231-Insider-P Series - Littelfuse 231-Insider-P Pump Monitor Provides Submersible System Protection

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The 231-Insider-P monitor fits inside ⅓, ½, ¾, and 1 hp, 230 V control boxes. It is designed to protect single-phase, submersible pumps from dry-well, dead-head, jammed impellers, rapid-cycle, overvoltage, and undervoltage conditions. A calibration adjustment allows the Insider to be calibrated to your specific pumping applications, reducing the possibility of false or nuisance tripping. A unique microcontroller-based voltage and current-sensing circuit constantly monitors the incoming power for fluctuations, overcurrent, and undercurrent. When an abnormality such as loss of suction is detected, the product deactivates its output relay and directly disconnects the pump motor. The relay then begins its user-selectable restart delay (dry-well recovery) timer. When the timer counts to zero or power is removed and reapplied, the relay reactivates its output relay and turns the pump back on. By leaving the restart delay knob in the reset position, the relay will operate in manual reset mode.

The Insider communicates with a hand-held diagnostics tool called the Informer (sold separately). The Informer displays parameters including calibration points, trip points, run time and last faults. An IR Kit-12 (12” fiber optic kit) is included with each Insider, allowing the Informer to access these parameters even when the Insider is enclosed in a control box. This is valuable for troubleshooting the pump while it is running.

NOTE: The 231-Insider-P model has a sensitivity adjustment for the dry-well trip point. After calibration is done, you can adjust the sensitivity for the dry-well/dead-head trip point from 70-90 % of the full load. This makes the unit even more adaptable to varying pumping applications. If you have a very low producing well, increase the sensitivity closer to the 90 % mark, or if you have a very heavy producing well, decrease the sensitivity around the 70 % mark.


  • Proprietary microcontroller-based circuitry
  • Onboard sensitivity adjustment
  • Adjustable restart delay
  • Built-in IR communications link
  • LED indication

Access specifications, certifications, check availability and order parts below

Catalog #Input
Voltage (V)
Input Load Range (hp)Output
Mounting MethodWeight (lbs/g)Overcurrent Trip ClassInput AC Line Frequency (Hz)Maximum Input PowerOutput Load Rating (VA)Overvoltage Trip Voltage (%)Rapid Cycle Timer (s)Restart Delay RangeTrip Delay RangeUnderload (%)Undervoltage Reset Voltage (%)StockSamples
231-INSIDER-P230 Vac1/3 - 1SPSTInside a Franklin™; Pente®; or CentriPro™ control box0 Kg125% of calibration point50 / 60 (50 will increase all delay timers by 20%)51 hp @ 240 Vac (17 A max.)265 Vac4 restarts allowed in 60 s periodOver/Under Voltage: 2 s; All other faults: Manual; 2 - 225 mOvercurrent: 5 s; Dry-well: 4 sAdjustable (70 to 90% of calibrated run power)190 VacCheckOrder
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