City & Guilds Level 2 Diploma in Refrigeration, Air Conditioning and Heat Pump Systems (C&G 6187-01) Overview
This study guide covers the six core subjects for the City & Guilds Level 2 Diploma in Refrigeration, Air Conditioning and Heat Pump Systems. It is designed for entry-level technicians seeking employment in the HVAC/R industry. The notes focus on health and safety, scientific principles, installation, service and maintenance, electrical systems, and environmental protection including F-Gas regulations. Candidates should verify specific pass marks, exam dates, and eligibility with City & Guilds.
For Technical Conquer practice planning, this module is tracked as 80 questions over about 120 minutes with a listed pass mark of 70%. Treat those numbers as practice baselines and verify the current official format before scheduling.
How This Guide Is Organized
The sections below turn the syllabus into studyable subject blocks. Read a subject first, explain the must-know ideas without notes, then use questions, flashcards, and mind maps to test whether the knowledge holds under field-style pressure.
- Health and Safety in Building Services Engineering
- Scientific Principles for Refrigeration and Air Conditioning
- Refrigeration and Air Conditioning System Installation
- Service and Maintenance of RACHP Systems
- Electrical Systems for RACHP
- Environmental Protection and F-Gas Regulations
Exam Snapshot and Readiness Target
Format: Multiple-choice and practical assessments; typical practice baseline: 80 questions, 120 minutes, 70% pass mark (verify with City & Guilds)
Candidate level: Entry-level technician
Readiness target: Employment-ready for installation, service, and maintenance roles
Most candidates should budget at least 36+ focused study hours, then adjust upward for unfamiliar equipment, code, regulatory, commissioning, controls, or calculation-heavy content.
Health and Safety in Building Services Engineering
Syllabus Focus
- Health and Safety at Work Act 1974
- Risk assessment and method statements
- Personal protective equipment (PPE)
- Safe handling of refrigerants and tools
- Working at height and confined spaces
- Electrical safety and isolation procedures
Key Notes
- The Health and Safety at Work Act 1974 places duties on employers and employees to ensure safety. Employers must provide safe systems of work, training, and PPE. Employees must cooperate and not endanger others.
- Risk assessment involves identifying hazards, evaluating risks, and implementing control measures. A method statement outlines the safe sequence of work.
- PPE includes safety glasses, gloves, hard hats, and high-visibility clothing. It must be suitable, maintained, and used correctly.
- Refrigerants can be flammable, toxic, or asphyxiant. Always use leak detection, ventilation, and proper handling procedures. Never mix refrigerants.
- Working at height requires a risk assessment and use of ladders, scaffolding, or mobile elevated work platforms (MEWPs). Confined space entry needs a permit and gas monitoring.
- Electrical isolation involves locking off and tagging (LOTO) the supply. Verify isolation with a voltage tester before working on equipment.
Must Know
- Duties under the Health and Safety at Work Act 1974
- Five steps of risk assessment: identify hazards, decide who might be harmed, evaluate risks, record findings, review
- Types and correct use of fire extinguishers (water, foam, CO2, dry powder) for different classes of fire
- Safe isolation procedure: identify source, isolate, lock off, tag, test for dead, prove tester works
Field and Exam Application
- Before installing a split AC unit, conduct a risk assessment for working at height and manual handling of the outdoor unit.
- When servicing a refrigeration system, use a refrigerant leak detector and ensure adequate ventilation to avoid asphyxiation.
- During electrical fault finding, follow safe isolation: isolate the circuit, lock off the isolator, and test with a calibrated voltage indicator.
High-Yield Distinctions
- COSHH (Control of Substances Hazardous to Health) vs. risk assessment: COSHH specifically covers hazardous substances like refrigerants.
- RIDDOR (Reporting of Injuries, Diseases and Dangerous Occurrences Regulations) requires reporting certain accidents and near misses.
- PUWER (Provision and Use of Work Equipment Regulations) requires equipment to be suitable, maintained, and used by trained persons.
- LOLER (Lifting Operations and Lifting Equipment Regulations) applies to lifting equipment like hoists and cranes.
Common Pitfalls
- Assuming a circuit is dead without testing; always test with a known working voltage tester.
- Using the wrong fire extinguisher on an electrical fire (water can cause shock); use CO2 or dry powder.
- Not securing ladders properly; ensure ladders are on firm ground, at the correct angle (1:4 ratio), and tied off.
