100+ Free City & Guilds 6187 RAC Practice Questions

Pass your City & Guilds 6187 Level 2/3 Diploma in Refrigeration, Air Conditioning and Heat Pump Technology exam on the first try — instant access, no signup required.

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2026 Statistics

Key Facts: City & Guilds 6187 RAC Exam

100

Practice Questions

City & Guilds 6187

60%

Pass Score

City & Guilds e-volve

<500

Target Microns Vacuum

UK RAC Code of Practice

5 tonnes

F-Gas Threshold (CO2e)

UK Retained F-Gas Regs

R290

Propane (A3 Flammable)

BS EN 378

OFN

Safe Testing Gas

HSE / C&G Standard

The City & Guilds 6187 RAC Diploma exam tests 100 core questions on vapor compression thermodynamics, compressor physics, heat exchangers, expansion valves, UK F-Gas rules, flammable refrigerant safety, vacuum evacuation, and electrical controls. Candidates must score at least 60% to pass e-volve theory modules.

Sample City & Guilds 6187 RAC Practice Questions

Try these sample questions to test your City & Guilds 6187 RAC exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which state of refrigerant leaves the evaporator coil in a correctly operating vapor compression refrigeration system?

A.Superheated low-pressure vapor

B.Subcooled high-pressure liquid

C.Saturated high-pressure mixture

D.Subcooled low-pressure liquid

Explanation: In a correctly operating vapor compression system, refrigerant absorbs latent heat in the evaporator until all liquid boils into vapor. It then absorbs sensible heat to become superheated low-pressure vapor before entering the compressor suction port.

2How is evaporator superheat calculated during system performance testing?

A.Suction line pipe temperature minus evaporating temperature corresponding to suction pressure

B.Evaporating temperature minus condensing temperature corresponding to discharge pressure

C.Liquid line pipe temperature minus condensing temperature corresponding to liquid pressure

D.Discharge line pipe temperature plus suction line pipe temperature

Explanation: Superheat is calculated by measuring the actual pipe temperature at the evaporator outlet (suction line) and subtracting the saturation temperature (evaporating temperature) corresponding to the suction pressure reading on a P-T chart.

3What type of heat transfer causes a change in temperature of a substance without changing its physical state?

A.Sensible heat

B.Latent heat of vaporization

C.Latent heat of condensation

D.Specific heat capacity of fusion

Explanation: Sensible heat is heat added to or removed from a substance that causes a measurable change in temperature registered on a thermometer, without altering its physical state.

4Which component in a basic vapor compression system divides the high-pressure side from the low-pressure side on the liquid line?

A.Expansion device (metering valve)

B.Compressor suction valve

C.Filter drier shell

D.Liquid line solenoid valve

Explanation: The expansion device (such as a TEV, EEV, or capillary tube) creates a pressure drop that separates the high-pressure liquid side from the low-pressure evaporator side.

5If a pressure gauge on an R404A system reads 4.0 bar gauge (bar g) evaporating pressure, what does the corresponding saturation temperature represent?

A.The boiling temperature of the refrigerant inside the evaporator

B.The temperature of the air leaving the evaporator coil

C.The discharge gas temperature entering the oil separator

D.The ambient air temperature surrounding the condensing unit

Explanation: Saturation temperature corresponding to evaporating pressure is the exact temperature at which liquid refrigerant boils into vapor inside the evaporator at that specific pressure.

6How is system Coefficient of Performance (COP) in cooling mode defined?

A.Useful cooling capacity (kW) divided by total electrical power input (kW)

B.Total electrical power input (kW) divided by useful cooling capacity (kW)

C.Mass flow rate of refrigerant multiplied by compressor pressure ratio

D.Condensing heat rejection (kW) divided by evaporator superheat (°C)

Explanation: COP in cooling mode is the ratio of useful refrigeration effect (heat absorbed by the evaporator in kW) to the net work input required to drive the system (compressor and fan power in kW).

7What thermodynamic effect occurs when subcooling is increased in the liquid line prior to entering the expansion valve?

A.Refrigerating effect per kilogram of refrigerant increases and flash gas volume decreases

B.Evaporating pressure rises significantly above condenser pressure

C.Compressor discharge temperature increases beyond safe limits

D.Refrigerant mass flow rate drops to zero due to vapor lock

Explanation: Increasing subcooling lowers the liquid enthalpy before expansion, resulting in less flash gas formed across the expansion valve and a higher net refrigerating effect per kg of circulating refrigerant.

8On a Pressure-Enthalpy (P-h) diagram, what process is represented by a vertical line moving downwards inside the saturation curve?

A.Constant-enthalpy (isenthalpic) expansion through a metering device

B.Isentropic compression inside a reciprocating compressor cylinder

C.Constant-pressure condensation inside an air-cooled condenser

D.Sensible superheating of suction gas inside a suction line heat exchanger

Explanation: On a P-h diagram, expansion through a metering valve is modeled as a constant-enthalpy (isenthalpic) process, represented by a vertical line dropping straight down from high pressure to low pressure.

9What is the primary cause of 'glide' in non-azeotropic refrigerant blends such as R407C?

A.Different constituent refrigerants boil and condense at different temperatures at a constant pressure

B.Refrigerant oil separates completely from the liquid refrigerant at low temperatures

C.High moisture content in the system alters the chemical saturation table

D.The compressor operates at variable speeds causing pressure fluctuations

Explanation: Temperature glide in zeotropic blends like R407C occurs because constituent components have different boiling points, causing the phase change temperature to rise gradually from bubble point to dew point at constant pressure.

