Four pipes coming from a piece of building equipment would most likely indicate which equipment?

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

Answer: (C)

Four pipes coming from equipment usually signal a heat exchanger, because it uses two separate fluid circuits to transfer heat between two fluids. Each circuit needs an inlet and an outlet, giving you four pipe connections in total. This setup lets hot and cold (or process and service) fluids move without mixing. The other options don’t typically show two distinct piping circuits: a chiller and an air handling unit are more about moving air or have more varied connections, and a boiler usually has just a single supply and return loop. So the four-pipe arrangement is a telltale sign of a heat exchanger.