34
18-CD25D1-2
Installer’s Guide
6.
To increase outlet pressure, turn the regu
lator adjust screw clockwise. To decrease
outlet pressure, turn the regulator adjust
screw counter-clockwise. 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, unless the unit is de-
rated for high altitude.
7.
Replace high adjustment regulator cover
screw and tighten securely.
8.
Cycle the Valve several times to verify
regulator setting.
g.
Turn off all electrical power to the system.
h. Remove the Manometer and flexible tubing.
Remove the barbed fitting and replace the plug
or tighten the pressure test screw.
i.
Turn on electrical power to the system and en-
ergize valve.
j.
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 equalizes
the Gas Valve pressure regulator. Manifold Pressure is
checked by installing a tee (field supplied) in the tub-
ing, 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 32.
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.
REINSTALLATION OF THE BURNER BOX COVER
Figure 34 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 with local codes, or in the
absence of local codes, the
National Fuel Gas Code,
ANSI Z223.1/ NFPA 54
or
National Standard of
Canada, Natural Gas and Propane Installation Code,
CSA B149.1
. Installation of this furnace 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. Input rate
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.
TABLE 8
TABLE 9
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
FINAL MANIFOLD PRESSURE SETTINGS (inches w.c.)
FUEL
2nd Stage Max.
1st Stage Max.
NATURAL GAS
3.5" W.C.
1.7" W.C.
LP GAS
10.5" W.C.
6.0" W.C.
See Table 10 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.
The vent length table on page 14 shows the required
vent lengths for installations at various altitudes. An op-
tional high altitude kit is available for installations
above 5000 feet. Installations above 12,000 feet are not
allowed.
