Certified Refrigeration Service Technician (CRST) — Questions and Answers

Question 1: How does the CRST body of knowledge relate to daily professional practice?

It is theoretical with limited application
It provides the foundational framework guiding decision-making and standard practices (Correct answer)
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 2: What is the purpose of a crankcase heater on a refrigeration compressor?

Prevent refrigerant migration into compressor oil during off cycles (Correct answer)
Increase discharge superheat
Warm refrigerant in the accumulator
Reduce compressor start current

Correct answer: Prevent refrigerant migration into compressor oil during off cycles

Crankcase heaters keep the oil warm to prevent refrigerant from migrating and diluting the compressor lubricant during the off cycle.

Question 3: What is the minimum vacuum level (in microns) required before charging most commercial refrigeration systems to ensure proper moisture removal?

500 microns (Correct answer)
50 microns
5,000 microns
2,000 microns

Correct answer: 500 microns

Most manufacturers and industry standards require evacuation to 500 microns or lower to ensure adequate moisture removal before charging.

Question 4: What is the primary purpose of vibration eliminators (flexible connectors) installed in refrigeration suction and discharge lines near the compressor?

To act as check valves preventing refrigerant backflow
To increase refrigerant flow velocity in the lines
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

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 5: A technician is installing a new TXV (thermostatic expansion valve) on a system. Where should the bulb be clamped?

On the suction line at the evaporator outlet, in good thermal contact (Correct answer)
On the liquid line upstream of the valve
On the discharge line near the compressor
On the suction line near the compressor inlet

Correct answer: On the suction line at the evaporator outlet, in good thermal contact

The TXV bulb senses suction line temperature at the evaporator outlet to control superheat, and must be clamped in firm thermal contact at that location.

Question 6: A compressor with a cracked discharge valve reed will MOST likely exhibit:

High discharge pressure and normal suction pressure
Low compression ratio and elevated suction pressure (Correct answer)
Excessive oil consumption only
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 7: What is the MOST important reason for maintaining equipment maintenance logs in CRST practice?

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

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

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

Question 8: How does root cause analysis improve repair effectiveness?

Ignore root causes
Identify underlying problems (Correct answer)
Fix symptoms only
Repeat repairs

Correct answer: Identify underlying problems

Root cause analysis goes beyond fixing immediate symptoms to uncover the fundamental reasons why a problem occurred in a refrigeration system. By identifying these underlying issues, technicians can implement permanent solutions that prevent recurrence. This approach leads to more effective and lasting repairs, reducing future breakdowns and improving overall system reliability.

Question 9: What is the FIRST step before operating any equipment in CRST practice?

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

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

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

Question 10: What is the PROPER procedure for decommissioning outdated equipment in Certified Refrigeration Service Technician?

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

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

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

Question 11: What is the correct method for determining the saturation temperature of a refrigerant at a known pressure?

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

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 12: A technician is working in a confined space with a suspected refrigerant leak. What is the first action to take?

Turn off all electrical equipment in the space
Put on a respirator and begin identifying the leak
Check the refrigerant type using a detector
Evacuate the space and ventilate before re-entry (Correct answer)

Correct answer: Evacuate the space and ventilate before re-entry

Immediate evacuation and ventilation of the confined space is required before re-entry to prevent oxygen displacement or toxic exposure.

Question 13: In what direction should horizontal suction lines be sloped to promote oil return?

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

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

Pump down the evaporator when the system shuts off to prevent liquid migration (Correct answer)
Regulate suction pressure
Control condenser fan speed
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 15: How can technicians stay updated on regulations?

Ignore updates
Attend training (Correct answer)
Rely on others
Avoid reading

Correct answer: Attend training

Environmental regulations and industry best practices are constantly evolving, especially concerning refrigerants and safety protocols. Attending regular training sessions, workshops, and seminars ensures technicians are up-to-date with the latest legal requirements, technological advancements, and safe work procedures. This continuous education is vital for compliance, efficiency, and professional development in the refrigeration field.

Question 16: Why is documentation important in troubleshooting?

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

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

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

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

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

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

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 20: Why is proper ventilation important in refrigeration work?

