228
JOHNSON CONTROLS
5276178-JIM-C-0118
Service
ANALOG INPUT OPERATION
This section describes the control operation of the (29)
twenty-nine analog inputs. These inputs are used by
the control to monitor and respond to unit temperatures,
pressures, enthalpy, etc. The location of each of these
connections on the Unit Controller is contained in
Table 79. Notice that the ID gives the jack connection
designated as “J” and then the identifying number of
the connector, followed by a – and then the pin number
of the connector. For example the SUPPLY AIR
TEMPERATURE analog input would be found at J1-1.
This is connector J1 – Pin 1. As the Unit Control board
is positioned in the control box the top row of the J series
connectors is the input, the middle row is the common,
and the bottom row is the 5VDC input to the sensor.
Also the pin in the right hand top corner is pin 1.
Temperature Sensors
The temperature sensors are all 10K Type III Thermistors.
The relationship between the temperature and the
voltage output and resistance is contained in Table 84.
The following analog inputs are of this type: Supply
Air Temperature, Heat Entering Temp, Flex Evap Temp,
Outside Air Temp, Return Air Temp, Zone Temp, and
Under Floor Temp.
Duct Pressure Transducer
The Duct Pressure Transducer is located in the supply air
section of the unit. The purpose of the transducer is to
sense and convert the static pressure in the supply-side
of the duct to a 0 to 5VDC voltage. The DC voltage
is sent to the Unit Controller and compared against the
“DUCT STATIC PRESS ACTIVE SP”
. The transducer
is factory wired, but pneumatic tubing must be field
supplied and installed
(refer to Section 2
“Installation”
in this manual).
The duct static pressure transducer
measures differential pressure between the pressure
in the duct and atmospheric pressure. When verifying
transducer operation, the technician must insert a tee in
the pneumatic tubing and connect a manometer to the
tee to verify the pressure being applied to the transducer.
Once this pressure is known, a comparison can be made
of the duct pressure vs. output VDC from the transducer.
Table 85 shows the relationship between the pressure
applied to the duct pressure transducer and the output
voltage. The output is linear between 0" WC and the
SPAN. The
“DUCT PRESS TRANSDUCER SPAN”
can be set to 1.25, 2.5 or 5" WC.
The
“DUCT PRESS TRANSDUCER SPAN”
must al-
ways be set based on the span of the transducer installed.
°F
VOLTAGE RESISTANCE
°C
-25
0.49
139,639
-30.6
-20
0.53
127,453
-28.9
-15
0.60
109,624
-26.1
-10
0.69
94,519
-23.34
-5
0.78
81,665
-20.55
0.0
0.88
70,750
-17.78
5
0.98
61,418
-15.00
10
1.10
53,426
-12.22
15
1.22
46,582
-9.44
20
1.35
40,703
-6.67
25
1.48
35,639
-3.89
30
1.62
31,269
-1.11
35
1.77
27,490
1.67
40
1.91
24,219
4.44
45
2.06
21,377
7.22
50
2.21
18,900
10.00
TABLE 94 - TEMPERATURE SENSOR RESISTANCE
°F
VOLTAGE RESISTANCE
°C
55
2.36
16,744
12.78
60
2.51
14,681
15.56
65
2.66
13,216
18.33
70
2.80
11,771
21.11
75
2.94
10,502
23.89
80
3.08
9,388
26.67
85
3.21
8,404
29.45
90
3.33
7,537
32.22
95
3.45
6,770
35.0
100
3.56
6,090
37.78
105
3.66
5,487
40.56
110
3.76
4,951
43.34
115
3.85
4,475
46.11
120
3.94
4,050
48.89
125
4.02
3,671
51.66
130
4.09
3,332
54.44
135
4.16
3,029
57.22
SECTION 8 – SERVICE
Summary of Contents for 40 25 TON
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