COOLING TERMS A-coil - The part of the air conditioner that is located inside the air handler. Its primary function is to absorb the heat from the air in your house. There’s probably a secondary function, but who knows what it is? Condensation line - A line that carries moisture to the floor drain. As heat is removed from the air passing through your air conditioning unit, water present in the air condenses into moisture. These condensation lines are an essential part of your home’s air conditioning system. Know them and love them. Condenser - The portion of central air conditioning system that is located outside the home and functions as a heat transfer point for dispelling heat to the outside air. Goodbye heat. Heat Gain - The amount of heat gained, measured in BTU's, from a space to be conditioned, at the local summer outdoor design temperature and a specified indoor design. Manual/Auto zone duct - Zone ducts (not ducks) separate trunk lines to each floor or zone. Thermostats in each zone control electronic zone dampers. Manual ones are operated by hand and must be adjusted seasonally. Plenum - Airflow passage made of duct board, metal, drywall, or wood. Joins supply and return ducts with HVAC equipment. SEER - The Seasonal Energy Efficiency Ratio is an energy efficiency rating for air conditioners. The higher the SEER, the better the energy performance, the more you save. The DOE's established minimum SEER rating for cooling is 10.00. Has nothing to do with SEER sucker suits. Warm-air plenum - Plenum that takes air from a furnace and moves it into the duct system to circulate through the house. The air conditioner coil may be located inside this plenum. Zoned system - A method of partitioning a home into independently controlled comfort zones for enhanced comfort and efficiency. A zone is the area that one thermostat is controlling. For example: A two-story house with a thermostat on each floor has two zones, one for each floor. Zone Control Systems eliminate "hot and cold spots" and can help save energy. A Zone Control System splits your house into areas with common heating and cooling requirements, and puts every "zone" under the control of its own thermostat. Each zone is effectively heated or cooled independently of the others. A system of electronically controlled dampers directs heated or cooled air to where it is needed -- reducing energy bills as much as 30%. Now you can zone out.