Certified Refrigeration Service Technician (CRST) — Questions and Answers

Question 1: When pressure-testing a refrigeration system with nitrogen, what is the maximum test pressure typically used for medium-temperature applications?

500 psig
1,000 psig
150 psig (Correct answer)
50 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 2: What is the EPA's requirement regarding the sale of refrigerant to uncertified individuals?

Refrigerant sales are regulated by state law, not federal EPA rules
Only refrigerant in containers of 2 pounds or less may be sold without certification verification (Correct answer)
Refrigerant may only be sold to certified technicians regardless of container size
Refrigerant in any quantity may be sold to anyone

Correct answer: Only refrigerant in containers of 2 pounds or less may be sold without certification verification

EPA Section 608 allows refrigerant in containers of 2 pounds or less to be sold without certification, but containers larger than 2 pounds require buyer certification.

Question 3: What is the primary purpose of vibration eliminators (flexible connectors) installed in refrigeration suction and discharge lines near the compressor?

To absorb compressor vibration and prevent metal fatigue or cracking from transmitting through the piping (Correct answer)
To allow for seasonal thermal expansion of the piping
To act as check valves preventing refrigerant backflow
To increase refrigerant flow velocity in the lines

Correct answer: To absorb compressor vibration and prevent metal fatigue or cracking from transmitting through the piping

Vibration eliminators isolate compressor mechanical vibration from the connected piping, preventing cyclic stress that causes metal fatigue, cracking at brazed joints, and noise transmission.

Question 4: Which refrigerant blend is commonly used as a drop-in service replacement for R-22 in low-temperature commercial refrigeration applications?

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

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 5: 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)
Discharge temperature only
Compressor amperage 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 6: When brazing copper tubing to a brass fitting (such as a service valve body), what additional step is required that is NOT needed for copper-to-copper joints?

Use a higher flow-rate nitrogen purge
Apply brazing flux to the joint before heating, because BCuP alloys are not self-fluxing on brass (Correct answer)
Use a different torch tip to achieve higher heat concentration
Pre-tin the brass fitting with soft solder first

Correct answer: Apply brazing flux to the joint before heating, because BCuP alloys are not self-fluxing on brass

BCuP alloys are self-fluxing only on copper-to-copper joints; when brazing copper to brass, bronze, or steel, an appropriate brazing flux must be applied to prevent oxide formation and ensure proper alloy flow.

Question 7: Which type of compressor uses a rotating eccentric to compress refrigerant without inlet/outlet valves?

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

Correct answer: Scroll compressor

Scroll compressors use two interleaved spiral scrolls to compress refrigerant continuously without the need for suction or discharge valves.

Question 8: Which type of joint connection is recommended for permanent refrigerant piping installations in commercial refrigeration systems?

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

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

Immediately cease operation, secure the equipment, and report (Correct answer)
Continue operating while monitoring
Finish the current task first
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 10: A TXV-equipped system has low suction pressure and low superheat simultaneously. What is the MOST likely cause?

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

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

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

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: A scroll compressor has normal amperage but produces no cooling. What should the technician check FIRST?

Head pressure control valve
Phase rotation — scroll compressors must rotate in one direction (Correct answer)
Refrigerant charge
Crankcase heater operation

Correct answer: Phase rotation — scroll compressors must rotate in one direction

Scroll compressors operate in only one rotational direction; incorrect phase rotation causes the compressor to spin backwards, moving little or no refrigerant.

Question 13: What role does proper diagnosis play in repairs?

Correctly identify issues (Correct answer)
Replace multiple parts
Ignore root cause
Random repairs

Correct answer: Correctly identify issues

Proper diagnosis is the critical first step in any repair process, as it involves systematically identifying the exact root cause of a system malfunction. Without an accurate diagnosis, technicians might only address symptoms or replace unnecessary parts, leading to wasted time and resources. Correctly identifying issues ensures that the right repair is performed, leading to a lasting solution and preventing recurring problems.

