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Design the filter and associated ductwork for the best match of
pressure drop versus filter size. Best practice usually chooses filter
systems with pressure drops under 0.2 in. W.C. (50 Pa), with the
best blower electrical efficiency and system airflow performance
occurring with filter pressure drops under 0.1 in. W.C. (25 Pa).
Due to the relatively high pressure drops of 1- -in. (25 mm) thick
after- -market filter media, it is recommended that the filtration
system be designed for at least 2- -in. (51 mm) thick media.
TIPS FROM CONTRACTORS: Install a media cabinet capable
of incorporating a 4- -in. (102 mm) thick media filter. This allows
room for future upgrades to other IAQ devices.
14 x 25 Filter
CFM
L/s
600
(283)
800
(378)
1000
(472)
1200
(566)
16x 25 Filter
CFM
L/s
600
(283)
800
(378)
1000
(472)
1200
(566)
1400
(661)
1600
(755)
1800
(850)
20 x 25 Filter
CFM
(L/s)
800
(378)
1000
(472)
1200
(566)
1400
(661)
1600
(755)
1800
(850)
2000
(944)
2200
(1038)
25 x 25 Filter
CFM
L/s
800
(378)
1000
(472)
1200
(566)
1400
(661)
1600
(755)
1800
(850)
2000
(944)
2200
(1038)
Representative estimates from filter manufacturer data sheets.
*
See manufacturers' specifications for pressure drop versus airflow data for specific filter media.
If the filter size that you are looking for is not contained in Table 5, refer to 6 for a comparison of Pressure Drop (initial/clean
resistance to airflow) versus Face Velocity for a variety of filter media types.
The following equations relate Face Velocity (FPM), Filter Area and Airflow (CFM):
Filter Face Velocity = Airflow / Filter Area
Minimum Filter Area = Rated System Airflow / Maximum Filter Face Velocity
440 01 6101 00
Table 5 – Filter Media Pressure Drop (Clean) Versus Airflow - - In. W.C. (Pa)
Factory-Accy
Washable
(1-in. / 2.5 cm)
(1-in. / 2.5 cm)
0.04
(12)
0.07
0.06
(15)
0.10
0.07
(18)
0.13
0.08
(20)
0.17
Factory-Accy
Washable
(1-in. / 2.5 cm)
(1-in. / 2.5 cm)
0.04
(10)
0.06
0.05
(13)
0.08
0.06
(16)
0.11
0.07
(18)
0.14
0.08
(21)
0.18
0.09
(23)
0.21
0.10
(25)
0.26
Factory-Accy
Washable
(1-in. / 2.5 cm)
(1-in. / 2.5 cm)
0.04
(11)
0.06
0.05
(13)
0.08
0.06
(15)
0.11
0.07
(17)
0.13
0.08
(19)
0.16
0.08
(21)
0.18
0.09
(23)
0.21
0.09
(24)
0.25
Factory-Accy
Washable
(1-in. / 2.5 cm)
(1-in. / 2.5 cm)
0.03
(9)
0.05
0.04
(11)
0.06
0.05
(13)
0.08
0.06
(15)
0.10
0.06
(16)
0.11
0.07
(18)
0.13
0.08
(19)
0.16
0.08
(21)
0.18
Specifications subject to change without notice.
NOTICE
Design the duct system FIRST to determine how much
pressure drop may be allowed in the filter system. See the Air
Ducts
section.
Excessive
compromises system airflow and duct performance, causes
inadequate airflow to the furthest ends of the duct system, as
well as causes excess noise and higher than anticipated
electrical consumption.
Provide duct transitions, as required, to smoothly transition airflow
from the return duct system to the filter (or IAQ device) to the
furnace when the dimensions of the ductwork or furnace return air
opening do not match the required filter or IAQ device dimensions.
See the instructions supplied with factory- -accessory duct adapters.
Representative After-Market Filter Media*
Fiberglass*
(2-in. / 5 cm)
(17)
0.10
(26)
(25)
0.15
(39)
(34)
0.21
(52)
(43)
0.27
(68)
Representative After-Market Filter Media*
Fiberglass*
(2-in. / 5 cm)
(15)
0.09
(22)
(21)
0.13
(32)
(28)
0.17
(43)
(36)
0.22
(56)
(45)
0.28
(70)
(54)
-
-
(64)
-
-
Representative After-Market Filter Media*
Fiberglass*
(2-in. / 5 cm)
(16)
0.09
(24)
(21)
0.13
(32)
(27)
0.16
(41)
(33)
0.20
(51)
(40)
0.24
(61)
(47)
0.29
(73)
(54)
-
-
(62)
-
-
Representative After-Market Filter Media*
Fiberglass*
(2-in. / 5 cm)
(12)
0.07
(18)
(16)
0.09
(24)
(20)
0.12
(31)
(24)
0.15
(38)
(29)
0.18
(45)
(34)
0.21
(53)
(39)
0.24
(61)
(45)
0.28
(70)
filter
pressure
drop
Pleated*
(1-in. / 2.5 cm)
(2-in. / 5 cm)
0.24
(60)
0.16
0.34
(85)
0.23
-
-
0.32
-
-
-
Pleated*
(1-in. / 2.5 cm)
(2-in. / 5 cm)
0.20
(51)
0.13
0.29
(72)
0.20
-
-
0.27
-
-
-
-
-
-
-
-
-
-
-
-
Pleated*
(1-in. / 2.5 cm)
(2-in. / 5 cm)
0.22
(55)
0.15
0.29
(72)
0.20
-
-
0.25
-
-
0.31
-
-
-
-
-
-
-
-
-
-
-
-
Pleated*
(1-in. / 2.5 cm)
(2-in. / 5 cm)
0.17
(43)
0.11
0.22
(55)
0.15
0.27
(68)
0.18
-
-
0.23
-
-
0.28
-
-
-
-
-
-
-
-
-
often
(40)
(59)
(81)
-
(34)
(49)
(67)
-
-
-
-
(37)
(49)
(63)
(79)
-
-
-
-
(28)
(37)
(47)
(58)
(69)
-
-
-
27
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