Pumptrol – Loss Of Prime Pressure Switch

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Part No.PSIBarPre-Set (cut in/cut out)Phase


The Square D FSG2 -LOP pressure switches are a reliable and proven design with simple adjustable cut in/cut out set points for controlling a water pump up to 8 Amps (1.5kw 230v) The loss of prime (LOP) function is to protect a pump from LOP failure, it means the switch will mechanically turn off if pressure drops 10-15 psi below set cut in pressure and lever must be manually re-set to activate switch.

  • Max Amps: 8A/240V.
  • ¼” female connection.
  • Pressure range: 20-84psi.
  • Enclosure: IP20.
  • Fluid temperature: 0°C to +70°C.

The FSG2 pressure switch has an adjustable differential.
When setting the pressure switch, adjust the switching point on rising pressure first and then the switching point on falling pressure.

Switching point on falling pressure: The switching point on falling pressure is set by adjusting screw-nut 1.
Switching point on rising pressure: The switching point on rising pressure is set by adjusting screw-nut 2.

Low pressure cut out 10-15 psi below cut in pressure.