TERMINOLOGY USED IN HVAC PART-1 

Some common difinition used in hvac industry-

ABSOLUTE PRESSURE- Pressure measured with a base of zero.

ABSOLUTE TEMPERATURE- A temperarure scale expressed in °F or °C using absolute zero as a base. Refered to as the Rankine or Kelvin Scale. 

ABSOLUTE HUMUDITY- The weight of water vapour in a given amount of air. Grain per cubic foot.

AMBIENT- Refers to the temperature surrounding a body or units under test.

AIR CONDITIONING- The process of controlling the temperature, humidity, cleanliness and distribution of the air.

AIR STANDARD CONDITIONS- Conditions at which BTU ratings for summer air conditioning equpiment is rated. 95 °F  dry bulb, 75 °F  wet bulb at the condenser inlet and 80°F  dry bulb, 67°F  wet bulb at the evaporator inlet. 

ATMOSPHERIC PRESSURE- The weight of a 1 square inch column of the earth's atmospheric. At sea level this pressure is 14.696 pounds square inch (psi).

BIMETAL-  Two metals with different rates of expansion fastend together. When heated or cooled they will warp and can be made to open or close a switch or valve.

BOILING POINT- The temperture at which the addition of any heat will begin a change of state from a liquid to vapour. 

BRITISH  THERMAL UNIT (BTU)- The amount of heat necessary to change the temperature of 1 pound of pure water by 1 degree Fahrenheit(°F) 

CAPILLARY TUBE- A refrigerant control consisting of a small diameter tube which controls flow by restriction. They are carefully sized by inside diameter and leanth for each particular application.

CENTIGRADE- A temperature scale with the freezing point of water 0° and boiling point 100° at sea level.

CHEAK VALVE- A valve design to permit flow in one direction only.

 

COMPRESSION- The reduction of volume of a vapour or gas by mechanical means.

COMPRESSION RATIO- The ratio determined by dividing the discharege pressure in PSI, by the suction pressure in PSI.

COMPRESSOR- A mechanical device used to compress gases. Three main type are: reciprocating, centrifugal and rotrary.

CONDENSATION POINT- The temperature at which the removal of any heat will begin a change of state from vapour to liquid.

CONDENSING MEDIUM- The substance, usally air or water, to which the heat in a condensor is transferred.

CONDENSING UNIT- The portion of refregeration system where the compression and condensation of refrigerant is accomplished. Some refferd to as the "high side".

CONDUTION- The transfer of heat from molecule to molecule within a substance.

CONVECTION- The transfer of heat by a moving fluid.

COP- Ratio of work performed or a complished or accomplished as compared to the energy used.

CRANKCASE HEATER- Electric heating element that is used to heat the compressor crankcase to prevant migrating refrigerant from condensing and diluting the crankcase oil during the off-cycle.

CUBIC FEET PER MINUTE (CFM)- A common means of assiging quantitative values to volumes of air in transit, usually abbreviated CFM.