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Installer's Guide
6. To increase outlet pressure, turn the regulator
adjust screw clockwise. To decrease outlet
pressure, turn the regulator adjust screw
counterclockwise. The final Manifold Pressure
setting shall be as specified in Table 9 with an
input of no more than nameplate rating and
no less than 93% of the nameplate rating, un-
less the unit is derated for high altitude.
7. Replace high adjustment regulator cover screw
and tighten securely.
8. Cycle the Valve several times to verify regula-
tor setting.
f. Turn off all electrical power to the system.
g. Remove the Manometer and flexible tubing. Re-
move the barbed fitting and replace the plug or
tighten the pressure test screw.
h. Turn on electrical power to the system and ener-
gize valve.
i. Using a leak detection solution or soap suds,
check for leaks at plug or pressure boss screw.
NOTE: The Manifold Pressure must be referenced to
the Burner Box. The Burner Box pressure tap equal-
izes the Gas Valve pressure regulator. Manifold Pres-
sure 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 16.
Table 7 lists the main burner orifices used with the Fur-
nace. If a change of orifices is required to correct the
Furnace input rating refer to Table 10.
TABLE 8
GAS FLOW IN CUBIC FEET PER HOUR
2 CUBIC FOOT DIAL
SEC. FLOW SEC. FLOW SEC. FLOW SEC. FLOW
8
900
29
248
9
800
30
240
10
720
31
232
11
655
32
225
12
600
33
218
13
555
34
212
14
514
35
206
15
480
36
200
16
450
37
195
17
424
38
189
18
400
39
185
19
379
40
180
20
360
41
176
21
343
42
172
22
327
43
167
23
313
44
164
24
300
45
160
25
288
46
157
26
277
47
153
27
267
48
150
28
257
49
147
22
50
144
82
88
51
141
84
86
52
138
86
84
53
136
88
82
54
133
90
80
55
131
92
78
56
129
94
76
57
126
96
75
58
124
98
73
59
122
100
72
60
120
104
69
62
116
108
67
64
112
112
64
66
109
116
62
68
106
120
60
70
103
124
58
72
100
128
56
74
97
132
54
76
95
136
53
78
92
140
51
80
90
144
50
TABLE 9
FINAL MANIFOLD PRESSURE SETTINGS (inches w.c.)
FUEL
2nd Stage Max.
NATURAL GAS
3.5" W.C.
LP GAS
10.5" W.C.
REINSTALLATION OF THE BURNER BOX COVER
Figure 18 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.
HIGH ALTITUDE DERATE
Input ratings (BTUH) of these Furnaces are based on
sea level operation and should not be changed at eleva-
tions up to 2,000 ft.
If the installation is 2,000 ft. or above, the Furnace input
rate (BTUH) shall be reduced 4% for each 1,000 ft. above
sea level.
Installation of this furnace at altitudes above 2,000 ft.
(610m) shall be in accordance of local codes, the Na-
tional Fuel Gas Code, ANSI Z223.1/ NFPA 54 or Na-
tional Standard of Canada, Natural Gas and Propane
Installation Code, CSA 149.1. Installation of this fur-
nace at altitudes above 2,000 ft. (610m) shall be made in
accordance with the listed high Altitude Conversion Kit
available with this furnace.
The Furnace input rate shall be checked by clocking the
gas flow rate (CFH) and multiplying by the heating
value obtained from the local utility supplier for the gas
being delivered at the installed altitude.
changes can be made by adjusting the Manifold Pres-
sure (min 3.0 - max 3.7 in. W.C. - Natural Gas) or
changing orifices (orifice change may not always be re-
quired).
If the desired input rate can not be achieved with a
change in Manifold Pressure, then the orifices must be
changed. LP installations will require an orifice change.
IMPORTANT:
Reinstall the propane orifices to the same depth as the ori-
fices supplied with the equipment.
See Table 11 for help in selecting orifices if orifice change
is required. Furnace input rate and temperature rise
should be checked again after changing orifices to con-
firm the proper rate for the altitude.
An optional high altitude kit is available for installations
above 5000 feet. Installations above 12,000 feet are not
allowed.
1st Stage Max.
1.7" W.C.
6.0" W.C.
Input rate
18-CD24D1-2
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