JOHNSON CONTROLS
141
SECTION 9 – SERVICE AND TROUBLESHOOTING
FORM 150.27-NM1
ISSUE DATE: 09/30/2015
9
CHECKING INPUTS AND OUTPUTS
Digital Inputs
Refer to the unit wiring diagram.
All digital inputs are
connected to J13-1 of the I/O board. The term “digital”
refers to two states – either ON or OFF. As an example,
when the flow switch is closed, 30VDC will be applied
to J13, pin 9 (J13-9) of the I/O board. If the flow switch
is open, 0VDC will then be present at J13-9.
Typically, voltages of between 24 and 36VDC could be
measured for the DC voltage on the digital inputs. This
voltage is in reference to ground. The unit case should
be sufficient as a reference point when measuring digi-
tal input voltages.
Analog Inputs – Temperature
Refer to the unit wiring diagram.
Temperature inputs
are connected to the microboard on plug J6. These ana-
log inputs represent varying DC signals corresponding
to varying temperatures. All voltages are in reference
to the unit case (ground). Following are the connec-
tions for the temperature sensing inputs:
Liquid and Refrigerant Sensor Test Points
Entering Chilled Liquid Sensor
J6-5 = +5VDC regulated supply to sensor.
J6-8 = VDC input signal to the I/O board.
See Table
24 on page 141 for voltage readings that cor-
respond to specific liquid temperatures.
J6-2 = drain (shield connection = 0VDC) Return
Leaving Chilled Liquid Temperature Sensor
J6-4 = +5VDC regulated supply to sensor.
J6-7 = VDC input signal to the microboard.
24 on page 141 for voltage readings that cor-
respond to specific liquid temperatures.
J6-1 = drain (shield connection = 0VDC) Return
TABLE 24 -
ENTERING/LEAVING CHILLED LIQUID
TEMPERATURE SENSOR, TEMPERATURE/VOLT-
AGE CORRELATION
TEMP °F
VOLTAGE
(Signal Input
to Return)
TEMP °C
10
1.33
-12
12
1.39
-11
14
1.46
-10
16
1.51
-9
18
1.58
-8
20
1.65
-7
22
1.71
-6
24
1.78
-4
26
1.85
-3
28
1.91
-2
30
1.98
-1
32
2.05
0
34
2.12
1
36
2.19
2
38
2.26
3
40
2.33
4
42
2.40
6
44
2.47
7
46
2.53
8
48
2.60
9
50
2.65
10
52
2.73
11
54
2.80
12
56
2.86
13
58
2.92
14
60
2.98
16
62
3.05
17
64
3.11
18
66
3.17
19
68
3.23
20
70
3.29
21
72
3.34
22
74
3.39
23
76
3.45
24
78
3.5
26
80
3.54
27
