The plenum rated AG-3175E is a 2 in 1 auxiliary electronic water sensing probe is mounted directly in to the secondary drain port of the HVAC unit.  It also includes a secondary drain pan switch that can set in the bottom of the secondary pan.  The AG-3175E is a high-amperage, solid state switch with no moving parts to break down or become clogged. The low profile design makes it easy to install.

Also available is the AG-3176 primary pan clip on sensor, perfect for self-contained packaged units, and the AG-3177, primary probe extension wire adds an additional 6'.