10An R134a cooling system has a suction pressure corresponding to an evaporating saturation temperature of -5°C. If the measured suction line pipe temperature is +3°C, what is the superheat?

A.8 K (or 8°C)

B.-2 K (or -2°C)

C.15 K (or 15°C)

D.2 K (or 2°C)

Explanation: Superheat = Suction Line Temperature - Evaporating Saturation Temperature = (+3°C) - (-5°C) = 3 + 5 = 8 K.

About the City & Guilds 6187 RAC Exam

The City & Guilds 6187 qualification is the premier UK vocational credential for refrigeration, air conditioning, and heat pump (RAC) technicians. It validates comprehensive competence in thermodynamic cycles, compressor operation, heat exchanger maintenance, expansion device mechanics, F-Gas environmental regulations, flammable (hydrocarbon/A2L) refrigerant safety, system pressure testing and evacuation, and electrical fault diagnosis.

Questions

100 scored questions

Time Limit

2 hours

Passing Score

60%

Exam Fee

~£1,500 - £3,500 (full diploma tuition) (City & Guilds (UK))

City & Guilds 6187 RAC Exam Content Outline

15%

Refrigeration Cycle & Thermodynamics

Sensible vs latent heat, vapor compression cycle stages, superheat/subcooling calculations, P-h diagrams, and COP evaluation.

15%

Compressor Types & Operation

Reciprocating, scroll, screw, rotary compressor mechanics, lubrication, oil management, and capacity control.

13%

Condenser & Evaporator Maintenance

Air-cooled, water-cooled, and evaporative condensers, DX evaporators, defrost controls, and heat transfer efficiency.

13%

Metering Devices & Expansion Valves

TEV/TXV, EEV, capillary tube, equalizer lines, sensing bulb installation, superheat hunting, and valve sizing.

15%

F-Gas Regulations & Leak Detection

Retained EU 517/2014 & UK regulations, CO2 equivalent formulas, mandatory leak test schedules, logbooks, and recovery.

10%

Hydrocarbon & Flammable Refrigerants

A2L and A3 refrigerants (R290, R600a, R32), lower flammability limits, charge restrictions, EX-rated tools, and ATEX safety.

10%

Pressure Testing, Evacuation & Charging

Oxygen-Free Nitrogen (OFN) strength/tightness testing, deep evacuation (<500 microns), vacuum decay, and scale charging.

Electrical Controls & Fault Diagnosis

Single and three-phase motor circuits, DOL/star-delta starters, high/low pressure cut-outs, safe isolation (LOTO), and multimeters.

How to Pass the City & Guilds 6187 RAC Exam

What You Need to Know

Passing score: 60%
Exam length: 100 questions
Time limit: 2 hours
Exam fee: ~£1,500 - £3,500 (full diploma tuition)

Keys to Passing

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

City & Guilds 6187 RAC Study Tips from Top Performers

1Always calculate superheat by subtracting evaporating temperature from suction line pipe temperature.

2Remember F-Gas leak check intervals: 5 to 50 tonnes CO2e (annual or 24mo with ALDS), 50 to 500 tonnes CO2e (6mo or 12mo with ALDS), >500 tonnes CO2e (3mo or 6mo with ALDS).

3Calculate CO2 equivalent using formula: (Charge in kg / 1000) x GWP of the refrigerant.

4Never use compressed air or oxygen for pressure testing — ONLY use Oxygen-Free Nitrogen (OFN).

5Ensure EEV step motor positions and NTC thermistor resistance readings are checked against manufacturer P-T and resistance charts when diagnosing electronic metering issues.

6Verify safe electrical isolation (LOTO) using a proven voltage indicator tested against a proving unit before touching any electrical terminal.

Frequently Asked Questions

What is the City & Guilds 6187 qualification?

The City & Guilds 6187 is the standard UK vocational diploma for refrigeration, air conditioning, and heat pump engineers. It covers fundamental scientific principles, practical installation and maintenance techniques, environmental regulations, and electrical safety.

Does the 6187 qualification include F-Gas certification?

While the 6187 diploma covers theoretical F-Gas regulations in depth, official legal refrigerant handling in the UK requires the specific F-Gas Category 1 certificate (such as City & Guilds 2079-11 or BESA FGAS). Most 6187 training programs integrate 2079 assessment alongside the diploma.

What is the passing score for City & Guilds 6187 online unit tests?

The standard pass mark for City & Guilds e-volve online multiple-choice unit exams is 60%. Higher percentage thresholds achieve Merit or Distinction grades depending on center marking guidelines.

What tools are required for working with flammable refrigerants like R290?

Working with flammable refrigerants (A2L and A3) requires spark-proof (ATEX rated) vacuum pumps, recovery units, electronic leak detectors, non-sparking fans, and strict Oxygen-Free Nitrogen (OFN) purging prior to brazing.

How is vacuum evacuation measured in professional RAC practice?

Evacuation is measured in microns of mercury using an electronic vacuum gauge. Standard RAC practice requires pulling a deep vacuum down below 500 microns (0.67 mbar) to ensure non-condensable gases and moisture are thoroughly removed.

What is the difference between superheat and subcooling?

Superheat is measured at the evaporator outlet (suction line temperature minus evaporating temperature) to ensure no liquid refrigerant enters the compressor. Subcooling is measured at the condenser outlet (condensing temperature minus liquid line temperature) to ensure solid liquid reaches the expansion valve.