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100+ Free NVQ L4 Refrigeration & AC Practice Questions

Pass your Sri Lanka NVQ Level 4 Refrigeration and Air Conditioning Technician Written Examination exam on the first try — instant access, no signup required.

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Key Facts: NVQ L4 Refrigeration & AC Exam

D29S002

TVEC Code

National Standard

50%

Passing Score

Theory minimum

100

Practice Questions

This prep course

2 Hours

Exam Duration

TVEC schedule

500 Microns

Vacuum Level

Dehydration target

2+ Years

RPL Experience

NAITA eligibility

The written component of the NVQ Level 4 RAC qualification tests technical theory, troubleshooting, and safety standards under TVEC D29S002. Candidates are evaluated across refrigeration science, electrical controls, system diagnostics, and safe gas handling. Achieving a passing score of 50% or above on the written exam, combined with the hands-on practical assessment, grants the lifetime NVQ Level 4 technician credential.

Sample NVQ L4 Refrigeration & AC Practice Questions

Try these sample questions to test your NVQ L4 Refrigeration & AC exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which of the following represents the correct sequence of refrigerant states in the four main stages of a vapor compression refrigeration cycle?
A.Evaporator: low-pressure liquid-vapor mixture to low-pressure superheated vapor; Compressor: low-pressure superheated vapor to high-pressure superheated vapor; Condenser: high-pressure superheated vapor to high-pressure subcooled liquid; Expansion Device: high-pressure subcooled liquid to low-pressure liquid-vapor mixture
B.Evaporator: high-pressure liquid to low-pressure vapor; Compressor: low-pressure vapor to high-pressure liquid; Condenser: high-pressure liquid to low-pressure liquid; Expansion Device: low-pressure liquid to low-pressure vapor
C.Evaporator: low-pressure vapor to high-pressure vapor; Compressor: high-pressure vapor to high-pressure liquid; Condenser: high-pressure liquid to low-pressure liquid; Expansion Device: low-pressure liquid to low-pressure vapor
D.Evaporator: low-pressure liquid to high-pressure liquid; Compressor: high-pressure liquid to high-pressure vapor; Condenser: high-pressure vapor to low-pressure vapor; Expansion Device: low-pressure vapor to low-pressure liquid
Explanation: In a vapor compression cycle, the refrigerant enters the evaporator as a low-pressure liquid-vapor mixture and absorbs heat to become a low-pressure superheated vapor. The compressor compresses it to a high-pressure superheated vapor. The condenser rejects heat to turn it into a high-pressure subcooled liquid. The expansion device drops the pressure, producing a low-pressure liquid-vapor mixture, which restarts the cycle. The other options describe thermodynamically incorrect state progressions.
2On a standard Pressure-Enthalpy (p-h) diagram, which thermodynamic process is represented by a horizontal line moving from right to left inside the vapor dome?
A.Isentropic compression in the compressor
B.Constant-pressure condensation in the condenser
C.Constant-enthalpy expansion in the throttling valve
D.Constant-pressure evaporation in the evaporator
Explanation: On a p-h chart, pressure is on the vertical axis (y-axis) and enthalpy is on the horizontal axis (x-axis). A horizontal line represents a constant-pressure (isobaric) process. Moving from right (higher enthalpy, vapor) to left (lower enthalpy, liquid) inside the saturated mixture region (vapor dome) indicates condensation. Evaporation is also a horizontal line, but it moves from left to right (increasing enthalpy). Expansion is vertical (constant enthalpy), and compression is an upward curve (constant entropy).
3A refrigeration system has a refrigerating effect of 160 kJ/kg and the compressor work input is 40 kJ/kg. What is the Coefficient of Performance (COP) of this system?
A.0.25
B.2.0
C.4.0
D.5.0
Explanation: The Coefficient of Performance (COP) for a cooling system is calculated by dividing the desired refrigeration effect (cooling output) by the work input supplied to the compressor: COP = Refrigerating Effect / Work Input. Here, COP = 160 kJ/kg / 40 kJ/kg = 4.0. Option 0.25 is the inverse (Work / Effect), and the other values represent incorrect math.
4During the sensible heat transfer phase of a substance, what occurs to its physical parameters?
A.Its temperature changes while its state remains constant
B.Its state changes while its temperature remains constant
C.Both its temperature and state change simultaneously
