RSES Certifications (e.g., CM, CMS, RM, SM) — Questions and Answers

Question 1: An oil separator in a refrigeration system is located:

Between the condenser and expansion device
Between the evaporator and compressor
Between the expansion device and evaporator
Between the compressor and condenser (Correct answer)

Correct answer: Between the compressor and condenser

Oil separators are installed in the discharge line to capture oil carried over from the compressor before it reaches the condenser and evaporator.

Question 2: Which type of refrigerant cylinder is used exclusively for shipping and cannot be refilled with refrigerant for resale?

Recovery cylinder
Disposable/non-refillable cylinder (Correct answer)
Returnable cylinder
DOT-4BA cylinder

Correct answer: Disposable/non-refillable cylinder

Disposable (non-refillable) cylinders are single-use shipping containers; refilling them with refrigerant for resale is illegal under EPA and DOT regulations.

Question 3: A flooded condenser control valve modulates to:

Maintain constant suction pressure
Reduce refrigerant charge during high ambient conditions
Flood the condenser with liquid to raise head pressure in cold weather (Correct answer)
Control condenser fan speed

Correct answer: Flood the condenser with liquid to raise head pressure in cold weather

In cold ambient conditions, a flooded condenser control valve backs liquid refrigerant into the condenser to reduce effective surface area and maintain adequate head pressure.

Question 4: Why use color-coded wiring?

To maintain safety and standards (Correct answer)
To confuse others
For decoration
To mark insulation type

Correct answer: To maintain safety and standards

To ensure correct and safe electrical connections.

Question 5: What does a frost pattern that stops midway through an evaporator coil typically indicate?

High ambient humidity
Condenser coil fouling
Partially blocked or malfunctioning expansion device (Correct answer)
Excess refrigerant charge

Correct answer: Partially blocked or malfunctioning expansion device

A frost pattern ending midway indicates refrigerant is fully evaporating before the end of the coil, suggesting a restricted or undersized expansion device.

Question 6: Which refrigerant is classified as an HFC (hydrofluorocarbon) with zero ozone depletion potential?

R-22
R-134a (Correct answer)
R-11
R-502

Correct answer: R-134a

R-134a is an HFC containing no chlorine, giving it zero ozone depletion potential (ODP), unlike older CFC and HCFC refrigerants.

Question 7: When using a clamp-on ammeter to measure current in a two-wire single-phase circuit, the technician clamps both conductors simultaneously. The reading will be:

Equal to the ground fault current only
Equal to the sum of both conductors' current
Zero, because the currents cancel each other out (Correct answer)
Doubled compared to single conductor measurement

Correct answer: Zero, because the currents cancel each other out

When both conductors of a balanced single-phase circuit are clamped together, the equal and opposite currents cancel magnetically, producing a zero reading on the ammeter.

Question 8: An automatic expansion valve (AEV) maintains constant:

Suction superheat
Condensing temperature
Evaporator pressure (Correct answer)
Refrigerant flow rate

Correct answer: Evaporator pressure

The AEV modulates to maintain a constant evaporator (low-side) pressure regardless of load changes.

Question 9: A SPDT (single-pole double-throw) thermostat is used in a heat-cool system. In the heating mode, which terminals are typically energized?

R and Y
R and G
Y and G
R and W (Correct answer)

Correct answer: R and W

In standard HVAC/R thermostat wiring, R is the 24V power, W is the heating output terminal; R-W energizes the heating circuit when the thermostat calls for heat.

Question 10: Which federal agency regulates the transportation of refrigerant cylinders on public roads?

OSHA
EPA
NIOSH
DOT (PHMSA) (Correct answer)

Correct answer: DOT (PHMSA)

The Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) regulates the transportation of refrigerant cylinders as hazardous materials.

Question 11: What is the purpose of a time-delay relay (TDR) wired into a compressor control circuit?

Reduce voltage spikes during compressor shutdown
Monitor motor winding temperature continuously
Increase starting torque during high-load conditions
Prevent short cycling by delaying compressor restart (Correct answer)

Correct answer: Prevent short cycling by delaying compressor restart

A time-delay relay prevents short cycling by holding the compressor off for a set period (typically 3–5 minutes) after shutdown, allowing pressures to equalize before restart.

Question 12: A three-phase compressor motor is running but drawing unequal current on the three legs. The most likely cause is:

Voltage imbalance or open motor winding (Correct answer)
Defective crankcase heater
Overcharged refrigerant system
Shorted run capacitor

Correct answer: Voltage imbalance or open motor winding

Current imbalance in a three-phase motor typically indicates either a supply voltage imbalance or a partially shorted/open winding, both of which cause unequal current draw per phase.

Question 13: What is the fundamental principle behind evaporator systems in the RSES domain?

Balancing performance, reliability, and efficiency (Correct answer)
Cost minimization at all costs
Following a single vendor solution
Using the newest technology exclusively

Correct answer: Balancing performance, reliability, and efficiency

Effective technical design requires balancing performance requirements with reliability needs and operational efficiency.

Question 14: Which safety standard governs the safe use of refrigerants in refrigerating systems in the United States?

OSHA 1910.119
ASHRAE 34
ASHRAE 15 (Correct answer)
EPA 40 CFR Part 82

Correct answer: ASHRAE 15

ASHRAE Standard 15 (Safety Standard for Refrigeration Systems) governs the safe design, construction, installation, and operation of refrigerating systems.

