This device deactivates your condenser in the event that your pan is filling up with water. We have seen countless clients with ceiling damage becuase thier system was not equipped with a float switch. In the event that water fills your pan, this switch floats and kills the 24v control to your condensing unit. Comes with a sticker on the outside condenser to check the float switch first. Once the drain is clear, the system turns right back on again, preventing damage.