Cert III Air Conditioning & Refrigeration key terms

A ranked order of risk treatments, from eliminating a hazard through substitution, engineering controls, administrative controls and finally personal protective equipment, used to choose the most reliable safeguard first.

A structured process of identifying hazards, judging how severe and likely the harm is, and recording controls before work starts. It is reviewed whenever conditions or tasks change.

A planning technique that breaks a task into steps, names the hazards at each step and lists the controls, often recorded on a form and discussed with the crew before starting.

A supplier document summarising a chemical's hazards, safe handling, first aid, firefighting and spill response. It must be readily accessible to workers who store or use that substance.

The danger that leaking refrigerant displaces oxygen in a confined space or low-lying area, causing dizziness, loss of consciousness or death. Oxygen depletion is measured before entry.

Entering an enclosed or partly enclosed area with restricted access, such as a plant room pit or vessel, under a permit with atmospheric testing, ventilation, a standby person and rescue arrangements.

A formal written authorisation for high-risk activity that records the task, the isolations applied, the precautions required and the sign-off releasing the area for work or return to service.

A procedure for isolating energy sources with locks and warning tags so equipment cannot be re-energised or started while someone is working on it. Only the person who fitted a lock removes it.

Removing refrigerant from a system into a suitable container without venting it to atmosphere, so it can be reclaimed, recycled or destroyed in accordance with environmental obligations.

A relative number expressing how strongly a substance destroys stratospheric ozone compared with a reference refrigerant, used to judge which refrigerants and practices are environmentally acceptable.

A relative measure of how much heat a gas traps in the atmosphere over a set period compared with carbon dioxide, used to report refrigerant emissions and choose lower-impact alternatives.

Heat added to or removed from a substance that changes its temperature but not its state, such as warming air across a coil. It is calculated from mass, specific heat and temperature change.

Heat absorbed or released when a substance changes state at constant temperature, such as a liquid boiling to vapour in the evaporator. It does not show on a thermometer.

The number of degrees a vapour is above its saturation temperature at the measured pressure. Evaporator superheat indicates how well the expansion device is feeding the coil.

The number of degrees a liquid is below its saturation temperature at the measured pressure. Condenser subcooling shows how much liquid is stacked in the condenser and confirms a solid liquid seal.

The temperature at which a refrigerant boils or condenses at a given pressure. It is read from a pressure-temperature chart and is the reference for superheat and subcooling calculations.

The fixed link between a refrigerant's pressure and its boiling or condensing temperature, allowing a gauge reading to be converted into a temperature and used for diagnosis.

The temperature difference between the bubble and dew points of a zeotropic blend at a given pressure, which means its saturation temperature changes as it boils or condenses.

The quantity of heat needed to turn a unit mass of liquid refrigerant into vapour at its boiling point, which sets how much cooling effect each kilogram of circulating refrigerant delivers.

A measure of the total heat energy content of a refrigerant at a given point, used on a pressure-enthalpy diagram to work out refrigerating effect and compressor work.

A component such as a thermostatic expansion valve or capillary tube that throttles refrigerant from condensing to evaporating pressure and regulates the flow into the evaporator.

The heat exchanger where low-pressure liquid refrigerant boils and absorbs heat from the space or product being cooled. Its performance depends on airflow, load and correct refrigerant feed.

The relationship stating that voltage equals current multiplied by resistance in a circuit. It is used to calculate expected current, voltage drop and heater or winding resistance during testing.

An electrically operated switch with heavy-duty main contacts and a coil, used to start and stop compressors, fans and heaters from a control circuit. Contacts and coils are common fault points.

A protective device that senses excessive motor current or heat and opens the control circuit to stop the motor, preventing winding damage. Some types must be reset manually after tripping.

Disconnecting and proving dead all supply conductors to equipment before work, then securing the isolation, so no shock or unexpected start-up can occur.

A temperature-sensing control that opens or closes a circuit to hold a space or product within a set range. Its sensor position and differential affect cycling and energy use.

A control that responds to refrigerant or air pressure to make or break a circuit, providing high-pressure cut-out, low-pressure cut-out or fan cycling protection.

A timer or demand device that initiates and terminates defrost cycles on the evaporator, using heaters, hot gas or off-cycle methods, so frost is cleared without excessive temperature rise.

Pulling a deep vacuum on a system to remove air, moisture and non-condensables before charging. A standing vacuum test confirms the system holds and is dry.

A commissioning technique of evacuating, breaking the vacuum with dry nitrogen and repeating, which dilutes residual moisture and air so the final vacuum is achieved reliably.

Checking joints and components for refrigerant loss using methods such as dry nitrogen pressure testing, electronic detectors or soap solution, done before charging and after repairs.

Adding refrigerant to a system in the correct state and amount, using weight, subcooling or superheat targets, so the charge matches the manufacturer's specification.

The structured process of proving an installed system works as designed, including pressure testing, evacuation, charging, control setting, airflow adjustment and recording of measured results.

Adjusting dampers, fan speed and grilles so each circuit delivers its design air quantity, measured with instruments, which is essential before refrigerant charge and controls are finalised.

A logical process of gathering symptoms, forming likely causes, testing to confirm or eliminate each one, and repairing the confirmed fault rather than replacing parts by guesswork.

A control sequence that closes the liquid line and runs the compressor until suction pressure falls to a set point, storing refrigerant in the receiver and preventing liquid migration.

Scheduled inspection, cleaning, tightening, lubrication and measurement carried out to keep equipment efficient and to catch deterioration before it becomes a breakdown.

The planned removal of a system from service, including safe isolation, recovery of all refrigerant, disposal of components and updating of records and labels.

A written record of the work performed, measurements taken, parts used, tests passed and any outstanding items, signed off and given to the customer or site representative.

A log of refrigerant quantities added, recovered and removed from equipment, kept so environmental reporting and leak-checking obligations can be demonstrated.

A document authorising a specific job, stating the site, scope, priority, safety requirements and any permits, which is updated as the task progresses.

Giving full attention to a speaker, confirming understanding by summarising and asking clarifying questions, so instructions and customer concerns are captured accurately.

An approved written instruction describing how a routine task is performed safely and consistently, including tools, sequence, checks and records required.

A short pre-task briefing on hazards, controls, roles and coordination for the day's work, recorded with attendees' names to demonstrate consultation.

Clothing and gear worn to reduce exposure to hazards, such as gloves, goggles, hearing protection and respirators. It is the last line of defence after higher controls.

Recording near misses, injuries, equipment damage and dangerous occurrences promptly and accurately so causes can be investigated and controls improved.

The requirement that refrigerant handling, electrical work and other regulated tasks be performed by people holding the prescribed qualifications, under supervision where permitted.