user manual

16
Application, Operation, & Maintenance Manual DXM2 UNIT CONTROLS Heat Controller, Inc.
Table 9: Nominal resistance at
various temperatures
DXM2 Service & Application Notes
Table 8: 1% Sensor Calibration Points
Temp (°F)
Minimum
Resistance
(Ohm)
Maximum
Resistance
(Ohm)
Nominal
Resistance
(Ohm)
78.5 9523 9715 9619
77.5 9650 9843 9746
76.5 10035 10236 10135
75.5 10282 10489 10385
33.5 30975 31598 31285
32.5 31871 32512 32190
31.5 32653 33310 32980
30.5 33728 34406 34065
1.5 80624 82244 81430
0.5 83327 85002 84160
0.0 84564 86264 85410
Pressure Switches
All pressure switches are designed to be normally closed
during normal operating conditions, and to open upon fault.
Condensate Sensor – The Condensate Sensor input will
fault upon sensing impedance less than 100,000 Ohms for
30 continuous seconds. The recommended design uses
a single wire terminated with a male 1/4” quick connect
located in the drain pan at desired trip level. Upon a high
condensate level the water will short between the air coil
and the quick connect producing a resistance less than
100,000 Ohms. Since condensate is free of impurities,
it has no conductivity. Only the impurities from the drain
pan and coil dust or dirt create the conductance. A second
ground wire with appropriate terminal to the drain pan can
be used with the control to replace the air coil ground path.
The Condensate Sensor can also essentially be any open
contact that closes upon a fault condition.
Thermistor Temperature Sensors – The thermistors used
with the DXM2 are NTC (negative temperature coeffi cient)
type. Table 7 shows the replacement part numbers for the
LT1 and LT2 thermistors. The sensors have a 1% tolerance
and follow the characteristics shown in Table 8. Table 9
shows the nominal resistance at any given temperature
and can be used for fi eld service reference. The sensor will
use a minimum of 24 awg wire.
Temp (ºC) Temp (ºF)
Resistance
(kOhm)
Temp (ºC) Temp (ºF)
Resistance
(kOhm)
-17.8 0.0 85.34 55 131.0 2.99
-17.5 0.5 84.00 56 132.8 2.88
-16.9 1.5 81.38 57 134.6 2.77
-12 10.4 61.70 58 136.4 2.67
-11 12.2 58.40 59 138.2 2.58
-10 14.0 55.30 60 140.0 2.49
-9 15.8 52.38 61 141.8 2.40
-8 17.6 49.64 62 143.6 2.32
-7 19.4 47.05 63 145.4 2.23
-6 21.2 44.61 64 147.2 2.16
-5 23.0 42.32 65 149.0 2.08
-4 24.8 40.15 66 150.8 2.01
-3 26.6 38.11 67 152.6 1.94
-2 28.4 36.18 68 154.4 1.88
-1 30.2 34.37 69 156.2 1.81
0 32.0 32.65 70 158.0 1.75
1 33.8 31.03 71 159.8 1.69
2 35.6 29.50 72 161.6 1.64
3 37.4 28.05 73 163.4 1.58
4 39.2 26.69 74 165.2 1.53
5 41.0 25.39 75 167.0 1.48
6 42.8 24.17 76 168.8 1.43
7 44.6 23.02 77 170.6 1.39
8 46.4 21.92 78 172.4 1.34
9 48.2 20.88 79 174.2 1.30
10 50.0 19.90 80 176.0 1.26
11 51.8 18.97 81 177.8 1.22
12 53.6 18.09 82 179.6 1.18
13 55.4 17.26 83 181.4 1.14
14 57.2 16.46 84 183.2 1.10
15 59.0 15.71 85 185.0 1.07
16 60.8 15.00 86 186.8 1.04
17 62.6 14.32 87 188.6 1.01
18 64.4 13.68 88 190.4 0.97
19 66.2 13.07 89 192.2 0.94
20 68.0 12.49 90 194.0 0.92
21 69.8 11.94 91 195.8 0.89
22 71.6 11.42 92 197.6 0.86
23 73.4 10.92 93 199.4 0.84
24 75.2 10.45 94 201.2 0.81
25 77.0 10.00 95 203.0 0.79
26 78.8 9.57 96 204.8 0.76
27 80.6 9.16 97 206.6 0.74
28 82.4 8.78 98 208.4 0.72
29 84.2 8.41 99 210.2 0.70
30 86.0 8.06 100 212.0 0.68
31 87.8 7.72 101 213.8 0.66
32 89.6 7.40 102 215.6 0.64
33 91.4 7.10 103 217.4 0.62
34 93.2 6.81 104 219.2 0.60
35 95.0 6.53 105 221.0 0.59
36 96.8 6.27 106 222.8 0.57
37 98.6 6.01 107 224.6 0.55
38 100.4 5.77 108 226.4 0.54
39 102.2 5.54 109 228.2 0.52
40 104.0 5.33 110 230.0 0.51
41 105.8 5.12 111 231.8 0.50
42 107.6 4.92 112 233.6 0.48
43 109.4 4.72 113 235.4 0.47
44 111.2 4.54 114 237.2 0.46
45 113.0 4.37 115 239.0 0.44
46 114.8 4.20 116 240.8 0.43
47 116.6 4.04 117 242.6 0.42
48 118.4 3.89 118 244.4 0.41
49 120.2 3.74 119 246.2 0.40
50 122.0 3.60 120 248.0 0.39
51 123.8 3.47 121 249.8 0.38
52 125.6 3.34 122 251.6 0.37
53 127.4 3.22 123 253.4 0.36
54 129.2 3.10