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% to 100% setpoint and 0% to 100% differential control. It accepts a 4-20 mA dc 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 a built-in loop power supply and can also accept a remotely powered 4-20 mA dc signal. The 351 must be located in a safe area; the input signal wires may extend into the ignition hazard area.

The 351 is potted and sealed in epoxy which is optional for all configurations and is recommended when any control is mounted in a moist or corrosive area.


  • Microprocessor based
  • Available for mounting in 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 mA dc 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
  • Relay operate time delays
  • 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


  • Input Range: 4-20 mA dc
  • Relay:SPDT 10 A @ 250 VAC
  • Switching Action: : Alarm or adjustable differential for On/Off pump control
  • Accuracy and Repeatability (Dial Markings are only Approximate): > 1% of full scale
  • Transmitter Loop Power Supply: > 24 DCV
  • Power Supply: 120 ACV, 240 ACV, or 24 DCV
  • Temperature Range: -20 °F to +170 °F (-30 °C to 80 °C)
  • Signal Loop: Classes 1 & 2, Divisions 1 & 2, Groups B, C, D, E, F, G
  • Action: Direct or reverse fail-safe

Required Ordering Information

  • Detailed model number
  • Tag or nameplate detail (if required)
  • Documentation/testing tiers (if required, refer to Additional Resources in the product catalog)

Additional Information


Pump Controller, One Relay, 4-20mA

Level Measurement

Point, Pump Controllers

Accessories and Related Products