Question 14: 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 15: What is the correct method for determining the saturation temperature of a refrigerant at a known pressure?

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

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

Recover the refrigerant from the system (Correct answer)
Pressurize with nitrogen to 400 PSIG
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 17: In a cascade refrigeration system, what is the function of the cascade heat exchanger?

Recover heat from both circuits for space heating
Act as the condenser for the low-temperature circuit and evaporator for the high-temperature circuit (Correct answer)
Superheat refrigerant in both circuits simultaneously
Store refrigerant from both circuits during off cycles

Correct answer: Act as the condenser for the low-temperature circuit and evaporator for the high-temperature circuit

The cascade heat exchanger links two separate refrigerant circuits, rejecting heat from the low-stage condenser into the high-stage evaporator.

Question 18: In refrigeration copper tubing work, what does the term 'swaging' refer to?

Bending tubing to a precise angle without a bender
Expanding the end of a tube so another tube of the same diameter can be inserted for a brazed connection (Correct answer)
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 19: What is the FIRST step before operating any equipment in CRST practice?

Ask a colleague if it seems okay
Read the manual only if issues occur
Begin operation to test it
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 20: Which preventive maintenance approach is MOST effective for CRST professionals?

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

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

Scheduling based on manufacturer recommendations and usage patterns optimizes reliability.

Question 21: Which pressure-enthalpy diagram characteristic indicates a refrigeration system is operating with excessive head pressure?

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

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 22: What is the primary hazard associated with using nitrogen to pressure-test a refrigeration system?

Overpressurization if pressure is not controlled (Correct answer)
Nitrogen reacts with refrigerant oil
Nitrogen causes copper tubing to corrode
Moisture introduction from nitrogen cylinders

Correct answer: Overpressurization if pressure is not controlled

Nitrogen is used at high pressures, and without a pressure regulator and relief valve, systems can be overpressurized, leading to catastrophic failure.

Question 23: What is the function of a head pressure control valve on an air-cooled condenser in cold ambient conditions?

Open bypass around the condenser when pressure is too high
Prevent refrigerant from migrating to the condenser during off cycles
Maintain minimum head pressure by flooding condenser coil with liquid refrigerant (Correct answer)
Reduce compressor speed when ambient drops below setpoint

Correct answer: Maintain minimum head pressure by flooding condenser coil with liquid refrigerant

Head pressure control valves flood condenser coils with liquid refrigerant in cold weather, reducing effective condensing area and maintaining minimum operating pressure.

Question 24: 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 suction service valve
As a liquid (cylinder inverted or using a liquid valve) (Correct answer)
It can be added as either liquid or vapor interchangeably
As a vapor only through the discharge service valve

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

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

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 26: 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?

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

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 27: How does the sight glass help in system maintenance?

Measure temperature
Increase pressure
Observe refrigerant flow (Correct answer)
Filter impurities

Correct answer: Observe refrigerant flow

A sight glass allows technicians to visually inspect the state of the refrigerant flowing through the liquid line. By observing the presence of bubbles or a clear flow, technicians can diagnose issues such as refrigerant undercharge, moisture in the system, or proper expansion valve operation. It's a crucial diagnostic tool for assessing system health and performance.

Question 28: 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)
300–400°F (149–204°C)
1,800–2,000°F (982–1,093°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 29: A heat pump in heating mode has frost building up on the outdoor coil when outdoor temperature is above 40°F. What is the MOST likely cause?

High indoor fan speed
Normal defrost cycle operation
Oversized reversing valve
Low refrigerant charge reducing evaporating temperature (Correct answer)

Correct answer: Low refrigerant charge reducing evaporating temperature

A low refrigerant charge drops the evaporating temperature below the frost point even in mild weather, causing premature frost accumulation on the outdoor coil.

Question 30: Which PPE is most critical when handling liquid refrigerant to prevent cryogenic burns?

