Glossary of Terms

Air Change: The amount of air required to completely replace the air in a room or building; not to be confused with re-circulated air.

Air Conditioner: Assembly of equipment for the simultaneous control of air temperature, relative humidity, purity, and motion.

Air Handler: The portion of the central air conditioning or heat pump system that moves heated or cooled air throughout a home’s ductwork. In some systems a furnace handles this function.

BTU (British Thermal Unit): The standard of measurement used for measuring the amount of heat required to raise the temperature of one pound of water by one degree (Fahrenheit).

BTUH: The number of BTUs in an hour.

Carbon Monoxide: Carbon Monoxide (CO) is a colorless, odorless gas produced by burning any fuel. CO is poisonous and symptoms of CO poisoning are similar to those of the flu: headaches, fatigue, shortness of breath, nausea and dizziness. The Consumer Product Safety Commission (CPSC) recommends a yearly, professional inspection.

CFM (Cubic Feet per Minute): The abbreviation for cubic feet per minute; commonly used to measure the rate of air flow in an air conditioning system.

Compressor: The pump that moves the refrigerant from the indoor evaporator to the outdoor condenser and back to the evaporator again. The compressor is often called “the heart of the system” because it circulates the refrigerant through the loop.

Freon: A general term used to identify, any of a group of partially or completely halogenated simple hydrocarbons containing fluorine, chlorine or bromine, which are used as refrigerants.

Heat Pump: An air conditioner that contains a valve that allows it to alternate between heating and cooling.

Heating Seasonal Performance Factor (HSPF): Total heating output of a heat pump in British Thermal Units during its normal usage period for heating divided by the total electrical energy input in watt-hours during the same period.

HVAC: Heating, Ventilation, and Air Conditioning.

Load Calculation: A mathematical design tool used to determine the heat gain and heat loss in a building so that properly sized air conditioning and heating equipment may be installed.

Matched System: A heating and cooling system comprised of products that have been certified to perform at promised comfort and efficiency when used together, and used according to design and engineering specifications.

Package System: A piece of air conditioning and heating equipment where all components are located in one cabinet. Used occasionally in residential applications, the package unit is installed either beside or on top of the home.

Refrigerant Lines: Set of two copper lines connection the outdoor unit and the indoor unit.

Relative Humidity: The ratio of the amount of vapor contained in the air to the greatest amount the air could hold at that temperature. Normally expressed as a percentage.

SEER (Seasonal Energy Efficiency Ratio): A rating that denotes the efficiency of air conditioning equipment. It is the amount of cooling your equipment delivers for every dollar spent on electricity. It is the ratio of cooling delivered by a system, measured in BTUs, to the dollar cost of the electricity to run the system, as measured in watt-hours. This ratio is determined using specified federal test procedures. The higher the SEER, the more efficient the unit. The more efficient the unit, the lower the operating cost.

Split System: A central air conditioner consisting of two or more major components. The system usually consists of a compressor-containing unit and condenser, installed outside the building and a non-compressor – containing air handling unit installed within the building. This is the most common type of system installed in a home.

Supplementary Heat: The auxiliary or emergency heat, usually electrical resistance heat, provided at temperatures below a heat pump’s balance point.

Tonnage: The unit of measure used in air conditioning to describe the cooling capacity of a system. One ton of cooling is based on the amount of heat needed to melt one ton (2000 lbs.) of ice in a 24 hour period. One ton of cooling is equal to 12,000 Btu/hr.

Ventilation: The process of supplying or removing air, by natural or mechanical means, to or from any space. Such air may or may not have been conditioned.

Zoning: The practice of providing independent heating and/or cooling to different areas in a structure. Zoning typically utilizes a system controller, zoning dampers controlled by a thermostat in each zone, and a bypass damper to regulate static pressure in the supply duct.