Certified Refrigeration Service Technician (CRST) — Questions and Answers

Question 1: How should Certified Refrigeration Service Technician professionals handle equipment showing signs of malfunction during operation?

Finish the current task first
Continue operating while monitoring
Immediately cease operation, secure the equipment, and report (Correct answer)
Attempt field repairs while running

Correct answer: Immediately cease operation, secure the equipment, and report

Immediate cessation prevents safety hazards, further damage, or compromised results.

Question 2: What is the correct preparation sequence before brazing a refrigeration copper fitting joint?

Heat the joint first to drive off moisture, then insert the fitting
Apply refrigerant oil inside the tube end to lubricate the fit
Clean mating surfaces with emery cloth until bright, then apply flux if joining dissimilar metals (Correct answer)
Apply water to the joint area to prevent overheating

Correct answer: Clean mating surfaces with emery cloth until bright, then apply flux if joining dissimilar metals

Surfaces must be mechanically cleaned to bare, shiny metal, and appropriate flux applied when needed, to ensure proper brazing alloy flow and a leak-free joint.

Question 3: In refrigeration copper tubing work, what does the term 'swaging' refer to?

Expanding the end of a tube so another tube of the same diameter can be inserted for a brazed connection (Correct answer)
Bending tubing to a precise angle without a bender
Pressure-testing a completed joint with refrigerant
Cutting tubing at an angle using a hacksaw

Correct answer: Expanding the end of a tube so another tube of the same diameter can be inserted for a brazed connection

Swaging mechanically expands the end of a copper tube to accept another tube of the same nominal size, allowing a direct brazed joint without a separate coupling fitting.

Question 4: What is the standard voltage for a single-phase residential refrigeration compressor in the US?

480V or 600V
208V or 460V
115V or 230V (Correct answer)
24V or 48V

Correct answer: 115V or 230V

Single-phase residential refrigeration compressors in the US typically operate on 115V or 230V circuits.

Question 5: A technician discovers an unknown refrigerant in a system. Why is mixing it with a known refrigerant in a recovery cylinder prohibited?

It increases the cylinder pressure above safe limits
It invalidates the technician's EPA certification
Mixed refrigerants cannot be reclaimed and must be destroyed (Correct answer)
It causes chemical reactions that damage the recovery machine

Correct answer: Mixed refrigerants cannot be reclaimed and must be destroyed

Reclaimers cannot process contaminated or mixed refrigerants, so blended unknown refrigerants must be destroyed rather than reclaimed.

Question 6: After completing a brazed joint in a refrigeration line, what is the correct method for allowing the joint to cool?

Use compressed air to blast cool the joint rapidly
Allow the joint to air cool naturally without applying water or forced cooling (Correct answer)
Quench immediately with cold water to lock in the joint structure
Apply ice directly to the joint to prevent overheating adjacent components

Correct answer: Allow the joint to air cool naturally without applying water or forced cooling

Brazed joints must air cool naturally because quenching with water causes thermal shock that can crack the braze alloy, stress the base metal, or weaken the joint.

Question 7: Under the GWP-based regulations in the AIM Act, which action is required for high-GWP HFCs in certain equipment sectors?

Immediate venting and system decommissioning
Phased reduction in production and use (Correct answer)
Annual emission reporting to the EPA
Mandatory conversion to natural refrigerants only

Correct answer: Phased reduction in production and use

The AIM Act authorizes EPA to phase down HFC production and use through an allowance system, targeting high-GWP refrigerants across equipment sectors.

Question 8: What is the role of a desuperheater in a refrigeration system?

Cool the compressor motor windings
Remove superheat from suction gas to protect the compressor
Add superheat to liquid refrigerant before the metering device
Extract heat from hot discharge gas for water heating (Correct answer)

Correct answer: Extract heat from hot discharge gas for water heating

A desuperheater is a heat exchanger that recovers heat from superheated discharge gas, commonly used to preheat domestic hot water.

Question 9: At approximately what temperature range does silver-phosphorus-copper (BCuP-5) brazing alloy flow and fill refrigeration copper joints?

700–800°F (371–427°C)
1,200–1,500°F (649–816°C) (Correct answer)
1,800–2,000°F (982–1,093°C)
300–400°F (149–204°C)

Correct answer: 1,200–1,500°F (649–816°C)

BCuP-5 has a solidus near 1,190°F and liquidus near 1,475°F, placing its working brazing range at approximately 1,200–1,500°F—well above soft-solder temperatures but below copper's melting point.

Question 10: When pressure-testing a refrigeration system with nitrogen, what is the maximum test pressure typically used for medium-temperature applications?

50 psig
150 psig (Correct answer)
500 psig
1,000 psig

Correct answer: 150 psig

For medium-temperature systems, nitrogen pressure tests are commonly performed at approximately 150 psig, consistent with low-side design pressure ratings.

Question 11: What thermodynamic process occurs in the evaporator of a vapor-compression refrigeration cycle?

Refrigerant absorbs heat from the load and vaporizes at constant pressure (Correct answer)
Refrigerant releases heat and condenses at constant pressure
Refrigerant expands from high to low pressure adiabatically
Refrigerant is compressed from low to high pressure

Correct answer: Refrigerant absorbs heat from the load and vaporizes at constant pressure

In the evaporator, liquid refrigerant absorbs latent heat from the refrigerated space and changes phase to vapor at a constant low pressure.

Question 12: What is the recommended minimum bend radius for ACR copper tubing to prevent kinking, flattening, or cracking during bending?

