GLOSSARY OF HVAC TERMS

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Neptune Air Conditioning, Inc.

Heating - Ventilation - Air Conditioning - Winter Storage - Air Duct Cleaning - NYC

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Neptune Air Conditioning, Inc.

477 Madison Avenue
6th Floor, # 6948

Phone:  646.863.2132  

E-mail: info@neptuneac.com

  • ABSOLUTE HUMIDITY - The weight of water vapor in a given amount of air.
  • ABSOLUTE PRESSURE - Pressure measured with the base of zero.
  • ABSOLUTE TEMPERATURE - A temperature scale expressed in degrees oF or oC using absolute zero as a base. Referred to as the Rankin or Kelvin scale.
  • ABSOLUTE ZERO - The temperature at which molecular activity theoretically ceases. -456.69 oF or -273.16oC.
  • AIR CONDITIONING - The process of controlling the temperature, humidity, cleanliness and distribution of the air.AIR, Standard Conditions - Conditions at which capacity ratings for air conditioning equipment is rated.
  • AMBIENT - Refers to the temperature surrounding a body or unit under test.
  • ATMOSPHERIC PRESSURE - The weight of a 1 unit column of the earth's atmosphere.
  • BIMETAL - Two metals with different rates of expansion fastened together. When heated or cooled they will warp and can be made to open or close a switch or valve.
  • BOILING POINT - The temperature at which the addition of any heat will begin a change of state from a liquid to a vapor.
  • BRITISH THERMAL UNIT (BTU) - The amount of heat necessary to change the temperature of 1 pound of pure water 1 degree Fahrenheit (oF).
  • CAPILLARY TUBE - A refrigerant control consisting of a small diameter tube which controls flow by restriction. They are carefully sized by inside diameter and length for each particular application.
  • CENTIGRADE - A temperature scale with the freezing point of water 0 oC and the boiling point 100 oC at sea level.
  • CHECK VALVE - A valve designed to permit flow in one direction only.
  • COMPRESSION - The reduction of volume of a vapor or gas by mechanical means.
  • COMPRESSION RATIO - The ratio determined by dividing the discharge pressure, in PSI (Pa), by the suction pressure in PSI (Pa).
  • COMPRESSOR - A mechanical device used to compress gases. Three main types - reciprocating, centrifugal and rotary.
  • CONDENSATION POINT - The temperature at which the removal of any heat will begin a change of state from a vapor to a liquid.
  • CONDENSING MEDIUM - The substance, usually air or water, to which the heat in a condenser is transferred.
  • CONDENSING UNIT - The portion of a refrigeration system where the compression and condensation of refrigerant is accomplished. Sometimes referred to as the 'high side'.
  • CONDUCTION - The transfer of heat from molecule to molecule within a substance.
  • CONTACTOR - An electromagnetic actuated relay. Usually used to refer to the relay which closes the circuit to a compressor.
  • CONVECTION - The transfer of heat by a moving fluid.
  • COOLING ANTICIPATOR - A resistance heater (usually not adjustable) in parallel with the cooling circuit. It is 'on' when the current is 'off", adding heat to shorten the off cycle.COP - Ratio of work performed or accomplished as compared to the energy used.
  • CUBIC FEET PER MINUTE - A common means of assigning quantitative values to volumes of air in transit, usually abbreviated CFM.
  • CYCLE - The complete course of operation of a refrigerant back to a selected starting point in a system.
  • DENSITY - Mass or weight per unit of volume.
  • DISCHARGE LINE - A tube used to convey the compressed refrigerant vapor from the compressor to the condenser inlet.
  • DISCHARGE PRESSURE - The pressure read at the compressor outlet. Also called head pressure or high side pressure.
  • DRY AIR - Air which contains no moisture vapor.
  • DRY BULB TEMPERATURE - Temperature read with an ordinary thermometer.
  • EFFECTIVE TEMPERATURE - An arbitrary concept which combines into a single value the effect of temperature, humidity, and air movement as sensed by the human body.
