A water level supervisory switch for a pressure tank must signal an off-normal condition when the water level in the pressure storage tank rises or lowers more than ______.

A water level supervisory switch for a pressure tank must signal an off-normal condition when the water level in the pressure storage tank rises or lowers more than ______.

• A. 3 inches
• B. 1 inch
• C. 6 inches
• D. 12 inches

Answer: (A)

When monitoring a water level in a pressure storage tank, the supervisory switch needs a threshold that triggers whenever the level deviates from normal by a defined amount. This threshold should catch true abnormal conditions without reacting to every small fluctuation. The best choice is a three‑inch deviation. This provides a reliable signal if the water level rises or falls enough to indicate a potential problem—such as the pump running dry, the tank overfilling, or a control fault—while avoiding nuisance trips from normal cycling, sensor drift, or minor fluctuations. A smaller deviation (like one inch) would cause frequent false alarms during normal operation, wasting time and wear on the system. A larger deviation (six or twelve inches) could let the tank operate in an unsafe state for too long, risking overflow or pump damage before the off-normal signal is issued. So, signaling off-normal when the level changes by about three inches strikes a practical balance between timely detection and stability.

When monitoring a water level in a pressure storage tank, the supervisory switch needs a threshold that triggers whenever the level deviates from normal by a defined amount. This threshold should catch true abnormal conditions without reacting to every small fluctuation.

The best choice is a three‑inch deviation. This provides a reliable signal if the water level rises or falls enough to indicate a potential problem—such as the pump running dry, the tank overfilling, or a control fault—while avoiding nuisance trips from normal cycling, sensor drift, or minor fluctuations. A smaller deviation (like one inch) would cause frequent false alarms during normal operation, wasting time and wear on the system. A larger deviation (six or twelve inches) could let the tank operate in an unsafe state for too long, risking overflow or pump damage before the off-normal signal is issued.

So, signaling off-normal when the level changes by about three inches strikes a practical balance between timely detection and stability.