Retrotec DucTester 341 Manuale Utente Scaricare il pdf (Pagina 73)

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Table 11: Factors for when a duct pressure of 25 Pa cannot be reached (assumed n value of 0.6).

Pressure

achieved

Cannot reach

25 factor

1.00

1.02

1.05

1.08

1.11

1.14

1.18

1.22

1.26

1.31

1.36

1.42

1.48

1.55

1.64

1.73

1.85

1.98

2.15

2.35

2.63

Cannot Reach 50 Pa Factors

Rather than using the equation in the situation where the 50 Pa test pressure cannot be achieved, you

can use tables with the factors already calculated and the following procedure. Take a flow (CFM)

reading at the pressure achieved and multiply by the "Cannot reach 50 Pa factor” from Table 12 to get

an estimate of the flow that would result at 50 Pa.

For example, if you read 1000 CFM at a building pressure of 30 Pa, the "Cannot reach 50 factor" from

Table 12 is 1.36. To get the estimated flow at 50 Pa, make the following calculation:

    

Thus the estimated result for CFM at 50 Pa will be 1360 CFM.

The factors depend on the “n” value chosen, and Table 12 is for “n” of 0.60 which is typical for ducts.

Table 12: 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

1.00

1.52

1.01

1.55

1 2 ... 68 69 70 71 72 73 74 75 76 77 78 ... 82 83

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