Description
The Littelfuse models 111P (115 volt, 1⁄3 to 1hp); 233P-1.5 (230 volt, 1⁄3 to 1.5hp); and 233P (230 volt, 1⁄3 to 3hp) are singlephase
pump monitors used in a variety of applications to protect from dry-well, dead-head, jammed impeller, rapid-cycling,
overvoltage, and undervoltage conditions.
Operation
A calibration adjustment allows the unit to be calibrated to your specific pumping applications, which reduces the possibility
of false or nuisance tripping. A unique microcontroller-based voltage and current-sensing circuit constantly monitor the
incoming power for fluctuations, overcurrent, and undercurrent conditions. 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. The infrared LED 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.
There are special considerations for pump cables larger than #10 AWG: In some cases where larger motors are installed
with deep-set pumps, pump cables are used that exceed the relay’s terminal size. In these conditions, a short splice of
#10 AWG or #12 AWG may be a solution at the control box. Note: All local, state, and national electric codes should be
followed when applying this solution.
Note: The description and operations apply to Littelfuse models 111P (115 V, 1⁄3 to 1 hp); 233P-1.5 (230 V, 1⁄3 to 1.5 hp); and 233P (230 V, 1⁄3 to 3 hp). These models have a sensitivity
adjustment for the dry-well trip point. After calibration is complete, 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, you increase the sensitivity closer to the 90 % mark, or if you have a very heavy
producing well, you should decrease the sensitivity around the 70 % mark.
*Informer: A hand-held diagnostic tool that uses an infrared receiver to access information that can be helpful for troubleshooting the system.

FEATURES BENEFITS
Proprietary microcontroller-based circuitry Constant monitoring of voltage, power factor, and current for reliable
pump protection
Onboard calibration process Calibrates unit to your specific individual pumping application and
reduces nuisance tripping
Onboard sensitivity adjustment User-adjustable sensitivity knob makes the unit more adaptable to
varying pumping applications