FORM 150.66-NM3
ISSUE DATE: 09/25/2020
149
JOHNSON CONTROLS
SECTION 9 - SERVICE AND TROUBLESHOOTING
9
CHECKING INPUTS AND OUTPUTS
Digital Inputs
Refer to the unit wiring diagram.
All digital inputs are
connected to J13 of the microboard. The term “digital”
refers to two states – either on or off. As an example,
when the flow switch is closed, 30 volts
DC
will be
applied to J13, pin 5 (J13-5) of the microboard. If the
flow switch is open, 0 volts DC will then be present at
J13-5.
Pin 1 of J13 is an
unregulated
30 VDC
source
used
to supply the DC voltage to the various user contacts,
unit switch, flow switch, etc. This
DC source is fac-
tory wired to CTB1, terminal 13. Any switch or con-
tact used as a digital input would be connected to this
terminal, with the other end connecting to its respec-
tive digital input on the microboard. Any time a switch
or contact is closed, 30 VDC would be applied to that
particular digital input. Any time a switch or contact is
open, 0VDC would be applied to that particular digital
input.
Typically, voltages as high as 34 VDC could be mea-
sured 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:
Outside Air Sensor
J6-6 = +5 VDC regulated supply to sensor.
J6-9 = VDC input signal to the microboard.
See Table 30 for voltage readings that corre
spond to specific outdoor temperatures.
J6-3 = drain (shield connection = 0 VDC) Return
TABLE 30 – OUTDOOR AIR SENSOR
TEMPERATURE/VOLTAGE/
RESISTANCE CORRELATION
TEMP°F
VOLTAGE
(SIGNAL INPUT
TO RETURN)
TEMP°C
0
0.7
-18
5
0.8
-15
10
0.9
-12
15
1.0
-9
20
1.1
-7
25
1.2
-4
30
1.4
-1
35
1.5
2
40
1.7
4
45
1.8
7
50
2.0
10
55
2.2
13
60
2.3
16
65
2.5
18
70
2.6
21
75
2.8
24
80
2.9
27
85
3.1
29
90
3.2
32
95
3.4
35
100
3.5
38
105
3.6
41
110
3.7
43
115
3.8
46
120
3.9
49
125
4.0
52
130
4.1
54
Summary of Contents for YCAL Series
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