  • EQUIVALENT LENGTH - That length of straight tubing which has the same pressure drop as the fitting, valve or accessory (of the same nominal size) being considered.
  • EVAPORATIVE COOLING - The cooling effect of vaporization of a liquid in a moving air stream.
  • EVAPORATOR - A device in which a liquid refrigerant is vaporized. Some superheating usually takes place.
  • EVAPORATOR SUPERHEAT - The actual temperature of the refrigerant vapor at the evaporator exit as compared to the saturated vapor temperature indicated by the suction pressure.
  • EXTERNAL STATIC PRESSURE - The sum of the static and velocity pressures of a moving air system at the point of measurement.
  • FAHRENHEIT - A temperature scale with the freezing point of water 32 oF and the boiling point 212 oF at sea level.
  • FEET PER MINUTE - A term assigned to a velocity of a moving air stream, usually express FPM.
  • FILTER-DRIER - A device that removes moisture, acid and foreign matter from the refrigerant.
  • FLASH GAS - Instantaneous evaporation of some liquid refrigerant at the metering device due to pressure drop which cools the remaining liquid refrigerant to desired evaporation temperature.
  • FREEZING POINT - The temperature at which the removal of any heat will begin a change of state from a liquid to a solid.
  • GAUGE PRESSURE - Pressure measured with atmospheric pressure as a base.
  • HEAT - A form of energy causing the agitation of molecules within a substance.
  • HEAT EXCHANGER - A device for the transfer of heat energy from the source to the conveying medium.
  • HEAT FLOW - Heat flows from a warmer to a cooler substance. The rate depends upon the temperature difference, the area exposed and the type of material.
  • HEAT OF COMPRESSION - The heat added to a vapor by the work done on it during compression.
  • HEAT OF THE LIQUID - The increase in total heat (Enthalpy) per pound of a saturated liquid as its temperature is increased above a chosen base temperature. (Usually - 40 oF for refrigerants).
  • HEAT TRANSFER - The three methods of heat transfer are conduction, convection and radiation.
  • INCHES OF MERCURY - Atmospheric pressure is equal to 29.92 inches of mercury.
  • LATENT HEAT - Heat that produces a change of state without a change in temperature; i.e., ice to water at32 oF or water to steam at 212 oF.
  • LATENT HEAT OF CONDENSATION - The amount of heat energy in BTU's that must be removed to change the state of one pound of a vapor to one pound of liquid at the same temperature.
  • LATENT HEAT OF FUSION - The amount of heat energy, in BTU's required to change the state of one pound of a liquid to one pound of solid at the same temperature.
  • LATENT HEAT OF MELTING - The amount of heat energy, in BTU'S, that must be removed to change the state of one pound of solid to one pound of liquid at the same temperature.
  • LATENT HEAT OF VAPORIZATION - The amount of heat energy in BTU's required to change the state of one pound of a liquid to one pound of vapor at the same temperature.LIFT - To elevate a fluid from one level to a higher level.
  • LIQUID LINE - A tube used to convey the liquid refrigerant from the condenser outlet to the refrigerant control device of the evaporator.MANOMETER - A tube filled with a liquid used to measure pressures.
  • MBH - One MBH is equivalent to 1,000 BTU's per hour.
  • MEAN TEMPERATURE DIFFERENCES - The mean of difference between the temperature of a fluid receiving and a fluid yielding heat.
  • MELTING POINT - The temperature at which the addition of any heat will begin a change of state from a solid to a liquid.
  • MERCURY MANOMETER - Used to measure vacuum in inches of mercury.
  • MICRON - A unit used to measure high vacuums. One micron equals 1/25,400 of one inch mercury.
  • MOLLIER CHART - A psychrometric chart. How-to convert between Mollier and Psyhrometric charts?
  • MUFFLER - Device installed in hot gas line to silence discharge surges.
  • OIL SEPARATOR - A device for separating out oil entrained in the discharge gas from the compressor and returning it to the crankcase.