A missing condensate drip tray risks leaks into the attic ceiling, where condensate can damage the building or cause a (hidden) mold problem, especially if condensate is leaking onto the upper, hidden (by insulation) attic side of drywall forming a ceiling of a room located below the equipment. Both the drywall and the insulation itself may become mold reservoirs.
When an air conditioning unit is located in an attic where damage may result from condensate overflow from the primary condensate collection and drain equipment, an additional water-tight corrosion-resistant pan (a condensate drip tray or "drip pan") should be installed below the cooling equipment to catch overflowing condensate should the primary condensate drain become clogged. An alternative design provides one pan with a standing overflow and a secondary drain.
The condensate drip tray requires its own separate drain. Alternatively, some installations provide a float switch in the tray which senses the presence of water and shuts down the air conditioning system. The discharge point of all of the condensate drain lines, that is the system condensate drain and the overflow pan drain, must be readily observable. (Ref. Uniform Mechanical Code Sec. 1205 and Sec. 510. Condensate overflow pan is suggested for attic space per UMC (Uniform Mechanical Code) Section 1205.)
Condensate tray shows evidence of leaks: since normally condensate produced in the indoor air handler is carried from the air handler interior to a condensate drain, we don't expect to see condensate falling into the condensate overflow drip tray. If we see evidence of leaks into the condensate tray, the air conditioning system service technician should investigate the cause of this condition.
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