Johnson Controls System 450 Series Technical Bulletin

Table 19: C450CCU condensing unit control system
Callout Description
12 OUTR4: Output relay 4 terminal block. Connects to and controls the defrost heater based on the condensing
unit’s daily defrost schedule that you configure. Defrost cycles are terminated by the temperature sensed at
the defrost termination sensor or switch, or the configured defrost duration time. You need a C450 expansion
module to provide OUTR4.
13 OUTR5: Optional output relay 5. Connects to and controls compressor pump down based on the suction
pressure sensed at Sn-3, the low-pressure pump down transducer. You need a C450 expansion module to
provide OUTR5.
14 OUTR6: Output relay terminal block. Connects to and controls an optional alarm output that may be used to
provide an onsite notification of any active alarm condition within the CCU.
Troubleshooting condensing unit control systems
Error messages display on the condensing unit control module LCD when the module detects
a failure in sensor, sensor wiring, sensor power, or power supply. The following table shows a
condensing unit control module error message that may display, and provides a possible cause and
solutions to the error message.
Table 20: Error message
Error screen Condition Cause Solution
SnF Sensor failure is
detected and SNF
displays instead of a
value.
Outputs that
reference the failed
sensor operate in the
sensor failure modes
that you select for the
output during setup.
Sensor, sensor
wiring, or sensor
connections
do not open or
close.
• Check the integrity of the sensor
wiring and connections.
• Measure the voltage between the
sensor terminal, Sn-1, Sn-2, Sn-3 and
the low-voltage common terminal
when the sensor is connected.
• If the sensor wiring and sensor
connections are acceptable, replace
the sensor and recheck the voltage.
Ordering information
The following tables provide ordering information for the modules, mounting accessories, and
condensing unit control module compatible sensors and transducers.
Table 21: System 450 modules
Product code Description
C450CCU-4C Condensing unit control module with LCD, four-button touchpad, UI, and two single-pole, double-
throw (SPDT) line-voltage relay outputs
The box includes two A99BB-500C temperature sensors with 5 m or 16.38 ft cable length.
Sensor temperature range: -40ºC to 120ºC or -40ºF to 250ºF
Cable jacket temperature range: -40ºC to 100ºC or -40ºF to 212ºF
C450YNN-1C Power module: Provides 24 V to System 450 module assembly: 120 VAC or 240 VAC supply power
input terminals
C450SBN-4C Relay expansion module with one SPDT relay output
C450SCN-4C Relay expansion module with two SPDT relay outputs
39System 450 Series C450CCU Condensing Unit Control System Technical Bulletin

Johnson Controls System 450 Series Specifications

General

Brand	Johnson Controls
Model	System 450 Series
Category	Control Unit
Language	English