How Does a Float Level Switch Work?

Float Level Switch Installation and Maintenance

The following is an introduction to how a liquid level switch is installed and how does it work.

Installation Orientation

A standard NPT female boss in the top of the tank, bottom or side is all that is required for rapid installation. Units operate normally in any attitude --from the vertical to a 30° inclination - with lead wires up or down. Standard IPS pipe extends units to any intermediate level in the tank.

Level Switch's Accuracy and Repeatability

The accuracy of many Gems Sensors level switches is ±1/8: (3.2 mm) of true liquid level. In order to assure the proper accuracy for your liquid, please specify the specific gravity of the media. Gems Sensors will automatically calibrate for the submergence of the float, based on this specific gravity information. Furthermore, accuracy may be enhanced by specifying whether the circuit condition should be measured on decreasing or increasing liquid level. The repeatability of the actuation point is approximately 1/32 inch (.79 mm).

Moisture Protection

When moisture exits the conduit and extension pipes, the potential for this moisture to wick down the wire leads and into the switch assembly exists. Should this happen, the switch may fail to close due to a high resistance path through the moisture.

There are several means that can be used to prevent this from happening.

1. Pitch conduit away from the level switch when possible so that condensation will drip away from the level switch assembly. 
2. When a vertical run of extension pipe is used to extend a level switch down from the top of the tank, a non-conductive silicone oil should be used to fill the vertical run. Alternately, an appropriate potting may be used to fill the vertical run to occupy the space in which condensation will normally form. 

By working closely with your Gems Sensors representative, there are many design considerations that can help lessen the effects of moisture.

1. Consider a product such as the Gems Sensors LS-270 Single Level Switch which has a water-tight molded cable.
2. Consider using a unit with a connector and gasket seal.
3. Consider using moisture resistant heat shrink tubing on the switch capsule assembly.
4. Consider using Scotchcast® 2114 sealing compound and electrical insulator. Part No. 157636.

A Word of Caution: Most of Gems Sensors level products incorporate a potting cap or are fully potted. Due to the bonding characteristics of the potting to the wire leads, there is no way of assuring a water tight seal at the potting joint. Our potting cap will resist moisture to some degree, but the precautions mentioned above should be used to assure moisture doesn't enter the switch and cause a short.