ONTARIO REFRIGERATION OPERATOR CLASS B EXAM (TSSA)
EXAM– QUESTIONS AND ANSWERS | VERIFIED AND WELL
DETAILED ANSWERS PLUS RATIONALES | GUARANTEED PASS |
LATEST EXAM UPDATE | EXAM PREP | STUDY GUIDE |
PRACTICE TEST| DOWNLOAD INSTANT PDF
1. A refrigeration operator is performing a routine check on a commercial R-134a vapor-
compression system. The operator notes that the compressor crankcase feels unusually cold
and is heavily frosted. What operating condition is most likely responsible for this
observation?
A. Inadequate condenser cooling water flow rate
B. Excessive refrigerant charge in the liquid receiver
C. Liquid refrigerant slugging returning directly to the compressor suction
D. Complete restriction in the liquid line filter-drier core
ANSWER: C. Liquid refrigerant slugging returning directly to the compressor suction
When liquid refrigerant enters the compressor crankcase instead of vaporizing completely in
the evaporator, it boils off and cools the crankcase excessively, leading to severe frosting. This
liquid slugging can destroy compressor valves and scroll mechanisms.
2. According to the TSSA and provincial safety codes, what is the primary purpose of
installing a pressure relief valve on a closed refrigeration receiver containing high-pressure
refrigerants?
A. To regulate operating discharge pressure during peak ambient summer loads
B. To protect the vessel from catastrophic rupture caused by excessive internal pressure from
fire exposure or system overcharge
C. To bypass high-pressure liquid directly into the low-pressure evaporator during defrost cycles
D. To automatically vent non-condensible gases from the top of the vessel during normal
shutdown periods
ANSWER: B. To protect the vessel from catastrophic rupture caused by excessive internal
pressure from fire exposure or system overcharge
,Pressure relief valves are safety devices designed as a last line of defense to prevent
catastrophic vessel failure and explosion when system pressures exceed maximum allowable
working pressure limits due to external heat sources or overcharging.
3. A facility operator notices that the oil pressure safety cutout switch on a multi-cylinder
ammonia compressor has tripped, shutting down the unit. Which parameter must the
operator calculate to determine net oil lubricating pressure?
A. Total discharge pressure minus suction pressure
B. Oil pump gauge pressure minus evaporator saturation pressure
C. Net oil pressure defined as absolute oil pump pressure minus crankcase (suction) pressure
D. Oil reservoir pressure plus intermediate stage pressure
ANSWER: C. Net oil pressure defined as absolute oil pump pressure minus crankcase
(suction) pressure
Net oil pressure is the actual effective pressure forcing oil through the lubrication bearings. It
is calculated by taking the gauge reading at the oil pump discharge and subtracting the
crankcase suction pressure acting against it.
4. During an annual inspection of an R-717 (ammonia) industrial refrigeration plant, the
operator smells a sharp, pungent odor near the purge unit discharge. What is the standard
and safest method to verify and locate a suspected small ammonia leak?
A. Spraying soapy water solution over all pipe joints and flange connections
B. Using a sulfur taper stick that produces dense white smoke in the presence of ammonia vapor
C. Applying an electronic halide torch directly to suspected pipe seams
D. Testing air samples using an acid-base litmus paper strip dipped in water
ANSWER: B. Using a sulfur taper stick that produces dense white smoke in the presence of
ammonia vapor
Ammonia reacts chemically with sulfur dioxide fumes produced by a burning sulfur taper,
creating a thick, distinct white cloud of ammonium sulfite. This traditional and reliable
method quickly pinpoints minor R-717 leaks.
5. An R-404A supermarket refrigeration rack is operating with an excessively high
superheat reading at the evaporator outlet, accompanied by reduced cooling capacity and a
starved evaporator coil. What is the most probable cause?
,A. Thermal expansion valve power head losing its volatile charge
B. Expansion valve thermal bulb strapped incorrectly on the bottom of a horizontal suction line
C. Stuck open thermostatic expansion valve flooding the suction accumulator
D. Undersized liquid line solenoid valve failing in the wide-open position
ANSWER: A. Thermal expansion valve power head losing its volatile charge
If the thermostatic expansion valve sensing bulb or power head loses its charge, pressure
inside the diaphragm assembly drops, forcing the valve closed. This starves the evaporator of
refrigerant, resulting in high superheat and low cooling capacity.
6. A refrigeration operator is preparing to recover R-22 refrigerant from a
decommissioned chiller. Which regulatory requirement governs the handling, recovery,
and recycling of ozone-depleting refrigerants in Ontario?
A. Ontario Building Code Part 7
B. Ontario Regulation 463/10 (Ozone Depleting Substances and Other Halocarbons) under the
Environmental Protection Act
C. National Electrical Code NFPA 70
D. Workplace Hazardous Materials Information System (WHMIS) Standard 2015
ANSWER: B. Ontario Regulation 463/10 (Ozone Depleting Substances and Other
Halocarbons) under the Environmental Protection Act
Ontario Regulation 463/10 strictly regulates the management, containment, recovery, and
disposal of regulated refrigerants to prevent venting into the atmosphere and protect the
stratospheric ozone layer.
