Testing a FS 90/FS 96 Float Switch

 

Tools:

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1) DVM (Digital Volt Meter)
2) Test Leads w/Alligator Clips

• Set the DVM so that it reads Ohms (i.e. resistance).

Testing the DVM’s Operation

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• Separate the DVM’s leads and ensure that the DVM reads an open circuit. Some DVMs display OL which indicates that the circuit’s resistance is Over-the-Limit (i.e. the resistance is beyond the DVM’s measurement capability).

• Touch the leads together. Confirm that the DVM reads (nominally) zero ohms resistance.

Testing the Normally Closed Contact

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• Connect one of the DVM’s leads to the float's common (white) and the other DVM lead to the float's NC (Normally Closed) contact (i.e. Red).

• Tilt the float downward. The DVM should respond to the switch’s closure by displaying a “switch closed” resistance of less than 5 ohms.

• Tilt the float upward. The DVM should respond to the switch’s opening by displaying an open circuit (e.g. Over Limit).

Testing the Normally Open Contact

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• Leave the DVM’s lead on the float's common (white) lead and move the other DVM lead from the Red wire to the float's NO (Normally Open) contact (i.e. the Black wire).

• Tilt the float upward. The DVM should respond to the switch’s closure by displaying a “switch closed” resistance of less than 5 ohms.

• Tilt the float downward. The DVM should respond to the switch’s opening by displaying an open circuit (e.g. Over Limit).

• Upon passing the above test the float may be placed into service. Thereafter, if the float exhibits errant operation 1) check all field wiring (e.g. crossed leads, loose connections and/or stray wire-strands bridging across connectors 2) remove the float from the installation and test the float for proper operation.