Equal to the tube outside diameter
1.5 times the tube outside diameter
8 times the tube outside diameter
3 times the tube outside diameter (Correct answer)

Correct answer: 3 times the tube outside diameter

Bending copper tubing to a radius of at least 3 times the outside diameter distributes stress gradually enough to prevent the tube wall from kinking, collapsing, or cracking.

Question 13: When a CRST professional encounters an unexpected result during a procedure, the FIRST action should be to:

Report without preliminary assessment
Stop, assess the situation, and determine whether to proceed or seek guidance (Correct answer)
Continue and address it later
Repeat the procedure immediately

Correct answer: Stop, assess the situation, and determine whether to proceed or seek guidance

Stopping to assess unexpected results is critical for safety and quality.

Question 14: Under EPA Section 608, which refrigerants are classified as Class I ozone-depleting substances?

R-11, R-12, and R-113 (Correct answer)
R-410A and R-32
R-134a and R-1234yf
R-404A and R-507

Correct answer: R-11, R-12, and R-113

Class I ODS include CFCs such as R-11, R-12, and R-113, which have the highest ozone depletion potential.

Question 15: What does the term 'subcooling' refer to in a refrigeration system?

Cooling liquid refrigerant below its condensing temperature at a given pressure (Correct answer)
Reducing the temperature of the compressor discharge gas
Cooling suction vapor below the evaporator saturation temperature
Dropping the refrigerant temperature below 0°F

Correct answer: Cooling liquid refrigerant below its condensing temperature at a given pressure

Subcooling is the number of degrees the liquid refrigerant is cooled below its saturation (condensing) temperature at the same pressure, ensuring all refrigerant is fully liquid entering the expansion device.

Question 16: What is the first step in troubleshooting a refrigeration system?

Replace parts immediately
Ignore the problem
Identify symptoms (Correct answer)
Increase refrigerant charge

Correct answer: Identify symptoms

The first and most crucial step in troubleshooting any refrigeration system is to accurately identify the symptoms of the problem. This involves gathering information about what is happening, such as unusual noises, inadequate cooling, or error codes. Clearly understanding the symptoms guides the technician towards the potential root cause and appropriate diagnostic tests, preventing unnecessary work.

Question 17: What happens to the pressure-temperature relationship of a refrigerant mixture that 'glides'?

The mixture separates into its components at low temperatures
The temperature changes during phase change at constant pressure (Correct answer)
The boiling point increases as pressure decreases
The pressure and temperature remain fixed during phase change

Correct answer: The temperature changes during phase change at constant pressure

Zeotropic refrigerant blends exhibit temperature glide, meaning the evaporation or condensation temperature shifts (slides) across a range during phase change at constant pressure.

Question 18: After repairing a refrigerant leak and recharging a system, the technician should verify proper charge by checking:

Only the sight glass clarity
Superheat or subcooling depending on the metering device type (Correct answer)
Compressor amperage only
Discharge temperature only

Correct answer: Superheat or subcooling depending on the metering device type

Superheat is used to verify charge on fixed orifice systems, while subcooling is used on TXV systems; both methods confirm accurate refrigerant quantity in the circuit.

Question 19: Which factor MOST significantly affects the quality of technical outcomes in CRST practice?

The time of day
The practitioner's training, preparation, and attention to detail (Correct answer)
Speed of procedure completion
The brand of equipment

Correct answer: The practitioner's training, preparation, and attention to detail

Quality depends primarily on training, preparation, and attention to detail.

Question 20: What is the primary purpose of a refrigerant receiver in a commercial refrigeration system?

Store liquid refrigerant to accommodate system demand changes and ensure liquid feed to the expansion device (Correct answer)
Remove moisture and contaminants from the refrigerant
Separate oil from refrigerant on the suction side
Reduce refrigerant velocity before entering the condenser

Correct answer: Store liquid refrigerant to accommodate system demand changes and ensure liquid feed to the expansion device

A liquid receiver stores excess refrigerant charge, provides a stable liquid supply to the expansion device, and accommodates load variations without flooding or starving the system.

Question 21: A technician is replacing a compressor on an R-410A system. Which recovery equipment pressure rating is required for this refrigerant?

Standard low-pressure recovery equipment rated to 50 psig
Medium-pressure equipment rated to 300 psig
Any recovery equipment since R-410A is non-toxic
High-pressure recovery equipment rated to at least 800 psig (Correct answer)

Correct answer: High-pressure recovery equipment rated to at least 800 psig

R-410A operates at significantly higher pressures than older refrigerants, requiring recovery equipment rated for high-pressure service (typically 800 psig or higher).

Question 22: A walk-in cooler is not maintaining setpoint even though the compressor runs continuously. The evaporator coil is heavily frosted. What is the FIRST action to take?

Defrost the evaporator coil (Correct answer)
Check the condenser fan motor
Add refrigerant
Replace the thermostat

Correct answer: Defrost the evaporator coil

Heavy frost blocks airflow across the evaporator, reducing heat transfer efficiency; defrosting restores normal operation before further diagnosis.

Question 23: How should ACR copper tubing be stored and handled on a job site to maintain its factory cleanliness?

Keep both ends capped or plugged with factory or field caps until the moment of installation (Correct answer)
Wrap the entire length in wet cloth to maintain metal flexibility
Store vertically only, with one end resting in a bucket of water
Leave both tube ends open so pressure equalizes with atmosphere

Correct answer: Keep both ends capped or plugged with factory or field caps until the moment of installation

ACR tubing is factory-cleaned, dehydrated, and sealed; keeping ends capped prevents moisture, dirt, and debris from contaminating the interior before and during installation.

Question 24: Why is documentation important in troubleshooting?