Increase humidity
No importance
Prevent harmful exposure (Correct answer)
Ignore airflow

Correct answer: Prevent harmful exposure

Many refrigerants, especially in high concentrations, can displace oxygen, leading to asphyxiation, or cause irritation to the skin, eyes, and respiratory system. Proper ventilation ensures that any leaked refrigerants or fumes are dispersed, maintaining a safe breathable atmosphere. This minimizes the risk of harmful exposure and ensures technician safety during work.

Question 21: 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)
1.5 times the tube outside diameter
8 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 22: Which refrigerant is classified as an A1 safety group per ASHRAE 34?

R-134a (Correct answer)
R-1234yf
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 23: What does the Global Warming Potential (GWP) of a refrigerant measure?

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

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 24: A walk-in freezer door gasket is worn and not sealing properly. Besides temperature loss, what additional problem can result?

Condenser coil icing
Refrigerant migration to the liquid line
Excessive frost buildup on evaporator due to warm, moist air infiltration (Correct answer)
Compressor overheating

Correct answer: Excessive frost buildup on evaporator due to warm, moist air infiltration

Warm, humid air entering through a faulty door gasket increases the moisture load on the evaporator, causing excessive frost accumulation and longer defrost cycles.

Question 25: How should ACR copper tubing be stored and handled on a job site to maintain its factory cleanliness?

Wrap the entire length in wet cloth to maintain metal flexibility
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
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 26: Which approach is MOST important for CRST professionals when applying technical procedures?

Using the fastest method regardless of standards
Adhering to established protocols while adapting to specific conditions (Correct answer)
Following personal shortcuts
Applying the same technique without variation

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

Technical procedures require adherence to protocols with professional judgment for adaptation.

Question 27: A brazed-plate heat exchanger used as an evaporator offers which advantage over a shell-and-tube evaporator?

Higher refrigerant charge requirement
Better suited for flooded operation only
Compact size with high heat transfer efficiency (Correct answer)
Easier to clean internally

Correct answer: Compact size with high heat transfer efficiency

Brazed-plate heat exchangers provide very high surface area-to-volume ratios, offering superior heat transfer in a compact package.

Question 28: What is the FIRST step before operating any equipment in CRST practice?

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

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

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

Question 29: 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
Apply water to the joint area to prevent overheating
Clean mating surfaces with emery cloth until bright, then apply flux if joining dissimilar metals (Correct answer)

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 30: Which personal protective equipment (PPE) principle applies to ALL CRST certified professionals regardless of their specific role?

PPE is optional if experienced in the field
Any PPE will provide adequate protection
PPE is only necessary during formal inspections
PPE must be properly fitted, maintained, and replaced as needed (Correct answer)

Correct answer: PPE must be properly fitted, maintained, and replaced as needed

Regardless of experience level, PPE must be properly fitted, regularly maintained, and replaced when worn or damaged.

Question 31: Which pressure-enthalpy diagram characteristic indicates a refrigeration system is operating with excessive head pressure?

The expansion process crosses the saturation curve
The evaporator line moves upward on the pressure axis
The compression line becomes horizontal
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 32: How should Certified Refrigeration Service Technician professionals handle equipment showing signs of malfunction during operation?

Finish the current task first
Immediately cease operation, secure the equipment, and report (Correct answer)
Attempt field repairs while running
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 33: How can a technician detect refrigerant leaks?

Add refrigerant without checking
Leak detectors and pressure checks (Correct answer)
Visual inspection only
Ignore leaks

Correct answer: Leak detectors and pressure checks

Technicians detect refrigerant leaks using specialized tools like electronic leak detectors, which sense refrigerant gases, and by performing pressure checks. Pressure checks, often involving nitrogen, can pinpoint pressure drops indicating a leak location. These methods are far more effective and reliable than visual inspection alone for finding often invisible refrigerant leaks, ensuring thorough repair.

Question 34: What thermodynamic process occurs in the evaporator of a vapor-compression refrigeration cycle?

