Copyright Goodheart-Willcox Co., Inc. Chapter 32 Residential Split Air-Conditioning Systems 805 10 32.4.1 Installing a Condensing Unit Most condensing units blow outdoor air over the con- denser coil in order to cool the coil. However, some sys- tems have water-cooled condensers. Condensing units can be installed in a number of different locations. Some Life Cycle Cost Analysis Often, the initial cost (purchase and installation) of a system is less than 10% of the lifetime cost of the system. When comparing systems, it is often beneficial to compare the total life cycle costs of the systems rather than the initial costs. This type of evaluation takes into consideration such factors as energy efficiency and maintenance costs. Thinking Green condensing units are mounted inside the building. In this arrangement, ducts bring outdoor air to the condenser and discharge warm air outside. Some condensing units are mounted on an outside wall. A popular practice is to mount a condensing unit on a permanent concrete slab or manufactured pad outside the building. This slab is located 12″ to 24″ (31 cm to 61 cm) away from the building. A concrete slab at least 4″ (10 cm) thick and reinforced with steel mesh is recommended. Manufactured pads are available in different size and thickness. Be mindful of local building codes to install a slab or pad having the proper thickness and the proper distance from any building or obstruction. Adequate work space is necessary. A condensing unit should be installed so that outlet air moves in the same direction as the pre- vailing summer winds. Figure 32-13 shows various con- densing unit arrangements. Top View Side View A B C Goodheart-Willcox Publisher Figure 32-13. Three types of air-cooled condensing units for residential air-conditioning installations. A—Condensing unit inside building. B—Unit hung on outer wall (usually through window). C—Unit mounted on concrete slab outside building.