Have a component called an air handling unit or AHU (often referred to simply as the “air handler”). If you have the option, choose a conditioned space for placement of the air handler. The advantages of placing the AHU in conditioned space include the following: it is in a more favorable environment; a central location can minimize duct lengths and optimize air flow; there is easier access for maintenance; and any air leaks occur in conditioned space.
Another often ill-considered area of installation concerns the placement of the outside unit (condenser). Manufacturers’ recommendations for proper clearance distances should be followed to the letter to ensure there is no blockage of air flow from the unit. Also, do not vent a clothes dryer within 10 feet of the outdoor unit as dryer lint will cling to the condensing coil, lowering both the system’s efficiency and service life.
Keep in mind that the major component of the system, such as the air handling unit and the condenser, are joined together for the first time at your home. The efficiency and reliability of the entire system are directly related to the care and quality of the work that goes into the planning and installation of the complete system, including the thermostat and duct system.