The air passing through the coil creates condensation on the coil which drips down upon the condensation pan or primary pan, and is then conducted by an appropriate outlet and a discharge pipe to a secondary pan and therefrom to a drain. Residential and commercial air conditioners include as a part thereof a fan coil unit. The fan coil unit includes a coil through which coolant is pumped, and normally the coil is supported above a condensation pan or convector tray having one or more openings through which air is blown by one or more fans powered by motors which are supported below and from the condensation pan.

Excessive rust also blocks or reduces normal drainage which results in fungus growth which in turn can cause odors and also can cause the normal drain opening to close or appreciably block with, of course, attendant overflow and damage.Such conventional convector trays or primary pans are generally made from galvanized metal and rust with relative ease. Once the convector tray rusts the water might, for example, drip down into the underlying motor which drives the digital thermostat, causing the motor to short-out.

However, even if this does not occur, water can drip through the fastener openings in the primary pan as the fasteners and the periphery of the metal surrounding the openings corrodes, and such leakage can enter the fan coil thermostat resulting in the shorting and permanent damage thereof.