- Ignoring manual handling risks; use mechanical aids or team lifts for heavy equipment.
Review Tasks
- Write a risk assessment for installing an indoor fan coil unit.
- List the PPE required for brazing copper pipes.
- Describe the safe isolation procedure for a condensing unit.
- Identify fire extinguisher types and their uses from a diagram.
Scientific Principles for Refrigeration and Air Conditioning
Syllabus Focus
- Basic thermodynamics: heat, temperature, pressure
- Refrigeration cycle: evaporation, compression, condensation, expansion
- Pressure-enthalpy (P-h) diagrams
- Heat transfer: conduction, convection, radiation
- Properties of refrigerants: boiling point, latent heat, global warming potential (GWP)
- Psychrometrics: dry-bulb, wet-bulb, dew point, humidity, enthalpy
Key Notes
- The refrigeration cycle uses a refrigerant that evaporates at low pressure (absorbing heat) and condenses at high pressure (releasing heat). The four main components are evaporator, compressor, condenser, and expansion device.
- On a P-h diagram, the cycle is represented as a closed loop. The evaporator is the horizontal line at low pressure (constant temperature), the compressor is the vertical line (increasing pressure and enthalpy), the condenser is the horizontal line at high pressure, and the expansion device is the vertical line (pressure drop).
- Heat transfer occurs via conduction (through solids), convection (through fluids), and radiation (electromagnetic waves). In HVAC, convection is dominant in air and water systems.
- Refrigerants have different boiling points at atmospheric pressure. For example, R-134a boils at -26.3°C. Latent heat of vaporization is the energy absorbed during evaporation.
- Psychrometrics describes moist air properties. Dry-bulb temperature is the air temperature; wet-bulb is measured with a wetted wick; dew point is the temperature at which moisture condenses. Relative humidity is the ratio of actual moisture to saturation moisture.
Must Know
- The four components of the refrigeration cycle and their functions
- How to read a P-h diagram: locate saturation lines, identify subcooling and superheat
- Relationship between pressure and temperature for a given refrigerant (use pressure-temperature chart)
- Sensible heat vs. latent heat: sensible changes temperature, latent changes state without temperature change
Field and Exam Application
- When charging a system, use a P-h diagram to determine target superheat and subcooling values for optimal efficiency.
- In a walk-in cooler, if the evaporator is frosting, check for low superheat (flooding) or low airflow (dirty coil).
- Psychrometric chart: to design an air conditioning system, plot supply and return air conditions to calculate cooling load and coil performance.
High-Yield Distinctions
- Superheat: temperature of vapor above saturation at evaporator outlet. Subcooling: temperature of liquid below saturation at condenser outlet.
- Critical point: temperature and pressure above which liquid and vapor phases cannot be distinguished.
- Flash gas: vapor formed when liquid refrigerant passes through an expansion device due to pressure drop; reduces system efficiency.
- Ton of refrigeration: 12,000 BTU/h or 3.517 kW, the cooling capacity needed to freeze one ton of water in 24 hours.
Common Pitfalls
- Confusing superheat and subcooling: superheat is measured at evaporator outlet, subcooling at condenser outlet.
- Assuming all refrigerants have the same pressure-temperature relationship; always use the correct PT chart.
- Ignoring the effect of altitude on boiling points; at higher altitudes, boiling point decreases.
- Misreading a P-h diagram: remember that enthalpy increases through the compressor and decreases through the expansion device.
Review Tasks
- Draw and label the refrigeration cycle on a P-h diagram for R-134a.
- Calculate superheat given evaporator outlet temperature and saturation temperature from PT chart.
- Explain the difference between sensible and latent heat with an example.
- Use a psychrometric chart to find relative humidity given dry-bulb and wet-bulb temperatures.
Refrigeration and Air Conditioning System Installation
Syllabus Focus
- Site preparation and positioning of equipment
- Pipework installation: copper tubing, brazing, flaring, and swaging
- Leak testing and evacuation
- Refrigerant charging procedures
- Electrical connections and controls
- Commissioning and handover
Key Notes
- Site preparation includes ensuring adequate space for airflow, access for maintenance, and structural support for equipment weight. Outdoor units must be on a level base and clear of obstructions.
- Copper pipework must be cut square, deburred, and cleaned before brazing. Use nitrogen purge during brazing to prevent oxide formation. Flare joints are used for smaller diameters; torque to manufacturer specifications.