Question 15: In a refrigeration system using a capillary tube, what happens during the off cycle?

Refrigerant migrates to the condenser only
Pressures equalize between high side and low side (Correct answer)
Low-side pressure drops further
High-side pressure continues to build

Correct answer: Pressures equalize between high side and low side

A capillary tube has no check valve function, so pressures equalize during the off cycle, making startup easier for the compressor.

Question 16: What role does collaboration play in expansion devices for RSES professionals?

It is only needed in emergencies
It enhances outcomes through diverse perspectives and shared expertise (Correct answer)
It reduces individual accountability
It slows down work unnecessarily

Correct answer: It enhances outcomes through diverse perspectives and shared expertise

Collaboration leverages diverse perspectives and combined expertise to achieve better outcomes than any individual could alone.

Question 17: Which of the following would cause a TXV to hunt (cycle open and closed rapidly)?

Oversized TXV for the system load (Correct answer)
Proper bulb insulation
Correct refrigerant charge
Correct superheat setting

Correct answer: Oversized TXV for the system load

An oversized TXV over-responds to load changes, causing hunting as it continually opens too far then closes too far.

Question 18: A glycol chiller evaporator shows reduced capacity but the refrigerant side readings are normal. What is the most likely cause on the glycol side?

Faulty TXV allowing too much refrigerant flow
Low refrigerant superheat causing liquid slugging
Refrigerant overcharge flooding the evaporator
High glycol concentration reducing heat transfer and flow rate (Correct answer)

Correct answer: High glycol concentration reducing heat transfer and flow rate

Excessive glycol concentration increases viscosity and reduces the glycol-side heat transfer coefficient, significantly cutting the chiller's effective capacity.

Question 19: What is the purpose of a capacitor in a motor circuit?

Boost motor performance (Correct answer)
Increase noise
Dim the lights
Heat the coil

Correct answer: Boost motor performance

To provide a starting or running boost for motors.

Question 20: What role does calibration play in maintaining technical accuracy for Refrigeration Service Engineers Society Certification professionals?

It ensures instruments and methods produce accurate, consistent results over time (Correct answer)
It only matters during formal inspections
It is only necessary for new equipment
It is an optional best practice for advanced professionals

Correct answer: It ensures instruments and methods produce accurate, consistent results over time

Regular calibration ensures that instruments, tools, and methods continue to produce accurate and consistent results over time. Without calibration, measurement drift and equipment wear can lead to unreliable outcomes.

Question 21: During a leak check using electronic leak detection, false positives are being triggered near a drain pan. What could cause this?

Excessive superheat in the evaporator
Refrigerant accumulation in the drain pan from a real leak
Non-condensables in the system
Cleaning solvents or certain drain pan treatments off-gassing halogen compounds (Correct answer)

Correct answer: Cleaning solvents or certain drain pan treatments off-gassing halogen compounds

Some cleaning agents and drain pan treatments contain halogenated compounds that can trigger halide-based electronic leak detectors.

Question 22: When replacing a contactor in a refrigeration system, the technician should verify that the replacement contactor has the correct:

Coil voltage and contact ampere rating (Correct answer)
Wire color coding matching the original
Physical size only
Number of auxiliary contacts only

Correct answer: Coil voltage and contact ampere rating

The replacement contactor must match the original's coil voltage (24V, 120V, 208V, etc.) and contact ampere rating to ensure proper operation and adequate current-carrying capacity.

Question 23: Which refrigerant was the primary replacement for R-12 in automotive air conditioning systems?

R-134a (Correct answer)
R-410A
R-404A
R-22

Correct answer: R-134a

R-134a replaced R-12 in automotive AC systems beginning in 1994 model year vehicles because it has zero ozone depletion potential.

Question 24: After completing repairs on a commercial refrigeration system, what is the correct sequence for returning the system to service?

Start compressor dry to verify mechanical operation before charging
Charge refrigerant, start compressor, then leak check with system running
Evacuate, charge, start compressor, pressure test during first run
Pressure test with nitrogen, evacuate, charge refrigerant, verify operation, document (Correct answer)

Correct answer: Pressure test with nitrogen, evacuate, charge refrigerant, verify operation, document

The correct return-to-service sequence is: leak test with nitrogen, pull deep vacuum, charge with correct refrigerant amount, verify system operation, then document all work performed.

Question 25: Which refrigerant property is measured by a gauge manifold's high-side gauge during normal operation?

Evaporator saturation pressure
Liquid line subcooling
Suction line superheat
Condenser saturation pressure (Correct answer)

Correct answer: Condenser saturation pressure

The high-side gauge reads the discharge pressure, which corresponds to the condenser saturation pressure.

Question 26: During hot-gas defrost of a low-temperature evaporator, the system pressure may rise significantly. What component protects the low-side from excessive pressure?

The liquid line solenoid valve
A defrost pressure-relief or pressure-limiting valve on the evaporator outlet (Correct answer)
The compressor suction service valve
The TXV, which closes under high pressure

Correct answer: A defrost pressure-relief or pressure-limiting valve on the evaporator outlet

A pressure-limiting or defrost relief valve vents excess pressure from the evaporator to the suction line or condenser to prevent low-side pressure from exceeding safe limits.

