Thermo Pride MODEL OPA User Manual
Page 72
All installations and services must be performed by qualified service personnel.
71
(
)
,
.
10
.
50
.
9
0614
.
0
392
*
75
.
48
5
*
00123174
.
0
2058
.
0
82
.
1
in
in
D
D
≅
=
⎥
⎦
⎤
⎢
⎣
⎡
+
=
or an increase in duct size of about 1 inch in diameter.
The pressure drops for the remaining branches of the system must be set. This
includes segment “G”; segments “I” and “J”; and segments “K”, “L”, and “M”. To
balance the system, the pressure drop for each branch must be approximately
equal to the pressure drops of the other branches. For example, segment “G”
must equal segments “D”, “E” and “F” combined. Thus,
.
F
E
D
G
P
P
P
P
∆
+
∆
+
∆
=
∆
Likewise for the other branches,
.
.
.
.
1
.
0
.
.
.
1
.
0
G
W
in
P
P
P
G
W
in
P
P
m
l
K
J
I
=
∆
+
∆
+
∆
=
∆
+
∆
Using the previous technique, duct sizes can be found for all the remaining
segments. The duct sizes adequate for the entire supply system are summarized
in Table 7, below.
Table 7: Required Duct Sizes for the Residence in Example 2
Duct
Segment
Air
Flowrate
(CFM)
Circular
Duct Dia.
(in.)
Air Velocity in
Circular Duct
(FPM)
Equivalent
Rectangular
Duct Dim.s
(in.)
A
120
7
449
6 x 6
B
235
9
532
8 x 8
C
350
11
530
10 x 10
D
392
10
719
9 x 9
E
196
7
733
6 x 6
F
742
14
694
13 x 13
G
56
3
1141
N/A
H
798
14
746
13 x 13
I
126
5
924
N/A
J
231
7
864
6 x 6
K
370
10
678
9 x 9
L
304
9
688
8 x 8
M
157
7
587
6 x 6
N/A - Not Applicable