An air-handling unit, defined as either “recirculating” or “once-through” design, made specifically for outdoor installation. They most often include, internally, their own heating and cooling devices. Very common in some regions, particularly in single-story commercial buildings. Also called a rooftop unit (RTU)
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An air conditioner and heater combined into a single, electrically powered unit, typically installed through a wall and often found in hotels. Abbreviated PTAC.
An air conditioning and/or heating system in which all components are located in one cabinet. Used in certain localities and for certain building types, the all-in-one system is installed either beside or on top of your home.
A measure of the air temperature outside a building. The temperature and humidity of air inside and outside the building are used in enthalpy calculations to determine when outside air can be used for free heating or cooling. Abbreviated OAT.
An automatic louver or damper that controls the fresh air flow into an air handler and modulates to the most energy efficient setting.