This calculation below is the max height for allowance.
Standard vision panel door.
Door size 2040 x 926 x 54 height x width x depth.
The 2012 ibc model building code contains size limits for vision panels in a 60 or 90 minute door.
With this measurement we subtract the top of the glass to the top of the door.
The vision panel bead design is generally a bolection type bead in fire applications although flush beads can be provided as shown.
To create the maximum vision panel size incompletion the formula is as follows.
If the vision panel is fire protective glass such as safety wired glass and safety ceramic its size is limited to no more than 100 square inches whether or not sprinklers are present.