Question 27: A system has normal suction pressure but abnormally high discharge pressure. The condenser coils are clean. What should be suspected?

Low condenser airflow due to fan blade slip
Refrigerant undercharge
Faulty expansion valve stuck open
Non-condensable gases in the system (Correct answer)

Correct answer: Non-condensable gases in the system

Non-condensable gases raise discharge pressure disproportionately because they do not condense and occupy condenser surface area.

Question 28: What is the FIRST step a RSES professional should take before operating any equipment?

Ask a colleague if the equipment seems okay
Begin operation to test if it works
Read the manual only if issues are encountered
Conduct a pre-operation inspection and verify safety systems (Correct answer)

Correct answer: Conduct a pre-operation inspection and verify safety systems

A pre-operation inspection is essential before using any equipment. This includes checking for visible damage, verifying safety systems are functional, confirming proper setup, and ensuring all components are in working order.

Question 29: Which factor primarily determines the refrigerant flow capacity of a capillary tube?

Ambient temperature only
Tube material composition
Refrigerant color and viscosity
Tube length and inside diameter (Correct answer)

Correct answer: Tube length and inside diameter

Capillary tube flow capacity is determined by its length and inside diameter, with shorter/larger diameter tubes passing more refrigerant.

Question 30: What symptom would a refrigeration technician observe if the TXV sensing bulb loses its refrigerant charge?

TXV operates normally with slight superheat error
TXV opens fully, flooding the evaporator
TXV closes fully, starving the evaporator (Correct answer)
High-side pressure drops dramatically

Correct answer: TXV closes fully, starving the evaporator

Without bulb pressure as the opening force, the spring pressure keeps the TXV closed, starving the evaporator and causing high superheat.

Question 31: The purpose of a liquid line solenoid valve in a refrigeration system is to:

Stop refrigerant flow to the evaporator when the system is off or on demand (Correct answer)
Regulate refrigerant flow rate continuously
Control discharge pressure
Separate oil from liquid refrigerant

Correct answer: Stop refrigerant flow to the evaporator when the system is off or on demand

A liquid line solenoid valve is an electrically operated on/off valve that stops refrigerant flow to prevent evaporator flooding or pump-down the system.

Question 32: What is the value of continuing education in expansion devices for RSES professionals?

It keeps professionals current with evolving standards and practices (Correct answer)
It is primarily a social activity
It replaces workplace experience
It is only needed for recertification

Correct answer: It keeps professionals current with evolving standards and practices

Continuing education ensures professionals stay current with the latest developments, standards, and best practices in their field.

Question 33: How often should safety training be conducted?

Once in a career
Regular intervals (Correct answer)
During emergencies only
Only for new hires

Correct answer: Regular intervals

Regularly, to keep technicians updated on protocols and hazards.

Question 34: During a compressor replacement, you discover the old compressor failed due to a flooded start. What maintenance step should be added going forward?

Replace the metering device with a larger orifice
Install a desuperheater
Add a hot gas bypass valve
Install a suction line accumulator (Correct answer)

Correct answer: Install a suction line accumulator

A suction line accumulator prevents liquid refrigerant from entering the compressor during startup, protecting against flooded starts.

Question 35: During operation, a system's compressor cycles on and off rapidly (short-cycles). Which condition is the LEAST likely cause?

Dirty condenser coil (Correct answer)
Faulty low-pressure control set too high
Oversized compressor for the load
Low refrigerant charge

Correct answer: Dirty condenser coil

A dirty condenser coil raises discharge pressure but does not typically cause rapid short-cycling on the low-pressure control.

Question 36: An electronic expansion valve (EEV) in a variable refrigerant flow (VRF) system is typically controlled by:

A manual pressure regulator
Direct high-side pressure feedback only
A microprocessor receiving inputs from multiple sensors (Correct answer)
A mechanical sensing bulb

Correct answer: A microprocessor receiving inputs from multiple sensors

EEVs in VRF systems are controlled by microprocessors using inputs such as suction superheat, coil temperature, and load demand for optimal performance.

Question 37: What color is the grounding conductor required to be in a 120/240V single-phase electrical system per NEC standards?

Green or bare copper (Correct answer)
Black
White or gray
Red

Correct answer: Green or bare copper

NEC Article 250 requires equipment grounding conductors to be green, green with yellow stripe, or bare copper; white/gray identifies the neutral (grounded) conductor.

Question 38: Which component in a refrigeration system is responsible for changing high-pressure liquid refrigerant to a low-pressure liquid/vapor mixture?

Accumulator
Compressor
Metering device (expansion valve or orifice) (Correct answer)
Condenser

Correct answer: Metering device (expansion valve or orifice)

The metering device (TXV, fixed orifice, or capillary tube) creates a pressure drop that flashes some liquid to vapor, lowering refrigerant temperature.

Question 39: When performing an oil change on a hermetic compressor, how is oil typically added to the system?

Through the high-side service valve only
By draining the crankcase and refilling with new oil
Through the suction service valve using an oil injector or pre-charged compressor (Correct answer)
Through the compressor oil fill port

Correct answer: Through the suction service valve using an oil injector or pre-charged compressor

Hermetic compressors lack an external oil fill port, so oil is introduced through the suction service valve using an oil injector while the system is under vacuum.

