Tell someone or document it before you close it up.
Wrong inlet/outlet orientation on VAV box
A VAV box installed backwards or with the inlet/outlet wrong will not control airflow correctly. Confirm the inlet, outlet, flow arrow, and box tag before connecting duct or flex.
This VAV box at [location/tag] looks like it may be hung with the inlet and outlet reversed - the round collar is facing [direction] but the drawing/submittal shows it facing [direction]. Can you confirm before I connect the flex?
Watch out
Do not connect duct or flex to a VAV box when the inlet/outlet orientation, flow arrow, or service side does not match the submittal or shop drawing.
Check
Find the VAV box tag and match it to the submittal or shop drawing. The submittal controls inlet direction, outlet direction, and service side.
Look at the actual box. The inlet is usually the round collar receiving supply from the main. The outlet is usually the discharge side going toward branches or diffusers.
Check for a stamped or labeled airflow arrow on the box if visible.
If the box is already hung in the wrong orientation, check whether it can be rotated in place or whether it needs to come down before duct/flex locks it in.
Do not connect flex, branch duct, or controls clearance around a box you believe is backwards. Connected work hides the orientation problem and adds rework.
Steps
Find the VAV box tag and match it to the submittal or shop drawing. The submittal controls inlet direction, outlet direction, and service side.
Look at the actual box. The inlet is usually the round collar receiving supply from the main. The outlet is usually the discharge side going toward branches or diffusers.
Check for a stamped or labeled airflow arrow on the box if visible.
If the box is already hung in the wrong orientation, check whether it can be rotated in place or whether it needs to come down before duct/flex locks it in.
Do not connect flex, branch duct, or controls clearance around a box you believe is backwards. Connected work hides the orientation problem and adds rework.
Say this to your foreman
This VAV box at [location/tag] looks like it may be hung with the inlet and outlet reversed - the round collar is facing [direction] but the drawing/submittal shows it facing [direction]. Can you confirm before I connect the flex?