Cut Sheet

© 2018 Littelfuse Protection Relays & Controls
Protection Relays
Motor and Pump Protection
www.littelfuse.com/235p
Rev: 1-B-111518
235P
Wiring Diagram
Description
The Littelfuse 235P is designed to protect 5-15 hp, 230V,
single-phase pumps from dry-well, dead-head, jammed impeller,
rapid-cycle and overvoltage and undervoltage conditions.
A calibration adjustment allows the 235P to be calibrated
to your specific pumping applications, thereby 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
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 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, you increase the sensitivity closer to the 90% mark, or if you have a
very heavy producing well, you would decrease the sensitivity around the 70% mark.
Features & Benefits
FEATURES BENEFITS
Proprietary
microcontroller
based circuitry
Constant monitoring of voltage and current protects
pumps from dry-well, dead-head, jammed impeller,
rapid cycling, and voltage faults
Onboard sensitivity
adjustment
Allows user to adjust the current sensitivity for the
dry-well / dead-head trip point from 70% - 90% of the
full load.
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
Used with the Informer, allows user to see stored
faults, run time, and also troubleshoot the pump while
it’s running
LED indication Provides status and diagnostics for troubleshooting
MODEL LINE VOLTAGE DESCRIPTION
235P 230VAC 5 - 15hp
235P-ENCL 230VAC 233P with NEMA3R enclosure
Ordering Information
PART* SIZE CURRENT (A) CT CURRENT RATIO
CT-0050-D10 5 - 7½ HP 27.5 - 42.1 50:5
CT-0075-D10 10 HP 51 75:5
CT-0100-D10 15 HP 75 100:5
* Current transformer sold separately
Model 235P
Shows Internal Connection
Single-Phase Pump Monitor