Question 40: According to ASHRAE 34, what refrigerant safety group classification indicates the highest flammability?

A1
A3 (Correct answer)
B3
A2L

Correct answer: A3

Group A3 indicates lower toxicity (A) and higher flammability (3), representing the highest flammability classification in the ASHRAE 34 safety group system.

Question 41: Which parameter is used to express the overall efficiency of a compressor by comparing actual work input to ideal isentropic compression work?

Isentropic (adiabatic) efficiency (Correct answer)
Coefficient of Performance (COP)
Mechanical efficiency
Volumetric efficiency

Correct answer: Isentropic (adiabatic) efficiency

Isentropic efficiency compares the actual work input to the theoretical minimum work of reversible adiabatic compression, quantifying how well the compressor converts power into refrigerant compression.

Question 42: How are condensate drains maintained?

Seal with glue
Spray with paint
Block them
Flush regularly (Correct answer)

Correct answer: Flush regularly

By cleaning and flushing to prevent blockages and overflow.

Question 43: What is the 'right-to-know' law that requires employers to inform workers about hazardous chemicals in the workplace?

ASHRAE Standard 15
EPA 40 CFR Part 82
OSHA 29 CFR 1910.1200 (HazCom) (Correct answer)
OSHA 29 CFR 1910.147

Correct answer: OSHA 29 CFR 1910.1200 (HazCom)

OSHA's Hazard Communication Standard (29 CFR 1910.1200), often called the Right-to-Know law, requires employers to inform and train workers about chemical hazards.

Question 44: What is the function of the distributor nozzle connected to a TXV outlet in a multi-circuit evaporator?

It prevents liquid floodback
It regulates superheat independently
It measures refrigerant quality
It evenly distributes refrigerant to all evaporator circuits (Correct answer)

Correct answer: It evenly distributes refrigerant to all evaporator circuits

The distributor nozzle splits the refrigerant mixture from the TXV into equal portions for each evaporator circuit to ensure uniform loading.

Question 45: A technician is replacing a burned-out compressor motor in a semi-hermetic compressor. What additional service step is mandatory due to the burn contamination?

Replace only the filter-drier and flush with refrigerant
Install a suction filter, replace the liquid line filter-drier, and perform an acid test after initial operation (Correct answer)
Evacuate to 500 microns and recharge with new refrigerant only
Replace the TXV bulb due to thermal contamination

Correct answer: Install a suction filter, replace the liquid line filter-drier, and perform an acid test after initial operation

A burned compressor leaves acid and carbon contaminants in the system; a suction filter and liquid line drier must be installed and the system acid-tested after initial run to verify cleanup.

Question 46: Which tool is commonly used for brazing refrigerant lines?

Heat gun
Vacuum pump
Pliers
Oxy-acetylene torch (Correct answer)

Correct answer: Oxy-acetylene torch

An oxy-acetylene torch is used to weld or braze copper tubing.

Question 47: A walk-in cooler compressor short-cycles on the high-pressure cutout. Condenser coil is clean and airflow is adequate. What should the technician check next?

Refrigerant overcharge (Correct answer)
Evaporator fan motor amperage
Low ambient thermostat setting
Suction line insulation integrity

Correct answer: Refrigerant overcharge

If the condenser is clean and airflow is adequate but high pressure is still tripping, refrigerant overcharge is the next likely cause, as excess refrigerant raises condensing pressure.

Question 48: A refrigeration system using R-717 (ammonia) requires special consideration because ammonia is classified as:

A1 — low toxicity, non-flammable
B2L — higher toxicity, lower flammability (Correct answer)
B1 — higher toxicity, non-flammable
A3 — low toxicity, high flammability

Correct answer: B2L — higher toxicity, lower flammability

Ammonia (R-717) is classified B2L under ASHRAE 34, indicating higher toxicity (B) and lower flammability with a low burning velocity (2L).

Question 49: When installing a liquid line solenoid valve, what is the correct orientation requirement?

Vertical with the flow upward
Any orientation as long as the coil is accessible
The body must be installed with the flow direction arrow matching refrigerant flow (Correct answer)
Horizontal with the coil facing up

Correct answer: The body must be installed with the flow direction arrow matching refrigerant flow

Solenoid valves have a directional flow arrow on the body that must align with the direction of refrigerant flow; incorrect orientation prevents proper valve seating and operation.

Question 50: Why must circuit diagrams be followed?

To replace fuses
To draw pictures
Label refrigerant
Ensure proper wiring (Correct answer)

Correct answer: Ensure proper wiring

They provide the correct wiring and operation layout.

Question 51: Which approach is recommended for troubleshooting evaporator systems issues?

Use systematic isolation and testing methods (Correct answer)
Replace all components simultaneously
Wait for the problem to resolve itself
Rely solely on past experience

Correct answer: Use systematic isolation and testing methods

Systematic isolation and testing methodically narrows down the root cause, making troubleshooting efficient and accurate.

Question 52: During maintenance of a cooling tower, a technician finds biological growth (Legionella risk). What is the immediate required action?

Increase condenser water flow rate
Reduce system operating hours
Perform shock chlorination and notify the facility manager (Correct answer)
Replace the cooling tower fill material

Correct answer: Perform shock chlorination and notify the facility manager

Biological growth in cooling towers poses a Legionella health hazard requiring immediate shock chlorination treatment and notification of facility management per safety protocols.