Chemical-resistant apron only
Insulated cryogenic gloves and face shield (Correct answer)
Standard work gloves and dust mask
Latex gloves and safety glasses

Correct answer: Insulated cryogenic gloves and face shield

Cryogenic gloves and a face shield protect against liquid refrigerant contact, which can cause severe frostbite-like burns.

Question 31: When a long horizontal suction line transitions into a vertical riser, what piping configuration is recommended at the base of the riser?

Increase the pipe diameter by one size at the riser base
Install a P-trap (inverted trap) to accumulate and batch-transport oil up the riser (Correct answer)
Install a check valve to prevent backflow
Install a Y-strainer to collect debris

Correct answer: Install a P-trap (inverted trap) to accumulate and batch-transport oil up the riser

A P-trap at the base of a vertical suction line riser collects oil so that once a sufficient slug accumulates, refrigerant velocity can carry it upward in a batch rather than a thin film.

Question 32: What does a bubbling or foamy sight glass indicate in a refrigeration system?

Refrigerant overcharge
Low refrigerant or liquid line restriction (Correct answer)
Moisture in the system
Normal subcooling

Correct answer: Low refrigerant or liquid line restriction

Bubbles in the sight glass indicate the liquid refrigerant is flashing to vapor, which points to a low charge or restriction upstream.

Question 33: Oil logging in the evaporator of a low-temperature system is MOST likely caused by:

Overcharge of refrigerant
Insufficient refrigerant velocity to return oil (Correct answer)
High discharge pressure
Excessive superheat setting

Correct answer: Insufficient refrigerant velocity to return oil

At low temperatures, refrigerant vapor density decreases, and if velocity is too low, oil cannot be carried back to the compressor crankcase.

Question 34: 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 35: Which foundational principle is MOST important for success in Certified Refrigeration Service Technician?

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

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

Success requires continuous learning, ethical practice, and focus on quality outcomes.

Question 36: What should be documented after maintenance?

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

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

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

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

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

Question 38: What device protects a compressor motor from overheating by interrupting power when winding temperature is excessive?

Start capacitor
Internal overload protector (Correct answer)
Crankcase heater
Run capacitor

Correct answer: Internal overload protector

An internal overload protector (thermal overload) senses motor winding temperature and opens the circuit to prevent damage from overheating.

Question 39: What is the refrigerant charge method used when a manufacturer specifies charging by weight?

Use a refrigerant scale to add the exact specified weight of refrigerant to the system (Correct answer)
Charge to the pressure listed on the outdoor unit nameplate
Charge until the sight glass shows clear flow and subcooling is approximately 10°F
Add refrigerant until suction superheat reaches 10–15°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 40: 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?

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

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 41: A refrigeration system is short-cycling on the low-pressure control. What is the MOST likely cause?

Low refrigerant charge (Correct answer)
Refrigerant overcharge
Condenser fan motor failure
Plugged liquid line filter-drier

Correct answer: Low refrigerant charge

A low refrigerant charge causes suction pressure to drop below the low-pressure control cutout setpoint, causing repeated short cycling.

Question 42: 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
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
Apply refrigerant oil inside the tube end to lubricate the fit

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

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

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 44: 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)
Low-pressure switch calibration
Crankcase heater and oil level
Suction strainer and accumulator

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

Certified professionals always have more experience
Certification validates competency through standardized assessment against benchmarks (Correct answer)
There is no meaningful difference
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 46: When evacuating a refrigeration system before opening it for service, what is the primary environmental reason for doing so?

To prevent moisture from entering the system
To prevent refrigerant release into the atmosphere (Correct answer)
To improve the efficiency of the recharge process
To reduce system pressure for technician safety

Correct answer: To prevent refrigerant release into the atmosphere

Evacuation captures refrigerant to prevent its venting to the atmosphere, which is required by EPA Section 608 to protect the ozone layer and climate.

Question 47: When recovering refrigerant from a system with a hermetic compressor burnout, the technician should:

Recover normally and reuse the refrigerant
Use a dedicated recovery cylinder and filter to avoid cross-contamination (Correct answer)
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 48: After completing a brazed joint in a refrigeration line, what is the correct method for allowing the joint to cool?

