Duct surface area, square feet, Air handler flow rate, cfm – Retrotec Commercial 441 and 451 DucTester User Manual
Page 48
Page 48 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 9 Duct Area that can be tested
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.
What Air Handler Flow Rate can be tested at one time?
The table below shows the maximum air handler flow rate that one Model 400 blower will test if the
ducts just pass. Since ducts will usually be tighter than the minimum specified, much flow rates can
normally be accommodated by the Model 400 than those shown on the table.
Test Pressure,
in WC
Allowable Loss Rate, %
1
2
3
4
5
6
8
20
4,066
2,033
1,355
1,017
813
678
508
10
6,380
3,190
2,127
1,595
1,276
1,063
798
6
8,893
4,446
2,964
2,223
1,779
1,482
1,112
4
11,575
5,787
3,858
2,894
2,315
1,929
1,447
3
13,955
6,977
4,652
3,489
2,791
2,326
1,744
2
18,162
9,081
6,054
4,541
3,632
3,027
2,270
1
28,500
14,250
9,500
7,125
5,700
4,750
3,563
0.5
44,721
22,361
14,907
11,180
8,944
7,454
5,590
0.1
127,305
63,652
42,435
31,826
25,461
21,217
15,913
Air Handler Flow Rate, CFM
Table 10 Airhandler Flow rate that can be tested