Delay updates
No use
Ignore paperwork
Track repairs and issues (Correct answer)

Correct answer: Track repairs and issues

Documentation provides a comprehensive record of all troubleshooting steps, repairs performed, parts replaced, and system performance data. This historical information is invaluable for future technicians, helping them quickly understand the system's history and identify recurring problems. It enables more efficient and effective repairs, saving time and resources in the long run.

Question 25: When recharging a system with an HFC blend refrigerant (such as R-410A), how must the refrigerant be added from the cylinder?

As a vapor only through the discharge service valve
As a vapor only through the suction service valve
It can be added as either liquid or vapor interchangeably
As a liquid (cylinder inverted or using a liquid valve) (Correct answer)

Correct answer: As a liquid (cylinder inverted or using a liquid valve)

HFC blends like R-410A must be charged as liquid to maintain the correct blend ratio, as vapor-charging can cause fractionation and alter the refrigerant composition.

Question 26: When new equipment is introduced in Certified Refrigeration Service Technician, what is REQUIRED before staff use it?

Formal training, competency verification, and documentation (Correct answer)
Reading the manual independently
A brief verbal overview
Watching a colleague use it once

Correct answer: Formal training, competency verification, and documentation

Formal training, competency verification, and documented training completion are required.

Question 27: A compressor that hums but fails to start most likely has a faulty:

Crankcase heater
Low-pressure switch
Start capacitor or start relay (Correct answer)
Discharge valve

Correct answer: Start capacitor or start relay

A failed start capacitor or start relay prevents the start winding from providing enough torque to overcome compressor inertia during startup.

Question 28: When conducting a risk assessment for CRST operations, which factor should receive the HIGHEST priority?

Cost of implementing safety measures
Probability and severity of potential harm (Correct answer)
Convenience for daily operations
Time required for safety training

Correct answer: Probability and severity of potential harm

The probability and severity of potential harm are the primary factors in risk assessment.

Question 29: What is the FIRST step before operating any equipment in CRST practice?

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

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

Pre-operation inspection ensures visible damage is checked and safety systems verified.

Question 30: During installation of a refrigeration system, the technician discovers the power supply voltage is 208V but the unit is rated for 230V. What should be done?

Use a voltage reducer on the control circuit only
Install a step-up transformer or notify the customer that voltage must be corrected before startup (Correct answer)
Rewire the unit internally to accept 208V
Proceed with installation; the difference is negligible

Correct answer: Install a step-up transformer or notify the customer that voltage must be corrected before startup

Operating a 230V-rated unit on 208V causes low-voltage conditions that can overheat motors and void the warranty; the supply voltage must be corrected.

Question 31: In a two-stage refrigeration system, what is the purpose of the intercooler?

Cool suction gas before the first stage
Cool discharge gas between compression stages (Correct answer)
Separate refrigerant from oil between stages
Superheat refrigerant before the evaporator

Correct answer: Cool discharge gas between compression stages

The intercooler removes heat from the refrigerant between the first and second compression stages, improving efficiency and reducing discharge temperature.

Question 32: A technician measures a 15°F superheat at the evaporator outlet and 80°F subcooling at the condenser outlet. What condition does this indicate?

Normal operation
TXV stuck open
Refrigerant overcharge (Correct answer)
Evaporator fan failure

Correct answer: Refrigerant overcharge

Excessive subcooling combined with normal or low superheat is a classic sign of refrigerant overcharge in the system.

Question 33: When recovering refrigerant from a system with a hermetic compressor burnout, the technician should:

Use a dedicated recovery cylinder and filter to avoid cross-contamination (Correct answer)
Recover normally and reuse the refrigerant
Vent the refrigerant outdoors
Only recover if the refrigerant is a blend

Correct answer: Use a dedicated recovery cylinder and filter to avoid cross-contamination

Burnout contaminates refrigerant with acids and carbon; it must be recovered into a dedicated cylinder and sent for reclamation or disposal.

Question 34: What is the purpose of the receiver in refrigeration?

Filter air
Compress refrigerant
Store liquid refrigerant (Correct answer)
Evaporate refrigerant

Correct answer: Store liquid refrigerant

The receiver is a storage tank located after the condenser in a refrigeration system. Its purpose is to store excess liquid refrigerant, ensuring a continuous and steady supply to the expansion valve and evaporator. This helps maintain system efficiency and prevents liquid refrigerant from backing up into the condenser, which could cause operational issues.

Question 35: What safety precautions should be taken during repairs?

Use PPE and lockout/tagout (Correct answer)
Ignore safety
Bypass safety
Rush repairs

Correct answer: Use PPE and lockout/tagout

Safety precautions like Personal Protective Equipment (PPE) such as gloves and safety glasses protect technicians from physical, chemical, and electrical hazards. Lockout/tagout procedures are crucial for de-energizing equipment and preventing accidental startup during maintenance or repair. These measures are essential for safeguarding against electrical shock, injury from moving parts, and creating a safe working environment.

Question 36: What is 'superheat' in a refrigeration system?

The temperature difference between discharge gas and ambient air
The temperature of suction vapor above the saturation temperature at suction pressure (Correct answer)
The excess heat removed by the condenser beyond condensation
The temperature rise of refrigerant through the compressor

Correct answer: The temperature of suction vapor above the saturation temperature at suction pressure

Superheat is the number of degrees that suction vapor exceeds the saturation temperature at the measured suction pressure, ensuring only dry vapor enters the compressor.

Question 37: A technician is installing copper refrigerant tubing and needs to make a brazed joint. What gas should be used to purge the line during brazing?

Carbon dioxide
Oxygen
Dry nitrogen (Correct answer)
Compressed air

Correct answer: Dry nitrogen

Dry nitrogen purging during brazing prevents internal oxidation scale that can clog metering devices and damage compressor valves.