Refrigerant is compressed from low to high pressure
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

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

1,000 psig
150 psig (Correct answer)
500 psig
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 36: When new equipment is introduced in Certified Refrigeration Service Technician, what is REQUIRED before staff use it?

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

Correct answer: Formal training, competency verification, and documentation

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

Question 37: 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?

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

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

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

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

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

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 40: What is the purpose of an equalizer line on a thermostatic expansion valve (TXV)?

Connect the valve to the receiver
Sense evaporator outlet pressure to compensate for coil pressure drop (Correct answer)
Supply refrigerant to the valve bulb
Balance refrigerant flow between parallel evaporators

Correct answer: Sense evaporator outlet pressure to compensate for coil pressure drop

An external equalizer line senses actual evaporator outlet pressure, allowing the TXV to accurately control superheat even when there is significant pressure drop across the coil.

Question 41: In Certified Refrigeration Service Technician practice, what is the FIRST step when a safety hazard is identified in the workplace?

Continue working and report at end of shift
Document it for the next safety audit
Wait for a supervisor to notice the issue
Immediately secure the area and report the hazard (Correct answer)

Correct answer: Immediately secure the area and report the hazard

When a safety hazard is identified, the immediate priority is to secure the area to prevent injury and report the hazard through proper channels.

Question 42: What is the maximum allowable leak rate for comfort cooling equipment containing more than 50 pounds of refrigerant before repair is required?

10% per year
15% per year (Correct answer)
5% per year
20% per year

Correct answer: 15% per year

EPA regulations require repair when leak rates exceed 15% of the system charge per year for comfort cooling appliances.

Question 43: 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?

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

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 44: A refrigeration technician installs a new evaporator and notices the coil temperature is uneven across its face. What is the MOST likely cause?

Excessive superheat at the TXV bulb
Unequal refrigerant distribution due to a faulty distributor or plugged distributor nozzle (Correct answer)
Overcharged refrigerant
High ambient temperature at the condenser

Correct answer: Unequal refrigerant distribution due to a faulty distributor or plugged distributor nozzle

A faulty or plugged refrigerant distributor causes uneven flow to evaporator circuits, resulting in uneven coil temperatures and reduced capacity.

Question 45: When brazing copper-to-copper refrigeration joints, which brazing alloy family is self-fluxing and most commonly used in the industry?

Aluminum brazing rod
50/50 tin-lead solder
Zinc-tin alloy
Silver-phosphorus-copper (BCuP) alloys (Correct answer)

Correct answer: Silver-phosphorus-copper (BCuP) alloys

BCuP (silver-phosphorus-copper) alloys are self-fluxing on copper-to-copper joints because phosphorus acts as its own flux, making them the industry standard for refrigeration brazing.

Question 46: 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 is only for academic research
It only applies during exams

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

Concentric reducer, because it centers both pipes on the same axis
Concentric reducer, because it creates less turbulence
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)

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

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

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 49: 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)
-40°F (-40°C)
32°F (0°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 50: When mounting a remote condenser on a rooftop, which installation requirement is most critical for proper oil return?

Use only hard-drawn copper tubing for all line sets
Install a suction line accumulator at the condenser
Slope the liquid line upward toward the evaporator
Pitch refrigerant lines toward the compressor and install traps on long vertical risers (Correct answer)

Correct answer: Pitch refrigerant lines toward the compressor and install traps on long vertical risers

Proper pitch and oil traps on vertical suction risers ensure oil entrained in refrigerant vapor is carried back to the compressor.

Question 51: What does the term 'subcooling' refer to in a refrigeration system?

Cooling liquid refrigerant below its condensing temperature at a given pressure (Correct answer)
Dropping the refrigerant temperature below 0°F
Cooling suction vapor below the evaporator saturation temperature
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 52: 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 53: When checking a hermetic compressor for an open motor winding, which instrument should be used?

Clamp-on ammeter
Megohmmeter
Ohmmeter (Correct answer)
Manometer

Correct answer: Ohmmeter

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

Question 54: Why must oxygen NEVER be used to pressure-test or purge a refrigeration system?

