Bryant Series B 345MAV - Manual (Page 38)

c. Measure time (in sec) for gas meter test dial to complete
1 revolution.
d. Refer to Table 9 for cu ft of gas per hr.
e. Multiply gas rate (cu ft/hr) X heating value (Btu/cu ft)
using natural gas heating value from local gas
utility/supplier.
EXAMPLE:
Btu heating input = Btu/cu ft X cu ft/hr
Heating value of gas = 975 Btu/cu ft
Time for 1 revolution of 2-cu ft dial = 70 sec
Gas rate = 103 cu ft/hr (from Table 9)
Btu heating input = 103 X 975 = 100,425 Btuh
In this example, the orifice size and manifold pressure
adjustment is within
±
2 percent of the furnace input
rate.
B. Set Temperature Rise
CAUTION: Temperature rise must be within limits
specified on unit rating plate. Recommended operation is
at midpoint of rise or above. Failure to follow this caution
may result in condensing or overheating the heat ex-
changers.
Determine and adjust air temperature rise as follows:
1. Place thermometers in return and supply ducts as close to
furnace as possible. Be sure thermometers do not see heat
exchanger so that radiant heat does not affect readings. This
practice is particularly important with straight-run ducts.
2. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine air
temperature rise.
3. Adjust temperature rise by adjusting blower speed. Increase
blower speed to reduce temperature rise. Decrease blower
speed to increase temperature rise.
WARNING: Disconnect 115-v electrical power before
changing speed tap. Failure to follow this warning could
result in personal injury.
4. To change blower motor speed selections for heating mode,
remove blower motor lead from control center HEAT
terminal. (See Fig. 27.) Select desired blower motor speed
lead from 1 of the other terminals and relocate it to HEAT
terminal. See Table 10 for lead color identification. Recon-
nect original lead on SPARE terminal.
Follow this same procedure for proper COOL speed selec-
tion.
C. Blower Off Delay (Heat Mode)
The main blower off time delay period is factory-set at 135 sec and
is not field-adjustable.
D. Set Thermostat Heat Anticipator
Thermostat heat anticipator must be set to match amp draw of
components in R-W circuit. Accurate amp draw measurements can
be obtained at thermostat subbase terminals R and W.
Fig. 42 illustrates an easy method of obtaining these measure-
ments. Amp reading should be taken after blower motor has
started. See thermostat manufacturer’s instructions for adjusting
heat anticipator and for varying heating cycle length.
TABLE 9—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
TABLE 10–SPEED SELECTOR
COLOR SPEED
FACTORY-
SHIPPED
CONNECTION
Black High Cool
Yellow (When Present) Medium High Spare
Blue Medium Low Heat
Red Low Spare
White Common Com
Fig. 42—Amp Draw Check with Ammeter
A80201
R Y W G
10 TURNS
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
HOOK-AROUND
VOLT/AMMETER
EXAMPLE:
5.0 AMPS ON AMMETER
10 TURNS AROUND JAWS = 0.5 AMPS FOR THERMOSTAT SETTING
FROM UNIT 24-VOLT
TERMINAL BLOCK
—38—