Retrotec DM-2 - Manual (Page 64)

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©Retrotec Inc. 2012
45 -1.0% -0.5% 0.0% 0.5% 1.1% 1.6%
50 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%
55 1.0% 0.5% 0.0% -0.5% -0.9% -1.4%
60 1.8% 0.9% 0.0% -0.9% -1.8% -2.7%
65 2.7% 1.3% 0.0% -1.3% -2.6% -3.9%
70 3.4% 1.7% 0.0% -1.7% -3.3% -4.9%
Achieved pressure is the actual maximum pressure achieved in the enclosure during the test.
𝐸𝑟𝑟𝑜𝑟 = (
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑜𝑓 𝐼𝑛𝑡𝑒𝑟𝑒𝑠𝑡
𝐴𝑐ℎ𝑖𝑒𝑣𝑒𝑑 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒
)
(𝐴𝑐𝑡𝑢𝑎𝑙 𝑛−𝐴𝑠𝑠𝑢𝑚𝑒𝑑 𝑛)
In the tables, the Pressure of Interest is 50Pa, and Assumed n is 0.65 or 0.60
The actual flow exponent n for an enclosure can be calculated by measuring building leakage at
multiple pressure differences, from 10 to 50 Pa, and determining the slope of the line:
Flow = C ×𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑛
The graph of pressure versus flow will be linear if graphed on a log-log scale, and the slope will be n.