A refrigerated merchandiser (10) includes a cabinet (20) having a top wall (22), a lower wall (24), a rear wall (34), and side walls (36, 38) defining an interior product display space (100) housing a product (110) in a refrigerated environment for consumer selection. A refrigeration unit (50) is disposed in operative association with the interior product display space in a compartment (55) beneath the lower wall (24). A first opening in the lower wall provides an air return inlet (102) establishing a flow passage from the interior product display space (1000 to the compartment (55) beneath the lower wall. A sealing member (58) is disposed between the under surface of the lower wall (24) and the upper surface of the refrigeration unit cassette (50) about the first opening; and a positioning apparatus (150) for raising the refrigeration unit cassette (50) unit into sealing relationship with the lower wall.