Epson Pro 5000 Reference Manual page 56

Feeding paper from the lower paper tray
To print on the paper that is loaded in the lower paper tray, set
the Paper Source setting in the printer driver to Paper Tray
(Lower). The printer also feeds from the lower paper tray if the
Paper Source setting in the printer driver is set to Auto Select
and you select the paper size and media type settings in the
printer driver that match the size and type of media loaded in
the lower paper tray.
Note:
When the Paper Source setting in the printer driver is set to Auto
Select and the standard paper tray runs out of paper, the printer
automatically switches and loads paper from the lower paper tray
under any of the following conditions:
The paper size and media type lever settings are the same for both
paper trays.
The paper size and media type levers are set to Other for the
lower paper tray.
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Paper Handling