In the Horizontal orientation, a field supplied accessory drain trap grommet is required to seal the gap between the casing and the condensate trap for Direct Vent applications. The condensate trap outlet extends 2 inches (51 mm) below the furnace casing. To allow for servicing the trap, the condensate drain tube in the loose parts bag can be modified to make a coupler to allow for future service of the condensate trap and drain line.
The drain trap grommet seals the burner compartment of the furnace to prevent ambient air from being drawn into the furnace vestibule. It is only required for Horizontal installations when a Direct Vent (2-pipe) or Ventilated Combustion Air venting application is used. It is not required for other orientations or when a Non-Direct Vent (1-pipe) application is used. A Non-Direct Vent application is when the combustion air for the furnace comes from the same location as the furnace.
Warning: this product contains a chemical known to the State of California to cause cancer. P65Warnings.ca.gov