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

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

It can be added as either liquid or vapor interchangeably
As a vapor only through the suction service valve
As a liquid (cylinder inverted or using a liquid valve) (Correct answer)
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 56: At approximately what temperature range does silver-phosphorus-copper (BCuP-5) brazing alloy flow and fill refrigeration copper joints?

1,800–2,000°F (982–1,093°C)
700–800°F (371–427°C)
1,200–1,500°F (649–816°C) (Correct answer)
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 57: Oil logging in the evaporator of a low-temperature system is MOST likely caused by:

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

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

Dry nitrogen (Correct answer)
Compressed air from a shop compressor
Oxygen from a welding cylinder
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 59: 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
Quench immediately with cold water to lock in the joint structure
Apply ice directly to the joint to prevent overheating adjacent components
Allow the joint to air cool naturally without applying water or forced cooling (Correct answer)

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

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

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

Outsource all maintenance
Fix equipment only when it breaks
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 62: A technician measures a 15°F superheat at the evaporator outlet and 80°F subcooling at the condenser outlet. What condition does this indicate?

TXV stuck open
Normal operation
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 63: In refrigeration copper tubing work, what does the term 'swaging' refer to?

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

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

R-134a
R-404A
R-422D (Correct answer)
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 65: 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 66: A TXV-equipped system has low suction pressure and low superheat simultaneously. What is the MOST likely cause?

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

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

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

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 68: What is the purpose of a discharge muffler in a reciprocating compressor system?

Filter solid particles from discharge vapor
Dampen pulsations in the discharge line (Correct answer)
Cool discharge gas before entering the condenser
Reduce refrigerant velocity to aid oil separation

Correct answer: Dampen pulsations in the discharge line

A discharge muffler attenuates pressure pulsations caused by the reciprocating action of the compressor pistons, reducing vibration and noise.

Question 69: A three-phase compressor motor that hums but does not start is most likely experiencing which problem?

Overcharged refrigerant system
Defective crankcase heater
Faulty start capacitor on the single-phase winding
Single-phasing — loss of one supply phase (Correct answer)

Correct answer: Single-phasing — loss of one supply phase

Single-phasing (loss of one phase) causes a three-phase motor to hum without starting because it cannot produce sufficient rotating magnetic field torque.

Question 70: 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?

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
Use a higher flow-rate nitrogen purge
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 71: 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)
Non-condensables in the system
Condenser coil fouled
Refrigerant overcharge

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

To justify replacement budgets
To satisfy insurance requirements only
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 73: What is the PROPER procedure for decommissioning outdated equipment in Certified Refrigeration Service Technician?

Simply discard in regular waste
Donate without preparation
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 74: How should hazardous waste be managed?

Discard in drains
Ignore labeling
Label and dispose properly (Correct answer)
Mix with regular trash

Correct answer: Label and dispose properly

Hazardous waste, such as used oils, solvents, and contaminated refrigerants, poses significant risks to human health and the environment if not managed correctly. Proper labeling ensures that the contents are clearly identified, allowing for safe handling, storage, and transportation. Disposing of these materials according to specific regulations prevents pollution, avoids legal penalties, and protects public health.

Question 75: What is the purpose of a filter-drier installed in the liquid line of a refrigeration system?

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
Reduce refrigerant velocity to prevent erosion of the liquid line
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 76: Which refrigerant has an Ozone Depletion Potential (ODP) of zero and is commonly used in new commercial refrigeration systems in the US?

R-12
R-502
R-404A (Correct answer)
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 77: What does the term 'latent heat of vaporization' mean in refrigeration?

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
The heat removed by the condenser from superheated discharge gas
The total heat content of the refrigerant at any given condition

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

Perform maintenance annually regardless of usage
Schedule regular maintenance based on manufacturer recommendations and usage (Correct answer)
Fix equipment only when it breaks
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 79: Why is proper electrical connection critical?

Ensure safe operation (Correct answer)
Ignore wiring
Increase faults
No effect

Correct answer: Ensure safe operation

Proper electrical connections are fundamental for the safe and reliable operation of any refrigeration system. Loose, corroded, or incorrectly wired connections can lead to electrical shorts, overheating, component damage, and fire hazards. Ensuring secure and correct wiring prevents dangerous electrical failures, maintains system integrity, and protects both equipment and personnel.

