Carrier 58DH - Page 6

Table 2 — Gas Rate (Cu Ft Per Hr)
SECONDS
SIZE OF
SECONDS
SIZE OF
FOR ONE
TEST DIAL
FOR ONE
TEST DIAL
REVOLU-
1
2 5
REVOLU-
1
2
5
TION
cu ft cu ft
cu ft
TION
cuft
cu ft
cu ft
10
360
720 1800 50
72
144
360
11
327 655
1636 51
71
141
355
12
300 600
1500 52
69 138 346
13
277
555 1385 53
68
136 340
14 257
514 1286
54
67
133 333
15
240 480
1200
55
65 131
327
16
225 450
1125 56
64
129
321
17
212
424 1059 57
63
126 316
18
200 400
1000 58
62 124 310
19
189
379
947
59
61 122
305
20
180 360
900 60
60
120 300
21
171
343
857 62
58
116 290
22
164 327
818
64
56 112
281
23
157 313
783
66
54
109
273
24
150
300
750
68
53 106 265
25
144
288
720
70
51
103 257
26 138
277
692
72 50
100 250
27
133
267
667
74
48
97 243
28
129
257
643
76
47
95 237
29
124 248
621 78
46
92
231
30
120
240
600 80
45
80
225
31
116
232 581
82
44
78
220
32
113 225
563
84 43
76
214
33
109
218 545 86
42
75
209
34 106
212 529 88
41
74
205
35
103 206
514
90
40 80
200
36
100 200
500 92
39 78
196
37
97 195
486 94
38 75 192
38
95 189
474 96
38 75 188
39
92
185 462 98
37 74 184
40
90 180
450 100
36 72 180
41 88
176 439 102
35
71 178
42 86
172 429
104
35 69 173
43
84 167 419
106
34 68 170
44
82 164 409
108
33 67
167
45
80 160
400
110
33 65
164
46
78
157
391
112
32 64 161
47
76 153
383
116
31 62 155
48 75
150
375
120 30
60 150
49
73 147
367
f. To adjust input rate, remove cap that conceals regu¬
lator adjustment. Turn adjusting screw counterclock¬
wise (out) to decrease input When adjusting, DO
NOT change manifold pressure more than 0.3 in. wg.
Make any major adjustment by changing main burner
orifices.
HIGH ALTITUDE — Ratings are approved for altitudes
to 2000 ft for all gases. Ratings for altitudes over 2000 ft
are 4% less for each 1000 ft above sea level. (Furnace must
be derated by changing main burner orifices.)
BURNER AND PILOT FLAMES — The main burner
flame should be clear blue, almost transparent. The pilot
flame should be well defined. See Fig. 6.
Temperature Rise — Do not exceed the range of
temperature rise specified on the unit rating plate. Deter¬
mine the air temperature rise as follows:
1. Place duct thermometers in return and supply ducts
as near furnace as possible. Be sure thermometers do
not “see" heat element so that radiant heat will not
affect thermometer readings. This is particularly
important with straight-run ducts.
2. When thermometer readings stabilize, subtract return-
air temperature from supply-air temperature to deter¬
mine air temperature rise.
3. Adjust air temperature rise by adjusting blower speed.
Increase blower speed to reduce temperature rise.
Decrease blower speed to increase temperature rise.
Thermostat Heat Anticipator Check — Thermo¬
stat heat anticipator must be set to match amp draw of
gas valve and electrical components in R-W circuit.
Accurate amp draw readings can be obtained at thermo¬
stat subbase terminals R & W. Figure 7 illustrates an easy
method of obtaining actual amp draw. Amp reading
should be taken after blower motor has started.
Fig. 7 — Amp Draw Check with Ammeter
Limit Control Safety Check — This control shuts
off the combustion control system and energizes the
circulating-air blower motor if the furnace overheats.
The recommended method of checking the limit con¬
trol is to gradually block off the return air after the
furnace has been operating for at least 5 minutes. As soon
as the limit has proven safe, the return air opening should
be unblocked to permit normal air circulation. By
using this method to check the limit control, it can be
established that the limit is functioning properly and will
“fail-safe” if there is a motor failure. The downflow/
horizontal furnaces have a manual reset limit switch
located on blower housing.
Flow-Sensing Switch Safety Check — This con¬
trol proves operation of the draft inducer blower. Check
as follows:
1. Turn off 115-volt power to furnace.
2. Remove control door and disconnect inducer motor
lead wires from inducer printed-circuit board.
3. Turn on 115-volt power to furnace.
4. Close thermostat switch as if making a normal furnace
start. The pilot should light and then cycle off and on.
If main burners do not light, flow-sensing switch is
functioning properly.
5. Turn off 115-volt power to furnace.
6. Reconnect inducer motor wires, replace control door,
turn on 115-volt power.
Draft Safeguard Switch Safety Check — This
control permits safe shutdown of furnace during certain
blocked flue conditions. Check as follows:
1. Disconnect power to furnace and remove vent pipe
from furnace outlet collar. Allow time for vent pipe
to cool before removing.
2. Set room thermostat above room temperature and
restore power to furnace.
3. After normal start-up, allow furnace to operate 2
minutes. Block (100%) flue outlet. Furnace should
cycle off within 2 minutes.
4. Reconnect vent pipe to furnace outlet collar.
5. Wait 5 minutes. Reset draft safeguard switch.
6