OM0280
Page 42 of 63
Rev 3 July/2021
Alternate Procedure:
The alternative procedure to determine inflow velocity uses a Thermo anemometer in a constricted window access opening
of 3 inches (76mm) with the armrest removed. Inflow air velocity is measured in the center of the constricted opening
1-1/2 inches (38mm) blow the top of the work access opening on the following specified grid.
Use the correction factor table to calculate the inflow velocity.
c. Test Data - Inches (mm):
1. Dim Measurement
Inflow Volume
ft.
3
/min.(m
3
/s)
Access Opening
ft.
2
(m
2
)
Inflow Velocity fpm(mps)
2. Constricted 3 inch (76mm) high access opening measurement - Inches (mm):
300E
4
8.396
12.792
17.188
21.584
25.980
30.375
(102)
(213)
(325)
(437)
(548)
(660)
(771)
400E
4
8.264
12.528
16.792
21.056
25.320
29.584
33.848
38.112
42.375
(102)
(210)
(318)
(426)
(535)
(643)
(751)
(860)
(968)
(1076)
500E
4
8.198
12.396
16.594
20.792
24.990
29.188
33.386
37.584
41.782
45.980
50.178
54.375
(102)
(208)
(315)
(421)
(528)
(635)
(741)
(848)
(955)
(1061)
(1168)
(1274)
(1381)
600E
4
8.158
12.316
16.474
20.632
24.790
28.948
33.106
37.264
41.422
45.580
49.738
53.896
58.054
62.212
66.375
(102)
(207)
(313)
(418)
(524)
(630)
(735)
(841)
(946)
(1052)
(1158)
(1263)
(1369)
(1475)
(1580)
(1686)
Number of Readings:
Average Velocity of Constricted Area fpm(mps)
1.
Average Velocity of Constricted Area
fpm (m/s)
2.
X
Constricted Access Area
ft
2
(m
2
)
3.
=
Constricted Area Volume
CFM(m
3
/s)
4.
Constricted Area Volume
CFM(m
3
/s)
5.
10”(254) Access Window Area
ft
2
(m
2
)
6.
=
Average Velocity of 10”(254)
Access Window Area
fpm (m/s)
7.
Average Velocity of
10”(254)
Access Window Area
fpm (m/s)
8.
X
Correction Factor for Window Height
9.
=
Average Inflow Velocity
fpm (m/s)
d. Acceptance Criteria: Access Opening Inflow Velocity = 100 to 110 fpm (.51 to .56 m/s)
Areas/Correction Factors for Calculations
Cabinet
Size
3" (76mm) Constricted
Window Access Area
10" (254mm)
Window Access
Opening
Correction Factor for
10" (254mm) Window
300E
.72
(.067)
2.39
(.222)
1.01
400E
.97
(.090)
3.22
(.299)
1.0
500E
1.22
(.113)
4.05
(.376)
1.0
600E
1.47
(.137)
4.89
(.454)
1.02
Summary of Contents for LabGard NU-540-300E
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