Diffuser Blowing Across an Open Refrigerated Case

Fast answer

Hold the branch or diffuser layout until the discharge direction is checked against the reflected ceiling plan, refrigeration layout, case lineup, and case manufacturer information. The problem is the actual air pattern at the case—not a guessed duct velocity.

What to check

1. Confirm the diffuser location, type, orientation, and throw shown on the approved plan.
2. Identify the case discharge and return openings and the final case lineup.
3. Check whether the ceiling layout or case locations changed after coordination.
4. Photograph the relationship and mark the grid/location before asking for direction.

Do not

Do not rotate the diffuser, relocate the branch, or invent a velocity rule to solve the conflict in the field.

Ask the foreman

“This diffuser is aimed across an open refrigerated case. I checked the reflected ceiling plan and refrigeration layout, and the case lineup appears current. Can we verify the throw and final diffuser orientation before I finish this branch?”

Why it matters

Supply air can interfere with the case air curtain, increase condensation or energy use, and create a problem that will not be obvious from the duct connection alone.