Greenheck Waterwash (458292) - Manual (Page 32)

32 April 2005
920 937 924 935 927 925
Measuring Hood Exhaust Volume:
A digital 2-3/4 in. rotating vane anemometer can be used to measure exhaust CFM when the more accurate
pilot traverse is not available. Accuracy of the rotating vane anamometer has been tested at + 15%.
Measuring Velocity and Calculating Volume
1. Turn off all cooking equipment and hood supply fan (if applicable).
2. Remove the deflector panel on short circuit hoods.
3. Place the anemometer head in the hood exhaust airstream as shown in Fig. 25. It must be
placed in the slot as close to the back wall of the hood as possible and at a 90° angle to it.
4. Take measurements at 8 in. intervals along the entire length of the hood.
5. Calculate the average slot velocity.
6. Calculate the CFM per lineal foot by dividing the average velocity by a conversion factor of 3.9.
7. Calculate the hood's exhaust volume by multiplying the CFM per lineal foot by the length of the hood.
Example:
1. Measured slot velocities in FPM for a hood 4 ft.-0 in.
2. Average slot velocity = (Sum of velocity readings)
(Number of readings)
= 920 + 937 + 924 + 935 + 927 + 925 = 5568 = 928 FPM
6 6
3. CFM per lineal foot = Average velocity in FPM
3.9
= 928 = 238 CFM/lineal foot
3.9
4. Hood exhaust volume = (CFM/lineal foot) x (hood length)
= 238 x 4 = 952 CFM
Fig. 25
Digital Rotating
Vane Anemometer
Exhaust
Airflow
®