An air handling unit condensate drain connects from the draw-through unit drain pan using a full-size connection matching the unit outlet. The piping drops into a P-trap assembly with a tee fitting installed instead of an elbow for a cleanout. A 4-inch standpipe extends upward with a vent open to the atmosphere to prevent air lock. The horizontal drain line pitches downward at not less than 1/8 inch per foot toward the nearest approved receptor, with trap dimensions X and Y specified as 9.75 inches and 2.75 inches respectively for the HRU unit.
Y" UNIT TRAP DIMENSION X(IN) Y(IN) 9.75 2.75 DRAIN TO BE FULL SIZE OF UNIT CONNECTION DRAW-THROUGH UNIT DRAIN PAN CONNECTION X" VENT OPEN TO ATMOSPHERE 4" STANDPIPE PITCH DRAIN NOT LESS THAN 1/8" PER FOOT TO NEAREST APPROVED RECEPTOR PITCH HRU SEE SHEET M13-12 FOR CONTINUATION OF AHU CONDENSATE DRAINS PROVIDE TEE INSTEAD OF ELBOW FOR CLEAN OUT. (TYPICAL ALL CONDENSATE DRAIN PIPING ELBOWS)
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