Retrotec DM32X - Page 71

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20
-12.8%
-8.8%
-4.5%
0.0%
4.7%
9.6%
25
-9.9%
-6.7%
-3.4%
0.0%
3.5%
7.2%
30
-7.4%
-5.0%
-2.5%
0.0%
2.6%
5.2%
35
-5.2%
-3.5%
-1.8%
0.0%
1.8%
3.6%
40
-3.3%
-2.2%
-1.1%
0.0%
1.1%
2.3%
45
-1.6%
-1.0%
-0.5%
0.0%
0.5%
1.1%
50
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
55
1.4%
1.0%
0.5%
0.0%
-0.5%
-0.9%
60
2.8%
1.8%
0.9%
0.0%
-0.9%
-1.8%
65
4.0%
2.7%
1.3%
0.0%
-1.3%
-2.6%
70
5.2%
3.4%
1.7%
0.0%
-1.7%
-3.3%
If the “n” value on the gauge is set to 0.60 and the enclosure n is different, an error, as shown in Table 13
will result if the [@ Pressure] function is used at the Achieved Pressure to estimate result at 50 Pa.
Table 9: Errors in Estimated Flow at 50 Pa if gauge "n" = 0.60 differs from actual n
Actual Flow Exponent (n) of Enclosure
0.50
0.55
0.60
0.65
0.70
0.75
Achieved
Pressure (Pa)
10
-14.9%
-7.7%
0.0%
8.4%
17.5%
27.3%
15
-11.3%
-5.8%
0.0%
6.2%
12.8%
19.8%
20
-8.8%
-4.5%
0.0%
4.7%
9.6%
14.7%
25
-6.7%
-3.4%
0.0%
3.5%
7.2%
11.0%
30
-5.0%
-2.5%
0.0%
2.6%
5.2%
8.0%
35
-3.5%
-1.8%
0.0%
1.8%
3.6%
5.5%
40
-2.2%
-1.1%
0.0%
1.1%
2.3%
3.4%
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.



=





 





 




(
  
)
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: