Description
The Littelfuse 235P is designed to protect 5-15 hp, 230 V, single-phase pumps from dry-well, dead-head, jammed impellers,
rapid-cycle, and overvoltage and undervoltage conditions. A calibration adjustment allows the 235P 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 causing overcurrent and undercurrent.
When an abnormality such as loss of suction is detected, the 235P deactivates its output relay and directly disconnects the
pump motor. The 235P 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 external current transformer is
required for operation (sold separately).
Special considerations for pump cables larger than #10 AWG: In some cases where larger motors are installed with deepset
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 235P 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.

FEATURES BENEFITS
Proprietary microcontroller-based circuitry Constant monitoring of voltage and current for reliable pump
protection
Onboard sensitivity adjustment User-adjustable sensitivity knob makes the unit more adaptable to
varying pumping applications
Adjustable restart delay Allows user to select well recovery time delay after a dry-well
condition occurs, or to select manual reset
Built-in IR communications link When used with the Informer, allows user to see stored faults, run
time, and troubleshoot the pump while it’s running
LED indication Provides status and diagnostics for troubleshooting
Flexible reset Reset can be done through a push button on the relay or remotely with
optional 777-MRSW or OL-Reset remote reset kit