Question 80: 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 act as oil separators before the refrigerant reaches the compressor
To prevent liquid refrigerant from draining back into an idle evaporator during off-cycles (Correct answer)
To measure refrigerant flow from each evaporator independently
To equalize suction pressure between all evaporators

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 81: What safety precautions should be taken during repairs?

Ignore safety
Use PPE and lockout/tagout (Correct answer)
Rush repairs
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 82: Acid test results on refrigeration oil show high acid content. What is the CORRECT repair procedure?

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

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 83: 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 84: 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)
Finish the current task first
Attempt field repairs while running
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 85: When installing multiple evaporators on a single condensing unit, which component ensures proper refrigerant distribution and independent temperature control for each case?

Individual EPRs (evaporator pressure regulators) or individual TXVs per evaporator (Correct answer)
A common TXV sized for the total load
A common liquid line filter-drier only
A single solenoid valve at the condensing unit

Correct answer: Individual EPRs (evaporator pressure regulators) or individual TXVs per evaporator

Individual EPRs or TXVs for each evaporator allow independent temperature control and proper refrigerant metering regardless of load differences between cases.

Question 86: What role does proper diagnosis play in repairs?

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

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 87: 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
Mandatory conversion to natural refrigerants only
Annual emission reporting to the EPA
Phased reduction in production and use (Correct answer)

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

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

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

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

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 90: What does a high suction superheat combined with normal or low head pressure indicate in a refrigeration system?

Liquid flooding back to the compressor
Low refrigerant charge or metering device starving the evaporator (Correct answer)
Refrigerant overcharge
Condenser fan motor failure

Correct answer: Low refrigerant charge or metering device starving the evaporator

High superheat with normal or low head pressure points to insufficient refrigerant flow through the evaporator, typically from a low charge or restricted metering device.

Question 91: In a refrigeration control circuit, what is the primary function of a thermostat?

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

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

Identify symptoms (Correct answer)
Replace parts immediately
Ignore the problem
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 93: 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 rise of refrigerant through the compressor
The temperature of suction vapor above the saturation temperature at suction pressure (Correct answer)

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 94: 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 95: 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)
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 96: In a refrigeration ladder diagram, what symbol represents a normally open (NO) contact?

A circle with an X inside
Two diagonal lines crossing the circuit path
A zigzag line symbol
Two parallel vertical lines with a gap between horizontal lines (Correct answer)

Correct answer: Two parallel vertical lines with a gap between horizontal lines

A normally open contact is represented by two parallel vertical lines separated by a gap across the circuit path, indicating the contact is open in its de-energized state.

Question 97: What does the OSHA permissible exposure limit (PEL) for ammonia (R-717) in the workplace?

25 ppm TWA
50 ppm TWA (Correct answer)
100 ppm TWA
300 ppm TWA

Correct answer: 50 ppm TWA

OSHA sets the PEL for ammonia at 50 ppm as an 8-hour time-weighted average.

Question 98: What minimum refrigerant velocity is generally required in vertical suction line risers to ensure adequate oil return to the compressor?

700-1,000 fpm (Correct answer)
100-200 fpm
50-100 fpm
3,000-4,000 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 99: What is the refrigerant charge method used when a manufacturer specifies charging by weight?

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

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 100: Which refrigerant circuit component is most responsible for controlling system capacity in a variable-speed system?

Thermostatic expansion valve
Suction line filter-drier
Variable-frequency drive on the compressor motor (Correct answer)
Head pressure control valve

Correct answer: Variable-frequency drive on the compressor motor

A variable-frequency drive (VFD) modulates compressor speed, directly controlling refrigerant mass flow and system capacity.

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

Checking for saved progress...

Exam Rules

You can skip questions and return to them later
Flag questions for review before submitting
No feedback shown until you submit the entire exam
Unanswered questions count as wrong — answer everything
10 pretest questions are mixed in and don't affect your score
Timer auto-submits when time runs out
Your progress is auto-saved every 30 seconds