32
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.
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