Question 38: A compressor with a cracked discharge valve reed will MOST likely exhibit:

High discharge pressure and normal suction pressure
Excessive oil consumption only
Low compression ratio and elevated suction pressure (Correct answer)
Normal pressures but high amperage

Correct answer: Low compression ratio and elevated suction pressure

A cracked discharge valve allows high-pressure gas to re-expand into the cylinder, reducing pumping efficiency and causing elevated suction pressure and low compression ratio.

Question 39: Why are safety procedures critical in refrigeration work?

To prevent accidents (Correct answer)
To increase workload
To ignore risks
To save time

Correct answer: To prevent accidents

Safety procedures are critical in refrigeration work because technicians face numerous potential hazards, including high pressures, electrical components, hazardous refrigerants, and moving machinery. Adhering to these procedures minimizes the risk of accidents, injuries, and fatalities. These protocols are designed to create a safe working environment and protect the health and well-being of all personnel.

Question 40: What condition is indicated when both suction and discharge pressures are abnormally low?

TXV hunting
Condenser fouled
Large refrigerant leak or severe undercharge (Correct answer)
Refrigerant overcharge

Correct answer: Large refrigerant leak or severe undercharge

When both pressures are low together, the system has lost a significant amount of refrigerant, reducing the overall pressure throughout the circuit.

Question 41: What is the correct method for determining the saturation temperature of a refrigerant at a known pressure?

Add 40°F to the ambient temperature
Measure with a thermocouple directly in the refrigerant stream
Consult the refrigerant pressure-temperature (PT) chart for that specific refrigerant (Correct answer)
Use the universal gas law formula PV=nRT

Correct answer: Consult the refrigerant pressure-temperature (PT) chart for that specific refrigerant

Each refrigerant has a unique pressure-temperature relationship — technicians use the PT chart specific to that refrigerant to determine saturation temperature at any measured pressure.

Question 42: What is the FIRST step before operating any equipment in CRST practice?

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

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

Pre-operation inspection ensures visible damage is checked and safety systems verified.

Question 43: What refrigerant is classified as R-717 and widely used in large industrial refrigeration systems?

Carbon dioxide (CO2)
Ammonia (NH3) (Correct answer)
Propane (C3H8)
Nitrogen (N2)

Correct answer: Ammonia (NH3)

R-717 is ammonia (NH3), a natural refrigerant with excellent thermodynamic properties and zero ODP/GWP widely used in industrial cold storage and food processing.

Question 44: Which refrigerant has an Ozone Depletion Potential (ODP) of zero and is commonly used in new commercial refrigeration systems in the US?

R-502
R-12
R-22
R-404A (Correct answer)

Correct answer: R-404A

R-404A has an ODP of zero (no chlorine atoms) and became widely adopted for commercial refrigeration as a replacement for ozone-depleting R-502 and R-22.

Question 45: In what direction should horizontal suction lines be sloped to promote oil return?

Level with zero slope to minimize pressure drop
1/4 inch per foot sloping toward the compressor (Correct answer)
1/4 inch per foot sloping toward the evaporator
1 inch per foot sloping toward the condenser

Correct answer: 1/4 inch per foot sloping toward the compressor

Horizontal suction lines should slope 1/4 inch per foot toward the compressor so that gravity assists oil in draining back toward the suction inlet.

Question 46: A technician finds oil logged in an evaporator coil. What is the most likely contributing cause?

Overcharged system with excess refrigerant
Insufficient refrigerant velocity to carry oil through the coil (Correct answer)
Faulty TXV bulb losing charge
Too much subcooling in the liquid line

Correct answer: Insufficient refrigerant velocity to carry oil through the coil

When refrigerant velocity in the evaporator is too low, oil cannot be carried along and accumulates (logs) in the coil, reducing heat transfer.

Question 47: What is the primary purpose of flowing dry nitrogen through refrigeration piping during the brazing process?

To prevent internal oxidation and copper oxide scale formation inside the tubing (Correct answer)
To cool the pipe rapidly after brazing is complete
To increase the brazing temperature at the joint
To simultaneously pressure-test the joint while brazing

Correct answer: To prevent internal oxidation and copper oxide scale formation inside the tubing

Nitrogen purging displaces oxygen inside the tubing during heating, preventing the formation of copper oxide scale that could contaminate the refrigerant system and damage components.

Question 48: Which refrigerant blend is commonly used as a drop-in service replacement for R-22 in low-temperature commercial refrigeration applications?

R-134a
R-410A
R-422D (Correct answer)
R-404A

Correct answer: R-422D

R-422D is an HFC blend approved as a near-drop-in retrofit for R-22 systems, particularly in low- and medium-temperature applications with compatible lubricant.

Question 49: What does a low-pressure control (LPC) typically do in a commercial refrigeration system?

Open the liquid line solenoid when pressure falls too low
Energize the defrost heaters when suction pressure is low
Cycle the compressor off when suction pressure drops below the set point (Correct answer)
Alert the condenser fan to increase speed

Correct answer: Cycle the compressor off when suction pressure drops below the set point

A low-pressure control cycles the compressor off when suction pressure drops below a set point, protecting the system from operating in a deep vacuum or refrigerant loss condition.

Question 50: What is the PROPER procedure for decommissioning outdated equipment in Certified Refrigeration Service Technician?

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

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

Decommissioning requires safe shutdown, data clearing, proper disposal, and documentation.

Question 51: What distinguishes a Certified Refrigeration Service Technician certified professional from a non-certified practitioner?

