Two or four pipes or two or more ducts coming from a piece of equipment would most likely indicate which equipment?

• A. Boiler heater
• B. Heat exchanger
• C. Chiller
• D. Air handling unit

Answer: (D)

When you see two or more ducts attached to a single piece of equipment, it usually means you’re looking at an air handling unit. AHUs are the central devices that condition and move air through a building's ductwork, so they commonly have multiple connections for supply, return, and sometimes exhaust or other ducts. Boilers, heat exchangers, and chillers primarily handle fluids (hot water, chilled water, or refrigerant) and are connected by piping rather than large ductwork, so they do not typically present with multiple ducts coming off the unit.