D. Lowered Sash, Face Velocity Test for VAV Hoods 1. The sash is lowered to a height of 8 inches. A single row of readings is made horizontally, in the middle of the opening. Each row is divided into at least six equidistant test locations starting approximately 6 inches from the edges of the hood face. Test locations cannot be separated by more than 12 inches.
Velocity is measured at each of the test locations.
The probe is held at a test location until the reading is stabilized, and then the reading is taken, Individual velocity values are recorded and an average value is determined. A copy of the form is included at the end of this Standard. The average face velocity should remain between 80 and 125 feet per minute. Test locations are the same as those used for determination of average face velocity. Five velocity measurements approximately one second apart are taken at each of the test locations.