- Leak testing: pressurize the system with nitrogen (not oxygen) to the design pressure (typically 1.1 times the maximum allowable pressure). Use electronic leak detector or soap bubbles. Hold pressure for at least 15 minutes.
- Evacuation: use a vacuum pump to remove moisture and non-condensables. Pull vacuum to below 500 microns (0.5 Torr) and hold for 30 minutes to ensure no rise (indicating leaks or moisture).
- Charging: weigh in the correct refrigerant charge per manufacturer data. For systems without a sight glass, use superheat/subcooling method. Never overcharge.
- Commissioning: check all electrical connections, verify voltage and current, set controls, measure airflow, and record operating pressures and temperatures. Handover includes providing user manuals and explaining operation.
Must Know
- Correct brazing technique: use nitrogen flow, avoid overheating, and ensure joint penetration.
- Evacuation procedure: connect vacuum pump, run until vacuum gauge reads below 500 microns, isolate pump, and check for rise.
- Leak testing with nitrogen: never exceed the system design pressure; use a pressure regulator.
- Refrigerant charging: always charge as liquid into the liquid line (for blended refrigerants) or as vapor into the suction line (for pure refrigerants).
Field and Exam Application
- Installing a split AC: run line set, flare connections, evacuate, and charge by weight. Check superheat at service valve.
- For a commercial refrigeration system, after brazing, pressurize with nitrogen to 300 psi and hold for 24 hours to detect leaks.
- During commissioning of a heat pump, verify reversing valve operation and defrost cycle initiation.
High-Yield Distinctions
- Nitrogen vs. oxygen: nitrogen is inert and safe for pressure testing; oxygen supports combustion and can cause explosions with oil.
- Deep vacuum vs. standard vacuum: deep vacuum (below 500 microns) removes moisture; standard vacuum (around 1000 microns) may leave moisture.
- Liquid charging vs. vapor charging: liquid charging is faster but can slug the compressor if done on the suction side; vapor charging is safer for small systems.
- Triple evacuation: method to remove moisture by breaking vacuum with nitrogen between evacuations.
Common Pitfalls
- Brazing without nitrogen purge: causes copper oxide scale that can block expansion devices and damage compressor.
- Over-tightening flare nuts: can crack the flare or damage the cone; use a torque wrench.
- Charging liquid refrigerant into the suction line: can cause compressor slugging and damage valves.
- Skipping evacuation: leaves moisture and air in the system, leading to acid formation and compressor failure.
Review Tasks
- List the steps for brazing a copper pipe joint with nitrogen purge.
- Describe the procedure for leak testing a newly installed system.
- Explain why evacuation is critical and how to verify a good vacuum.
- Calculate the correct refrigerant charge for a system given the line lengths and manufacturer data.
Service and Maintenance of RACHP Systems
Syllabus Focus
- Routine maintenance tasks: cleaning coils, checking filters, lubricating fans
- Diagnostic procedures: pressure and temperature readings, electrical checks
- Common faults: refrigerant leaks, compressor failure, expansion device blockage
- Repair techniques: replacing components, brazing, leak repair
- Record keeping and service reports
- Safety during service: isolation, refrigerant recovery
Key Notes
- Routine maintenance: clean condenser and evaporator coils annually (or more often in dusty environments). Replace or clean air filters monthly. Check fan belts for tension and wear. Lubricate fan motors if equipped with oil ports.
- Diagnostics: measure suction and discharge pressures, calculate superheat and subcooling. Compare to manufacturer data. Check compressor amp draw and voltage. Use temperature clamps on lines.
- Common faults: low refrigerant charge (high superheat, low subcooling, low suction pressure), restricted expansion device (low suction pressure, high superheat), compressor not starting (check capacitor, contactor, overload).
- Leak repair: locate leak with electronic detector or UV dye. Recover refrigerant, repair (braze or replace component), pressure test, evacuate, and recharge.
- Service reports: document all readings, actions taken, parts replaced, and recommendations. Include date, system ID, and technician signature.
- Safety: isolate electrical supply before opening panels. Recover refrigerant into approved cylinders. Never vent refrigerant to atmosphere.
Must Know
- How to measure and interpret superheat and subcooling for system diagnosis
- Procedure for recovering refrigerant: connect recovery machine, recover liquid first, then vapor, until system reaches 0 psig or vacuum
- Common compressor failure causes: slugging, floodback, overheating, electrical faults
- Importance of log sheets: track system performance over time to identify trends
Field and Exam Application
- A walk-in cooler has high suction pressure and low superheat: possible overcharge or TXV stuck open. Check subcooling and adjust charge.
