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Table 15 — Thermistor Resistance vs Temperature Values for Supply-Air and Return Air Temperature Sensor
(10,000 ohms)
START-UP
General
Complete the Start-Up Checklist on page CL-1 before attempting
system start-up.
CRANKCASE HEATERS
The 50BVT,V,W,34-064 units include crankcase heaters. Crank-
case heaters are energized as long as there is power to the unit.
Wait 24 hours before starting the compressors to permit warming
by the crankcase heaters.
AFTER 24 hours
, continue with the procedures below.
CONFIRM THE INPUT POWER PHASE SEQUENCE
The input power phase rotation sequence must be L1-L2-L3 =
ABC (or forward or clockwise) as indicated with a phase rotation
meter. Incorrect input phase rotation will cause the compressors to
rotate in reverse, which results in no cooling capacity.
If the compressor is rotating in the wrong direction, it may: emit
increased noise; shut down due to internal overload protection;
have only a small decrease in suction pressure when it starts; or
have only a small increase in discharge pressure when it starts. Al-
so, no cooling will be produced at the evaporator. If any of these
conditions occurs, refer to the Service section to correct the com-
pressor rotation before continuing.
INTERNAL WIRING
Check all electrical connections in unit control boxes; tighten as
required.
RETURN-AIR FILTERS
Check that correct filters are installed in filter tracks (see Tables 2
and 4). Do not operate unit without return-air filters.
COMPRESSOR MOUNTING
Compressors are internally mounted on resilient rubber supports.
Do not loosen or remove compressor holddown bolts.
TEMP
(C)
TEMP
(F)
RESISTANCE
(OHMS)
TEMP
(C)
TEMP
(F)
RESISTANCE
(OHMS)
TEMP
(C)
TEMP
(F)
RESISTANCE
(OHMS)
-39
-39.44
323,839
37
2.78
28,365
113
45.00
4,367
-37
-38.33
300,974
39
3.89
26,834
115
46.11
4,182
-35
-37.22
279,880
41
5.00
25,395
117
47.22
4,006
-33
-36.11
260,410
43
6.11
24,042
119
48.33
3,838
-31
-35.00
242,427
45
7.22
22,770
121
49.44
3,679
-29
-33.89
225,809
47
8.33
21,573
123
50.56
3,525
-27
-32.78
210,443
49
9.44
20,446
125
51.67
3,380
-25
-31.67
196,227
51
10.56
19,376
127
52.78
3,242
-23
-30.56
183,068
53
11.67
18,378
129
53.89
3,111
-21
-29.44
170,775
55
12.78
17,437
131
55.00
2,985
-19
-28.33
159,488
57
13.89
16,550
133
56.11
2,865
-17
-27.22
149,024
59
15.00
15,714
135
57.22
2,751
-15
-26.11
139,316
61
16.11
14,925
137
58.33
2,642
-13
-25.00
130,306
63
17.22
14,180
139
59.44
2,538
-11
-23.89
121,939
65
18.33
13,478
141
60.56
2,438
-9
-22.78
114,165
67
19.44
12,814
143
61.67
2,343
-7
-21.67
106,939
69
20.56
12,182
145
62.78
2,252
-5
-20.56
100,218
71
21.67
11,590
147
63.89
2,165
-3
-19.44
93,909
73
22.78
11,030
149
65.00
2,082
-1
-18.33
88,090
75
23.89
10,501
151
66.11
2,003
1
-17.22
82,670
77
25.00
10,000
153
67.22
1,927
3
-16.11
77,620
79
26.11
9,526
155
68.33
1,855
5
-15.00
72,911
81
27.22
9,078
157
69.44
1,785
7
-13.89
68,518
83
28.33
8,653
159
70.56
1,718
9
-12.78
64,419
85
29.44
8,251
161
71.67
1,655
11
-11.67
60,592
87
30.56
7,866
163
72.78
1,594
13
-10.56
57,017
89
31.67
7,505
165
73.89
1,536
15
-9.44
53,647
91
32.78
7,163
167
75.00
1,480
17
-8.33
50,526
93
33.89
6,838
169
76.11
1,427
19
-7.22
47,606
95
35.00
6,530
171
77.22
1,375
21
-6.11
44,874
97
36.11
6,238
173
78.33
1,326
23
-5.00
42,317
99
37.22
5,960
175
79.44
1,279
25
-3.89
39,921
101
38.33
5,697
177
80.56
1,234
27
-2.78
37,676
103
39.44
5,447
179
81.67
1,190
29
-1.67
35,573
105
40.56
5,207
181
82.78
1,149
31
-0.56
33,599
107
41.67
4,981
183
83.89
1,109
33
0.56
31,732
109
42.78
4,766
185
85.00
1,070
35
1.67
29,996
111
43.89
4,561
187
86.11
1,034
IMPORTANT: On VAV units, fan rotation direction CANNOT
be used for the phase sequence check; fan rotation for VAV
units with a variable speed drive is independent of the unit input
wiring sequence.