There is no meaningful difference
Certified professionals always have more experience
Certification validates competency through standardized assessment against benchmarks (Correct answer)
Certified professionals only work in larger organizations

Correct answer: Certification validates competency through standardized assessment against benchmarks

Certification provides objective validation of competency through standardized assessment.

Question 52: What refrigerant recovery requirement applies to small appliances (systems containing 5 pounds or less of refrigerant)?

Full evacuation to 4 inches Hg vacuum before opening
No recovery required if the refrigerant is an HFC
Recovery using self-contained recovery equipment to EPA standards (Correct answer)
Recovery of at least 80% of the refrigerant using certified equipment

Correct answer: Recovery using self-contained recovery equipment to EPA standards

Small appliances require refrigerant recovery using EPA-approved self-contained recovery equipment, though specific vacuum levels differ from larger systems.

Question 53: What condition is indicated when frost forms uniformly across the entire evaporator coil?

Restricted metering device causing low superheat
Normal operation with adequate airflow (Correct answer)
Low refrigerant charge causing early evaporation
Refrigerant overcharge

Correct answer: Normal operation with adequate airflow

Uniform frost across the full coil typically indicates normal operation with proper refrigerant flow and adequate airflow.

Question 54: Which type of copper tubing is specifically manufactured, internally cleaned, and sealed for use in refrigeration and air conditioning systems?

Type L plumbing tubing
Type K plumbing tubing
ACR (Air Conditioning and Refrigeration) tubing (Correct answer)
Type M plumbing tubing

Correct answer: ACR (Air Conditioning and Refrigeration) tubing

ACR tubing is deoxidized, internally cleaned, dehydrated, and sealed at the factory to keep the interior free of moisture and contamination for refrigerant service.

Question 55: Which gas is the recommended medium for pressure-testing refrigerant piping after brazing is complete?

Oxygen from a welding cylinder
Dry nitrogen (Correct answer)
Compressed air from a shop compressor
The system refrigerant charge

Correct answer: Dry nitrogen

Dry nitrogen is inert, oil-free, moisture-free, and non-reactive, making it the safe and industry-accepted gas for pressure-testing refrigerant piping without contaminating the system.

Question 56: In a horizontal suction line where pipe size must be reduced, which type of reducer fitting is preferred and why?

Eccentric reducer with the flat side up, to keep vapor at the bottom
Eccentric reducer with the flat side down, so oil can drain continuously along the pipe bottom (Correct answer)
Concentric reducer, because it centers both pipes on the same axis
Concentric reducer, because it creates less turbulence

Correct answer: Eccentric reducer with the flat side down, so oil can drain continuously along the pipe bottom

An eccentric reducer installed flat-side-down keeps the bottom of the pipe at a consistent elevation, preventing a low-point pocket where oil could accumulate and block flow.

Question 57: What minimum refrigerant velocity is generally required in vertical suction line risers to ensure adequate oil return to the compressor?

3,000-4,000 fpm
100-200 fpm
700-1,000 fpm (Correct answer)
50-100 fpm

Correct answer: 700-1,000 fpm

Vertical suction line risers require approximately 700-1,000 fpm minimum velocity to carry entrained oil droplets upward against gravity back to the compressor.

Question 58: A TXV-equipped system has low suction pressure and low superheat simultaneously. What is the MOST likely cause?

Refrigerant undercharge
Liquid line restriction
TXV stuck closed (Correct answer)
TXV stuck open

Correct answer: TXV stuck closed

A TXV stuck in the closed position starves the evaporator, causing low suction pressure; low superheat indicates little refrigerant is vaporizing past the valve.

Question 59: What is the correct tool and technique for cutting ACR copper tubing to achieve a clean, square, burr-minimized cut?

Hacksaw with a coarse blade drawn across the tubing
Reciprocating saw with a metal-cutting blade
Aviation snips or pipe shears for quick cuts
Tubing cutter rotated around the circumference with gradually increasing blade pressure (Correct answer)

Correct answer: Tubing cutter rotated around the circumference with gradually increasing blade pressure

A tubing cutter produces a clean, square cut perpendicular to the tube axis and is the standard method for copper ACR tubing, minimizing deformation and maintaining the tube's roundness.

Question 60: What is the purpose of a ground fault circuit interrupter (GFCI) outlet near refrigeration equipment in a food service setting?

Filter harmonics from the compressor motor
Prevent compressor short-cycling by smoothing voltage
Regulate voltage to maintain stable operation
Protect personnel from electric shock by detecting small ground fault currents (Correct answer)

Correct answer: Protect personnel from electric shock by detecting small ground fault currents

A GFCI detects imbalances as small as 5mA between hot and neutral conductors, indicating current leaking to ground, and trips within milliseconds to prevent electrocution.

Question 61: A technician uses electronic leak detection and finds a leak at the evaporator coil. What is the NEXT step before brazing the repair?

Pressurize with nitrogen to 400 PSIG
Recover the refrigerant from the system (Correct answer)
Weld the coil while the system is under pressure
Add leak sealant to the charge

Correct answer: Recover the refrigerant from the system

Before any brazing or open-flame work, refrigerant must be completely recovered to prevent combustion of refrigerant decomposition products and to comply with EPA regulations.

Question 62: In a refrigeration control circuit, what is the primary function of a thermostat?

Measure system pressure
Control fan motor speed
Regulate refrigerant flow rate
Cycle the compressor on and off to maintain set temperature (Correct answer)

Correct answer: Cycle the compressor on and off to maintain set temperature

The thermostat senses space or product temperature and cycles the compressor on and off to maintain the desired set point.

Question 63: What is the PROPER procedure for decommissioning outdated equipment in Certified Refrigeration Service Technician?

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

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

Decommissioning requires safe shutdown, data clearing, proper disposal, and documentation.

