NVQ L4 Refrigeration & AC key terms

A structured process that identifies what could cause harm to people or the environment, judges how likely and how severe that harm is, and records the controls needed before work starts.

The ranked order of ways to reduce risk, from most to least reliable: eliminate the hazard, substitute it, apply engineering controls, then administrative controls, with personal protective equipment relied on last.

A written document describing how a specific task will be carried out safely, in what sequence, by whom, with what equipment, and which control measures apply at each stage.

A formal, signed authorisation allowing defined high-risk work to proceed under stated conditions for a limited period, confirming the area has been made safe and handed over to the work party.

A fall in breathable oxygen in a space, often caused by heavier refrigerant vapour displacing air in low-lying or confined areas, which can cause rapid unconsciousness with little warning.

A procedure for isolating energy sources such as electricity or pressure, fitting a personal lock and warning tag, and proving the isolation is effective before any work begins.

A sum of all the heat gains a system must remove, including transmission through the building fabric, solar gain, occupants, lighting, equipment, product load and fresh-air load.

The ratio of cooling or heating delivered to the energy consumed by the compressor and other driven parts, expressed as a number, where a higher value means a more efficient system.

The number of degrees a vapour is above its saturation temperature at a given pressure; measured at the evaporator outlet it shows whether the expansion device is feeding correctly.

The number of degrees a liquid is below its saturation temperature at a given pressure; measured at the condenser outlet it shows how much liquid is stored and how well the condenser performs.

The difference between the bubble point and the dew point of a zeotropic blend at constant pressure, which affects charging method, coil design and how superheat is measured.

The condensing temperature chosen at design stage from the highest expected ambient or cooling-medium temperature, which sets condenser size, operating pressure and overall system efficiency.

A hierarchical splitting of project scope into manageable packages of work, each with clear deliverables, so time, cost and responsibility can be planned, allocated and tracked.

The longest sequence of dependent activities through a project programme, which sets the shortest possible completion date; any delay on it delays the whole job.

The period between placing an order for equipment or materials and receiving it on site, which must be built into the programme to avoid delaying installation.

A recorded list of incomplete or defective items found at inspection before handover, each assigned to a person for correction and signed off once finished.

A test in which pipework or a system is pressurised, usually with dry nitrogen, above its operating pressure to prove mechanical integrity before any refrigerant is introduced.

A test in which the system is evacuated to a deep vacuum, isolated and left standing; a continued rise in pressure indicates moisture or a leak in the circuit.

Charging refrigerant by measuring the mass added from a calibrated scale rather than judging by gauges alone, so the system holds exactly the amount specified by the designer.

A test in which the system runs from a warm starting condition while temperatures and pressures are logged over time, proving it reaches and holds the design conditions.

The set of documents given to the client at completion, typically as-built drawings, commissioning records, operating instructions, maintenance schedules, refrigerant records and warranties.

The documented evidence of tests, measured readings and settings captured while bringing a system into service, used to prove performance and to form a baseline for future maintenance.

A structured investigation that moves beyond the immediate symptom to find the underlying reason a fault or failure occurred, so it can be corrected and prevented from repeating.

Scheduled servicing and inspection carried out at set intervals to keep equipment reliable and efficient, reduce breakdowns and meet legal and warranty obligations.

Air or other gases that cannot liquefy in the condenser, usually introduced by poor evacuation; they raise discharge pressure, cut capacity and cause high head pressure and hot compressor running.

Liquid refrigerant returning to the compressor crankcase or cylinders, which can wash out lubricant and cause mechanical damage, abnormal noise and valve failure.

The legal framework controlling fluorinated greenhouse gases, covering leak checking, record keeping, competent personnel, recovery, labelling and phased reductions in supply of high-GWP refrigerants.

A value comparing the climate impact of one kilogram of a gas with one kilogram of carbon dioxide over a set period, used to compare refrigerants and calculate a system's carbon footprint.

A value comparing how strongly a substance destroys stratospheric ozone relative to CFC-11, used to classify refrigerants and justify restrictions on their use and release.

A record kept for each system listing refrigerant type and charge, every addition or recovery with quantities, leak checks carried out and repairs made, as required by F-gas rules.

A statutory inspection of a system at a frequency set by its refrigerant charge and global warming potential, carried out with suitable detectors and formally recorded.

The controlled removal of refrigerant from a system into a suitable container for reuse, reclaim or destruction, ensuring it is never vented to atmosphere.

A short briefing given to the team before work covering the task, the hazards, the controls and any changes, and giving operatives the chance to raise concerns.

A chart showing each team member against the competencies required for the work, marking who is trained, competent, in training or not yet assessed, so gaps and cover can be planned.

A one-to-one development approach in which a supervisor asks questions and gives feedback so a person works out solutions and builds competence, rather than simply being told the answer.

Assigning a task, together with the authority and resources needed to complete it, to a team member while the supervisor keeps accountability for the outcome.

A document listing the inspections and tests required for an activity or system, the acceptance criteria, who carries them out and which stages need the client to witness.

A stage in a process where work cannot continue until a specified inspection or approval has been completed and recorded by the authorised person.

A formal record of work or material that does not meet the specification or standard, describing the problem, its cause, the agreed corrective action and the sign-off when closed.

A continuous improvement loop of planning a change, doing it on a small scale, checking the results against the aim, and acting to standardise or adjust what was learned.

The process of comparing an instrument's readings with a known reference and adjusting or certifying it, so measurements used for testing and compliance can be trusted.