Which system is characterized by controlled steam flow into radiators?

The two-pipe system is characterized by controlled steam flow into radiators, making it the most efficient and flexible option for heating applications. In a two-pipe system, one pipe is used for the supply of steam, while the second pipe returns condensate back to the boiler. This setup allows for better control of temperature regulation as valves can be used to adjust the steam flow into each radiator based on the heating demand of individual rooms.

This enhanced control contributes to energy efficiency and comfort, as it minimizes steam loss and maximizes heat delivered to spaces that require it. Furthermore, the ability to divert condensate separately prevents issues such as water hammer, which can affect the performance and longevity of the heating system.

In contrast, the other systems listed do not provide the same level of controlled steam flow. For instance, a single-pipe system releases steam to the radiator and returns condensate through the same pipe, which can lead to inefficiencies as well as uneven heating. Therefore, the two-pipe system is recognized as the optimal choice for managing steam flow effectively.