Question 53: In a hermetic compressor, the motor and compressor are:

Separately driven through a belt drive
Connected by a flexible coupling in an open housing
Enclosed in the same sealed housing sharing refrigerant (Correct answer)
Cooled by external water jackets only

Correct answer: Enclosed in the same sealed housing sharing refrigerant

A hermetic compressor seals both motor and compressor in one welded shell, with suction gas cooling the motor windings.

Question 54: When installing a refrigeration system in a machinery room, which code requirement governs the minimum ventilation rate?

OSHA 1910.119 specifies ventilation for all refrigerants above 100 lbs
ASHRAE Standard 15 specifies ventilation based on refrigerant quantity and room volume (Correct answer)
EPA Section 608 specifies ventilation for all refrigerant types
NEC Article 440 specifies minimum airflow in CFM per compressor horsepower

Correct answer: ASHRAE Standard 15 specifies ventilation based on refrigerant quantity and room volume

ASHRAE Standard 15 (Safety Standard for Refrigeration Systems) provides the formula and requirements for machinery room ventilation rates based on refrigerant type and quantity.

Question 55: A refrigeration system's low-pressure control is set to cut out at 10 psig and cut in at 25 psig. The differential of this control is:

35 psig
25 psig
15 psig (Correct answer)
10 psig

Correct answer: 15 psig

The differential is the difference between cut-in and cut-out pressures: 25 psig − 10 psig = 15 psig.

Question 56: What does a megohmmeter (megger) primarily measure in refrigeration system electrical diagnostics?

Voltage drop across windings
Capacitance of run capacitors
Insulation resistance of motor windings (Correct answer)
Continuity of control circuit fuses

Correct answer: Insulation resistance of motor windings

A megohmmeter applies high DC voltage (typically 500–1000V) to measure insulation resistance in megohms, revealing winding degradation or moisture ingress.

Question 57: What is the typical superheat setting range for a TXV used in air conditioning applications?

20-25°F
8-12°F (Correct answer)
1-3°F
30-40°F

Correct answer: 8-12°F

Most air conditioning TXVs are factory set for 8-12°F superheat to ensure full evaporator use while protecting the compressor.

Question 58: Which approach best demonstrates mastery of expansion devices in RSES practice?

Avoiding complex scenarios
Applying principles to novel situations with sound judgment (Correct answer)
Following procedures without understanding
Relying entirely on technology

Correct answer: Applying principles to novel situations with sound judgment

True mastery involves understanding underlying principles well enough to apply them to new and unfamiliar situations with professional judgment.

Question 59: What is subcooling in refrigeration?

Cooling below condensing point (Correct answer)
Freezing coils
Warming refrigerant
Insulating pipes

Correct answer: Cooling below condensing point

Subcooling in refrigeration refers to the process of cooling the liquid refrigerant below its saturation temperature (condensing point) at a given pressure. This additional cooling occurs after the refrigerant has fully condensed in the condenser. Subcooling increases the system's efficiency by ensuring that only liquid refrigerant enters the expansion device, preventing flash gas and improving cooling capacity.

Question 60: Which approach is MOST important for RSES professionals when applying technical procedures?

Applying the same technique in every situation without variation
Adhering to established protocols while adapting to specific conditions (Correct answer)
Following personal shortcuts developed through experience
Using the fastest method available regardless of standards

Correct answer: Adhering to established protocols while adapting to specific conditions

Technical procedures require adherence to established protocols as a foundation, with professional judgment to adapt appropriately to specific conditions. This balance ensures both consistency and effectiveness.

Question 61: A head pressure control valve in a refrigeration system's electrical controls is used to:

Maintain minimum condensing pressure during low ambient conditions (Correct answer)
Protect the compressor motor from overcurrent
Control the evaporator fan speed based on suction pressure
Regulate the defrost termination temperature

Correct answer: Maintain minimum condensing pressure during low ambient conditions

Head pressure control valves (or fan cycling controls) maintain minimum condensing pressure during cold ambient operation, ensuring adequate liquid pressure for proper expansion valve operation.

Question 62: In a low-temperature refrigeration application, the TXV sensing bulb charge should be:

A cross-charge designed to prevent valve closure at low ambient temperatures (Correct answer)
The same refrigerant as the system charge
A higher-pressure refrigerant than the system uses
Air or nitrogen for stability

Correct answer: A cross-charge designed to prevent valve closure at low ambient temperatures

Cross-charged bulbs use a different fluid blend to maintain valve responsiveness and prevent the bulb from condensing at low evaporating temperatures.

Question 63: A float valve in a flooded evaporator system responds to changes in:

Suction line pressure
Compressor discharge pressure
Refrigerant temperature
Refrigerant liquid level (Correct answer)

Correct answer: Refrigerant liquid level

The float valve maintains a constant liquid refrigerant level in the flooded evaporator by opening and closing based on liquid level.

Question 64: Which foundational principle is MOST important for success in the Refrigeration Service Engineers Society Certification profession?

