Table 15 – Retrotec DucTester 200 Series Residential Applications User Manual
Page 78
Page 78 of 91
©Retrotec Inc. 2015
For example, if you read 1000 CFM at a building pressure of 30 Pa, the "Cannot reach 50 factor" from
Table 15 is 1.36. To get the estimated flow at 50 Pa, make the following calculation:
1000 CFM × 1.36 = 1360 CFM
Thus the estimated result for CFM at 50 Pa will be 1360 CFM.
The factors depend on the “n” value chosen, and Table 15 is for “n” of 0.60 which is typical for ducts.
Table 15: Factors for when a duct pressure of 50 Pa cannot be reached (assumed “n” value of 0.60).
Pressure
achieved
Cannot reach
50 factor
Pressure
achieved
Cannot reach
50 factor
50
1.00
25
1.52
49
1.01
24
1.55
48
1.02
23
1.59
47
1.04
22
1.64
46
1.05
21
1.68
45
1.07
20
1.73
44
1.08
19
1.79
43
1.09
18
1.85
42
1.11
17
1.91
41
1.13
16
1.98
40
1.14
15
2.06
39
1.16
14
2.15
38
1.18
13
2.24
37
1.20
12
2.35
36
1.22
11
2.48
35
1.24
10
2.63
34
1.26
9
2.80
33
1.28
8
3.00
32
1.31
7
3.25
31
1.33
6
3.57
30
1.36
5
3.98
29
1.39
28
1.42
27
1.45
26
1.48