Question 64: What is the purpose of a filter-drier installed in the liquid line of a refrigeration system?

Filter oil from the refrigerant before it enters the evaporator
Remove moisture and solid contaminants from the refrigerant to protect the expansion valve and compressor (Correct answer)
Reduce refrigerant velocity to prevent erosion of the liquid line
Separate flash gas from liquid before the metering device

Correct answer: Remove moisture and solid contaminants from the refrigerant to protect the expansion valve and compressor

A liquid line filter-drier uses desiccant material to absorb moisture and a mesh filter to trap solid particles, preventing ice formation at the expansion device and acid formation in the system.

Question 65: When checking a hermetic compressor for an open motor winding, which instrument should be used?

Clamp-on ammeter
Megohmmeter
Manometer
Ohmmeter (Correct answer)

Correct answer: Ohmmeter

An ohmmeter measures resistance between terminals to identify an open winding, which shows infinite or very high resistance.

Question 66: What is the purpose of installing a suction line accumulator on a refrigeration system?

To reduce head pressure at startup
To prevent liquid refrigerant from entering the compressor (Correct answer)
To subcool liquid refrigerant before the metering device
To filter moisture from the refrigerant

Correct answer: To prevent liquid refrigerant from entering the compressor

A suction line accumulator traps liquid refrigerant and oil, allowing only vapor to enter the compressor, protecting it from liquid slugging.

Question 67: When troubleshooting a system that repeatedly trips on high-pressure cutout, the technician should inspect the:

Condenser airflow, refrigerant charge, and non-condensables (Correct answer)
Suction strainer and accumulator
Low-pressure switch calibration
Crankcase heater and oil level

Correct answer: Condenser airflow, refrigerant charge, and non-condensables

High head pressure is caused by poor condenser heat rejection from blocked airflow, refrigerant overcharge, or non-condensables — all three must be checked.

Question 68: Which wiring method is required for refrigeration equipment in a damp or wet location per the NEC?

THWN wire in liquid-tight flexible metal conduit or equivalent wet-rated method (Correct answer)
UF cable stapled directly to framing
NM cable (Romex) in open air runs
Dry-rated THHN wire in EMT

Correct answer: THWN wire in liquid-tight flexible metal conduit or equivalent wet-rated method

NEC requires wet-location rated conductors (such as THWN) and appropriate conduit methods like liquid-tight flexible metal conduit in damp or wet locations.

Question 69: What does the Global Warming Potential (GWP) of a refrigerant measure?

Its flammability rating per ASTM standards
Its heat-trapping potential relative to CO2 over 100 years (Correct answer)
Its toxicity level per ASHRAE 34 classification
The amount of ozone it depletes in the stratosphere

Correct answer: Its heat-trapping potential relative to CO2 over 100 years

GWP measures a refrigerant's ability to trap heat in the atmosphere relative to carbon dioxide (CO2 = 1) over a 100-year period.

Question 70: What is the MOST important reason for maintaining equipment maintenance logs in CRST practice?

To satisfy insurance requirements only
To justify replacement budgets
To track maintenance history, predict failures, and demonstrate compliance (Correct answer)
To assign blame when equipment fails

Correct answer: To track maintenance history, predict failures, and demonstrate compliance

Maintenance logs track history, predict failures, and demonstrate regulatory compliance.

Question 71: When new equipment is introduced in Certified Refrigeration Service Technician, what is REQUIRED before staff use it?

Formal training, competency verification, and documentation (Correct answer)
Watching a colleague use it once
Reading the manual independently
A brief verbal overview

Correct answer: Formal training, competency verification, and documentation

Formal training, competency verification, and documented training completion are required.

Question 72: When should system testing be performed after repair?

Never
Only during maintenance
Immediately after repair (Correct answer)
After several weeks

Correct answer: Immediately after repair

Performing system testing immediately after a repair is crucial to verify that the problem has been resolved and the system is operating correctly. This step ensures that all components are functioning as intended and that the repair itself hasn't introduced new issues. It confirms the system's integrity, efficiency, and readiness for service before it's put back into full operation.

Question 73: A technician discovers a system leaking R-22 at a rate of 25% per year. What is the required response timeline under EPA regulations?

No repair required if under 50 lbs charge
Repair within 60 days of discovery (Correct answer)
Repair within 90 days of discovery
Repair within 30 days of discovery

Correct answer: Repair within 60 days of discovery

EPA Section 608 requires that leaking systems exceeding threshold rates be repaired within 30 days, with a possible 60-day extension for complex repairs.

Question 74: Which preventive maintenance approach is MOST effective for CRST professionals?

Fix equipment only when it breaks
Perform maintenance annually regardless of usage
Schedule regular maintenance based on manufacturer recommendations and usage (Correct answer)
Outsource all maintenance

Correct answer: Schedule regular maintenance based on manufacturer recommendations and usage

Scheduling based on manufacturer recommendations and usage patterns optimizes reliability.

Question 75: A refrigeration system loses capacity gradually over several weeks. The most cost-effective FIRST diagnostic step is to:

Replace the compressor
Replace the filter-drier
Check and record system operating pressures and temperatures (Correct answer)
Add refrigerant immediately

Correct answer: Check and record system operating pressures and temperatures

Measuring and recording operating pressures and temperatures provides a baseline to compare against design specs and identify the root cause systematically.

Question 76: Which refrigerant is classified as an A1 safety group per ASHRAE 34?

R-290 (propane)
R-1234yf
R-717 (ammonia)
R-134a (Correct answer)

Correct answer: R-134a

R-134a is classified A1 — 'A' indicating lower toxicity and '1' indicating no flame propagation, making it a non-toxic, non-flammable refrigerant.