- A rooftop unit has low airflow: check filters, fan belt, and evaporator coil cleanliness. Measure static pressure.
- A heat pump in heating mode has low discharge pressure: check for refrigerant leak, outdoor coil frost, or defrost control failure.
High-Yield Distinctions
- Floodback vs. slugging: floodback is liquid refrigerant returning to compressor continuously (low superheat); slugging is a sudden liquid slug (can break valves).
- Short cycling: compressor runs for short periods, often due to low pressure control, dirty condenser, or oversized unit.
- TXV vs. capillary tube: TXV maintains constant superheat; capillary tube is fixed and relies on charge accuracy.
- Head pressure control: used in low ambient conditions to maintain minimum condensing pressure (fan cycling, damper, or VFD).
Common Pitfalls
- Adding refrigerant without fixing the leak: illegal under F-Gas regulations and wastes refrigerant.
- Replacing a compressor without finding the root cause: new compressor will fail again.
- Ignoring electrical checks: a bad capacitor can cause compressor start failure and overheating.
- Not recovering refrigerant properly: mixing refrigerants or overfilling recovery cylinders.
Review Tasks
- Diagnose a system with low suction pressure and low superheat: what are the possible causes?
- Write a step-by-step procedure for replacing a TXV.
- List the information that should be recorded on a service report.
- Explain the difference between floodback and slugging and how to prevent each.
Electrical Systems for RACHP
Syllabus Focus
- Basic electrical theory: voltage, current, resistance, power
- Single-phase and three-phase supplies
- Electrical components: contactors, relays, capacitors, transformers, motors
- Wiring diagrams and circuit tracing
- Safety: isolation, lockout/tagout, testing for dead
- Fault finding: using multimeter, megger, clamp meter
Key Notes
- Ohm's Law: V = I × R. Power: P = V × I (for resistive loads). For AC circuits, consider power factor: P = V × I × PF.
- Single-phase: 230V in UK, live-neutral-earth. Three-phase: 400V between phases, 230V phase to neutral. Motors can be star or delta connected.
- Contactors are electrically operated switches for high current loads. Relays are for low current control circuits. Capacitors (start and run) are used for single-phase motors.
- Transformers step down voltage for control circuits (e.g., 230V to 24V). Always check secondary voltage and fuse rating.
- Wiring diagrams: schematic shows electrical connections; ladder diagram shows power and control circuits. Trace circuits from supply through switches and loads back to neutral.
- Fault finding: use multimeter to measure voltage, continuity, and resistance. Megger for insulation resistance (test at 500V or 1000V). Clamp meter for current without breaking circuit.
Must Know
- How to test a capacitor: discharge, set multimeter to capacitance, read value; also check for short or open.
- Motor winding resistance: measure between terminals; all three windings should have similar resistance. Check for shorts to ground.
- Contactor coil voltage: must match control voltage; coil resistance should be within spec.
- Safe isolation procedure: identify source, isolate, lock off, tag, test for dead using a voltage tester, prove tester works on known source.
Field and Exam Application
- A compressor does not start: check voltage at contactor coil, then at compressor terminals. If voltage present but no start, check capacitor and overload.
- A fan motor runs slow: measure voltage at motor, check capacitor value, and check for loose connections.
- A system trips the breaker: use a megger to test insulation resistance of compressor and fan motors. Also check for shorted contactor.
High-Yield Distinctions
- Start capacitor vs. run capacitor: start capacitor is electrolytic (high capacitance, used briefly); run capacitor is oil-filled (lower capacitance, continuous duty).
- Star vs. delta connection: star gives lower starting current but lower torque; delta gives higher torque but higher starting current.
- PSC (permanent split capacitor) motor vs. shaded pole motor: PSC has higher efficiency and starting torque; shaded pole is simple but low torque.
- Overload protection: thermal overload (bimetallic) or electronic overload (current sensing). Must be sized correctly.
Common Pitfalls
- Testing voltage without proving the tester: always test on a known live source first.
- Assuming a capacitor is good because it looks fine: always measure capacitance.
- Mixing up live and neutral: in single-phase, reversing can cause safety issues but motor may still run.
- Not locking off isolation: can lead to accidental re-energization.
Review Tasks
- Draw a simple ladder diagram for a compressor contactor controlled by a thermostat.
