Retrotec Commercial 441 and 451 DucTester - Manual (Page 41)

Page 41 of 56
©Retrotec Inc. 2015
How much duct surface area can be tested at one time?
The table below shows the maximum surface area that one Model 400 blower will test if the ducts just
pass. Since ducts will usually be tighter than the minimum specified, much larger areas can normally be
tested than those shown on the table.
Test Pressure,
in WC
Duct Leakage Class ( C
L
), CFM/100 square feet at 1 in WC
1 2 4 8 16 32 48
20 4,066 2,033 1,017 508 254 127 85
10 6,380 3,190 1,595 798 399 199 133
6 8,893 4,446 2,223 1,112 556 278 185
4 11,575 5,787 2,894 1,447 723 362 241
3 13,955 6,977 3,489 1,744 872 436 291
2 18,162 9,081 4,541 2,270 1,135 568 378
1 28,500 14,250 7,125 3,563 1,781 891 594
0.5 44,721 22,361 11,180 5,590 2,795 1,398 932
0.1 127,305 63,652 31,826 15,913 7,957 3,978 2,652
Duct Surface Area, square feet
Table 7 Duct Surface area that can be tested with one Model 400
The extrapolation feature in the gauge allows accurate readings to be taken at 0.1 in WC, so the bottom
row may be used to determine the surface area of duct that can be tested at one time. Duct systems
with larger areas will have to be broken down into sections using barriers and the results added up.
If you cannot achieve 0.1 in WC for the surface areas listed, the ducts will fail the test and must be
sealed up more before additional testing is attempted. Also look for disconnect and sections that are not
correctly blanked off. Check all temporary plugs, plates, sheets, balloons, bags used to seal intentional
openings.