7. Why is synthetic polyolester (POE) oil exclusively required for modern HFC
refrigeration systems such as R-410A and R-407C, rather than traditional mineral oils?
A. Mineral oils are significantly cheaper and cause severe acid corrosion in copper piping
B. POE oils possess superior thermal stability and mutual miscibility with HFC refrigerants to
ensure proper oil return through the system
C. Mineral oils react with R-410A to create toxic phosgene gas
D. POE oils have a much lower viscosity index, preventing high starting torque loads in winter
, ANSWER: B. POE oils possess superior thermal stability and mutual miscibility with HFC
refrigerants to ensure proper oil return through the system
HFC refrigerants are not miscible with traditional mineral oils. Synthetic POE oils dissolve
readily in HFCs, ensuring the lubricating oil is carried smoothly through the loop and back to
the compressor crankcase.
8. An operator observes that a shell-and-tube water-cooled condenser is operating with an
unusually high condensing pressure and a large temperature difference between the liquid
refrigerant saturation temperature and the leaving cooling water temperature. What does
this condition indicate?
A. Severe fouling and scaling on the water-side heat transfer tubes
B. Excessive subcooling of liquid refrigerant in the condenser receiver
C. Presence of low-pressure non-condensible gases trapped in the evaporator
D. Undersized compressor displacement causing low mass flow rates
ANSWER: A. Severe fouling and scaling on the water-side heat transfer tubes
Mineral scale and organic fouling build up on water-side condenser tubes over time, acting as
a thermal insulator. This reduces heat transfer efficiency, forcing higher condensing
pressures and creating an abnormally high condensing temperature-to-water outlet
temperature difference.
9. When calculating the compression ratio of a single-stage reciprocating ammonia
compressor, which absolute pressure values must be utilized?
A. Gauge discharge pressure divided by gauge suction pressure
B. Absolute discharge pressure (psia) divided by absolute suction pressure (psia)
C. Atmospheric pressure plus compressor displacement volume
D. Net oil pressure multiplied by suction gas temperature in Rankine
ANSWER: B. Absolute discharge pressure (psia) divided by absolute suction pressure
(psia)*
Compression ratio is defined strictly as the absolute discharge pressure divided by the absolute
suction pressure. Using gauge pressures will yield incorrect theoretical ratios because
atmospheric pressure is excluded.
EXAM– QUESTIONS AND ANSWERS | VERIFIED AND WELL
DETAILED ANSWERS PLUS RATIONALES | GUARANTEED PASS |
LATEST EXAM UPDATE | EXAM PREP | STUDY GUIDE |
PRACTICE TEST| DOWNLOAD INSTANT PDF
1. A refrigeration operator is performing a routine check on a commercial R-134a vapor-
compression system. The operator notes that the compressor crankcase feels unusually cold
and is heavily frosted. What operating condition is most likely responsible for this
observation?
A. Inadequate condenser cooling water flow rate
B. Excessive refrigerant charge in the liquid receiver
C. Liquid refrigerant slugging returning directly to the compressor suction
D. Complete restriction in the liquid line filter-drier core
ANSWER: C. Liquid refrigerant slugging returning directly to the compressor suction
When liquid refrigerant enters the compressor crankcase instead of vaporizing completely in
the evaporator, it boils off and cools the crankcase excessively, leading to severe frosting. This
liquid slugging can destroy compressor valves and scroll mechanisms.
2. According to the TSSA and provincial safety codes, what is the primary purpose of
installing a pressure relief valve on a closed refrigeration receiver containing high-pressure
refrigerants?
A. To regulate operating discharge pressure during peak ambient summer loads
B. To protect the vessel from catastrophic rupture caused by excessive internal pressure from
fire exposure or system overcharge
C. To bypass high-pressure liquid directly into the low-pressure evaporator during defrost cycles
D. To automatically vent non-condensible gases from the top of the vessel during normal
shutdown periods
ANSWER: B. To protect the vessel from catastrophic rupture caused by excessive internal
pressure from fire exposure or system overcharge
,Pressure relief valves are safety devices designed as a last line of defense to prevent
catastrophic vessel failure and explosion when system pressures exceed maximum allowable
working pressure limits due to external heat sources or overcharging.
3. A facility operator notices that the oil pressure safety cutout switch on a multi-cylinder
ammonia compressor has tripped, shutting down the unit. Which parameter must the
operator calculate to determine net oil lubricating pressure?
A. Total discharge pressure minus suction pressure
B. Oil pump gauge pressure minus evaporator saturation pressure
C. Net oil pressure defined as absolute oil pump pressure minus crankcase (suction) pressure
D. Oil reservoir pressure plus intermediate stage pressure
ANSWER: C. Net oil pressure defined as absolute oil pump pressure minus crankcase
(suction) pressure
Net oil pressure is the actual effective pressure forcing oil through the lubrication bearings. It
is calculated by taking the gauge reading at the oil pump discharge and subtracting the
crankcase suction pressure acting against it.
