32 18-CD35D1-1
INSTALLER’S GUIDE
HIGH ALTITUDE DERATE
Input ratings (BTUH) of these furnaces are based on sea level
operation and should not be changed at elevations 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.
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 pressure (min 3.0 - max 3.7 in. W.C. - Natural Gas
for upflow models and min 3.0 - max 4.5 in. W.C. - Natural
Gas for downflow models) or changing orifices (orifice change
may not always be required). 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.
Installation of this furnace at altitudes above 2,000 ft. (610m)
shall be in accordance with the 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 149.1. 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.
IMPORTANT:
Re-install the propane orifices to the same depth
as the orifices supplied with the equipment.
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
TABLE 18
Y
ROTATE THE FRONT
COVER INWARD
MAKING SURE THAT ALL
SIDE FLANGES
ARE OUTSIDE OF THE
BOX.
INSERT THE TOP LANGE
OF THE FRONT COVER
UNDER THE LIP INSIDE
THE BOX
ALL SIDE FLANGES
MUST BE OUTSIDE OF
THE BOX
ROTATE THE FRONT
COVER AS SHOWN