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The Intrinsically Safe Duplexer (ISD-P, ISD-D, or ISD-S) is a UL913 low cost SCADA ready intrinsically safe pump controller designed to perform level control for duplex lift station applications.

The I.S. Float Input Controller comes in one of three options: Surface Mount, Din Rail Mount, or Panel Mount. The I.S. Level Probe Input Controller comes standard with a serial port and has an optional Ethernet port.

The controller's level inputs may be connected to either five float switches, five single point conductance probes, or five selected points on a ten point conductance probe.

The level inputs are intrinsically safe and allow maintenance personnel to safely handle the float switches or conductance probes while the unit is in operation.

Unit of Measure


UL File No.

N/A #E189808

Product Type

N/A Intrinsically Safe Duplex Controller ISD-D

Maximum Input Power

N/A 7.7 V·A

Input Voltage (AC)

N/A 120 V

Input Voltage Tolerance

N/A ± 10%

Agency Approval


Display Indicator



N/A White with Blue Silkscreen

Ambient Operating Temperature

N/A -4 to +140 ºF-20 to +60 ºC

Relay Current at 120 V (AC)

N/A 6 A

Enclosure Material

N/A Aluminum

Case Options

N/A Din Rail Mount



  • 5 Intrinsically Safe Float Switch or Conductance Level Probe Inputs
  • Float Out of Sequence Indication
  • Pump Called to Run Indication
  • Push-Button for Alarm Reset and Level Simulation
  • Lead/Lag/Auto Switch
  • High Level Alarm Indicator
  • Low Level Alarm Indicator
  • Lag Pump Delay
  • Phoenix Style Connectors
  • Duplex Alternation
  • Level Indication
  • 120VAC Input Power, Transient Protected
  • 6 Amp Pump Call Relay Outputs
  • 6 Amp High Level Alarm Relay
  • 6 Amp Low Level Alarm Relay
  • Lead Select Toggle Switch
  • HOA Toggle Switches
  • RS232 Modbus Serial Port

Additional Description

Additional Description

N/A The unit provides a 10 second power-up start delay, a 5 second lag pump delay, and duplex alternation.

The unit has LEDs that show power on status, level input status, pump call status, high & low alarm status, and level input out-of-sequence indication.

Relay contacts are provided for the pump 1 & 2 call, and high & low level alarm outputs.

Toggle switches allow the operator to set the Hand, Off, or Auto mode for each pump, to select automatic alternation, or to set one pump as lead.

Level simulation (Push-to-Test) is accomplished by pressing and holding the push-button. Releasing the push-button allows the simulated level to return to normal.

The high level status indication latches upon high level, until reset by pressing the reset push-button (the high level relay does not stay latched).

The out-of-sequence logic detects when the inputs fail to close in the correct order. The logic also compensates for most out-of-sequence conditions and allows for continued pump operation.

Connecting the RS-232 serial port (or optional Ethernet Port) to a SCADA system allows the lift station to be monitored and controlled remotely.

Additional setup and troubleshooting features are available using the separately supplied Touch Screen Interface Device (TSID).