What are the key differences between 3-pipe and 4-pipe systems?

The main difference between 3-pipe and 4-pipe systems is the addition of a separate pipe for condenser water in 4-pipe systems. In 3-pipe systems, the same pipe is used for both chilled water and condenser water, which can lead to inefficiencies and reduced system performance. 4-pipe systems, on the other hand, provide a dedicated pipe for condenser water, allowing for more efficient heat rejection and improved system performance. However, 4-pipe systems are typically more expensive to install and maintain than 3-pipe systems.