Home Education Glossary of Terms
Glossary of Technical Terms - H

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Halide Refrigerants: Family of refrigerants containing halogen chemicals

Halide Torch: Type of torch used to detect halogen refrigerant leaks

Head: As used in this course, head refers to a pressure difference (See Pressure Head, Pump Head, Available Head)

Header: A piping arrangement for inter-connecting two or more supply or return tapping of a boiler

Head Pressure: Pressure which exists in condensing side of refrigerating system

Head-Pressure Control: A pressure-activated control that prevents the head pressure from falling too low.

Head, Static: Pressure of fluid expressed in terms of height of column of the fluid, such as water or mercury.

Head, Velocity: In flowing fluid, height of fluid equivalent to its velocity pressure.

Heat: Form of energy the addition of which causes substances to rise in temperature; energy associated with random motion of molecules

Heat Anticipator: A resistor in a room thermostat that shuts the heating cycle off prematurely

Heat Exchanger: Device used to transfer heat from a warm or hot surface to a cold or cooler surface.

Heat Lag: When a substance is heated on one side, it takes time for the heat to travel through the substance.

Heat Load: The amount of heat that must be removed from the air conditioned or refrigerated space in order to maintain the design temperature.

Heat Loss: The rate of heat transfer from a heated building to the outdoors

Heat of Compression: The heat added to the refrigerant by the work being done by the compressor

Heat of fusion: The heat released in changing a substance from a liquid state to a solid state.

Heat of Respiration: When carbon dioxide and water are given off by foods in storage.

Heat Pump: Air conditioning system that is reversible so as to be able to remove heat from or add heat to a given space.

Heat Sink: The material in which the refrigeration system discards unwanted heat.

Heat Transfer: Movement of heat from one substance to another

Heating Value: The number of Btu produced by the combustion of one cubic foot of gas

Henry: Abbreviated H. The unit of inductance

Hermetic: Completely sealed

Hermetic Motor: Compressor drive motor sealed within same casing which contains compressor

High Side: Parts of a refrigerating system which are under condensing or high side pressure

High Velocity System: Usually large commercial or industrial air distribution systems designed to operate with static pressures of 6 to 9 inches water gauge.

Horsepower: A unit of power equal to 33,000 foot pounds of work per minute

Hot Gas Defrost: A defrosting system in which hot refrigerant gas from the high side is directed through evaporator.

Hot Gas Line: The line that carries the hog discharge gas from the compressor to the condenser

Hot Junction: That part of thermoelectric circuit which releases heat

Humidifiers: Device used to add humidity

Humidistat: An electrical control which is operated by changing humidity

Humidity: Moisture in air

Hydrocarbon: Any of a number of compounds composed of carbon and hydrogen

Hydrometer: Floating instrument used to measure specific gravity of a liquid

Hydronics: Pertaining to heating or cooling with water or vapor

Hygrometer: An instrument used to measure degree of moisture in atmosphere

Hygroscopic: Ability of a substance to absorb and retain moisture

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