HVAC Directory



ASHRAE -The American Society of Heating, Refrigerating and Air-Conditioning Engineers(​ASHRAE​ /ˈæʃreɪ/ ASH-ray) is an American professional association seeking toadvance heating, ventilation, air conditioning and refrigeration (HVAC&R) systemsdesign and construction.

ANSI - ​ANSI​ (American National Standards Institute) is the primary organization for fostering thedevelopment of technology standards in the United States. ​ANSI​ works with industry groups and isthe U.S. member of the International Organization for Standardization (ISO) and the InternationalElectrotechnical Commission (IEC).

Approach - The temperature difference between the water leaving the cooling tower and the wet bulbtemperature of the tower’s entering air.

Approach temperature - The difference in temperature between the refrigerant and the leaving waterin a chilled water system

Atmospheric pressure - the weight of the atmosphere’s gases pressing down on the earth. Equal to14.696 at sea level and 70 degrees fahrenheit.

Automatic Defrost - Using automatic means to remove ice from a refrigeration coil at timedintervals


Back electromotive Force - This is the voltage generating effect of an electric motor’s rotor turningwithin the motor

Baseboard heating - Convection heaters providing whole house, spot, or individual room heating. Theheat is normally provided by electrical resistance or hot water

Boiler - A container in which a liquid may be heated using any heat source. When the liquid is heatedto the point that vapor forms and is used to circulating medium, it is called a steam boiler.

BTU - British Thermal unit the amount of heat required to raise the temperature of 1 lb. of water 1degree fahrenheit.

B-Vent - Doubled wall venting system for gas stoves or other gas appliances using approved pipingthrough the roof or ino a chimney.


Capacitor - electrical storage device usd to start motors and to improve the efficiency of motors.Capacity - The ratings system of equipment used to heat or cool substances.

Carbon Dioxide - A by-product of natural gas combustion that is not harmful

Carbon Monoxide - A poisonous, colorless, odorless, tasteless gas generated by incompletecombustion.

CFM - cubic feet per minute

Check Valve - a device that permits fluid to flow in one direction

Circuit breaker - a device that opens a electric circuit when an overload occurs

Combustion air - primary and/or secondary air. Primary air enter the furnace before the combustionprocess take place. Secondary air is air introduced into a furnace after combustion and supports combustion.

Compression Ratio - a term used with compressors to describe the ratio between the high and lowpressure sides of the compression cycle. It is calculated by dividing the absolute discharge pressureby the absolute suction pressure

Compressor - a vapor pump that pumps vapor refrigerant or air from one pressure level to a highpressure level

Condensate - the moisture that forms of the evaporator coil

Contactor - a larger version of a relay. It can be repaired or rebuilt and has movable and stationarycontacts.

Corrosion - A chemical action that eats into or wears away material from a substance.

Crankcase heater - A ​crankcase heater​ is an electrical component in a compressor in an air-conditioning system, heat pump system, or chiller system. The ​crankcase heater​ is normally onall the time, even when the unit is not running, though temperature sensors and set points may turn itoff when not needed.


Dust mites - microscopic spider-like insects. ​Dust mites​ in the air conditioning are ahygiene nightmare waiting to drop into a room. ... These ​Mites​ are found in filters, bedding, carpets, clothing and many other soft furnishings. People allergic to ​dust mitesare allergic to the proteins in their droppings which cause the allergy.

Diffuser - ​device for reducing the velocity and increasing the static pressure of a fluidpassing through a system”. The fluid's static pressure rise as it passes though a duct iscommonly referred to as pressure recovery.

Damper - An ​HVAC damper​ (also called a duct ​damper​) is a movable plate, located in the ductwork,that regulates airflow and redirects it to specific areas of the home. ​Dampers​ are typically used inzoning or “zone control” systems.


Economizer - ​The device is built in or retrofitted to rooftop equipment. It allows the unit to useoutdoor air for cooling, provided the ambient air is below a certain temperature and the humidityis below a certain percentage. This type of cooling is often referred to as "free cooling" becauseit cools the building without the use of energy required to run a compressor.

ERV (energy recovery ventilator) - he energy recovery process of exchanging the energycontained in normally exhausted building or space air and using it to treat (precondition)the incoming outdoor ventilation air in residential and commercial ​HVAC​ systems.

Enthalpy - the amount of heat a substance contains from a predetermined base or point.

PA - ​The United States Environmental Protection Agency (​EPA​) has established a mandatoryprogram that requires all technicians to be certified before performing maintenance, service, repair,or disposal of an appliance that contains ​refrigerant​ chemicals. ... UNIVERSAL - for servicing allappliances.


Filter Drier - A type of refrigerant filter that includes a desiccant material that has an attraction formoisture. The filter drier will remove particles and moisture from the refrigerant and oil.

Freon - the cooling agent used in most air conditioning systems. Every air conditioning system needsa refrigerant (also called a coolant) that actually creates the cool air. As of 2020 Freon is no longerbeing created due to Federal Restrictions.

Furnace - Used to convert heating energy such as fuel oil, gas, or electricity, to usable heat. It usuallycontains a heat exchanger , a blower and the controls to operate the system.


Gasket - A thin piece of flexible material used between two metal plates to prevent leakage.

Glycol - Antifreeze solution used in the water loop of geothermal heat pumps.