What is the purpose of a pressure sensor in a hydronic system?

• A. To detect leaks in pipes
• B. To measure air velocity
• C. To monitor boiler flame
• D. To monitor system pressure, protect pumps, ensure proper flow, and control valve actuation

Answer: (D)

A pressure sensor in a hydronic system provides real-time feedback of the loop water pressure, and that feedback is used to control how the system operates. By knowing the pressure, the control system can keep the loop within its designed range, ensure there’s enough head to push water to all zones, and detect when pressure is out of bounds.

Protecting pumps is a key part: if pressure gets too low, there may not be enough flow and the pump can run inefficiently or be damaged; if pressure gets too high, it can cause stress or cavitation. The sensor lets the controller adjust pump speed or shut the pump off if necessary to prevent damage. Ensuring proper flow follows from maintaining the correct pressure throughout the system; the controller uses the sensor reading to keep the desired flow across all circuit paths and to respond if demand changes.

Valve actuation relies on accurate pressure feedback as well: as load changes, the controller can modulate zone valves or boiler valves to maintain the target pressure and flow, keeping the system balanced and responsive.

Leaking detection isn’t the primary purpose of a pressure sensor, and measuring air velocity or monitoring boiler flame involve different sensors and goals, so they aren’t what the pressure sensor is intended to provide.