FloAire Canopy Hood - Manual (Page 35)

35
If both the length and width are measured in inches, use the following formula:
Area (ft²) = Length (in) x Width (in) / 144
2. Record velocity of air through supply openings from left to right on raw data sheet.
3. Compute and record average velocity through supply openings.
4. Compute and record CFM through supply openings.
CFM = Free area x Average Velocity
5. Compute total CFM through all supply openings for each hood.
Calculating Exhaust Air CFM with a Shortridge Instrument and Spreadsheet
1. Use the Velgrid mode of the Shortridge instrument to measure the velocity at each filter.
2. Locate the appropriate Excel spreadsheet for the exhaust velocity and record all necessary data.
This spreadsheet will calculate the total exhaust CFM for the hood.
Calculating Exhaust CFM without a Shortridge Instrument
1. Record filter sizes of each hood on raw data sheet.
2. Compute free area of the filters.
Examples:
16”x16” = 14x14 = 1.36 ft²
10”x20” = 8x18 = 1.00 ft²
12”x16” = 10x14 = 0.97 ft²
3. Record velocity of exhaust gases through filters starting top left to right (5 reading/filter).
4. Find average velocity through each filter.
5. Compute CFM through each filter.
CFM = Free area x Average Velocity
6. Total the exhaust CFM for each hood.
7. Multiply total exhaust CFM x 0.78 (this is the K factor necessary when using the EDRA
velometer).