Specializing in only one narrow area of practice
Maintaining the minimum requirements for certification
Commitment to continuous learning, ethical practice, and quality outcomes (Correct answer)
Maximizing financial returns on every engagement

Correct answer: Commitment to continuous learning, ethical practice, and quality outcomes

Success in any professional field requires a commitment to continuous learning to stay current, ethical practice to maintain trust and integrity, and a focus on quality outcomes that serve stakeholders and the public interest.

Question 65: When decommissioning a system with a refrigerant blend, which recovery method is preferred to minimize fractionation?

Push-pull recovery method using two cylinders
Vapor-only recovery through the high side
Vapor recovery through both high and low sides simultaneously
Liquid recovery followed by vapor recovery (Correct answer)

Correct answer: Liquid recovery followed by vapor recovery

Liquid recovery first (followed by vapor recovery) minimizes fractionation of blended refrigerants by keeping the components together rather than allowing lighter components to boil off preferentially.

Question 66: What is the proper technique for straightening bent condenser or evaporator fins during maintenance?

Apply moderate heat with a heat gun to relax the aluminum before straightening
Fins should never be straightened and require coil replacement
Use a fin comb sized to match the fins-per-inch rating of the coil (Correct answer)
Use a flat-blade screwdriver to carefully bend fins back individually

Correct answer: Use a fin comb sized to match the fins-per-inch rating of the coil

A fin comb matched to the coil's fins-per-inch count is designed to straighten multiple fins simultaneously without further damage to the delicate coil surface.

Question 67: What is the PROPER procedure for decommissioning outdated equipment in Refrigeration Service Engineers Society Certification practice?

Store it indefinitely in case it might be needed
Follow established protocols for safe decommissioning, data clearing, and proper disposal (Correct answer)
Donate it without any preparation or documentation
Simply discard it in regular waste disposal

Correct answer: Follow established protocols for safe decommissioning, data clearing, and proper disposal

Equipment decommissioning requires following established protocols that may include safe shutdown procedures, clearing any stored data, proper disposal of hazardous components, documentation of the decommissioning, and compliance with environmental regulations.

Question 68: A TXV that is overfeeding (flooding) the evaporator will most likely cause:

Reduced refrigerant charge
Liquid refrigerant entering the compressor (Correct answer)
High superheat at the evaporator outlet
High condensing pressure

Correct answer: Liquid refrigerant entering the compressor

Overfeeding sends excessive liquid through the evaporator, and unevaporated liquid entering the compressor causes liquid slugging damage.

Question 69: When performing a standing pressure test on a newly installed refrigeration system, what is the recommended holding time before declaring the system leak-free?

15 minutes at operating pressure
1 hour with electronic leak detector confirmation
30 minutes followed by nitrogen purge
24 hours minimum at test pressure (Correct answer)

Correct answer: 24 hours minimum at test pressure

A minimum 24-hour standing pressure test is recommended to allow temperature stabilization and confirm that pressure remains constant, indicating a leak-free system.

Question 70: What does the 'system balance point' mean in refrigeration system design?

The point at which the compressor oil pressure equals suction pressure
The operating condition where system capacity exactly matches the refrigeration load (Correct answer)
The midpoint between high-side and low-side pressures
The electrical balance between phase voltages on a three-phase system

Correct answer: The operating condition where system capacity exactly matches the refrigeration load

The balance point is where the system's capacity curve intersects the load curve, meaning the equipment removes heat exactly as fast as it enters the space.

Question 71: A clogged or restricted TXV will cause the suction pressure to:

Remain at normal operating pressure
Fluctuate erratically between high and low
Increase above normal
Drop below normal (Correct answer)

Correct answer: Drop below normal

A restricted TXV starves the evaporator of refrigerant, reducing suction pressure and causing abnormally low evaporator temperatures.

Question 72: What is the primary advantage of an electronic expansion valve (EEV) over a TXV?

Eliminates the need for a compressor
No need for a refrigerant charge
More precise refrigerant flow control across varying conditions (Correct answer)
Lower cost and simpler installation

Correct answer: More precise refrigerant flow control across varying conditions

EEVs use electronic controls and stepper motors for precise modulation, outperforming TXVs in variable-load or multi-evaporator applications.

Question 73: When installing a TXV sensing bulb on a suction line larger than 7/8 inch OD, the bulb should be mounted at:

The 4 or 8 o'clock position (Correct answer)
Any position since size doesn't matter
The 12 o'clock (top) position
The 6 o'clock (bottom) position

Correct answer: The 4 or 8 o'clock position

On larger suction lines, mounting the bulb at the 4 or 8 o'clock position ensures it contacts refrigerant vapor rather than oil that pools at the bottom.

Question 74: Which component compresses the refrigerant gas in a system?

Compressor (Correct answer)
Evaporator
Thermostat
Condenser

Correct answer: Compressor

The compressor is often considered the 'heart' of a refrigeration system. Its primary function is to draw in low-pressure, low-temperature refrigerant vapor from the evaporator and compress it into a high-pressure, high-temperature gas. This compression is essential for raising the refrigerant's temperature and pressure, allowing it to release heat in the condenser.

Question 75: A solid-state motor protector monitors which parameters to provide comprehensive motor protection?

Voltage only
Current, voltage, and phase sequence (Correct answer)
Only current draw
Only winding temperature

Correct answer: Current, voltage, and phase sequence

Solid-state motor protectors monitor current, voltage, phase loss, phase imbalance, and often phase sequence to provide complete protection against all common motor failure modes.

