Bryant 987MB Installation, Start-Up, Operating And Service And Maintenance Instructions page 56

987MB: Installation, Start-up, Operating and Service and Maintenance Instructions
Table 17 – Gas Rate (CU ft./hr) (Continued)
240 480 1200
15
225 450 1125
16
212 424 1059
17
200 400 1000
18
189 379
19
180 360
20
21 171 343
22 164 327
23 157 313
24 150 300
25 144 288
26 138 277
27 133 267
28 129 257
29 124 248
30 120 240
31 116 232
32 113 225
33 109 218
106 212
34
103 206
35
100 200
36
97 195
37
95 189
38
92 185
39
90 180
40
88 176
41
86 172
42
84 167
43
82 164
44
80 160
45
78 157
46
76 153
47
75 150
48
73 147
49
Adjust Temperature Rise
NOTE: Blower door must be installed when taking temperature rise
reading. Leaving blower door off will result in incorrect temperature
measurements, due to possible changes in duct static pressure and
airflow.
CAUTION
!
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in:
S Overheating the heat exchangers or condensing flue gases in heat
exchanger areas not designed for condensate.
S Shortened furnace life
S Component damage.
Temperature rise must be within limits specified on furnace rating plate.
Recommended operation is at midpoint of rise range or slightly above.
When setup switch SW1-4 is ON, operation will be near the high end of
the rise range for improved comfort.
Furnace must operate within ranges of temperature rise specified on the
furnace rating plate. Determine air temperature rise as follows:
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
55 65 131
56 64 129
57 63 126
58 62 124
947 59 61 122
900 60 60 120
857 62 58 116
818 64 56 112
783 66 54 109
750 68 53 106
720 70 51 103
692 72 50 100
667 74 48 97
643 76 47 95
621 78 46 92
600 80 45 90
581 82 44 88
563 84 43 86
545 86 42 84
529 88 41 82
514 90 40 80
500 92 39 78
486 94 38 76
474 96 38 75
462 98 37 74
450 100 36 72
439 102 35 71
429 104 35 69
419 106 34 68
409 108 33 67
400 110 33 65
391 112 32 64
383 116 31 62
375 120 30 60
367
1. Place thermometers in return and supply ducts as near furnace as
possible. Be sure thermometers do not see heat exchanger so that
327
radiant heat does not affect readings. This practice is particularly
321
important with straight-run ducts.
316
2. When thermometer
310
temperature from supply-air temperature to determine air
305
temperature rise.
300
NOTE: Temperature rise can be determined for Minimum Heat,
Intermediate Heat and Maximum Heat operation by locking the furnace
290
in each mode of operation. The mode of operation is based on the
281
position of Set-up switch SW1-2 and SW4-2 on the furnace control
273
board.
265
The furnace is capable of automatically providing proper airflow to
257
maintain the temperature rise within the range specified on furnace
250
rating plate. If temperature rise is outside this range, proceed as follows:
243
1. Check gas input for minimum, intermediate and maximum heat
237 operation.
231 2. Check derate for altitude if applicable.
225 3. Check all return and supply ducts for excessive restrictions causing
static pressure greater than 0.5-in. w.c.
220
4. Ensure Min/Int Heat Rise Adjust switch SW1-3 on furnace control
214
is in ON position when a bypass humidifier is used. See
209
for switch location.
205
5. Check Troubleshooting Guide for Variable-Speed Step Modulating
200
Condensing Furnaces.
196
6. Verify correct model plug is installed.
192
To lock the furnace in Minimum Heat:
188
1. Turn SW1-2 ON at the furnace control. Setup switch SW4-2 must
184
be OFF.
180
2. Connect a jumper across R and W/W1 at the thermostat terminals at
178
the furnace control.
173
3. Allow the burners to ignite and the blower to turn on.
170
4. Allow the supply temperature to stabilize and verify the proper rise
range.
167
If the temperature rise is too high or too low in Minimum Heat:
164
1. Remove jumpers from R and W/W1.
161
2. Wait until the blower off delay is completed.
155
3. Turn 115 VAC power off.
150
4. Check the position of setup switch SW1-3. When set to ON, airflow
is raised 18% for Minimum Heat and for Intermediate Heat.
Factory default position is OFF.
5. Turn 115 VAC power on.
6. Re-check Minimum Heat Temperature Rise
To lock the furnace in Intermediate Heat:
1. Turn SW1-2 OFF and SW4-2 ON at the furnace control.
2. Connect a jumper across R and W/W1 at the thermostat terminals at
the furnace control.
3. Allow the burners to ignite and the blower to turn on.
4. Allow the supply temperature to stabilize and verify the proper rise
range.
If the temperature rise is too high or too low in Intermediate Heat:
1. Remove jumpers from R and W/W1.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of setup switch SW1-3. When set to ON, airflow
is raised 18% for Minimum Heat and for Intermediate Heat.
Factory default position is OFF.
5. Turn 115 VAC power on.
6. Re-check Minimum Heat Temperature Rise.
56
readings stabilize, subtract return-air
Table 60