What is the normal temperature limit for water in a hot water heating system with an open expansion tank?

In a hot water heating system that utilizes an open expansion tank, the normal temperature limit for the water is typically around 80°C (175°F). This temperature is considered suitable for maintaining heating efficiency while also ensuring safety within the system.

Operating at or below this temperature minimizes the risk of causing excessive pressure and potential system failures due to overheating. Additionally, water temperatures above 80°C can lead to the risk of scalding and other hazards, especially in residential applications where water may be used for domestic purposes.

While the other temperature options are higher, they exceed the recommended safe operating limits for systems with open expansion tanks. Therefore, maintaining water temperature around 80°C balances efficiency and safety, making it the most appropriate choice in this context.