Adding or Replacing a Float Level Switch on a Sump Pump

Float level switch empty controlIt is estimated (by the American Society of Home Inspectors) that 60% of homes in the U.S. have what is called "below ground wetness." What this really means is that the 60% have high water tables, either just below or above the ground floor of either a basement or a crawlspace.

That high water table can easily lead to a flood whenever rainfall, melting snow, a broken sprinkler line, or any number of events cause the ground water to rise. To combat the rising tide, you need to install a sump pump. These are very common and have been around for a while. A sump pump sits in a pit in the lowest part of your building where water collects naturally.

Sump pumps with a built in float level switch are the most popular solution to keep water away. However, the switch on these pumps are cheap, and usually fail long before the pump. You can also buy a sump pump without a built in float level sensor. So what do you do when you end up with a pump that is missing a float level switch?

Leaving the pump on all of the time will ruin it, and wastes a lot of electricity in the mean time. Manually checking the pump and turning it on and off as needed might help, but would be time consuming. Installing a new float level switch will turn a regular sump pump into an automatic one.

You simply need to use a float level sensor with two switch points (High and Low) such as the FLE series, and a powered pump relay such as the inexpensive RCU-7000. This provides hysteresis (delay) logic between the switch points, and will enable the sump pump to automatically turn on and off as needed.

Wiring the FLE float level switch and pump to the RCU is done in only a few easy steps.

  1. Ensure that the RCU-7000 is mounted away from the water in a dry place.
  2. Connect the pump to Terminals 1 (NO), 2 (Common) and 3 (NC) on the RCU.
  3. Connect both L1 (High Level) black wires on the float level switch to Terminals 9 and 11 on the RCU with one wire in each terminal.
  4. Connect both L2 (Low Level) white wires on the float level switch to Terminals 10 and 11 on the RCU with one wire in each terminal.
  5. Choose the Empty Control (High) logic from the selector switch found on the front of the RCU-7000.
  6. Connect source voltage to terminals 5 and 6 (90-132 VAC) or 6 and 7 (180-264 VAC) on the RCU.
  7. Here is an example of how an FLE float level switch and RCU-7000 powered relay properly installed and with the above connections would work in a basement sump pump application:
  8. Suppose you wanted to pump out high water - which is what a sump pump does. Your pump is designed for 12 inches of water, but must stop at 1 inch.

    When the water rises to the 12 inches, the high level float switch point is energized and the pump starts pumping the water out. When the water level falls to 1 inch, the second float switch point will cause the pump to turn off. The pump will stay off until the water rises again to 12 inches where the process will repeat.

With an FLE float level switch and an RCU-7000 logic controller, any sump pump can be made to work automatically - so you can rest easy and enjoy a dry basement. Contact us if you have any questions!


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