Which type of HVAC system allows for both heating and cooling through separate pipes?

A four-pipe HVAC system is designed to facilitate both heating and cooling simultaneously by using two separate sets of pipes. One set is dedicated to hot water for heating, while the other is for chilled water used in cooling. This configuration allows the system to provide climate control to different areas within a building at the same time, something that is particularly beneficial in applications where varying temperature needs are required, such as offices, hospitals, or hotels.

In contrast, a two-pipe system can only provide either heating or cooling at a given time, requiring a changeover when the season or temperature demand shifts, which limits flexibility. A single-pipe system typically circulates water for heating but will not provide separate temperature control for cooling. A multi-zoned system may employ various configurations such as the four-pipe system, but it does not exclusively define the separate piping needed for heating and cooling. Hence, the four-pipe system is the most effective choice for simultaneously managing both heating and cooling in a single building infrastructure.