Refrigeration Operator B key terms

The repeating sequence in which refrigerant absorbs heat at low pressure and releases it at high pressure. It includes evaporation, compression, condensation and expansion, and it moves heat rather than creating cold.

The heat exchanger where low-pressure liquid refrigerant boils and absorbs heat from the space or product being cooled. Its performance depends on refrigerant feed, airflow or fluid flow, and keeping the coil free of frost and oil.

The heat exchanger that rejects heat from hot compressed refrigerant vapour to a cooling medium such as air or water, causing the refrigerant to condense into liquid. Poor heat rejection raises discharge pressure and power consumption.

The machine that draws low-pressure refrigerant vapour from the evaporator and raises its pressure and temperature so heat can be rejected in the condenser. Types include reciprocating, scroll, screw and centrifugal.

A metering device that throttles high-pressure liquid refrigerant down to evaporator pressure while regulating flow to maintain the required superheat. Thermostatic and electronic types respond to temperature and pressure signals.

The number of degrees a refrigerant vapour is above its saturation temperature at a given pressure. Measured at the evaporator outlet, it confirms the refrigerant is fully boiled and protects the compressor from liquid slugging.

The number of degrees a liquid refrigerant is below its saturation temperature at a given pressure. Measured at the condenser outlet, it indicates how much liquid is stacked in the condenser and helps confirm adequate charge.

The temperature at which a refrigerant changes between liquid and vapour at a given pressure. It is the reference point for reading superheat and subcooling and for setting pressure controls.

A chart plotting refrigerant pressure against enthalpy that shows the four cycle processes, work input, heat absorbed and rejected, and the effect of changes such as higher condensing pressure. Used for troubleshooting and efficiency analysis.

The quantity of refrigerant contained in a system. Correct charge is confirmed by subcooling, superheat and sight-glass or receiver-level checks; undercharge and overcharge both cause abnormal pressures and temperatures.

The controlled removal of refrigerant from a system into a suitable container without venting it to atmosphere. Recovery is required before opening a circuit and is governed by environmental and safety rules.

A relative measure of how much a refrigerant can damage stratospheric ozone compared with a reference substance. It drives refrigerant selection and restrictions on certain chemicals.

A relative measure of the heat-trapping effect of a gas compared with carbon dioxide over a set time horizon. It is a key factor in choosing refrigerants and in leak reduction programs.

A refrigerant blend whose components behave as a single substance, boiling and condensing at one temperature at a given pressure. It can be charged as a liquid or vapour without changing composition.

A refrigerant blend whose components boil over a range of temperatures at a given pressure, producing a temperature glide. It must be charged as a liquid to avoid fractionation and changing the blend composition.

The difference between the bubble point and dew point temperatures of a zeotropic refrigerant at a constant pressure. It affects superheat and subcooling readings and must be accounted for when charging.

The pressure of refrigerant vapour leaving the compressor. High discharge pressure can result from poor condenser cooling, non-condensable gases or overcharge, and it increases power draw and wear.

The pressure of refrigerant vapour entering the compressor. It reflects evaporator load and temperature; low suction reduces capacity and can cause freezing, while high suction raises motor loading.

Lubricant that reduces friction and seals clearances in the compressor. Oil type must match the refrigerant, and oil level, acidity and moisture are monitored because oil travels through the circuit.

A device that removes entrained oil from hot discharge gas and returns it to the compressor crankcase. It protects the compressor and helps keep oil out of the evaporator, where it reduces heat transfer.

A small window in the liquid line that shows refrigerant flow. Bubbles can suggest a shortage of liquid or flash gas, and a moisture indicator changes colour to warn of water contamination.

A device in the liquid line that traps debris and absorbs moisture from the refrigerant. A restricted drier causes a pressure drop and can produce flash gas at the expansion valve.

A check of compressor oil or refrigerant for acidity caused by moisture, overheating or motor burn-out. A positive result calls for oil change and corrective action before the acid damages windings and bearings.

The presence of water in a refrigeration circuit, which can form ice at the expansion valve, create acids and corrode metals. Prevented by proper evacuation and drying, and detected by moisture indicators and acid tests.

The process of removing air and moisture from a system with a vacuum pump before charging. Reaching and holding a deep vacuum confirms the circuit is dry and leak-free.

Methods used to find escaping refrigerant, including electronic detectors, soap solutions, pressure tests and ultraviolet dye. Regular leak checks are part of environmental compliance and plant reliability.

A pressure vessel for storing refrigerant. Rules cover fill limits, colour and marking, valve protection, transport and storage, and only approved cylinders may be filled or recovered into.

A protective device that opens automatically at a set pressure to release refrigerant and prevent vessel or piping rupture. It must be correctly sized, unobstructed and tested or replaced on schedule.

A one-time pressure-relief device that bursts at a set pressure to protect equipment. Unlike a relief valve it does not reseat, so it must be replaced after it operates.

A safety control that stops the compressor when discharge pressure exceeds a set limit. It prevents equipment damage and must be tested and reset only after the cause is found and corrected.

A safety control that stops the compressor when suction pressure falls below a set limit, protecting against freezing, low charge or loss of load. Reset should follow fault finding, not repeated manual restarting.

A control that stops the compressor if lubricating oil pressure does not build up within a set time after start. It protects bearings from damage caused by low oil level or a failed oil pump.

A method of maintaining adequate discharge pressure in low ambient conditions by reducing condenser heat rejection, for example by fan cycling, damper control or flooding the condenser. It keeps the expansion valve feeding properly.

A control sequence that pumps refrigerant out of the evaporator into the receiver or condenser before the compressor stops. It prevents liquid migration to the compressor during off cycles.

A timed or demand cycle that removes frost from an evaporator using heaters, hot gas or off-cycle air. Proper termination and drain operation prevent ice build-up and water damage.

Scheduled inspection, cleaning, lubrication and testing of refrigeration equipment to prevent breakdowns and keep efficiency. Records of completed work support compliance and demonstrate due diligence.

A record of readings such as pressures, temperatures, oil levels and alarm events taken during rounds. Trends in the log reveal developing faults and provide evidence of monitoring.

A person who operates and maintains registered pressure equipment and holds the certificate of qualification required for that class of plant under provincial law. Duties include safe operation, monitoring and record keeping.

Ontario's Technical Standards and Safety Authority, which administers and enforces safety legislation for pressure equipment, fuels and certain refrigeration plants under provincial regulation.

The formal recording of a pressure vessel with the authority having jurisdiction, supported by design and inspection documentation. Registration and periodic inspection are conditions of lawful operation.