An air handler (also called an air handling unit or AHU) is the indoor component of a split HVAC system. It houses the evaporator coil, blower motor, filter, and sometimes the electric heating elements or heat pump components, and circulates conditioned air throughout the building via ductwork.
In a typical split system, the air handler works in conjunction with an outdoor condenser or heat pump unit. Refrigerant lines connect the two units. The air handler is usually installed in a closet, attic, basement, or utility room.
Air handler sizing must match the outdoor unit’s capacity. Mismatched systems operate inefficiently and experience increased wear. Air handlers should be inspected annually and filters changed every 1-3 months depending on usage.