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100+ Free AZ ROC C-49 Industrial Refrigeration Practice Questions

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Key Facts: AZ ROC C-49 Industrial Refrigeration Exam

80 Questions

Official Question Count

PSI Candidate Information Bulletin

210 Minutes

Time Limit

PSI Candidate Information Bulletin

70%

Passing Score

Arizona Registrar of Contractors

$66

Exam Fee

PSI Services LLC

Open Book Computerized MCQ

Exam Format

PSI / AZ ROC Guidelines

100 Questions

Practice Question Bank

OpenExamPrep Practice Bank

The Arizona ROC C-49 Industrial Refrigeration Examination comprises 80 scored multiple-choice questions administered during a 210-minute open-book PSI computer test session requiring a 70% score to pass ($66 exam fee). This practice question bank delivers 100 realistic English-language practice questions with comprehensive explanations aligned to the official PSI blueprint.

Sample AZ ROC C-49 Industrial Refrigeration Practice Questions

Try these sample questions to test your AZ ROC C-49 Industrial Refrigeration exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Under ASHRAE Standard 34, what is the safety classification for anhydrous ammonia (R-717)?
A.A1 (lower toxicity, no flame propagation)
B.B2L (higher toxicity, lower flammability with burning velocity ≤ 10 cm/s)
C.A2L (lower toxicity, lower flammability)
D.B1 (higher toxicity, no flame propagation)
Explanation: Anhydrous ammonia (R-717) is classified as B2L under ASHRAE Standard 34. The letter 'B' indicates higher toxicity with an Occupational Exposure Limit (OEL) of 25 ppm, while '2L' denotes lower flammability with a maximum burning velocity of 10 cm/s or less.
2What is the approximate critical temperature and critical pressure above which carbon dioxide (R-744) operates in a transcritical cycle?
A.87.8°F (31.1°C) and 1,055 psig (7.38 MPa)
B.120.4°F (49.1°C) and 650 psig (4.48 MPa)
C.45.2°F (7.3°C) and 1,450 psig (10.0 MPa)
D.104.0°F (40.0°C) and 850 psig (5.86 MPa)
Explanation: Carbon dioxide (R-744) has a relatively low critical point of 87.8°F (31.1°C) and 1,055 psig (7.38 MPa). When ambient heat rejection temperatures force condensing above 87.8°F, the system operates in a transcritical state where gas is cooled without undergoing phase condensation.
3In an industrial rotary screw compressor package, how does the hydraulic slide valve modulate refrigeration capacity?
A.By throttling the main suction stop valve to restrict gas entering the rotors.
B.By adjusting the motor frequency via an external resistance grid.
C.By moving axially along the rotor bore to bypass uncompressed suction gas back to the suction port before compression begins.
D.By opening a high-pressure bypass valve that recirculates hot discharge gas into the oil separator.
Explanation: The slide valve in a rotary screw compressor modulates capacity by sliding axially along the bottom of the rotor housing. Moving the slide valve opens a bypass slot, allowing a portion of the trapped suction gas to return to the suction inlet before compression starts, effectively shortening the active rotor compression length.
4What are the two primary thermal functions of a flash-type intercooler in a two-stage ammonia (R-717) refrigeration system?
A.To condense high-stage discharge gas and warm low-stage liquid feed.
B.To subcool high-pressure suction gas and heat low-stage compressor oil.
C.To generate superheated vapor for hot gas defrost and drain high-side receiver oil.
D.To desuperheat low-stage (booster) compressor discharge gas and subcool liquid refrigerant feeding low-stage evaporators.
Explanation: A flash intercooler in a two-stage system desuperheating the hot discharge vapor coming from the low-stage (booster) compressor by bubbling it through liquid refrigerant at intermediate pressure, while simultaneously subcooling high-pressure liquid from the condenser before it travels to low-temperature evaporators.
5What is the primary thermodynamic advantage of utilizing a liquid overfeed (recirculator pump) system in a commercial cold storage facility compared to a direct expansion (DX) system?
A.Evaporator internal tube surfaces remain completely wetted with liquid, maximizing the overall heat transfer coefficient without requiring superheat at the coil outlet.
B.It eliminates the requirement for low-side suction accumulators and surge drums.
C.It allows the system to operate with zero compressor discharge superheat.
D.It reduces total system refrigerant charge by 80% compared to DX systems.
