ASHRAE Terminology

A Comprehensive Glossary of Terms for the Built Environment
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net positive suction head (NPSH)

minimum head at the pump inlet to prevent the liquid being pumped from flashing into a vapor at that temperature and pressure and potentially causing the pump to cavitate. There are 2 types of NPSH values: net positive suction head available (NPSHA) and net positive suction head required (NPSHR). NPSHA is actual or available head at the pump impeller and should be greater than the vapor pressure of operating fluid at the operating temperature. NPSHR is the value stated by the pump manufacturer that is the minimum required head at the pump impeller. NPSHA should be greater than NPSHR. Values of NPSH are expressed as head in units of feet (kPa).

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About ASHRAE Terminology

ASHRAE Terminology, a free resource, is a comprehensive online glossary of more than 3700 terms and definitions related to the built environment, with a focus on heating, ventilating, and air conditioning (HVAC), as well as refrigeration, building envelope, electrical, lighting, water and energy use, and measurement terms.

This searchable glossary was designed for use by engineering professionals but is also useful for architects, building owners and operators, educators, public officials, and homeowners.

The terms in ASHRAE Terminology have been assembled and defined and are updated on an ongoing basis by ASHRAE Technical Committee (TC) 1.6, Terminology. TC 1.6 is concerned with terminology, nomenclature, definitions, abbreviations, symbols, and the International System (SI) and Inch-Pound (I-P) units used in the fields of heating, ventilating, air conditioning, water heating, and refrigeration.

To request a free electronic file of the complete list of terms and definitions, email ashraetermseditor@ashrae.org.