¶ PID Trim Mode
PID Trim (image 1.2) monitors source water level to protect pumps from running dry. When level falls below the Trim Start threshold, the controller scales the pump setpoint downward—reducing pump speed—to prolong operation. As the level continues to drop toward Trim Min, the trimmed setpoint reduces further until either normal conditions return, a low‑level fault occurs, or the min discharge setpoint is trimmed beyond that min setpoint.
This mode utilized the Source Level Transmitter to work properly.
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When PID Trim is enabled, the controller reduces the discharge setpoint based on the source water level to protect pumps during low‑supply conditions.
- Min System Setpoint (image 1.3): the lowest discharge pressure the system is permitted to run. Once the trimmed setpoint reaches this value, the pumps remain at that speed until a low‑level fault occurs.
- Trim Start / Trim Min (image 1.4): define the level range used for scaling. Trim Start is the source level where trimming begins; Trim Min is the lowest source level at which the pumps may continue operating.
Example: if Trim Start = 85" H2O and the normal setpoint is 100 psi, the controller begins reducing the setpoint once the source level falls below 85". The setpoint is decreased proportionally as level falls until it reaches the Min System Setpoint, at which point the pumps run at that reduced speed or fault if levels worsen.
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The PID filter delay is the time it takes for the station to apply the next adjustment (image 1.5). If PID trim conditions are met, the station will adjust the setpoint of the station every 5 seconds till the station stops on low level, or the water levels rise back to normal operating levels again.