D.Neither its temperature nor its state changes
Explanation: Sensible heat is the heat added to or removed from a substance that results in a change in temperature without changing its physical state (liquid, gas, solid). In contrast, latent heat is the heat associated with a change of state (e.g., boiling or condensing) that occurs at a constant temperature.
5What is the thermodynamic benefit of subcooling the liquid refrigerant before it enters the expansion valve?
A.It reduces the compressor discharge temperature
B.It increases the refrigeration effect and prevents flash gas in the liquid line
C.It lowers the pressure drop across the evaporator
D.It decreases the density of the liquid refrigerant
Explanation: Subcooling reduces the enthalpy of the liquid refrigerant entering the expansion device. This shifts the starting point of the evaporation process further to the left on the p-h diagram, increasing the refrigerating effect (more cooling per kg of refrigerant). Additionally, subcooling ensures that the refrigerant remains a 100% liquid state in the liquid line, preventing premature flashing (bubbling) due to pressure drops or vertical rises, which would disrupt expansion valve operation.
6Which of the following best defines the term 'Superheat' as applied to suction vapor entering a compressor?
A.The temperature of the vapor above its corresponding saturation temperature at that pressure
B.The total heat contained in the vapor measured from 0°C
C.The temperature difference between the discharge gas and suction gas
D.The temperature of the liquid refrigerant inside the evaporator coil
Explanation: Superheat is defined as the temperature of a vapor above its saturation temperature (boiling point) at a given pressure. Measuring suction superheat is vital for verifying that all liquid refrigerant has evaporated, preventing harmful liquid slugging in the compressor while ensuring high evaporator utilization.
7An air conditioning system operates with a suction pressure of 4.5 bar gauge (5.5 bar absolute) and a discharge pressure of 16.5 bar gauge (17.5 bar absolute). What is the compression ratio of the compressor?
A.3.67
B.3.18
C.4.12
D.2.85
Explanation: Compression ratio must always be calculated using absolute pressures. Suction pressure (absolute) = 4.5 + 1.0 = 5.5 bar. Discharge pressure (absolute) = 16.5 + 1.0 = 17.5 bar. Compression Ratio = Discharge Pressure (Abs) / Suction Pressure (Abs) = 17.5 / 5.5 = 3.18. Using gauge pressures (16.5 / 4.5 = 3.67) is a common mistake and is incorrect.
8What state is the refrigerant in when its temperature is at the boiling point for its pressure but it has not absorbed latent heat yet?
A.Superheated vapor
B.Saturated liquid
C.Saturated vapor
D.Subcooled liquid
Explanation: A refrigerant at its boiling point (saturation temperature) that is still entirely liquid is a saturated liquid. If any heat is added, it will begin to boil and change state into a vapor. If it is 100% vapor at the saturation temperature, it is a saturated vapor. If it is cooled below the saturation temperature, it is a subcooled liquid. If it is heated above the saturation temperature, it is a superheated vapor.
9What is the term used to describe the temperature above which a refrigerant gas cannot be liquefied, regardless of the amount of pressure applied?
A.Boiling point
B.Critical temperature
C.Saturation point
D.Triple point
Explanation: The critical temperature is the temperature limit above which a gas cannot be liquefied, no matter how much pressure is exerted. Above this point, the refrigerant behaves as a supercritical fluid with no boundary between liquid and vapor phases. This is key for carbon dioxide (R744) transcritical cycles.
10What causes a portion of liquid refrigerant to 'flash' into vapor inside the expansion device?
A.Heat absorption from the warm expansion valve body
B.Pressure drop forcing the refrigerant temperature to drop to its new saturation temperature by evaporating a fraction of the liquid
C.High friction between the liquid and the expansion valve orifice
D.Agitation and mixing with compressor lubricant oil
Explanation: As the high-pressure liquid passes through the expansion device, its pressure drops abruptly. For the refrigerant's temperature to fall to the lower saturation temperature corresponding to this lower pressure, a small percentage of the liquid evaporates (flashes). The latent heat needed for this evaporation is drawn from the remaining liquid, cooling the bulk of the refrigerant to the evaporator temperature. This is a constant-enthalpy throttling process.

