Inspect, service and maintain heat pump installations _non-refrigerant circuits_
This subtopic focuses on the inspection, servicing, and maintenance of the non-refrigerant circuits within air and ground source heat pump installations, encompassing components such as circulating pumps, controls, valves, filters, and heat exchangers. Learners will develop the practical skills to perform routine servicing, conduct systematic fault diagnosis, and carry out effective rectifications, ensuring systems operate efficiently and safely without handling refrigerants.
Assessment criteria
Topic Overview
The City & Guilds Level 3 NVQ Diploma in Domestic Plumbing and Heating is a work-based qualification designed for experienced plumbers who are ready to demonstrate advanced competence in the installation, maintenance, and repair of domestic plumbing and heating systems. This diploma covers complex tasks such as designing and installing hot and cold water systems, central heating systems, and sanitation systems, as well as fault diagnosis and rectification. It is the final step towards becoming a fully qualified plumber in the UK, often required for Gas Safe Register registration and to work on unvented hot water systems.
This qualification is assessed through on-site observations, professional discussions, and a portfolio of evidence, meaning you must prove your skills in real working conditions. It builds on the Level 2 Diploma and focuses on advanced techniques, including system design, energy efficiency, and compliance with current Building Regulations (e.g., Part G, Part L, and Part P). Mastering this diploma not only validates your technical expertise but also prepares you for supervisory roles or self-employment, as it demonstrates your ability to manage complex projects and ensure safety and quality in all aspects of domestic plumbing and heating.
Key Concepts
Core ideas you must understand for this topic
- →Unvented hot water systems: Understanding the design, installation, and safety requirements for unvented cylinders, including expansion vessels, pressure relief valves, and compliance with Building Regulations Part G.
- →Central heating system design: Calculating heat loss, selecting appropriate boilers (combi, system, or regular), and designing pipework layouts to ensure efficient heat distribution and zoning.
- →Fault diagnosis and rectification: Using systematic approaches to identify faults in heating and plumbing systems, such as diagnosing pump failures, thermostat issues, or boiler lockouts, and carrying out effective repairs.
- →Water regulations and safety: Applying the Water Supply (Water Fittings) Regulations to prevent contamination, including backflow prevention, pipe sizing, and material selection.
- →Energy efficiency and sustainability: Implementing measures to improve system efficiency, such as installing thermostatic radiator valves (TRVs), weather compensation controls, and renewable technologies like solar thermal or heat pumps.
Learning Objectives
What you need to know and understand
- Perform routine service and maintenance on non-refrigerant circuits of air source heat pump systems
- Perform routine service and maintenance on non-refrigerant circuits of ground source heat pump systems
- Diagnose common faults in non-refrigerant circuits of heat pump installations
- Implement effective fault rectification measures for non-refrigerant circuit issues
- Evaluate system performance following maintenance or repair activities
- Apply health and safety legislation and manufacturer instructions throughout all tasks
Assessment Criteria
Key criteria assessors look for in your portfolio
- Correct isolation of electrical supplies and water circuits before commencing work
- Accurate measurement and recording of flow rates, temperatures, and system pressures
- Identification of faulty components such as seized pumps, blocked filters, or faulty sensors
- Selection and fitting of appropriate replacement parts as per manufacturer specifications
- Cleaning and checking of strainers, heat exchangers, and non-return valves
- Verification of system operation and parameter settings after servicing or repair
- Completion of service records and documentation in line with regulatory requirements
Assessment Guidance
Guidance for achieving higher grades
- 💡Always perform a full functional test after servicing to demonstrate competence
- 💡Use a structured diagnostic approach, such as checking power, signal, and mechanical operation in sequence
- 💡Familiarise yourself with typical wiring diagrams and control logic for common heat pump brands
- 💡Ensure all remedial work is accompanied by clear photographic evidence and written reports
- 💡Reference relevant building regulations and industry standards (e.g., MIS 3005) in your documentation
- 💡When being observed, always talk through your actions step-by-step. Explain why you are doing each task, referencing regulations (e.g., 'I'm fitting this check valve to comply with Water Regulations to prevent backflow'). This shows deep understanding and can earn you extra marks.
- 💡Keep your portfolio organised with clear photos, annotated diagrams, and written explanations. Use a consistent format for each piece of evidence, and cross-reference to the relevant NVQ unit and performance criteria. This makes it easier for your assessor to see how you meet the standards.
- 💡For fault diagnosis tasks, use a logical process: identify symptoms, gather information (e.g., from customer or system history), test components systematically, and confirm the fault before repairing. Document each step in your professional discussion to demonstrate your problem-solving skills.
Common Mistakes
Common errors to avoid in your coursework
- Neglecting to isolate electrical power before working on pumps or controls
- Misdiagnosing a system control fault as a mechanical pump failure
- Failing to clean or inspect inline strainers during routine service
- Incorrectly setting system flow temperatures or differentials after rectification
- Using generic components not approved by the manufacturer, voiding warranties
- Misconception: Unvented systems are the same as vented systems, just without a tank. Correction: Unvented systems operate at mains pressure and require specific safety devices (e.g., expansion vessel, pressure relief valve) and must be installed by a competent person with a relevant qualification (e.g., G3 unvented hot water certificate).
- Misconception: You can use any pipe material for central heating. Correction: Pipe material must be suitable for the system type and water quality. For example, copper is common but plastic (e.g., PEX) may be used with correct oxygen barrier to prevent corrosion in sealed systems.
- Misconception: A system boiler is the same as a combi boiler. Correction: A system boiler heats water stored in a cylinder, while a combi boiler heats water on demand. System boilers are better for homes with high hot water demand, while combis are more compact and efficient for smaller properties.
Frequently Asked Questions
Common questions students ask about this topic
Pass / Merit / Distinction Evidence Checklist
How your portfolio evidence is graded for CITY & GUILDS LIMITED Inspect, service and maintain heat pump installations _non-refrigerant circuits_
Every vocational unit is marked against named criteria rather than an exam percentage. Your tutor's brief lists the exact codes for this unit — here is what each band is asking you to do.
Demonstrate baseline knowledge, accurate terminology, and core practical application.
Provide detailed analysis, structured explanations, and clear workplace reasoning.
Deliver thorough evaluation, original problem solving, and fully justified recommendations.
Before You Start
Prior knowledge that will help with this topic
- •Level 2 Diploma in Plumbing and Heating (or equivalent) – you must have a solid foundation in basic plumbing skills, including pipework, soldering, and understanding of vented systems.
- •Knowledge of Building Regulations – familiarity with Parts G (sanitation, hot water safety), L (conservation of fuel and power), and P (electrical safety) is essential before tackling Level 3.
- •Practical experience in domestic plumbing – ideally at least 2-3 years of on-the-job experience, as the NVQ requires you to demonstrate competence in real work situations.
Coursework AI Review
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Key Terminology
Essential terms to know
- Non-refrigerant circuit components
- Routine servicing procedures
- Fault diagnosis methods
- Rectification techniques
- System performance testing
- Safety and regulatory compliance
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