Model 351

SKU: 351

Pump Controller, One Relay, 4-20mA

The Delta Controls Model 351 is designed to be operated as an alarm unit and/or adjustable differential controller. The 351 has a 0-100% “SETPOINT” and 0-100% “DIFFERENTIAL” control. It accepts a 4-20 mADC input signal that is proportional to level (or some other process variable). The 351 is microprocessor based and checks its input signal loop for integrity. The relay may be set up for “Direct” or “Reverse” “Fail-safe” action.

A variable Delay controls the timing of the relay operation to eliminate false switching due to transient conditions of the liquid level or process variable.

The unit is equipped with an intrinsically safe built-in loop power supply. It can also accept a remotely powered 4-20 mADC signal. The transmitter must be intrinsically safe for the loop and the Model 351 input to be intrinsically safe. The 351 must be located in a “Safe” area; the input signal wires may extend into the ignition hazard area.

The Model 351 is potted and sealed in epoxy when it’s rated as intrinsically safe. Epoxy potting is optional for all configurations and is recommended when any control is mounted in a moist or corrosive area.


  • Microprocessor Based
  • Available For Mounting Delta Controls housings or in in Enclosures by Others. Housings may be surface or Pipe Stand Mounted
  • Optional Direct Reading LCD Display
  • Accepts 4-20 mADC Signal From Any Type Transmitter; 2, 3 or 4 wire
  • Supplies DC Power For 2-Wire Loops and for 3 or 4-Wire Transmitters
  • Field Selectable Fail Safe Action
  • Optional Pump Control Functions
  • Lead/Lag Control
  • Adjustable Time Delays on Relay Operation
  • Two Alarm Points
  • Built-in Loop Power Supply
  • Selectable Starting Time Delay
  • Self Checking Diagnostic Routine
  • Will Not Lose Memory
  • Continuous Setpoint Indication
  • Optional Explosion Proof Housing


  • General Type: Microprocessor based
  • Supply Power: 120 or 240 VAC, or 24 VDC
  • Input Range: 4-20 mADC
  • Relay: SPDT 10 amp @ 250VAC
  • Switching Action: Alarm or adjustable differential for on/off pump control
  • Accuracy and Repeatability: Better than 1% of full scale; dial markings are only approximate
  • Transmitter Loop Power Supply: 24 VDC
  • Temperature Range: -20 to +170°F (-30 to 80°C)
  • Signal Loop: Optional Intrinsically safe, Classes 1&2, Divisions 1&2, Groups B,C,D,E,F,G; Third Party I.S. Certification has not yet been received.
  • Action: Direct or Reverse fail-safe

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