DE HVAC key terms

The useful cooling rate divided by the energy-input rate for a clearly stated system boundary and set of operating conditions.

The difference between actual vapour temperature and the appropriate local saturation temperature at the same pressure, using the correct refrigerant reference.

The difference by which a liquid temperature is below the appropriate saturation reference at its pressure, interpreted with the correct product data.

Pressure referenced to an ideal vacuum, obtained from a positive gauge reading by adding the relevant local atmospheric pressure.

A comparison of admitted or delivered suction-volume flow with geometric displacement, using compatible reference conditions for the specified compressor calculation.

An abnormal entry of liquid into a vapour compressor that can create damaging forces because liquid is much less compressible than vapour.

The useful oil-delivery pressure differential evaluated against the relevant opposing compressor pressure rather than using the gallery indication alone.

An unstable operating phenomenon in a dynamic compressor associated with flow and pressure conditions outside the appropriate stable operating range.

A specifically defined temperature difference between process streams or a stream and refrigerant reference, used with flow and load information to assess performance.

The temperature at which a given moist-air state begins to condense water when cooled at the relevant pressure without changing its moisture content beforehand.

A refrigeration arrangement with separate circuits coupled thermally through an intermediate heat exchanger, rather than one common mixed refrigerant inventory.

A fluid that carries heat between the load and a primary refrigeration heat exchanger, selected for its thermal, hydraulic, and protection requirements.

A range between control switching thresholds in which the output state may depend on the preceding operation, preventing an assumption from one temperature alone.

A control condition that must be satisfied for an operation to be allowed or continued, according to the designed sequence and protection requirements.

A pressure-reference connection used by an appropriate expansion valve to account for the relevant evaporator-outlet pressure in its control force balance.

An established relationship between an instrument indication and a reference quantity, documented so measurement accuracy and any required correction can be assessed.

The facility-specific arrangement of responsibilities, communication, protective actions, evacuation, and competent response for identified abnormal or hazardous situations.

A controlled process addressing the relevant energy and material sources and checking the required safe condition before maintenance or other exposed work.

The required competent verification and authorization that an affected space is suitable for the intended entry, not merely an absence of odor.

A protective function that limits specified overpressure conditions through an approved device and discharge arrangement, rather than serving as routine temperature regulation.

The range of saturation temperatures across phase change for a zeotropic blend at a specified pressure, requiring appropriate dew or bubble references.

A change in blend proportions that can occur because components partition differently between phases during leakage or handling under particular conditions.

A time-linked record of actual plant readings, states, alarms, observations, and actions that supports trend analysis, handover, and accountable follow-up.

The defined set of plant components and energy transfers included in a performance calculation, necessary for consistent interpretation and comparison of results.

The heat-transfer requirement associated with temperature change under the stated model, distinct from latent moisture-removal effects.

The energy associated with moisture or phase change under the actual air-conditioning model, distinct from dry-bulb temperature change alone.

The allocation and verification of appropriate air quantities through the actual distribution system, not merely opening every damper fully.

The planned drainage, trapping, pumping and discharge arrangements for moisture removed by the equipment under its actual operating conditions.

The recorded actual settings, conditions, observations and required tests used to evaluate installation performance and restored protection.

The suitability of refrigerant piping, joints, material, sizing and service conditions for the actual system rather than a similar-looking installation.