Which device isolates a heat exchanger when pressure drops below a preset level to protect water quality?

Which device isolates a heat exchanger when pressure drops below a preset level to protect water quality?

• A. Flow Switch
• B. Check Valve
• C. Pressure Gradient Monitor
• D. Pressure Reducing Valve

Answer: (C)

Protecting potable-water quality during pressure fluctuations relies on a device that reacts to pressure changes across a heat exchanger and automatically isolates it when risk is detected. A pressure gradient monitor does this by continuously comparing the potable supply pressure to the pressure on the non-potable side of the exchanger. If the differential falls below a preset level—indicating a potential backflow or siphon condition—the monitor actuates a valve to isolate the heat exchanger, preventing contaminated water from entering the supply. Flow switches respond to whether water is moving, not to the pressure differential that signals a cross-connection risk, so they don’t reliably protect against backflow in this scenario. A check valve prevents reverse flow but doesn’t actively monitor pressure differences to trigger isolation. A pressure reducing valve lowers pressure but does not isolate the heat exchanger.

Protecting potable-water quality during pressure fluctuations relies on a device that reacts to pressure changes across a heat exchanger and automatically isolates it when risk is detected. A pressure gradient monitor does this by continuously comparing the potable supply pressure to the pressure on the non-potable side of the exchanger. If the differential falls below a preset level—indicating a potential backflow or siphon condition—the monitor actuates a valve to isolate the heat exchanger, preventing contaminated water from entering the supply.

Flow switches respond to whether water is moving, not to the pressure differential that signals a cross-connection risk, so they don’t reliably protect against backflow in this scenario. A check valve prevents reverse flow but doesn’t actively monitor pressure differences to trigger isolation. A pressure reducing valve lowers pressure but does not isolate the heat exchanger.