About the NVQ L4 Refrigeration & AC Exam

The Sri Lanka NVQ Level 4 Refrigeration and Air Conditioning Technician written exam (D29S002) is a theoretical validation of core competencies for HVAC/R professionals. It evaluates knowledge in the refrigeration cycle, major component servicing (compressors, condensers, evaporators, metering devices), single-phase and three-phase electrical control circuits (relays, overloads, inverter systems), refrigerant recovery, evacuation, leak testing, environmental protocols, transport refrigeration, and occupational safety.

Questions

100 scored questions

Time Limit

2 hours

Passing Score

50%

Exam Fee

Rs. 2,000 (Tertiary and Vocational Education Commission (TVEC), Sri Lanka)

NVQ L4 Refrigeration & AC Exam Content Outline

15%

Refrigeration Cycle & Thermodynamics

Vapor compression cycle operations, phase changes, pressure-enthalpy (p-h) charts, and heat transfer principles.

20%

Compressors, Condensers, Evaporators & Metering

Servicing and troubleshooting major RAC components: scroll/reciprocating/rotary compressors, water/air-cooled condensers, capillary tubes, and thermostatic expansion valves (TXV).

20%

Electrical Circuits & Control Systems

Wiring diagrams, component testing (capacitors, overload protectors, potential/current relays, thermostats), single-phase and three-phase power supplies, and inverter drive signals.

15%

Refrigerant Handling, Recovery & Retrofitting

Refrigerant properties (R22, R134a, R410A, hydrocarbon R290/R600a), recovery machines, evacuation levels (microns), leak checking, and ODP/GWP environmental regulations.

20%

HVAC/R System Diagnostics & Maintenance

Troubleshooting split, window, and package AC units; analyzing manifold gauge readings; solving cooling capacity degradation; cleaning and preventative maintenance.

10%

OHS, Tools & Cost Estimation

Safety procedures for oxy-acetylene brazing, pressurized nitrogen leak testing, PPE standards, customer communication, and job costing estimates.

How to Pass the NVQ L4 Refrigeration & AC Exam

What You Need to Know

  • Passing score: 50%
  • Exam length: 100 questions
  • Time limit: 2 hours
  • Exam fee: Rs. 2,000

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

NVQ L4 Refrigeration & AC Study Tips from Top Performers

1Memorize the four core stages of the vapor compression refrigeration cycle and how the pressure/state changes in each component.
2Learn to interpret electrical schematic diagrams, especially control circuits using contactors, potential relays, thermostats, and compressor windings (Common, Start, Run).
3Practice interpreting manifold gauge readings: know what causes low suction pressure, high head pressure, or high suction with low head pressure.
4Understand the difference between superheat (measured at evaporator outlet) and subcooling (measured at condenser outlet) and how to calculate both.
5Know the safety vacuum target of 500 microns and why triple evacuation is used for moisture removal.
6Be prepared to compute job estimates, including prices of compressor replacement, pipe installation labor, and refrigerant weights.

Frequently Asked Questions

What is the passing criteria for the NVQ Level 4 Refrigeration and AC written test?

A candidate must score at least 50% on the written theory exam to be graded competent in the theoretical knowledge modules. Certification also requires passing the practical assessment.

What is the TVEC code for this qualification?

The National Competency Standard code is D29S002, titled 'Refrigeration and Air Conditioning Mechanic'.

Can I obtain this certification through industry experience without formal training?

Yes, through the RPL (Recognition of Prior Learning) system. Technicians with 2+ years of verified work experience can apply directly to NAITA or VTA for Level 4 assessment.

Does the exam cover inverter air conditioning technology?

Yes, modern NVQ Level 4 exams include questions on inverter AC systems, variable frequency drive operation, DC motor controls, and troubleshooting inverter error codes.

What safety precautions are emphasized for refrigerant handling?

Safety standards emphasize avoiding atmospheric release of ozone-depleting and greenhouse gases, handling flammable hydrocarbons (R290, R600a) with spark-free tools, using pressure regulators on nitrogen cylinders, and wearing proper safety goggles and gloves.