Halide Refrigerants - Refrigerants containing halogen chemicals.

 

	Halide Torch - A propane torch used in the process of leak checking.
	Halogens - Substance containing fluorine, chlorine, bromine, and iodine.

 

Hanger – A device attached to walls or other structure for support of pipe lines.

Head – Is another word for Pressure.

 

Head, Static - Is the amount of pressure a pump has to work against.

 

Head, Total Static - Static head from the surface of the supply source to the free discharge surface.

Head Friction - Head required to overcome friction of the interior sur­face of a conductor and between fluid particles in motion.

 

	Head Pressure - The discharge pressure in the system.
	Head Pressure Control - A Pressure actuated safety  control which opens elec­trical circuit if high-side pressure becomes too high.

 

Head Velocity - Height of fluid equivalent to its velocity pressure inflow­mg fluid.

 

Header - A piping arrangement where several pipes are distributed from one common pipe.

 

	Heat - Basic form of energy that may be partially converted into other forms of energy.
	Heat Anticipator - Is a wire-wound variable resistor that is placed near the bimetal element of a thermostat to provide extra sources of heat to help prevent the thermostat from allowing the system to overheat the room.  Connected in series with the R-W circuit. Causes the spiral bi-metal element to open before  room set-point is reached.
	Heat Content-  See total heat.
	Heat Exchanger - A refrigeration component used to transfer heat from one source to another.

 

Heat Intensity – The heat in a substance as measured by the dry bulb temperature.

 

Heat Lag - The time it takes for heat to travel through a substance.

 

Heat Leakage -Flow of heat through a substance.

 

Heat Load – The amount of heat removed by a given system over a 24hour period.

 

Heat Source - The area or media from which heat is removed from .

 

Heat of Compression - Mechanical energy of pressure changed into energy of heat.

 

Heat of Fusion - Heat released from a substance when a change of state occurs from a liquid to solid state.

 

Heat of Respiration - Process by which oxygen and carbohydrates are assimilated by a substance; also when carbon dioxide and water are given off by a substance.

 

Heat Recovery System - Produces and stores hot water by transfer­ring heat from condenser to cooler water.

 

Heat Sink - The area or media where heat is absorbed into.

 

Heat Transfer - Movement of heat from one body or substance to another.

 

Heat Transfer Module - Primary system of heat transfer in a glycol water solution forced-air furnace. The heat transfer module contains the ignitor, burner, and primary solution-circulating coil.

 

Heating Coil - Heat transfer device consisting of a coil of piping, which releases heat.

 

Heating Control – A device that controls the temperature of a substance by operating a unit which releases heat.

 

Heating Value -  Amount of heat which may be obtained by burning a fuel. The heating value is usually expressed in Btu per lb

 

Hermetic Compressor – A sealed compressor that the internal motor is not serviceable.  housing.

 

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

 

Hermetic system - Refrigeration system which has a compressor driven by a motor contained in compressor dome or housing.

 

Hertz (Hz) - Correct terminology for cycles per second.

 

Hg. (MERCURY) - Heavy silver-white metallic element; only metal that is liquid at ordinary room temperature.

 

High Efficiency Gas Furnace – A furnace with efficiencies from 85 to 95 percent.

 

High Side – The side of the refrigeration system that the condensing takes place.

 

High Pressure Cut Out – See head Pressure Control

 

High Side Float – A metering device that controls the level of the liquid refrigerant in the high-pressure side of the device.

 

High-Vacuum Pump – A pump that can create a vacuum in the 1000 to 1 micron range.

 

Hollow-Tube Gasket – A sealing device made of rubber or plastic with tubular cross section.

 

Holdover - The ability to stay cold after heat removal from the evaporator stops.

 

Horsepower-A unit of power. Work done at a rate of 33,000 foot-pounds per minute, or 550 foot -pounds per second.

 

Hot Gas Bypass – A piping system that by passes hot refrigerant gas from condenser into low-pressure side.

 

Hot Gas  Defrost - Defrosting system in which hot refrigerant gas from the high side is directed through evaporator for short period of time and at predetermined intervals, in order to remove frost from evaporator.

 

Hot Junction - That part of thermoelectric circuit which releases heat.

 

Hot water Heating System – A system in which water is circulated through heating coils

Hot Wire – The wire that has the voltage difference between it and ground.

Humidifier – A device used to add humidity to a space.

Humidistat - A control which is operates the humidifier and is affected by changing humidity

Humidity – Is Moisture in the air.

 

HVAC- Heating Ventilation and Air Conditioning

 

Hydraulics - Branch of physics having to do with the mechanical prop­erties of water and other liquids in motion.

 

	Hydrocarbons - A series of chemicals of similar chemical nature ranging from methane through butane , octane ... to heave oils.
	Hydrochloric Acid - An acid formed when appreciable quantity of moisture are present in A CFC or methyl chloride.
	Hydrolysis - Reaction of a CFC with water . Acids are generally formed.
	Hydrostatic Pressure - The pressure created when trying to compress a liquid.
	Hydrometer - A instrument used to measure specific gravity of a liquid.
	Hydraulic – A heating system which circulates a heated fluid, usually water, through baseboard coils by means of a circulating pump which is con­trolled by a thermostat.
	Hygrometer – An instrument used to measure the amount of moisture in the air.
	Hygroscopic - Ability of a substance to absorb and release moisture and change physical dimensions as its moisture content changes.