The plenum rated AG-3180E is a 2 in 1 electronic water sensing probe mounted directly on the primary drain pan inside of the HVAC unit.  It also includes a secondary drain pan switch that can set in the bottom of the secondary pan.  Designed for rooftop commercial package units 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. This switch complies with the 2009 International Mechanical Code 307.2.3.1.