a. Place duct thermometers in return and supply ducts as near
furnace as possible. Be sure thermometers do not "see" heat
exchangers so that radiant heat will not affect thermometer
readings. This is particularly important with straight-run
ducts.
b. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine tem-
perature rise.
c. Adjust air temperature rise by adjusting blower speed.
Increase blower speed to reduce temperature rise. Decrease
blower speed to increase temperature rise.
Disconnect the electrical power before changing the speed
tap. A failure to follow this warning could result in personal
injury.
d. To change motor speed taps, remove the motor tap lead and
relocate it on the desired terminal on the plug-in terminal
block/speed selector located on the blower housing. (See
Table 9.)
Table 8—Canadian Orifice Size
GAS
SEA LEVEL
0—2000
HIGH ALTITUDE
2001—4500 FT
Natural
44
45
Propane
54
55
Table 9—Speed Selector
SPEED
TAP NO.*
Common
C
High
1
Med-High
2
Med-Low
3
Low
4
* White wire from control box to common; black wire from control box to cooling
speed selection; red wire from control box to heating and constant fan speed
selection.
Recheck the temperature rise. It must be within the limits
specified on the unit rating plate. Recommended operation is
at midpoint of rise or above.
3. Set thermostat heat anticipator
The thermostat heat anticipation must be set to match the amp
draw of the electrical components in the R-W circuit. Accurate
amp draw readings can be obtained at thermostat subbase
terminals R and W. Fig. 14 illustrates an easy method of
obtaining the actual amp draw. The amp reading should be
taken after the blower motor has started. See the thermostat
manufacturer’s instructions for adjusting the heat anticipator
and for varying the heating cycle length.
NOTE:
When using an electronic thermostat, set cycle rate for 3
cycles per hr.
CHECK SAFETY CONTROLS
1. Check operation of gas shut-off control for 100 percent
shutoff.
NOTE:
The furnace pilot must be lit so the thermocouple
energizes the thermal magnet circuit of gas valve GV, which
permits gas flow to the remaining portion of the valve.
If the pilot flame is extinguished, the thermocouple will no
longer energize the thermal magnet circuit of the gas valve.
Gas flow to the pilot and main burners will cease until the pilot
is manually relit.
a. With furnace operating, unscrew pilot thermocouple lead
from gas valve. The pilot and main burner gas must shut
off. No gas should flow through valve.
b. After valve is found to operate satisfactorily, reconnect
thermocouple to gas valve (fingertight position only).
Fig. 13—Burner Flame
A84076
BURNER FLAME
PILOT FLAME
BURNER
MANIFOLD
Table 7—Gas Rate Cu Ft/Hr
SECONDS
FOR 1
REVOLUTION
SIZE OF TEST DIAL
SECONDS
FOR 1
REVOLUTION
SIZE OF TEST DIAL
1
cu ft
2
cu ft
5
cu ft
1
cu ft
2
cu ft
5
cu ft
10
11
12
13
14
360
327
300
277
257
720
655
600
555
514
1800
1636
1500
1385
1286
50
51
52
53
54
72
71
69
68
67
144
141
138
136
133
360
355
346
340
333
15
16
17
18
19
240
225
212
200
189
480
450
424
400
379
1200
1125
1059
1000
947
55
56
57
58
59
65
64
63
62
61
131
129
126
124
122
327
321
316
310
305
20
21
22
23
24
180
171
164
157
150
360
343
327
313
300
900
857
818
783
750
60
62
64
66
68
60
58
56
54
53
120
116
112
109
106
300
290
281
273
265
25
26
27
28
29
144
138
133
129
124
288
277
267
257
248
720
692
667
643
621
70
72
74
76
78
51
50
48
47
46
103
100
97
95
92
257
250
243
237
231
30
31
32
33
34
120
116
113
109
106
240
232
225
218
212
600
581
563
545
529
80
82
84
86
88
45
44
43
42
41
90
88
86
84
82
225
220
214
209
205
35
36
37
38
39
103
100
97
95
92
206
200
195
189
185
514
500
486
474
462
90
92
94
96
98
40
39
38
38
37
80
78
76
75
74
200
196
192
188
184
40
41
42
43
44
90
88
86
84
82
180
176
172
167
164
450
439
429
419
409
100
102
104
106
108
36
35
35
34
33
72
71
69
68
67
180
178
173
170
167
45
46
47
48
49
80
78
76
75
73
160
157
153
150
147
400
391
383
375
367
110
112
116
120
33
32
31
30
65
64
62
60
164
161
155
150
12