Apply ice directly to the joint to prevent overheating adjacent components
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

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 49: How often should maintenance be performed on refrigeration systems?

Only when broken
Every 5 years
Regularly as per guidelines (Correct answer)
Never

Correct answer: Regularly as per guidelines

Regular maintenance, performed according to manufacturer guidelines and industry standards, is essential for the longevity and efficiency of refrigeration systems. It helps identify and address minor issues before they escalate into major failures, ensuring consistent performance and preventing costly downtime. This proactive approach extends equipment life, maintains optimal energy efficiency, and ensures reliable operation.

Question 50: What is the MOST effective way to remove non-condensables from a refrigeration system?

Recover refrigerant, evacuate the system, and recharge with virgin refrigerant (Correct answer)
Run the system at high load to purge them through the condenser
Add refrigerant to dilute the non-condensables
Install a purge valve on the high side

Correct answer: Recover refrigerant, evacuate the system, and recharge with virgin refrigerant

Non-condensables cannot be separated in the field; the only correct method is full recovery, deep evacuation to remove air and moisture, and recharge with new refrigerant.

Question 51: In a two-stage refrigeration system, what is the purpose of the intercooler?

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

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

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

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 53: What safety precaution must be taken before performing brazing work on a refrigeration system that contains or previously contained refrigerant?

Pressurize the system to check for leaks first
Ensure the system is fully recovered and purged with nitrogen before applying heat (Correct answer)
Perform brazing while refrigerant is still present to prevent air entry
Only braze in areas with a fire extinguisher nearby, no purge required

Correct answer: Ensure the system is fully recovered and purged with nitrogen before applying heat

Refrigerant must be fully recovered and the system purged with dry nitrogen before brazing, as heat applied to refrigerant can produce toxic decomposition products.

Question 54: What is a key part of maintenance?

Only clean filters
Replace parts unnecessarily
Check levels and pressures (Correct answer)
Ignore refrigerant

Correct answer: Check levels and pressures

Checking refrigerant levels and pressures is a critical part of refrigeration system maintenance because these parameters directly impact system performance and efficiency. Incorrect levels or pressures can indicate leaks, overcharging, or other system imbalances that severely reduce cooling capacity and increase energy consumption. Monitoring these helps diagnose potential issues, optimize operation, and prevent expensive compressor damage.

Question 55: What is the purpose of a filter-drier installed in the liquid line of a refrigeration system?

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

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

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

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

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

Question 57: What is the function of a liquid line solenoid valve in a refrigeration system?

Control condenser fan speed
Pump down the evaporator when the system shuts off to prevent liquid migration (Correct answer)
Regulate suction pressure
Bypass the filter-drier during high flow conditions

Correct answer: Pump down the evaporator when the system shuts off to prevent liquid migration

A liquid line solenoid valve closes on shutdown to pump down the low side, preventing liquid refrigerant from migrating to the compressor crankcase.

Question 58: 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 equalize suction pressure between all evaporators
To prevent liquid refrigerant from draining back into an idle evaporator during off-cycles (Correct answer)
To act as oil separators before the refrigerant reaches the compressor
To measure refrigerant flow from each evaporator independently

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

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)
Hacksaw with a coarse blade drawn across the tubing

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 condition is indicated when both suction and discharge pressures are abnormally low?

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

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

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

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

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

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

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

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 64: Which component in a refrigeration system is specifically designed to separate oil from refrigerant vapor on the high-pressure side?

Suction accumulator
Oil separator (Correct answer)
Desuperheater
Filter-drier

Correct answer: Oil separator

An oil separator is installed in the discharge line to capture oil before it enters the condenser, returning it directly to the compressor crankcase.

Question 65: What happens to the pressure-temperature relationship of a refrigerant mixture that 'glides'?

The boiling point increases as pressure decreases
The temperature changes during phase change at constant pressure (Correct answer)
The mixture separates into its components at low temperatures
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 66: When new equipment is introduced in Certified Refrigeration Service Technician, what is REQUIRED before staff use it?

