Ceiling protection switch

Ceiling protection switches are installed in secondary condensate drain pans in split system HVAC applications. The switch has a buoyant component that floats when the secondary condensate drain pan fills with water from the primary drain pan and shuts down the HVAC system to avoid overflowing. 
The ceiling protection switch is mainly used in applications where a piece of HVAC equipment is located in an attic or interior space where water damage is likely to occur. The switch does not guarantee the prevention of overflow, but may reduce the amount. Overflow water occurs when the condensate drain line becomes clogged restricting the flow of condensation from the interior to the exterior of the space. Overflow also occurs when an indoor HVAC coil becomes frozen, which when thaws creates excess water.