Terms & Definitions

AFUE (Annual Fuel Utilization Efficiency)
The AFUE is the most widely used measure of a furnace's heating efficiency. It measures the amount of heat actually delivered to your house compared to the amount of fuel you must supply to the furnace. Thus a furnace that has an 80% AFUE rating converts 80% of the fuel that you supply to heat - the other 20% is lost out of the chimney.

Air Handler
The evaporator section of an air conditioning system that circulates and delivers the conditioned air. The air handler is often referred to as the indoor unit. It contains the evaporator coil, indoor fan motor and heat strip.

BTU (British Thermal Unit)
A measure of the quantity of heat required to raise the temperature of a pound of water 1 degree Fahrenheit. Used to describe how much cooling or heating a home needs. One ton of cooling is equivalent to 12,000 BTUs per hour.

Compressor
Part of a heat pump or air conditioner outdoor unit that controls the pressure applied to the refrigerant. It is responsible for pumping refrigerant throughout the system.

Condensing Unit
This section of an air conditioning system pumps vaporized refrigerant from the air handler, compresses it, liquefies it and returns it. It is often referred to as the outdoor unit.

Defrost Cycle
The process of removing ice or frost buildup from the outdoor coil during the heating cycle.

Efficiency
A rating on comfort equipment required by the federal government to allow consumers to compare systems. Similar to gas mileage, the higher the rating number, the more efficient the system.

Emergency Heat
The back up electric heat built into a heat pump system. Also called auxiliary heat.

Heat Pump
Cooling and heating equipment which provides a cooling cycle during the summer and a heating cycle during the winter by absorbing heat from the outside air and transferring it inside.

HSPF
Stands for Heating Seasonal Performance Factor. It is a measure of average annual heating efficiency of a heat pump in BTUs per watt of electricity. A higher number means the unit works more efficiently.

Load Calculation
A calculation performed to determine the heating and cooling requirements of your home.

Package Unit
A self contained air conditioning unit that includes both the evaporator and condenser sections within a single cabinet.

Refrigerant
A chemical that cools air as it evaporates.

SEER
Stands for Seasonal Energy Efficiency Rating. It is a measure of annual average cooling efficiency of an air conditioner or heat pump in BTUs per watt of electricity. Similar to miles per gallon for cars, the higher the number, the more efficient the system is.

Straight Cool System
An air conditioning system that includes a cooling cycle only. Gas, oil, or electric strip heating are added to provide heat.

Strip Heating
Also called resistance heating. Air is blown over electrically heated metal coils and circulated into the living space.

Thermostat
A device that allows you to control the temperature inside your home by controlling the heating and cooling cycle of the system.

Ton
Heat pumps and air conditioners are sized in tons. Each ton equals 12,000 BTUs per hour.