AAON MHGRV-X, Полевое техническое руководство

Страница: 18 / 30

18
MHGRV-X Field Technical Guide
TROUBLESHOOTING
Other Checks
Supply Air Temperature Sensor
If you suspect the Supply Air Temperature Sensor is not reading
correctly, make sure the wiring terminal connections are tight and
that any wiring splices are properly connected. You can check the
operation of the Supply Air Temperature Sensor by measuring
the resistance or voltage using a digital multimeter.
Measuring Voltage
Set the meter to DC Volts. Place the positive probe on the AIN
terminal and the negative probe on the GND terminal. Read the
DC Volts and find that voltage in Table 6, this page and Table 7,
page 19 . Read the temperature corresponding with that voltage
and determine if this is close to the actual temperature the sensor
is exposed to. If the temperature from the chart is different by
more than a few degrees, you probably have a defective or
damaged sensor.
Thermistor Sensor Testing
Instructions
1. Use the resistance column to check the thermistor
sensor while disconnected from the controllers (not
powered).
2. Use the voltage column to check sensors while
connected to powered controllers. Read voltage with
meter set on DC volts. Place the “-” (minus) lead on
GND terminal and the “+” (plus) lead on the sensor
input terminal being investigated.
Measuring Resistance
To read the resistance, set the meter to Ohms. Unplug the
sensor connector from the board and measure the resistance
across the disconnected wires. This resistance should match the
corresponding temperature from Table 6, this page and Table
7, page 19 .
Temp
(°F)
Temp
(°C)
Resistance
(Ohms)
Voltage @
Input (VDC)
-10 -23.3 93333 2.98
-5 -20.6 80531 2.94
0 -17.8 69822 2.89
5 -15 60552 2.83
10 -12.2 52500 2.77
15 -9.4 45902 2.71
20 -6.6 40147 2.64
25 -3.9 35165 2.57
30 -1.1
30805 2.49
35 1.7 27140 2.41
40 4.4 23874 2.33
45 7.2 21094 2.24
50 10
18655 2.15
52 11.1 17799 2.11
54 12.2 16956 2.08
56 13.3 16164 2.04
58 14.4 15385 2.00
60 15.6 14681 1.96
62 16.7 14014 1.93
64 17.8 13382 1.89
66 18.9 12758 1.85
68 20 12191 1.81
69 20.6 11906 1.79
70 21.1 11652 1.78
71 21.7 11379 1.76
Temp
(°F)
Temp
(°C)
Resistance
(Ohms)
Voltage @
Input (VDC)
72 22.2 11136 1.74
73 22.8 10878 1.72
74 23.3 10625 1.70
75 23.9 10398 1.68
76 24.4 10158 1.66
78 25.6 9711 1.63
80 26.7 9302 1.59
82 27.8 8893 1.55
84 28.9
8514 1.52
86 30 8153 1.48
88 31.1 7805 1.45
90 32.2 7472 1.41
95 35
6716 1.33
100 37.8 6047 1.24
105 40.6 5453 1.16
110 43.3 4923 1.09
115 46.1 4449 1.02
120 48.9 4030 .95
125 51.7 3656 .88
130 54.4 3317 .82
135 57.2 3015 .76
140 60 2743 .71
145 62.7 2502 .66
150 65.6 2288 .61
TEMPERATURE TO RESISTANCE/VOLTAGE CHART
Table 6: 0-3V Temperature Sensor - Voltage and Resistance for Type III Sensors
Note: If the voltage is above 3.3 VDC the sensor or wiring is “open.” If the voltage is less than 0.05 VDC, the sensor or wiring is shorted.