34
18-CD37D1-2-EN
Installer’s Guide
Table 16
GAS FLOW IN CUBIC FEET PER HOUR
2 CUBIC FOOT DIAL
SEC. FLOW SEC. FLOW SEC. FLOW SEC. FLOW
8
900
29
248
50
144
82
88
9
800
30
240
51
141
84
86
10
720
31
232
52
138
86
84
11
655
32
225
53
136
88
82
12
600
33
218
54
133
90
80
13
555
34
212
55
131
92
78
14
514
35
206
56
129
94
76
15
480
36
200
57
126
96
75
16
450
37
195
58
124
98
73
17
424
38
189
59
122
100
72
18
400
39
185
60
120
104
69
19
379
40
180
62
116
108
67
20
360
41
176
64
112
112
64
21
343
42
172
66
109
116
62
22
327
43
167
68
106
120
60
23
313
44
164
70
103
124
58
24
300
45
160
72
100
128
56
25
288
46
157
74
97
132
54
26
277
47
153
76
95
136
53
27
267
48
150
78
92
140
51
28
257
49
147
80
90
144
50
REINSTALLATION OF THE BURNER BOX COVER
Figure 59 shows the correct way to reinstall the burner box
cover if adjustment or replacement of the flame sensor, hot
surface igniter, or main burner orifices have required removal
of the cover.
Figure 59
NOTE: The manifold pressure must be referenced to the
burner box. The burner box pressure tap equalizes the gas
valve pressure regulator. Manifold pressure is checked by
installing a tee (field supplied) in the tubing, between the
tee coming from the burner box tube and the gas valve,
in addition to the regular gas valve pressure tap on the
outlet side of the gas valve. See Figure 59.
Table 19 lists the main burner orifices used with the furnace.
If a change of orifices is required to correct the furnace input
rating refer to Table 17.
▲
WARNING
!
HAZARD OF EXPLO-
SION
REPLACE AND/ OR
TIGHTEN ALL PLUGS
REMOVED OR LOOS-
ENED WHEN ADJUST-
ING GAS PRESSURE.
LEAK CHECK THE FIT-
TINGS BEFORE PLAC-
ING THE FURNACE INTO
REGULAR SERVICE.
FAILURE TO FOLLOW
THIS WARNING COULD
RESULT IN FIRE, EX-
PLOSION, PROPERTY
DAMAGE, OR DEATH.
See
inset
Field supplied barb fitting
with manometer tube is
attached to the “OUTLET
PRESSURE TAP” on the
outlet side of the gas valve.
Separate the tube
at the unit Tee and
reconnect with a
short piece of field
supplied tube and
another Tee with
the “U” Manometer
attached.
Be sure to reconnect
unit tubing to original
position after testing
the manifold pressure!
CORRECT METHOD OF CHECKING DIRECT VENT MANIFOLD
PRESSURE WITH BURNER BOX REFERENCED