Question 76: Which approach best describes risk-based compliance management in the RSES field?

Prioritizing resources based on risk severity and likelihood (Correct answer)
Eliminating all possible risks
Focusing only on past incidents
Treating all risks equally

Correct answer: Prioritizing resources based on risk severity and likelihood

Risk-based compliance management involves assessing and prioritizing risks by their severity and likelihood to allocate resources effectively.

Question 77: When a technician observes a high condenser approach temperature on a water-cooled unit, what is the most likely cause?

Overcharged system
Low ambient temperature
Low refrigerant charge
Fouled condenser tubes or inadequate water flow (Correct answer)

Correct answer: Fouled condenser tubes or inadequate water flow

Fouled tubes or restricted water flow reduce heat transfer, causing the condensing temperature to rise well above the leaving water temperature.

Question 78: On a pressure-enthalpy (P-H) diagram, the horizontal distance across the evaporator represents:

Refrigerant mass flow rate
Condenser heat rejection
Compression work input
Latent heat absorbed (refrigerating effect) (Correct answer)

Correct answer: Latent heat absorbed (refrigerating effect)

The evaporator process appears as a horizontal line at low pressure; its horizontal length equals the enthalpy change, which is the refrigerating effect.

Question 79: A technician measures 120V across a contactor's coil terminals but the contactor does not pull in. The most likely cause is:

Shorted compressor motor winding
Tripped high-pressure switch
Low supply voltage to the coil
Open or burned-out coil (Correct answer)

Correct answer: Open or burned-out coil

Correct voltage across the coil terminals with no contactor pull-in means the coil itself is open or burned out and cannot generate the electromagnetic field needed to close the contacts.

Question 80: The coefficient of performance (COP) of a refrigeration system is calculated as:

Condenser heat divided by evaporator heat
Refrigerating effect divided by work input to the compressor (Correct answer)
Work input divided by heat rejected at the condenser
Compressor power divided by system capacity

Correct answer: Refrigerating effect divided by work input to the compressor

COP = Q_evaporator / W_compressor, expressing how many units of heat are moved per unit of energy consumed.

Question 81: What causes a frozen evaporator coil?

Too much sunlight
Low airflow or refrigerant (Correct answer)
Over-lubrication
Loose screws

Correct answer: Low airflow or refrigerant

Low airflow or low refrigerant levels are common causes.

Question 82: Which device controls the refrigerant flow into the evaporator?

Accumulator
TXV (Correct answer)
Solenoid coil
Filter-drier

Correct answer: TXV

The TXV, or Thermostatic Expansion Valve, is a crucial component that controls the flow of liquid refrigerant into the evaporator. It meters the amount of refrigerant based on the superheat of the refrigerant vapor leaving the evaporator, ensuring optimal cooling and preventing liquid refrigerant from returning to the compressor. This precise control maximizes system efficiency.

Question 83: In a three-phase electrical system, voltage imbalance exceeding what percentage is generally considered harmful to motor operation?

10%
1%
5% (Correct answer)
2%

Correct answer: 5%

NEMA standards specify that voltage imbalance should not exceed 1% for optimal motor operation, and imbalance above 2% will cause current imbalance roughly 6–10 times greater, leading to overheating; 5% is the practical threshold where damage becomes significant.

Question 84: What is the fundamental principle behind condenser systems in the RSES domain?

Using the newest technology exclusively
Cost minimization at all costs
Following a single vendor solution
Balancing performance, reliability, and efficiency (Correct answer)

Correct answer: Balancing performance, reliability, and efficiency

Effective technical design requires balancing performance requirements with reliability needs and operational efficiency.

Question 85: A capacitor-start, capacitor-run (CSCR) motor fails to start but hums loudly. Which component is most likely faulty?

Start capacitor or centrifugal switch (Correct answer)
Overload protector
Main winding
Run capacitor

Correct answer: Start capacitor or centrifugal switch

Humming without starting indicates the start winding circuit is open, typically caused by a failed start capacitor or a defective centrifugal switch that won't close.

Question 86: What happens to refrigerant pressure as it passes through a thermostatic expansion valve (TXV)?

Pressure remains constant
Pressure drops from high-side to low-side pressure (Correct answer)
Pressure fluctuates based on compressor speed
Pressure increases significantly

Correct answer: Pressure drops from high-side to low-side pressure

The TXV creates a pressure drop that allows the refrigerant to flash from liquid to a low-pressure mixture entering the evaporator.

Question 87: A scroll compressor differs from a reciprocating compressor in that it:

Uses pistons and connecting rods to compress refrigerant
Can only operate in a single speed mode
Uses two interleaving spiral scrolls without intake and discharge valves (Correct answer)
Requires external lubrication through a separate oil pump

Correct answer: Uses two interleaving spiral scrolls without intake and discharge valves

Scroll compressors use two meshing spiral scrolls to trap and compress refrigerant, eliminating the need for suction and discharge valves.

Question 88: What tool measures voltage and current?

Thermometer
Multimeter (Correct answer)
Caliper
Wrench

Correct answer: Multimeter

A multimeter is used to test electrical circuits.

Question 89: What is the purpose of the MOP (Maximum Operating Pressure) feature in some TXVs?

