Can direct return systems be used in combination with other piping configurations, such as loop systems?

Yes, direct return systems can be used in combination with other piping configurations, such as loop systems. In fact, many modern HVAC systems incorporate a hybrid approach, where direct return systems are used for certain branches of the piping network, while loop systems are used for others. This hybrid approach can help to optimize piping costs, simplify system design, and improve overall system performance.