
discharge temperatures manageable and improving volumetric efficiency at low
evaporator temperatures .
9. What is the primary benefit of installing an intercooler between stages in a two-
stage compression system?
A) It desuperheats the booster discharge gas, reducing final stage temperatures
B) It allows oil to return faster to the evaporator
C) It eliminates the need for an expansion valve
D) It decreases the overall mass flow rate of the plant
Correct Answer: A
Explanation: Intercooling cools down the hot superheated discharge vapor coming out
, of the low-stage compressor before it enters the high-stage compressor, keeping the
final discharge temperature within safe limits .
10. In a cooling tower, what is "blowdown"?
A) The intentional draining of water to control dissolved solids
B) The evaporation of water droplets into the atmosphere
C) The process of cleaning the fill media
D) The sound of water falling into the basin
Correct Answer: A
Explanation: Blowdown (or bleed-off) removes a portion of the highly concentrated
recirculating water to prevent scale formation due to mineral buildup .
11. What is the primary cause of "flash gas" in a liquid line?
A) Excessive subcooling
B) Pressure drop due to friction or vertical lift
C) Over-sized liquid line
D) Low condenser water temperature
Correct Answer: B
Explanation: As liquid refrigerant travels through the line, pressure drops. If it drops
below the saturation pressure corresponding to the liquid temperature, some liquid
flashes to vapor .
12. Why does an evaporative condenser require less airflow than an air-cooled
condenser of identical capacity?
A) It operates at much higher baseline temperatures
B) Air density increases significantly inside the housing
C) Latent heat of vaporization removes far more heat per kilogram
D) Sensible heat transfer is completely eliminated
Correct Answer: C
Explanation: Evaporative condensers utilize the evaporation of water on the condenser
coil surfaces. Because the latent heat of vaporization of water is exceptionally high,
