ASHRAE Terminology

A Comprehensive Glossary of Terms for the Built Environment
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instantaneous heater

a self-contained packaged water-heating device that is capable of providing a continuous supply of hot water at a predetermined temperature without any storage capacity. Energy sources can be fuel fired (natural gas/propane), electric, or steam fired. The term is typically utilized for domestic water-heating applications, but pool, spa, and radiant heating systems are also an application. Another term that is used on smaller heaters is point-of-use heaters. Some manufacturers allow for multiple unit installations when the need for larger capacity is required.

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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.