4. During an annual inspection of an R-717 (ammonia) industrial refrigeration plant, the
operator smells a sharp, pungent odor near the purge unit discharge. What is the standard
and safest method to verify and locate a suspected small ammonia leak?
A. Spraying soapy water solution over all pipe joints and flange connections
B. Using a sulfur taper stick that produces dense white smoke in the presence of ammonia vapor
C. Applying an electronic halide torch directly to suspected pipe seams
D. Testing air samples using an acid-base litmus paper strip dipped in water
ANSWER: B. Using a sulfur taper stick that produces dense white smoke in the presence of
ammonia vapor
Ammonia reacts chemically with sulfur dioxide fumes produced by a burning sulfur taper,
creating a thick, distinct white cloud of ammonium sulfite. This traditional and reliable
method quickly pinpoints minor R-717 leaks.
5. An R-404A supermarket refrigeration rack is operating with an excessively high
superheat reading at the evaporator outlet, accompanied by reduced cooling capacity and a
starved evaporator coil. What is the most probable cause?
,A. Thermal expansion valve power head losing its volatile charge
B. Expansion valve thermal bulb strapped incorrectly on the bottom of a horizontal suction line
C. Stuck open thermostatic expansion valve flooding the suction accumulator
D. Undersized liquid line solenoid valve failing in the wide-open position
ANSWER: A. Thermal expansion valve power head losing its volatile charge
If the thermostatic expansion valve sensing bulb or power head loses its charge, pressure
inside the diaphragm assembly drops, forcing the valve closed. This starves the evaporator of
refrigerant, resulting in high superheat and low cooling capacity.
6. A refrigeration operator is preparing to recover R-22 refrigerant from a
decommissioned chiller. Which regulatory requirement governs the handling, recovery,
and recycling of ozone-depleting refrigerants in Ontario?
A. Ontario Building Code Part 7
B. Ontario Regulation 463/10 (Ozone Depleting Substances and Other Halocarbons) under the
Environmental Protection Act
C. National Electrical Code NFPA 70
D. Workplace Hazardous Materials Information System (WHMIS) Standard 2015
ANSWER: B. Ontario Regulation 463/10 (Ozone Depleting Substances and Other
Halocarbons) under the Environmental Protection Act
Ontario Regulation 463/10 strictly regulates the management, containment, recovery, and
disposal of regulated refrigerants to prevent venting into the atmosphere and protect the
stratospheric ozone layer.
7. Why is synthetic polyolester (POE) oil exclusively required for modern HFC
refrigeration systems such as R-410A and R-407C, rather than traditional mineral oils?
A. Mineral oils are significantly cheaper and cause severe acid corrosion in copper piping
B. POE oils possess superior thermal stability and mutual miscibility with HFC refrigerants to
ensure proper oil return through the system
C. Mineral oils react with R-410A to create toxic phosgene gas
D. POE oils have a much lower viscosity index, preventing high starting torque loads in winter
, ANSWER: B. POE oils possess superior thermal stability and mutual miscibility with HFC
refrigerants to ensure proper oil return through the system
HFC refrigerants are not miscible with traditional mineral oils. Synthetic POE oils dissolve
readily in HFCs, ensuring the lubricating oil is carried smoothly through the loop and back to
the compressor crankcase.
8. An operator observes that a shell-and-tube water-cooled condenser is operating with an
unusually high condensing pressure and a large temperature difference between the liquid
refrigerant saturation temperature and the leaving cooling water temperature. What does
this condition indicate?
A. Severe fouling and scaling on the water-side heat transfer tubes
B. Excessive subcooling of liquid refrigerant in the condenser receiver
C. Presence of low-pressure non-condensible gases trapped in the evaporator
D. Undersized compressor displacement causing low mass flow rates
ANSWER: A. Severe fouling and scaling on the water-side heat transfer tubes
Mineral scale and organic fouling build up on water-side condenser tubes over time, acting as
a thermal insulator. This reduces heat transfer efficiency, forcing higher condensing
pressures and creating an abnormally high condensing temperature-to-water outlet
temperature difference.
9. When calculating the compression ratio of a single-stage reciprocating ammonia
compressor, which absolute pressure values must be utilized?
A. Gauge discharge pressure divided by gauge suction pressure
B. Absolute discharge pressure (psia) divided by absolute suction pressure (psia)
C. Atmospheric pressure plus compressor displacement volume
D. Net oil pressure multiplied by suction gas temperature in Rankine
ANSWER: B. Absolute discharge pressure (psia) divided by absolute suction pressure
(psia)*
Compression ratio is defined strictly as the absolute discharge pressure divided by the absolute
suction pressure. Using gauge pressures will yield incorrect theoretical ratios because
atmospheric pressure is excluded.