To control condenser fan cycling
To regulate refrigerant charge quantity
To limit compressor discharge pressure
To prevent the evaporator pressure from exceeding a set maximum during pulldown (Correct answer)

Correct answer: To prevent the evaporator pressure from exceeding a set maximum during pulldown

MOP prevents the TXV from opening fully during high-load pulldown conditions, protecting the compressor motor from overloading.

Question 90: Which of the following best describes 'approach temperature' for a water-cooled condenser?

Temperature difference between entering and leaving water
Temperature difference between condensing refrigerant and leaving water (Correct answer)
Temperature rise of refrigerant across the condenser
Saturation temperature at the condenser inlet

Correct answer: Temperature difference between condensing refrigerant and leaving water

Approach temperature is the difference between the refrigerant condensing temperature and the leaving condenser water temperature, indicating heat exchanger efficiency.

Question 91: Which document typically outlines the compliance requirements for RSES professionals?

Annual financial report
Employee handbook
Marketing brochure
Standards of practice and code of conduct (Correct answer)

Correct answer: Standards of practice and code of conduct

Standards of practice and codes of conduct define the professional and ethical requirements practitioners must follow.

Question 92: Which device protects the system from electrical overload?

Pressure switch
Relay
Thermostat
Fuse or breaker (Correct answer)

Correct answer: Fuse or breaker

A fuse or circuit breaker cuts off current when it exceeds safe limits.

Question 93: A technician installs a new evaporator coil and finds that the refrigerant distributor tubes are different lengths to various coil circuits. Why?

Longer tubes are used for the lower circuits to compensate for gravity effects
Tube length is random and does not affect performance
Longer tubes reduce refrigerant velocity to prevent noise
Different tube lengths compensate for unequal pressure drops to balance refrigerant distribution (Correct answer)

Correct answer: Different tube lengths compensate for unequal pressure drops to balance refrigerant distribution

Unequal distributor tube lengths are intentional engineering to create equal pressure drops across all coil circuits, ensuring balanced refrigerant distribution and uniform coil performance.

Question 94: Sensible heat transfer in a refrigeration system occurs when:

Refrigerant condenses from vapor to liquid
Temperature of a substance changes without a phase change (Correct answer)
Refrigerant changes phase from liquid to vapor
Latent heat is absorbed in the evaporator

Correct answer: Temperature of a substance changes without a phase change

Sensible heat transfer changes the temperature of a substance without a phase change, unlike latent heat which involves phase changes at constant temperature.

Question 95: Which type of compressor uses a fixed-volume ratio and cannot adjust to varying system pressure ratios?

Scroll compressor
Centrifugal compressor
Screw compressor (Correct answer)
Reciprocating compressor

Correct answer: Screw compressor

Screw compressors have a fixed built-in volume ratio determined by the rotor geometry, making them less efficient when operating far from their design pressure ratio.

Question 96: In a two-speed condenser fan motor control scheme, the motor switches from high speed to low speed when outdoor ambient temperature drops. This design primarily:

Increases system capacity during low-load periods
Reduces compressor discharge pressure during cold weather (Correct answer)
Reduces the risk of motor winding overheating
Prevents evaporator coil freeze-up

Correct answer: Reduces compressor discharge pressure during cold weather

Reducing condenser fan speed in cold weather slows the rate of heat rejection, maintaining adequate condensing pressure and liquid subcooling necessary for proper system operation.

Question 97: When calculating refrigeration load, what is the 'equipment load' component?

The weight of the refrigeration equipment installed
Heat load caused by the refrigerant compressor
The rated BTU capacity of the condensing unit
Heat generated by lights, fan motors, and other equipment inside the space (Correct answer)

Correct answer: Heat generated by lights, fan motors, and other equipment inside the space

Equipment load includes heat added by evaporator fan motors, defrost heaters, lights, forklifts, and any other heat-generating equipment operating inside the refrigerated space.

Question 98: The TXV sensing bulb must be mounted in proper thermal contact with the suction line because:

It provides structural support for the valve
It measures system amperage
It measures ambient humidity
It must accurately sense refrigerant temperature to control superheat (Correct answer)

Correct answer: It must accurately sense refrigerant temperature to control superheat

The sensing bulb contains a refrigerant charge that expands or contracts based on suction line temperature, which opens or closes the TXV.

Question 99: Which refrigerant blend is classified as 'zeotropic' and exhibits temperature glide during phase change?

R-410A
R-134a
R-407C (Correct answer)
R-744

Correct answer: R-407C

R-407C is a zeotropic HFC blend whose components boil at different temperatures, resulting in a temperature glide (change in temperature during evaporation or condensation).

Question 100: A dual-element time-delay fuse is preferred over a standard fast-blow fuse for protecting motor circuits because it:

Provides lower cost replacement
Responds faster to short circuits
Withstands high inrush current during motor starting without nuisance blowing (Correct answer)
Provides ground fault protection

Correct answer: Withstands high inrush current during motor starting without nuisance blowing

Dual-element fuses have a separate time-delay element that tolerates the brief high inrush current during motor starting while still providing fast protection against short circuits.

RSES Certifications (e.g., CM, CMS, RM, SM)

RSES offers various certifications for HVACR professionals, demonstrating expertise in specific areas like commercial refrigeration, domestic refrigeration, or HVACR electrical.

100

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150 min

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70%

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