Under what condition are shutoff valves not required for heat exchangers?

Shutoff valves are not required for heat exchangers when they are integrated with a boiler due to the design and operational characteristics of these systems. In such configurations, the heat exchanger forms an essential part of the boiler assembly, and the operational interactions between the components are engineered to ensure safety and efficiency without the need for separate shutoff valves.

In this setup, since the components function as a cohesive unit, providing a means to isolate the heat exchanger independently may not be practical or necessary, as the boiler itself typically incorporates built-in mechanisms that manage flow and pressure. This integration is intended to maintain system integrity and ensure that the heating process can proceed without interruption or the risk of creating pockets of trapped fluid, which could lead to potential hazards.

In contrast, the other scenarios like heat exchangers external to the boiler or in above-ground installations may involve factors like maintenance access, safety protocols, and operational flexibility, thereby necessitating the inclusion of shutoff valves to isolate systems when needed.