Brochure

PFG Perforated Face Grille (Page 11)

PFG Perforated Face Grille

Return Air Grille Balancing Data

To Determine CFM:

1. Use an ALNOR Velometer with No. 2220 or 2220A Tip or a 4" rotating vane anemometer. If a 4" rotating vane anemometer is used,

place dial face against perforated plate, and sample in a random manner for at least 1 minute.

2. Select proper Ak from Table by unit size and instrument used for measuring velocity.

3. Determine CFM by the following equation: CFM = Ak x Average Velocity.

Sample Problem

Determine Return Airflow Rate (CFM) through a 10 x 10, using an ALNOR Velometer with Tip No. 2220 or 2220A.

Solution

1. Assume the average of 6 velocity readings taken with an ALNOR Velometer is 2000 FPM.

2. From Table, the Area Factor for a 10 x 10 using an ALNOR Velometer is Ak = .39 sq. ft.

3. CFM = Ak x Average Velocity = .39 sq. ft. x 2000 FPM = 780 CFM

Neck Velocity 200 300 400 500 600 650 700 750 800 900

S.P. Drop w/OBD .012 .027 .049 .078 .110 .130 .150 .170 .190 .240

Size

ALNOR

4" ROT.

Vane

10 x 10 .39 .55 140 210 285 350 415 450 485 520 555 625

12 x12 .46 .79 200 300 400 500 600 650 700 750 800 900

14 x 14 .62 1.07 270 410 545 680 815 885 955 1020 1090 1225

10 x 22 .71 1.21 305 460 610 765 915 995 1070 1150 1220 1375

16 x 16 .82 1.40 355 530 710 890 1065 1155 1245 1335 1425 1600

18 x 18 1.05 1.77 450 675 900 1125 1350 1460 1575 1690 1800 2030

20 x 20 1.28 2.25 555 835 1110 1390 1665 1805 1945 2080 2220 2500

22 x 22 1.55 2.70 670 1010 1345 1680 2020 2180 2350 2520 2690 3020

Air Capacities - CFM

Engineering Data

Recommended Noise Criteria and Face Velocity Ranges are on page 75

Engineering Data