Carrier WeatherExpert 48N2 Controls, Start-Up, Operation, Service, And Troubleshooting page 129

This alarm will disable mechanical cooling and will require a
manual reset. This alarm may be disabled once the reverse ro-
tation check has been verified by setting Configuration
 COOL  RR.VF = Yes.
It is important to note that in Service Test mode, reverse rota-
tion is checked on every compressor start.
A150 (Unit is in Emergency Stop)
If the CCN point name "EMSTOP" in the System table is set to
emergency stop, the unit will shut down immediately and
broadcast an alarm back to the CCN indicating that the unit is
down. This alarm will clear when the variable is set back to
"enable."
A152 (Unit Down due to Failure)
This alarm occurs whenever both cooling circuits are unavail-
able to cool. Mechanical cooling is impossible due to a failure
in the system explained through other current alarms.
Possible problems are:
• plenum pressure switch trips on a return fan tracking unit
• the supply fan status alarms have been instructed to shut
down the unit
• both circuits incapable of cooling due to multiple alerts of
compressors and/or pressure alerts
• a hardware failure of the main board's analog to digital
converter or EEPROM chip
• a critical storage failure in EEPROM has rendered the unit
inoperable
• the unit is configured for inlet guide vanes and the actuator
controlling the vanes is in fault.
Reset is automatic.
T153 (Real Time Clock Hardware Failure)
The RTC clock chip on the MBB is not responding. Recovery
is automatic but typically board replacement may be necessary.
A154 (Serial EEPROM Hardware Failure)
The unit will be completely shut down. The serial EEPROM
chip on the MBB which stores the unit's configurations is not
responding. Recovery is automatic but typically board replace-
ment is necessary.
T155 (Serial EEPROM Storage Failure Error)
Configuration data in the serial EEPROM chip cannot be veri-
fied which may mean MBB replacement. It is possible a re-ini-
tialization of the database or particular storage area(s) may
clean up this problem. Reset is automatic.
A156 (Critical Serial EEPROM Storage Fail Error)
The unit is completely shut down. Critical configuration data
in the serial EEPROM chip cannot be verified which may
mean MBB replacement. Recovery is automatic but typically
board replacement is necessary.
NOTE: The machine will shut down. This may happen after
downloading via the CCN if the device code was corrupted. Try
downloading again or use the LEN connection to download.
A157 (A/D Hardware Failure)
The unit will be completely shut down. The analog to digital
conversion chip on the MBB has failed. Recovery is automatic
but typically board replacement is necessary.
A169 (EXV board Communication Failure)
Cooling is disabled until communication with the EXV control
board is re-established. Recovery is automatic. Reason for fail-
ure may be due to incorrect wiring, power loss to the control
board, or damage to the RS-485 drivers on the LEN bus.
T170 (Loss of communication with the Compressor Expan-
sion Module)
Compressors A3, A4, B3 and B4 are disabled until communi-
cation with the CEB control board is re-established. Recovery
is automatic. Reason for failure may be due to incorrect wiring,
power loss to the control board, or damage to the RS-485 driv-
ers on the LEN bus.
A171 (Staged Gas Control Board Comm Failure)
Staged Heating is disabled until communication with the staged
gas control board is re-established. Recovery is automatic. Rea-
son for failure may be due to incorrect wiring, power loss to the
staged gas control board, or damage to the RS-485 drivers on the
LEN bus.
T172 (Control Expansion Module Comm Failure)
Any function associated with a sensor configured for use that
resides on the controls expansion module will be disabled until
communication is re-established. Recovery is automatic. Rea-
son for failure may be due to incorrect wiring, power loss to
the control expansion module, or damage to the RS-485 drivers
on the LEN bus.
A173 (RXB board Communication Failure)
As the RXB board is integral to all N Series units, the error will
cause a system shutdown until communication is re-estab-
lished. Recovery is automatic. Reason for failure may be due to
incorrect wiring, power loss to the RXB board, or damage to
the RS-485 drivers on the LEN bus.
A174 (EXB board Communication Failure)
The EXB board is responsible for building pressure control.
Building Pressure control configurations that require this board
will cause a complete system shut down when communication
failure occurs. Recovery is automatic. Reason for failure may
be due to incorrect wiring, power loss to the EXB board, or
damage to the RS-485 drivers on the LEN bus.
A175 (VFD1 Communication Failure)
The supply fan is disabled until communication with the sup-
ply fan VFD is re-established. Recovery is automatic. Reason
for failure may be due to incorrect wiring, power loss to the
VFD, or damage to the RS-485 drivers on the LEN bus.
T176 (VFD2 Communication Failure)
The exhaust fan is disabled until communication with the ex-
haust fan VFD is re-established. Recovery is automatic. Rea-
son for failure may be due to incorrect wiring, power loss to
the VFD, or damage to the RS-485 drivers on the LEN bus.
T177 (4-20 MA Demand Limit Failure)
If this transducer fails, and the unit is configured to perform
demand limiting with this transducer, no capacity limiting will
be performed and an alert will be generated. Recovery is auto-
matic. Reason for error is either a faulty sensor, wiring error, or
damaged input on the CEM control board.
T178 (4-20 MA Static Pressure Reset Fail)
If this transducer fails, and the unit is configured to perform
static pressure reset with this transducer, no static pressure re-
set will be performed and an alert will be generated. Recovery
is automatic. Reason for error is either a faulty sensor, wiring
error, or damaged input on the CEM control board.
A179 (Cir. A EXV board Communication Failure)
A180 (Cir. B EXV board Communication Failure)
Alarm codes 179 and 180 are for Circuits A and B respectively.
The EXV PCBs are integral to the proper functionality of each
refrigeration circuit. The corresponding circuit is disabled until
communications with the EXV is re-established. Recovery is
automatic. Reason for failure may be due to incorrect wiring,
power loss to the EXB board, or damage to the RS-485 drivers
on the LEN bus.
A200 (Linkage Timeout Error — Comm Failure)
If linkage is established via the CCN with ComfortID™ termi-
nals, a 5-minute timeout on loss of communication will be moni-
tored. If 5 minutes expire since the last communication from a
VAV Linkage Master, the unit will remove the link and flag the
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