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

Correct answer: Formal training, competency verification, and documentation

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

Question 67: What is 'superheat' in a refrigeration system?

The temperature difference between discharge gas and ambient air
The excess heat removed by the condenser beyond condensation
The temperature of suction vapor above the saturation temperature at suction pressure (Correct answer)
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 68: A technician suspects a leaking discharge valve on a reciprocating compressor. Which test can confirm this?

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

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

Remove moisture and contaminants from the refrigerant
Store liquid refrigerant to accommodate system demand changes and ensure liquid feed to the expansion device (Correct answer)
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 70: Which refrigerant has an Ozone Depletion Potential (ODP) of zero and is commonly used in new commercial refrigeration systems in the US?

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

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

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

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

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

Question 72: A technician measures compressor amperage at 110% of nameplate rating. What is the most likely cause?

Low refrigerant charge
Low suction pressure
High head pressure due to condenser fouling or airflow restriction (Correct answer)
Open discharge valve

Correct answer: High head pressure due to condenser fouling or airflow restriction

High head pressure forces the compressor to work harder against greater discharge pressure, drawing excessive amperage.

Question 73: What type of capacitor provides an extra boost of starting torque for a PSC or CSCR compressor motor?

Electrolytic capacitor
Start capacitor (Correct answer)
Run capacitor
Film capacitor

Correct answer: Start capacitor

A start capacitor provides a high momentary capacitance to boost starting torque and is switched out of the circuit once the motor reaches operating speed.

Question 74: Which type of copper tubing is specifically manufactured, internally cleaned, and sealed for use in refrigeration and air conditioning systems?

ACR (Air Conditioning and Refrigeration) tubing (Correct answer)
Type K plumbing tubing
Type L plumbing tubing
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 75: Frost forming on the suction line all the way back to the compressor indicates:

Refrigerant undercharge
Low superheat and possible liquid floodback (Correct answer)
Condenser fan failure
High superheat

Correct answer: Low superheat and possible liquid floodback

Suction line frost extending to the compressor indicates liquid refrigerant is returning, which can cause liquid slugging and compressor damage.

Question 76: What is the boiling point of R-134a at atmospheric pressure (14.7 psia)?

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

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 77: 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?

Check the condenser fan motor
Add refrigerant
Defrost the evaporator coil (Correct answer)
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 78: What is the purpose of the receiver in refrigeration?

Store liquid refrigerant (Correct answer)
Filter air
Evaporate refrigerant
Compress 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 79: 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
3 times the tube outside diameter (Correct answer)
8 times the tube outside diameter
1.5 times the tube outside diameter

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 80: Why must oxygen NEVER be used to pressure-test or purge a refrigeration system?

Oxygen combined with compressor oil under pressure creates an explosive mixture capable of detonation (Correct answer)
It is too costly compared to alternative gases
It reacts with the refrigerant to form a non-condensable gas
It causes the copper tubing to turn green from oxidation

Correct answer: Oxygen combined with compressor oil under pressure creates an explosive mixture capable of detonation

Oxygen in contact with petroleum-based compressor oil under pressure can form a highly explosive mixture—similar to a diesel engine—posing a severe fire and detonation hazard.

Question 81: Acid test results on refrigeration oil show high acid content. What is the CORRECT repair procedure?

Replace only the filter-drier
Replace compressor oil, install suction and liquid line filter-driers, and monitor acid levels (Correct answer)
Add oil neutralizer and continue operating
Flush the system with nitrogen only

Correct answer: Replace compressor oil, install suction and liquid line filter-driers, and monitor acid levels

High acid content indicates a burnout or severe contamination; the correct procedure is to replace the oil, install acid-rated filter-driers, and recheck acid levels after operation.

Question 82: When should system testing be performed after repair?

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

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 83: What happens to refrigerant subcooling when liquid line length increases significantly?