Question 77: Which type of joint connection is recommended for permanent refrigerant piping installations in commercial refrigeration systems?

Compression fittings
Threaded NPT connections
Push-to-connect quick couplings
Brazed connections (Correct answer)

Correct answer: Brazed connections

Brazed connections provide permanent, leak-resistant joints that withstand pressure cycling, thermal expansion, and vibration typical in refrigeration systems over their service life.

Question 78: What is the refrigerant charge method used when a manufacturer specifies charging by weight?

Charge to the pressure listed on the outdoor unit nameplate
Add refrigerant until suction superheat reaches 10–15°F
Use a refrigerant scale to add the exact specified weight of refrigerant to the system (Correct answer)
Charge until the sight glass shows clear flow and subcooling is approximately 10°F

Correct answer: Use a refrigerant scale to add the exact specified weight of refrigerant to the system

When charging by weight, a refrigerant scale is used to measure and add the exact factory-specified charge weight, which is the most accurate method for sealed system charging.

Question 79: In a refrigeration system with multiple evaporators at different elevations, what is the function of individual suction line traps installed at each evaporator outlet before a common riser?

To prevent liquid refrigerant from draining back into an idle evaporator during off-cycles (Correct answer)
To equalize suction pressure between all evaporators
To measure refrigerant flow from each evaporator independently
To act as oil separators before the refrigerant reaches the compressor

Correct answer: To prevent liquid refrigerant from draining back into an idle evaporator during off-cycles

Individual suction line traps (P-traps) at each evaporator outlet prevent liquid refrigerant from draining back into an idle evaporator coil during off-cycles, which would cause flooding on restart.

Question 80: Which statement BEST describes the relationship between Certified Refrigeration Service Technician certification and industry evolution?

Requirements become less stringent over time
Certification requirements never change
Changes only occur when government mandates them
Requirements evolve periodically to reflect advances in knowledge and practice (Correct answer)

Correct answer: Requirements evolve periodically to reflect advances in knowledge and practice

Certification requirements evolve to keep pace with professional and technological advances.

Question 81: What should be documented after maintenance?

Ignore records
No documentation
Only date
Work details and performance (Correct answer)

Correct answer: Work details and performance

Documenting work details, including tasks performed, parts replaced, readings taken, and any observations, creates a comprehensive service history for the refrigeration system. This record is invaluable for future troubleshooting, warranty claims, and tracking system performance over time. It ensures accountability, helps in making informed decisions for subsequent maintenance or repairs, and provides a clear audit trail.

Question 82: What is the correct procedure before working on energized refrigeration electrical panels according to NFPA 70E?

Perform an arc flash risk assessment and wear appropriate PPE (Correct answer)
Test with a non-contact tester from 6 feet away
Install a lock only if voltage exceeds 240V
Simply turn off the main breaker and proceed

Correct answer: Perform an arc flash risk assessment and wear appropriate PPE

NFPA 70E requires an arc flash risk assessment and appropriate arc-rated PPE before working on or near energized electrical equipment.

Question 83: During a preventive maintenance visit on a walk-in cooler, the technician measures a high condensing temperature. Which maintenance item is MOST likely the root cause?

Defective evaporator fan motor
Low refrigerant charge
Dirty or blocked condenser coil (Correct answer)
Worn compressor valve plates

Correct answer: Dirty or blocked condenser coil

A dirty or blocked condenser coil reduces heat rejection, directly raising condensing temperature and system head pressure.

Question 84: What maintenance task should be performed on evaporator coil drain pans to prevent biological growth and drain blockage?

Spray the pan with CO2 each month
Apply petroleum jelly to the pan surface
Insulate the pan to keep it above dew point
Add biocide tablets or clean and treat the pan and drain with approved algaecide (Correct answer)

Correct answer: Add biocide tablets or clean and treat the pan and drain with approved algaecide

Biocide tablets or algaecide treatments prevent algae, mold, and slime from blocking condensate drains and creating health hazards.

Question 85: A technician suspects a leaking discharge valve on a reciprocating compressor. Which test can confirm this?

Check discharge superheat
Measure motor winding resistance
Perform a pump-down test and observe suction pressure rise after shutdown (Correct answer)
Measure the subcooling

Correct answer: Perform a pump-down test and observe suction pressure rise after shutdown

After pump-down, a rapid rise in suction pressure with the compressor off indicates high-pressure gas is leaking back through the discharge valve.

Question 86: What is the boiling point of R-134a at atmospheric pressure (14.7 psia)?

-40°F (-40°C)
32°F (0°C)
20°F (-6.7°C)
-15.07°F (-26.15°C) (Correct answer)

Correct answer: -15.07°F (-26.15°C)

R-134a has a boiling point of approximately -15.07°F at atmospheric pressure, making it suitable for medium-temperature refrigeration applications.

Question 87: How does the expansion valve function?

Compress refrigerant
Regulate flow and reduce pressure (Correct answer)
Increase refrigerant pressure
Filter refrigerant

Correct answer: Regulate flow and reduce pressure

The expansion valve, also known as a metering device, regulates the flow of liquid refrigerant into the evaporator. It also causes a significant pressure drop, which lowers the refrigerant's boiling point. This pressure reduction is critical for the refrigerant to readily absorb heat and evaporate in the evaporator, initiating the cooling cycle.

Question 88: Per EPA Section 608, what is the maximum allowable leak rate for refrigeration equipment with a charge of 50 lbs or more used in commercial processes before repair is required?

10% per year
5% per year
50% per year
30% per year (Correct answer)

Correct answer: 30% per year

EPA Section 608 requires owners of commercial refrigeration equipment with charges of 50 lbs or more to repair leaks when the annual leak rate exceeds 30%.

