Where should shutoff valves be installed concerning a heat exchanger?

The correct choice emphasizes the need for shutoff valves to be located on both the supply and return side of a heat exchanger. This placement is crucial for several reasons:

1. Operational Access: Having shutoff valves on the supply and return sides allows for the complete isolation of the heat exchanger during maintenance or repairs. This is essential for ensuring the safety of personnel and preventing water leakage or pressure issues when working on the system.

2. System Balance: These valves enable better control over the flow rates in the heating or cooling system. Balancing the flow can enhance the efficiency of the system, optimizing the performance of the heat exchanger.

3. Flexible Configuration: With valves on both sides, technicians can isolate the heat exchanger without disrupting the entire HVAC system. This flexibility is vital for diagnostic testing or during routine servicing.

Other options, while they mention appropriate locations, lack the specific combination of both supply and return requirements which is critical for effective operation and maintenance of the heat exchanger system.