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156+ Free NVQ L4 Refrigeration & AC Practice Questions

Prepare for the Sri Lanka NVQ Level 4 Refrigeration and Air Conditioning Technician Written Examination exam with instant access — no signup required.

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Key Facts: NVQ L4 Refrigeration & AC Exam

D29S002

TVEC Code

National Standard

40%

Passing Score

Theory minimum

150+

Practice Questions

This prep course

90 minutes

Exam Duration

TVEC schedule

Procedure-specific

Vacuum Acceptance

Manufacturer and job procedure

4 Years

RPL Experience

National external RPL portal

The NVQ Level 4 RAC qualification combines a common written knowledge assessment with competency-based assessment against D29S002. The official 2022 model paper has 50 MCQs in 90 minutes, and TVEC guidance sets a 40% knowledge-assessment minimum; the qualification is awarded only after the required units are assessed as competent.

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 156+ question experience with AI tutoring.

1Which of the following gives the four principal vapor-compression-cycle processes in their correct order?
A.Evaporation, vapor compression, condensation, then throttling
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 the basic cycle, low-pressure refrigerant evaporates while absorbing heat, the compressor raises vapour pressure, the condenser rejects heat and condenses the refrigerant, and the expansion device throttles high-side liquid to the low side. Practical DX systems normally provide some outlet superheat and may provide subcooling; the ideal reference cycle can use saturated endpoint states.
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.Greater refrigerating effect and a solid liquid supply
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.Vapour temperature minus saturation temperature at the same 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 reduction flashes some liquid and cools the remainder
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

50 scored questions

Time Limit

1 hour 30 minutes in the official 2022 Level 4 model paper

Passing Score

40% minimum for the NVQ Level 4 common knowledge assessment; unit competency is also required for certification

Exam Fee

Not published as one national fee; provider and assessment-route charges vary (Tertiary and Vocational Education Commission (TVEC), Sri Lanka)

NVQ L4 Refrigeration & AC Exam Content Outline

No published percentage

Refrigeration Cycle & Thermodynamics

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

No published percentage

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).

No published percentage

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.

No published percentage

Refrigerant Handling, Recovery & Retrofitting

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

No published percentage

HVAC/R System Diagnostics & Maintenance

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

No published percentage

OHS, Tools & Cost Estimation

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

No published percentage

D29S002U09-U10: Transport Refrigeration & Central Installation

Refrigerated-truck inspection, servicing, cargo-airflow and standby-power checks; and central-system lifting, piping, insulation, flushing, alignment, balancing, commissioning, and safety-interlock tests.

No published percentage

D29S002U11-U14: Workplace Competencies

Occupational safety, customer and team communication, authorization and handover, workplace calculations, and coordinated team working.

How to Pass the NVQ L4 Refrigeration & AC Exam

What You Need to Know

  • Passing score: 40% minimum for the NVQ Level 4 common knowledge assessment; unit competency is also required for certification
  • Exam length: 50 questions
  • Time limit: 1 hour 30 minutes in the official 2022 Level 4 model paper
  • Exam fee: Not published as one national fee; provider and assessment-route charges vary

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.
5Learn how evacuation acceptance depends on the manufacturer and job procedure, including target absolute pressure, isolation or standing-vacuum stability, and moisture-control steps rather than relying on one universal micron value or evacuation sequence.
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?

TVEC guidance sets a 40% minimum for the NVQ Level 4 common knowledge assessment. Passing that written component alone does not award the qualification; the candidate must also be assessed as competent in the required units.

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. The national external RPL portal states that Level 4 applicants need four years (48 months) of relevant experience; the assessing body verifies evidence against the competency standard.

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.