RETA CARO key terms

The fluid that absorbs heat by evaporating at low pressure and releases heat by condensing at high pressure as it circulates through a refrigeration system.

A naturally occurring refrigerant with excellent thermodynamic efficiency and strong, pungent odor, but which is toxic and flammable at sufficient concentrations in air.

The machine that raises refrigerant vapor from low evaporating pressure to high condensing pressure, doing the work that drives the refrigeration cycle.

The heat exchanger in which liquid refrigerant boils at low pressure, absorbing heat from the space or product being cooled.

The heat exchanger that rejects heat from hot high-pressure refrigerant vapor to a cooling medium such as air or water, causing the vapor to condense to liquid.

A metering device that throttles high-pressure liquid refrigerant down to low pressure and regulates the flow of liquid into the evaporator.

The low-side pressure measured at the compressor inlet, which corresponds to the evaporating temperature and the temperature of the refrigerated space.

The high-side pressure measured at the compressor outlet, which corresponds to the condensing temperature and rises with warmer condensing conditions.

The number of degrees a refrigerant vapor is above its saturation temperature at a given pressure, confirming that no liquid droplets remain.

The number of degrees a liquid refrigerant is below its saturation temperature at a given pressure, indicating the liquid has been cooled further after condensing.

The temperature at which a refrigerant boils or condenses at a given pressure; changing the pressure changes this temperature.

The heat energy absorbed or released when a substance changes phase, such as boiling to vapor or condensing to liquid, without changing temperature.

Vapor that forms when liquid refrigerant pressure is suddenly reduced, which must be separated or pumped away so it does not reduce cooling capacity.

A pressure vessel that stores liquid refrigerant condensed from the condenser and supplies it to the evaporators at a controlled rate.

A device on the compressor discharge line that removes entrained lubricating oil from hot discharge gas and returns it to the compressor crankcase.

A condition in which liquid refrigerant or oil enters the compressor and can damage valves and other internal parts, often caused by flooding or low superheat.

The repeating sequence of compression, condensation, expansion, and evaporation that moves heat from a colder space to a warmer environment.

The manual shutoff valve at the outlet of the liquid receiver that can isolate the liquid supply to the rest of the system.

A procedure that removes refrigerant vapor and liquid from a section of the system into a receiver or isolated vessel before maintenance, reducing the amount released indoors.

A pressure-relief device set to open automatically and discharge refrigerant before system pressure rises to a dangerous level.

A piping system that collects discharge from safety relief valves and carries it to a safe outdoor location away from occupied areas and air intakes.

A closed container such as a receiver or surge drum designed to hold refrigerant under pressure and subject to periodic inspection and code requirements.

The airborne concentration of ammonia at which exposure can harm health; even low concentrations irritate eyes and lungs, and higher levels can be fatal.

The range of ammonia concentration in air, roughly 15 to 28 percent by volume, within which the mixture can ignite if an ignition source is present.

Immediately Dangerous to Life or Health, the airborne concentration above which a person could escape without irreversible health effects or impairment; for ammonia it is 300 ppm.

Permissible Exposure Limit, the regulatory maximum average airborne concentration of ammonia a worker may be exposed to over an eight-hour shift, set at 50 ppm.

A fixed sensor that continuously monitors the air for ammonia and triggers alarms or ventilation when a set concentration is exceeded.

The ammonia concentration at which a detection system activates a warning or action, commonly set at 25 ppm for a low alarm and 100 ppm for a high alarm.

Mechanical exhaust fans, often triggered automatically by gas detection, that remove ammonia-contaminated air from a machinery room and discharge it outdoors.

The space housing compressors and other ammonia equipment, which requires restricted access, ventilation, detection, and specific construction features for safety.

Personal breathing protection, such as a full-face air-supplied or self-contained unit, worn when entering areas where ammonia may exceed safe breathing levels.

Self-Contained Breathing Apparatus, a portable air supply worn by responders for entry into areas where ammonia concentration is unknown or immediately dangerous.

A safety practice in which workers enter hazardous areas in pairs so one can summon help or assist the other if exposure or injury occurs.

Any flame, spark, hot surface, or electrical equipment that could ignite a flammable ammonia-air mixture within its flammable range.

A written authorization required before welding, cutting, grinding, or other spark-producing work is done near ammonia equipment, documenting precautions and fire watch.

A procedure that isolates energy sources and applies locks and tags so equipment cannot be started while maintenance or repair work is in progress.

A documented set of procedures telling personnel how to respond to an ammonia release, including alarms, evacuation routes, shutdown steps, and notification of responders.

A pre-planned path that leads personnel upwind and away from an ammonia release to a designated assembly area.

A wind sock or similar device that shows which way the wind is blowing so responders can approach and evacuate upwind of a release.