28
TIME FOR
TIME FOR
ONE REVOLUTION
ONE REVOLUTION
(SECONDS)
1
5
10
(SECONDS)
1
5
10
24
150
750
1500
80
45
225
450
26
138
692
1385
82
44
220
439
28
129
643
1286
84
43
214
429
30
120
600
1200
86
42
209
419
32
113
563
1125
88
41
205
409
34
106
529
1059
90
40
200
400
36
100
500
1000
92
39
196
391
38
95
474
947
94
38
191
383
40
90
450
900
96
38
188
375
42
86
429
857
98
37
184
367
44
82
409
818
100
36
180
360
46
78
391
783
102
35
176
353
48
75
375
750
104
35
173
346
50
72
360
720
106
34
170
340
52
69
346
692
108
33
167
333
54
67
333
667
110
33
164
327
56
64
321
643
112
32
161
321
58
62
310
621
114
32
158
316
60
60
300
600
116
31
155
310
62
58
290
581
118
31
153
305
64
56
281
563
120
30
150
300
GAS FLOW RATE (CUBIC FEET PER HOUR)
CUBIC FEET PER REVOLUTION OF
METER
CUBIC FEET PER REVOLUTION OF
METER
Table 11. Gas Flow Rate
after the gas valve is closed. This timing can be
changed using the BLOWER OFF timing switch
opposite the terminal block on the control board
(See Figure 27).
Verifying Burner Operation
To verify operation of the burners, remove front
door and ensure that the door switch is in the “on”
position (see Figure 29). Set the thermostat above
room temperature and observe the ignition se-
quence. The flame can be observed through the
small clear window on the burner box. The burner
flame should carry over between all burners. The
flames should be blue, without yellow tips. Flames
should extend from each burner without lifting,
curling, or floating. After verifying ignition, set the
thermostat below room temperature and verify
that the burner flame extinguishes completely.
Replace the front door.
Verifying Operation of the Supply Air
Limit Switch
To verify operation of the supply air limit switch,
make sure that the blower door is in place and
that there is power to the furnace. Completely
block the return airflow to the furnace by install-
ing a close-off plate in place of or upstream of
the filter(s). Set the thermostat above room
temperature and verify that the Sequence of
Operation is as described in these instructions.
The supply air limit switch should function to
turn off the gas valve within approximately five
minutes. The circulating air and combustion
blowers should continue to run when the supply
air limit switch opens. Remove the close-off
plate immediately after the supply air limit switch
opens. If the furnace operates for more than five
minutes with no return air, set the thermostat
below room temperature, shut off the power to
the furnace, and replace the supply air limit
switch.
DESCRIPTION OF COMPONENTS
Figure 29 shows the location of each of the
functional components described below. If any
component of the furnace must be replaced,
use only factory authorized replacement parts.
Contact your distributor for the approved re-
placement parts.
Flame Sensor – The flame sensor acts to
prove that flame has carried over from the
ignitor to the opposite end burner. If no flame is
sensed, the furnace will be shut down automati-
cally.
