AFUE: Annual Fuel Utilization Efficiency, a rating that reflects the efficiency of a gas furnace in converting fuel to energy. A rating of 90 means that approximately 90% of the fuel is utilized to provide warmth to your home, while the remaining 10% escapes as exhaust.

BTU: British Thermal Unit. In scientific terms, it represents the amount of energy required to raise one pound of water one degree Farenheit. One BTU is the equivalent of the heat given off by a single wooden kitchen match. For your home, it represents the measure of heat given off when fuel is burned for heating or the measure of heat extracted from your home for cooling.

Carbon Monoxide: carbon monoxide is a colorless, odorless gas that is created by the incomplete combustion of fossil fuel ( natural gas, oil) If inhaled carbon monoxide could cause illness or death. At levels up to 35 ppm (parts-per-million) carbon monoxide can cause headaches, dizziness, nausea and fatigue. At levels over 200 ppm, carbon monoxide can cause death.

CFM: A standard of airflow measurement. Cubic Feet Per Minute. A typical system produces 400 CFM per ton of air conditioning.

Evaporator The coil is a network of tubes filled with refrigerant .The coil located inside the home takes the heat and moisture out of the air as liquid refrigerant evaporates Called the evaporator coil or cooling coil.

Condenser: The coil is a network of tubes filled with refrigerant. Located in the outdoor unit, the coil dissipates heat from the refrigerant, changing the refrigerant from a Gas or vapor to liquid.

Compressor: The compressor is a pump that circulates refrigerant from the indoor coil to the outdoor condensing unit and back again. It's called the heart of the system.

Heat Exchanger: On a gas furnace, the heat exchanger is a large metal item which is heated by the gas burners and transfers it heat energy to the air stream where the blower convey the heated air into the home.

HSPF: Heating Seasonal Performance Factor, the rating system for the heating efficiency of the heat pump in a home comfort system. The higher the HSPF. the more efficient the system is when called upon to heat your home.The lowest HSPF rating is 6.8

Humidifier: A device that injects water vapor into heated air as the air is expelled from the furnace. An humidity level of 55% RH is a good comfort level for most people.

Line Set: The line set is the two copper lines used to transfer refrigerant between the condensing unit and the evaporator coil. The larger of the two lines , the SUCTION LINE ,is insulated to maintain the cool refrigerant gases or vapors so that the cool gases can cool the compressor motor. The smaller copper line, called the LIQUID LINE, transfers liquid refrigerant to the metering device of the evaporator coil. Note: on a heat pump unit, operating in the heating mode, the suction line gas flow and gas temperature changes, toward the evaporator and is hot gas from the outdoor section of the heat pump.

Package Unit: A comfort system that contains both the condenser and the air handling sections in a single unit. Installed at ground level outside a home, it's connected to the duct system inside through the side wall of the home. Package units can be Heat pumps, Gas furnaces with air conditioning (sometimes Called a GasPack) , Electric furnace with air conditioning, Cooling only package units, and Heating only package units..

REVERSING VALVE: A device in a heat pump that reverses the flow of refrigerant as the system is switched from cooling to heating. Also called a changeover valve or Four way valve .

SEER: Seasonal Energy Efficiency Ratio. SEER rates the cooling efficiency of an air conditioning system, much like the "mile per gallon" rating used for automobiles. The higher the SEER rating, the more efficient the system.The SEER number is the total amount of cooling per season divided by the electricity the unit uses during the season. In other words, if the unit produces 10.0 BTU's of cooling for each watt consumed by the unit; the SEER would be 10.0 SEER. If the unit produces 11.15 BTU's per watt, the SEER would be 11.15..

Split System: A split system separates the condenser section and the air handling section into two units. The condenser unit is installed outside your home and is connected to the air handler inside, via two copper pipes to transfer refrigerant between the condenser coil and the evaporator coil in the air handler. This type of system offers many advantages including better operating efficiency, lower noise levels and versatility of installation...

TON: A unit of measurement used for determining cooling capacity. One ton is the equivalent of 12,000 BTU's per hour. One ton is equal to the BTU's required to melt one TON of ice in 24-hour period. Since there are 12,000 BTU's in a ton, a 3 ton air conditioning unit will produce 36,000 BTU's and so forth..