- Describe how to test a run capacitor with a multimeter.
- Explain the difference between star and delta motor connections.
- List the steps for safe isolation of a condensing unit.
Environmental Protection and F-Gas Regulations
Syllabus Focus
- F-Gas Regulation (EU) 517/2014 and UK equivalent
- Ozone depletion potential (ODP) and global warming potential (GWP)
- Refrigerant handling: recovery, recycling, reclamation
- Leak detection and repair obligations
- Record keeping and log books
- Disposal of equipment and refrigerants
Key Notes
- F-Gas Regulation aims to reduce emissions of fluorinated greenhouse gases. It covers HFCs, PFCs, and SF6. Key requirements: leak checking, recovery, record keeping, and certification of personnel and companies.
- ODP measures ozone depletion; CFCs have high ODP, HCFCs lower, HFCs zero. GWP measures global warming impact relative to CO2. High GWP refrigerants are being phased down.
- Recovery: remove refrigerant from system into approved cylinders. Recycling: cleaning refrigerant for reuse on same system. Reclamation: processing to new product specifications.
- Leak detection: systems with >5 tonnes CO2 equivalent must be leak checked annually (or more frequently based on charge size). Fixed leak detection systems may be required for large systems.
- Record keeping: maintain log of refrigerant added, recovered, and leak checks. Records must be kept for at least 5 years.
- Disposal: recover all refrigerant before scrapping equipment. Dispose of cylinders properly. Follow WEEE regulations for electrical waste.
Must Know
- F-Gas qualification requirements: personnel must hold a valid F-Gas certificate (Category I, II, III, or IV) for the type of work.
- Leak check intervals: systems with 5-50 tonnes CO2 equivalent: annually; 50-500 tonnes: every 6 months; >500 tonnes: every 3 months (or with fixed detection).
- Refrigerant recovery: must be done before any repair that could release refrigerant. Use recovery machine and appropriate cylinder.
- Log book: must include system identification, refrigerant type and charge, quantities added/removed, leak checks, and service actions.
High-Yield Distinctions
- Category I vs. Category II F-Gas: Category I allows work on all systems (including those with >3 kg charge); Category II is limited to systems with <3 kg or hermetically sealed.
- Phase-down: HFC consumption is being reduced in steps; quotas apply to producers and importers.
- ODP vs. GWP: ODP is about stratospheric ozone; GWP is about climate change. Both are important but regulated differently.
- Recovery vs. recycling vs. reclamation: recovery is removal; recycling is cleaning on-site; reclamation is off-site processing to AHRI 700 standard.
Common Pitfalls
- Venting refrigerant to atmosphere: illegal and harmful. Always recover.
- Not keeping records: can result in fines and loss of certification.
- Using non-approved recovery cylinders: cylinders must be marked for the refrigerant type and have a current test date.
- Mixing refrigerants in recovery cylinder: can cause contamination and safety issues.
Review Tasks
- List the leak check intervals for a system with 100 kg of R-404A (GWP 3922).
- Describe the procedure for recovering refrigerant from a split AC system.
- Explain the difference between Category I and Category II F-Gas certification.
- What information must be recorded in a refrigerant log book?
How To Use These Notes With Practice Questions
Do not jump straight from reading to a full mock. Work by subject first: review the key notes, make a short recall sheet from memory, then answer a focused question set. After each miss, decide whether the problem was missing theory, weak code/source recall, poor measurement setup, calculation error, or a field sequence you did not visualize.
Technical Conquer's question bank, flashcards, mind maps, and spaced review tools are most useful after this instruction layer because they reveal which parts of the notes are not yet retrievable.
Final Review Checklist
- Review health and safety legislation: HSWA, COSHH, RIDDOR, PUWER, LOLER.
- Master the refrigeration cycle and P-h diagram: identify components and calculate superheat/subcooling.
- Practice installation procedures: brazing, evacuation, leak testing, charging.
- Develop diagnostic skills: use pressure, temperature, and electrical measurements to find faults.
- Understand electrical circuits: read wiring diagrams, test components, and follow safe isolation.
- Know F-Gas regulations: leak check intervals, recovery procedures, record keeping, and certification levels.
- Use official sources: City & Guilds website, ASHRAE Handbook, IMC, and UK government F-Gas guidance.
Official Sources and Further Reading
Use these sources as the final authority for format, eligibility, rules, regulatory limits, and exam updates. Study notes are a preparation layer, not a replacement for official candidate guidance.