What is mandatory to have installed on a separate connection on a hot water heating boiler?

A thermometer is essential for monitoring the temperature of the water in a hot water heating boiler. It allows operators to ensure that the system is running within the desired temperature range, which is crucial for both the efficiency and safety of the heating process. Maintaining the appropriate temperature is important to prevent issues such as overheating, which can damage the system or create safety hazards.

While pressure gauges, drain valves, and flow switches are also important components of a boiler system, they do not specifically address temperature monitoring in the same direct manner as a thermometer does. The thermometer provides immediate, visible feedback that helps in maintaining optimal boiler operation, ultimately ensuring that the heating system functions efficiently and safely.