Explanation: Liquid overfeed systems circulate excess liquid refrigerant through evaporator coils (typically 2:1 to 4:1 overfeed ratio for ammonia). Because liquid is always present throughout the entire coil length, no portion of the surface area is dedicated to superheating gas, resulting in superior heat transfer rates and lower room-to-refrigerant temperature differences (TD).
6In industrial ammonia (R-717) liquid overfeed systems, what is the standard recommended liquid recirculation rate (overfeed ratio) for forced-convection unit coolers?
A.1.1:1 to 1.5:1
B.3:1 to 4:1
C.8:1 to 10:1
D.12:1 to 15:1
Explanation: For industrial ammonia forced-air evaporator coils, a recirculation rate of 3:1 to 4:1 is standard. This means 3 to 4 times the mass of liquid evaporated is pumped through the coil, ensuring continuous wetted tube surfaces while returning a manageable liquid-vapor mixture to the recirculator vessel.
7How does an economizer port on a single-stage rotary screw compressor increase system capacity and operating efficiency?
A.It injects liquid refrigerant into the compressor suction line to lower motor winding temperatures.
B.It bleeds off high-pressure discharge gas directly into the oil cooler matrix.
C.It introduces intermediate-pressure flash gas from a liquid subcooler directly into the rotor thread mid-way through the compression stroke.
D.It bypasses oil from the discharge separator directly into the low-pressure suction housing.
Explanation: An economizer port admits flash gas generated in an intermediate-pressure shell-and-tube or subcooling heat exchanger into rotor flutes after they have closed off from the suction port but before final discharge. Subcooling the main liquid line increases net refrigerating effect at the evaporator while compressing intermediate vapor requires less work per pound than suction gas.
8What is the primary physical heat rejection process utilized by an evaporative condenser in industrial refrigeration?
A.Sensible heat transfer through dry air convection across steel fins.
B.Radiant heat dissipation into the surrounding building structure.
C.Sensible heat conduction into a closed-circuit ethylene glycol loop.
D.Latent heat absorption via water evaporation into forced airflow moving across heat exchanger tubes.
Explanation: Evaporative condensers reject heat primarily through latent heat of vaporization of water (approximately 1,060 Btu per pound of water evaporated). Water sprayed over condensing tube bundles evaporates into air pulled through the unit by fans, allowing condensing temperatures to approach ambient wet-bulb temperature.
9In industrial ammonia screw compressor packages, what multi-stage oil separator design is required to limit oil carryover to less than 5 ppm?
A.A combination of mechanical impinging baffles, centrifugal swirl mesh, and high-efficiency coalescing filter elements.
B.A single magnetic screen filter placed in the main suction header.
C.An electrostatic precipitator mounted in the liquid receiver drop leg.
D.A gravity oil settling drum without internal baffles or filter elements.
Explanation: Rotary screw compressors inject large quantities of oil into compressed gas. To reduce carryover below 5 ppm, high-efficiency separators combine mechanical velocity reduction/impingement baffles, centrifugal separation, and final-stage glass-fiber coalescing filter elements that force micro-droplets to merge and drain.
10How is the liquid refrigerant level maintained inside a flooded shell-and-tube liquid chiller?
A.By a thermal expansion valve sensing compressor discharge superheat.
B.By a low-side float valve, pilot-operated level control, or electronic level sensor modulating liquid feed into the shell or surge drum.
C.By a manual needle valve adjusted once per season based on ambient wet-bulb temperature.
D.By an internal thermal siphon loop regulated by oil pressure.
Explanation: Flooded chillers submerge heat transfer tubes in liquid refrigerant. The liquid level must be precisely maintained by a low-side float valve, modulating float switch, or electronic level transmitter operating a liquid solenoid or modulating feed valve on the surge drum/shell.

About the AZ ROC C-49 Industrial Refrigeration Exam

The Arizona ROC C-49 Industrial Refrigeration (Commercial) Examination is a computer-delivered open-book trade exam administered by PSI Services LLC for contractors installing, servicing, and repairing commercial and industrial refrigeration systems. Key test topics include ammonia (R-717) and halocarbon refrigeration machinery, rotary screw and reciprocating compressors, liquid overfeed systems, evaporative condensers, ASME B31.5 piping and dual pressure relief valves, motor controls/VFDs, system evacuation and start-up, pressure testing, troubleshooting, load calculations, and OSHA 1910.119 PSM / ASHRAE 15 / IIAR safety standards.

