If you want to monitor liquid levels in commercial or residential applications, then you should be utilizing float switch technology. Before you start installing anything, you need to determine what type of float switch you require.

Normally Open Vs. Normally Closed Float Switches: What Do You Want Your Float Switch To Do?

In order to figure out what kind of float switch you need, you should ask: what do I need this float switch to do? Do you need a pump to turn on to prevent depletion? Or do you need it to turn off to prevent overflow? There are 2 main types of float switches: Normally open, and normally closed.  Essentially, normally open flat switches fill, and normally closed float switches drain.  For a detailed breakdown of the differences, see this post.

How to Install a Normally Open, Single Float Switch

Normally open, single float switches are single-pole, single-throw with two wires.. The rising action of the float will close (turn on or energize) a “Normally Open” circuit. The schematic below is an example of an open float switch turning on a pump to empty a tank. Terminal 1 in the control circuit represents the connection point for the positive (+) wire, and terminal 2 for the negative (-) wire.

How to Install a Normally Closed, Single Float Switch

When placed in an empty tank a, normally closed float switch would have current flowing through it, activating the circuit and turning on a pump. In the below schematic, terminal 1 in the control circuit represents the connection point for the positive (+) wire, and terminal 2 for the negative (-) wire.

Need Help Installing Float Switches? Contact SMD Fluid Controls Today!

We do more than install float switches. We build custom sensor solutions for applications across a variety of industries. If your project requires temperature or liquid level sensors, then we can help make your dream into a reality.


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