Subcooling increases
Subcooling decreases due to heat gain (Correct answer)
Subcooling is unaffected by line length
Subcooling doubles with each 10 ft of line

Correct answer: Subcooling decreases due to heat gain

Longer liquid lines expose refrigerant to more ambient heat, reducing subcooling and risking flash gas formation before the metering device.

Question 84: A technician notices the suction pressure is pulsing rhythmically on the gauge. This is MOST often caused by:

Condenser fan cycling
TXV hunting due to improper superheat setting or bulb position (Correct answer)
Refrigerant overcharge
A defective low-pressure switch

Correct answer: TXV hunting due to improper superheat setting or bulb position

TXV hunting occurs when the valve over-corrects repeatedly, causing cyclic swings in suction pressure that appear as gauge pulsation.

Question 85: 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 86: 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 assign blame when equipment fails
To satisfy insurance requirements only

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

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

Question 87: When new equipment is introduced in Certified Refrigeration Service Technician, what is REQUIRED before staff use it?

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

Correct answer: Formal training, competency verification, and documentation

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

Question 88: 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 89: What label information is required on a recovered refrigerant cylinder before it can be sent to a reclaimer?

System operating pressure and temperature only
Only the customer's name and service date
Only the technician's EPA certification number
Refrigerant type, whether it contains oil, and whether it is mixed with other refrigerants (Correct answer)

Correct answer: Refrigerant type, whether it contains oil, and whether it is mixed with other refrigerants

Recovered refrigerant cylinders must be labeled with the refrigerant type, oil contamination status, and whether the refrigerant is a mixture.

Question 90: 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 91: What does the Global Warming Potential (GWP) of a refrigerant measure?

Its heat-trapping potential relative to CO2 over 100 years (Correct answer)
Its flammability rating per ASTM standards
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 92: What refrigerant is classified as R-717 and widely used in large industrial refrigeration systems?

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

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 93: A technician discovers a refrigerant leak at a flare fitting during a maintenance visit. What is the correct corrective action?

Re-tighten the flare nut with a wrench
Apply refrigerant-rated leak sealant and re-pressurize
Replace the entire line segment
Cut off the flare and remake it, then re-tighten (Correct answer)

Correct answer: Cut off the flare and remake it, then re-tighten

Flare fittings that leak are usually deformed; the proper fix is to cut off the old flare and create a new one, then reassemble correctly.

Question 94: 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)
Store vertically only, with one end resting in a bucket of water
Wrap the entire length in wet cloth to maintain metal flexibility
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 95: What is a common cause of refrigeration system failure?

Correct refrigerant charge
Clean components
Refrigerant leaks (Correct answer)
Proper maintenance

Correct answer: Refrigerant leaks

Refrigerant leaks are a very common and critical cause of refrigeration system failure. A loss of refrigerant reduces the system's cooling capacity, increases energy consumption, and can eventually lead to compressor damage due to overheating. Detecting and repairing leaks promptly is vital for system longevity, efficiency, and environmental protection.

Question 96: Which condition makes it legal under EPA Section 608 to vent a small amount of refrigerant during service?

When the amount is less than 1 pound
De minimis releases that occur during good-faith repair attempts (Correct answer)
When the refrigerant is R-410A
When the system charge is under 5 pounds

Correct answer: De minimis releases that occur during good-faith repair attempts

EPA allows de minimis refrigerant releases that unavoidably occur during good-faith attempts to recover, recycle, or reclaim refrigerants.

Question 97: What safety precautions should be taken during repairs?

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

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

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

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 99: What is the primary function of a receiver in a refrigeration system?

Store liquid refrigerant after the condenser (Correct answer)
Superheat refrigerant before the compressor
Separate oil from refrigerant vapor
Subcool refrigerant before the evaporator

Correct answer: Store liquid refrigerant after the condenser

A receiver stores liquid refrigerant downstream of the condenser to ensure a steady supply to the metering device.

Question 100: How should Certified Refrigeration Service Technician professionals handle equipment showing signs of malfunction during operation?

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

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

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

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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