Questions

80 scored questions

Time Limit

210 minutes

Passing Score

70%

Exam Fee

$66 (Arizona ROC / PSI Services LLC)

AZ ROC C-49 Industrial Refrigeration Exam Content Outline

37.5%

Commercial and Industrial Refrigeration

Ammonia (R-717), CO2 (R-744), halocarbons, single/two-stage vapor compression systems, rotary screw compressors, centrifugal chillers, flooded evaporators, liquid overfeed systems, evaporative condensers, and cascade freezing systems.

15%

Piping and Tubing including Valves

ASME B31.5 refrigeration piping code, Schedule 40/80 carbon steel pipe, ACR copper tubing, brazing/welding procedures, dual safety relief valves, TXV, EEV, EPR, suction pressure regulators, and oil drain valves.

10%

Controls and Motors

Motor starters, VFDs, NEMA enclosures, 3-phase motor protection, high/low pressure cutouts, differential oil pressure switches, float switches, PLCs, safety interlocks, and control transformers.

10%

Installation, Start-up and Operation

System evacuation to 500 microns, pressure testing with dry nitrogen per IIAR 2, liquid refrigerant charging, compressor oil charging, hot gas defrost operations, and oil pot purging safety.

10%

Testing and Trouble Shooting

Compressor diagnostics, non-condensable gas purgers, subcooling/superheat diagnostics, electrical motor troubleshooting, vibration analysis, and leak detection methods.

10%

General Knowledge and Theory

Thermodynamic cycles, Mollier P-h diagrams, COP, compression ratios, ASHRAE 34 classifications (B2L for R-717), ASHRAE 15 machinery room rules, IIAR standards, EPA 608 recovery, and OSHA 1910.119 PSM rules.

5%

Sizing and Estimating

Refrigeration load calculations (transmission, product, infiltration, equipment), tonnage calculations (12,000 Btu/h-ton), refrigerant mass flow rates, compressor displacement CFM, and evaporator coil sizing.

2.5%

Box Construction and Cases

Walk-in freezer/cooler panel insulation (polyurethane, PIR), floor insulation, sub-floor frost heave heating systems, vapor barriers, heated doors, strip curtains, and room pressure relief valves.

How to Pass the AZ ROC C-49 Industrial Refrigeration Exam

What You Need to Know

  • Passing score: 70%
  • Exam length: 80 questions
  • Time limit: 210 minutes
  • Exam fee: $66

Keys to Passing

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

AZ ROC C-49 Industrial Refrigeration Study Tips from Top Performers

1Focus heavily on industrial ammonia (R-717) system design, safety classifications (B2L), two-stage economized systems, and liquid overfeed ratios.
2Review ASME B31.5 piping standards for Schedule 80 steel pipe connections, dual relief valve manifold requirements, and relief valve discharge piping sizing.
3Study ASHRAE Standard 15 machinery room requirements including emergency mechanical ventilation rates, leak detection alarm setpoints (25 ppm OEL for R-717), and external emergency stop switches.
4Practice refrigeration capacity calculations: mass flow rate ($lb/min = \text{Btu/min} / \Delta h$), CFM displacement, compression ratio, and sensible/latent product cooling loads.
5Master electrical motor and control schematics, including 3-phase motor starters, VFD parameters, differential oil pressure switches, and PLC safety interlocks.

Frequently Asked Questions

How many questions are on the official Arizona ROC C-49 exam?

The official PSI C-49 Industrial Refrigeration exam consists of 80 scored multiple-choice questions. Candidates are allotted 210 minutes (3.5 hours) to complete the test.

What is the passing score for the AZ ROC C-49 exam?

A passing score of 70% (56 correct out of 80 questions) is required by the Arizona Registrar of Contractors.

Is the C-49 Industrial Refrigeration examination open book?

Yes. The examination is open-book, allowing candidates to bring approved references such as ASHRAE Standard 15, IIAR standards, ASME B31.5, and standard refrigeration textbooks into the PSI testing room.

What subject carries the most weight on the C-49 examination?

Commercial and Industrial Refrigeration is the largest section, representing 37.5% of the exam (30 out of 80 questions), followed by Piping and Tubing including Valves at 15% (12 questions).

How do I schedule the Arizona C-49 trade exam?

Examinations are scheduled online via PSI Services LLC at https://test-takers.psiexams.com/azcon or by calling PSI candidate services after submitting your application to the Arizona ROC.