Question 89: A technician finds the compressor discharge temperature is 280°F. What is the MOST likely cause?

High subcooling
High superheat due to low suction pressure (Correct answer)
Low superheat
Condenser flooding

Correct answer: High superheat due to low suction pressure

Excessive superheat entering the compressor raises compression temperature dramatically, often caused by low refrigerant or high evaporator load.

Question 90: How should Certified Refrigeration Service Technician professionals handle equipment showing signs of malfunction during operation?

Attempt field repairs while running
Immediately cease operation, secure the equipment, and report (Correct answer)
Finish the current task first
Continue operating while monitoring

Correct answer: Immediately cease operation, secure the equipment, and report

Immediate cessation prevents safety hazards, further damage, or compromised results.

Question 91: A scroll compressor produces a rattling noise on startup. What is the most likely cause?

Liquid refrigerant in the suction line
Worn scroll wraps due to normal aging
Reverse rotation of the compressor (Correct answer)
Clogged discharge muffler

Correct answer: Reverse rotation of the compressor

Scroll compressors are rotation-sensitive; reverse rotation causes the scrolls to separate and produces a characteristic rattling or grinding noise.

Question 92: A system has high head pressure and low suction pressure. The superheat is normal and subcooling is low. What is the MOST probable cause?

Restricted metering device (Correct answer)
Condenser coil fouled
Refrigerant overcharge
Non-condensables in the system

Correct answer: Restricted metering device

A restricted metering device causes high head pressure upstream and starves the evaporator, resulting in low suction pressure and low subcooling.

Question 93: A technician is troubleshooting an intermittent low-pressure lockout on a system. The MOST likely cause is:

Refrigerant leak that worsens under load (Correct answer)
Defrost cycle ending
Oversized metering device
Condenser fan cycling on high ambient

Correct answer: Refrigerant leak that worsens under load

A slow refrigerant leak may not trip the low-pressure control at startup but causes suction pressure to drop below cutout as the system runs under load.

Question 94: What is the role of Material Safety Data Sheets (MSDS)?

Only for customers
Ignore them
No role
Provide safety info (Correct answer)

Correct answer: Provide safety info

Material Safety Data Sheets (MSDS), now often called Safety Data Sheets (SDS), are crucial documents that provide comprehensive information about hazardous chemicals. They detail potential health effects, first-aid measures, safe handling procedures, storage requirements, and emergency contact information. Technicians must consult MSDS/SDS to understand the risks associated with refrigerants, oils, and other chemicals, ensuring their safety and proper response in emergencies.

Question 95: High condensing pressure accompanied by a hot condenser inlet and a cool condenser outlet MOST likely indicates:

Refrigerant overcharge
Non-condensables in the system
Condenser coil fouled with dirt (Correct answer)
Liquid line solenoid stuck closed

Correct answer: Condenser coil fouled with dirt

A fouled condenser coil reduces heat transfer, causing high condensing pressure; the coil feels hot at the inlet but cool at the outlet because heat is not transferring through the dirty coil.

Question 96: What does the term 'latent heat of vaporization' mean in refrigeration?

The total heat content of the refrigerant at any given condition
The heat removed by the condenser from superheated discharge gas
The heat absorbed or released when a substance changes between liquid and vapor at constant temperature and pressure (Correct answer)
The heat required to raise refrigerant temperature by 1°F without phase change

Correct answer: The heat absorbed or released when a substance changes between liquid and vapor at constant temperature and pressure

Latent heat of vaporization is the energy absorbed or released during phase change (liquid↔vapor) without any temperature change, and it is the primary mechanism of heat transfer in refrigeration.

Question 97: Which pressure-enthalpy diagram characteristic indicates a refrigeration system is operating with excessive head pressure?

The expansion process crosses the saturation curve
The compression line becomes horizontal
The evaporator line moves upward on the pressure axis
The condensing process line moves to the right (higher enthalpy/temperature) at elevated pressure (Correct answer)

Correct answer: The condensing process line moves to the right (higher enthalpy/temperature) at elevated pressure

High head pressure shifts the condensing portion of the P-H diagram to the right and upward, indicating the refrigerant must be cooled to a higher temperature before condensing, which reduces system efficiency.

Question 98: Which preventive maintenance approach is MOST effective for CRST professionals?

Fix equipment only when it breaks
Schedule regular maintenance based on manufacturer recommendations and usage (Correct answer)
Perform maintenance annually regardless of usage
Outsource all maintenance

Correct answer: Schedule regular maintenance based on manufacturer recommendations and usage

Scheduling based on manufacturer recommendations and usage patterns optimizes reliability.

Question 99: How does the CRST body of knowledge relate to daily professional practice?

It provides the foundational framework guiding decision-making and standard practices (Correct answer)
It is theoretical with limited application
It only applies during exams
It is only for academic research

Correct answer: It provides the foundational framework guiding decision-making and standard practices

The body of knowledge provides the framework guiding daily decision-making and practices.

Question 100: What is the MOST important reason for maintaining equipment maintenance logs in CRST practice?

To justify replacement budgets
To track maintenance history, predict failures, and demonstrate compliance (Correct answer)
To satisfy insurance requirements only
To assign blame when equipment fails

Correct answer: To track maintenance history, predict failures, and demonstrate compliance

Maintenance logs track history, predict failures, and demonstrate regulatory compliance.

Certified Refrigeration Service Technician (CRST)

The CRST certification validates a technician's expertise in installing, maintaining, and troubleshooting refrigeration systems.

100

Questions

120 min

Time Limit

70%

To Pass

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