The Ultimate Stock Tank De-Icer is only designed to be plugged in when it is submerged in water. It will not turn off automatically if there is no water. Never plug the unit in unless the heating element is completely submerged in water. Otherwise, the unit will be damaged.
To use your Ultimate Stock Tank De-Icer as a floating de-icer, use it with the float ring attached. To use it as a submersible de-icer, unscrew and remove the float ring.
The temperature of the heating element will depend on the temperature of the water. When submerged in water, the heating element doesn’t feel that warm to the touch, but it is designed to keep a stock tank from freezing over when choosing the correct deicer as per out zone chart.