JOHNSON CONTROLS
199
SECTION 8 – SERVICE
FORM 145.05-NOM7
ISSUE DATE: 10/31/2019
8
Flash Code 6 – Discharge Thermistor
Fault
This code indicates the Digital Compressor Controller
is not receiving a signal from the discharge tempera-
ture thermistor. If the Digital Compressor Controller is
not receiving an input signal it continues to operate the
compressor at 1/3 capacity. When the discharge tem-
perature thermistor input is restored the Digital Unit
Controller resumes normal operation.
Flash Code 8 – Compressor Contactor
Fault
This code indicates compressor current is detected
when the demand signal input is below 1.44VDC. This
would normally be caused by welded contactor con-
tacts. The compressor continues to run in this condi-
tion because the Digital Compressor Controller cannot
open the compressor contactor.
The Digital Compressor Controller energizes the com-
pressor contactor. The unloader solenoid remains ener-
gized causing the compressor to run unloaded as long
as the input demand signal is less than 1.44VDC. If the
demand input is greater than 1.44VDC, the unloader
solenoid de-energizes causing the compressor to run
loaded.
The ALERT code is reset when current is no longer
detected while the demand input is below 1.44VDC.
Flash Code 9 – Low 24VAC Supply
This indicates the supply voltage to the Digital Com-
pressor Controller has dropped below 18.5VAC. The
Digital Compressor Controller de-energizes the com-
pressor contactor and unloader solenoid. The ALERT
code resets when the supply voltage to the Digital
Compressor Controller rises above 19.5VAC.
FAULTS
A fault is defined as an abnormal condition, which
results in the shutdown of an operating system or the
complete unit. The presence of a fault condition indi-
cates a situation in which possible damage to the unit
may occur if the unit or system were allowed to con-
tinue to operate. There are four types of faults.
• UNIT LOCKOUT – The complete unit is shut-
down and locked out. A manual reset is required
to restart the unit after the fault has been corrected.
• SYSTEM LOCKOUT – One of the compres-
sor systems or other component is shutdown and
locked out. A manual reset is required to restart
the system after the fault has been corrected.
• UNIT AUTO RESET – The complete unit is shut-
down but the unit restarts automatically when the
fault condition is cleared.
• SYSTEM AUTO RESET – One of the compres-
sor systems or other component is shut down but
the system or component restarts automatically
when the fault condition is cleared.
A UNIT LOCKOUT can be reset by turning the “LO-
CAL STOP” switch OFF for 5 seconds and back ON.
If the cause of the lockout has been corrected the unit
resets and begins proper operation.
A SYSTEM LOCKOUT except for COMPR # LOCK-
OUT and LOCKOUT - LOW PRESS SYS # can be
reset by turning the “LOCAL STOP” switch OFF for
5 seconds and back ON. A COMPR # LOCKOUT and
LOCKOUT - LOW PRESS SYS # must be reset by
entering the PROGRAM key and the COMPRESSOR
SYSTEMS # subsection, which has the lockout. Use
the ▲ and ▼ key to go to COMP SYS # STATE. The
current status is LOCKOUT. Press the CHECK key (√)
and use the right arrow key to change LOCKOUT to
RUN.
In addition to faults the User Interface also displays
warnings. A warning is defined as an abnormal condi-
tion under which the unit continues to operate. Warn-
ings do not require the unit to shut down; however,
they may require the Unit Controller to disable certain
functions that may result in the unit operating less ef-
ficiently or eliminate certain features.
Table 50 on page 205, Table 51 on page 206 and
Table 52 on page 207 list the faults / warnings that
are displayed under the STATUS and HISTORY keys
of the User Interface. When a fault is present line
two of the effected STATUS screen display (UNIT-
OVERALL STATUS, COMPRESSOR SYSTEM
A, COMPRESSOR SYSTEM B, COMPRESSOR
SYSTEM C, COMPRESSOR SYSTEM D, COM-
PRESSOR SYSTEM E, COMPRESSOR SYSTEM
F, HEATING SYSTEM, ECONOMIZER SYSTEM,
SUPPLY SYSTEM or VENTILATION SYSTEM)
changes the nomenclature to indicate a WARN-
ING, SAFETY TRIP, SAFETY FAULT, or SAFETY
LOCKOUT is present. A fault / warning description,
method of reset and conditions under which the infor-
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