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Simplex pump control is a relatively simple task. A float switch with a bit of hysteresis will do just fine. There are, of course, continuous level sensors that may be advantageous under the right circumstances. However, for this article, we will focus on wiring a KA series cable suspended float switch for simplex pump control.

For this example, we will use the KA-2L, which is simple a dual-level float switch with hysteresis for fill control applications. Here we go:

The contacts in the KA-2L are high performance miniature switches. Because the float will be immersed in liquid, it is not recommended to switch pump motor currents directly through the float switch. Rather use a heavy duty relay, or contactor, between the float switch and the pump.

Wiring the KA-2L sensor is done in only a few easy steps as shown in the below illustration.

Fill control wiring diagram for KA-2L float switch

  1. Connect conductor # 1 (white) to the Line Power.
  2. Connect conductor # 2 (black) to the switch side of relay/contactor.
  3. Connect the power side of the relay/contactor to the Line Power.
  4. Connect the relay/contactor power contacts to the pump.

Note: The relay/contactor R1 should be a Double Pole Single Throw (DPST) type with one contact R1B rated to carry the voltage and current required by the pump’s horsepower rating.

When the liquid is at the low level, the pump will start filling the tank with liquid. When the liquid reaches the full level point, the pump will turn off.  The pump will stay off until the liquid falls back to the low level point where the process will repeat.

As always, let us know if you have any questions!

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