16
RSMZ Technical Guide
SEQUENCE OF OPERATIONS
Alarms
Alarm Detection and Reporting
The RSMZ continuously performs self diagnostics during normal
operation to determine if any operating failures have occurred.
These failures (alarms) will be reported to the AAON unit
controller which allows them to be monitored via a BACnet
®
Building Automation System or with a user interface.
The following are the available alarm designations with detailed
descriptions for the RSMZ.
Alarm Warnings
Low Suction Pressure Warning
Low Suction Pressure will be ignored for the rst minute of initial
compressor operation. If Suction Pressure is below 95 psig for
20 seconds, the VFD compressor will modulate down 1% per
second. This warning will clear once the Suction Pressure rises
above 95 psig.
Low Suction Pressure – Startup Warning
The initial compressor on the circuit cannot start unless the
Suction Pressure is at least 120 psig. A warning will occur if
the circuit is o and the Suction Pressure drops below120 psig.
High Discharge Pressure – Level 1 Warning
If the Discharge Pressure rises above 540 psig, the condenser
fan will be forced to 100%. The VFD compressor will limit the
minimum and maximum RPM limits from 1800 rpm to 5400
rpm, according to envelope protection.
High Discharge Pressure – Level 2 Warning
If the Discharge Pressure rises above 575 psig, the VFD
compressor will modulate down 1% per second until the
Discharge Pressure drops below 475 psig.
Discharge Pressure Not Detected Warning
If the Discharge Pressure Transducer is not detected and a
compressor is running, the condenser fan will be forced to 100%.
Danfoss VFD Alarms Warning
If an alarm occurs from the VFD compressor, the Danfoss Alarm
Menu screens will show information on what the alarm code is.
The screens break up the alarms into bytes. If a display is not
installed on the VFD, these alarm bytes will aid in knowing which
specic alarm has occurred.
Parameter 16-90 Alarm Word 1
“DNFSALM1”
Parameter 16-90, alarm bits 0 – 7
“DNFSALM1”, “B1 ###”
Parameter 16-90, alarm bits 8 – 15
“DNFSALM1”, “B2 ###”
Parameter 16-90, alarm bits 16 – 23
“DNFSALM1”, “B3 ###”
Parameter 16-90, alarm bits 24 – 31
“DNFSALM1”, “B4 ###”
Same with Parameter 16-91 Alarm Word 2
“DNFSALM2”
There are two alarm parameters from the VFD 16-90 and 16-91.
Each contain 32 dierent alarms as a binary biteld, each bit
is a specic alarm. Refer to Danfoss “Operating Instructions”
“VLT Compressor Drives CDS 302/CDS 303” that is provided
with the unit.
High Superheat Warning
A high superheat warning will occur if a compressor is active and
the superheat is above 25ºF for two minutes or longer.
High Discharge Line Temperature
This sensor is installed for modulating VFD compressors
only. If the Discharge Line Temperature rises above 260ºF, the
VFD compressor will modulate down 1% per second until the
Discharge Line Temperature drops below 260ºF.
Compressor 1 False Active Warning
This warning will occur if Compressor 1 is not activated and
the running verication signal is active for at least 45 seconds.
For Danfoss VFD compressors, the running verication is sent
from Modbus Communications. For xed On/O compressors,
the running verication is a binary input signal to the module.
Compressor 2 False Active Warning
This warning will occur if Compressor 2 is not activated and
the running verication signal is active for at least 45 seconds.
For Danfoss VFD compressors, the running verication is sent
from Modbus Communications. For xed On/O compressors,
the running verication is a binary input signal to the module.
Discharge Line Temp Sensor Not Detected
This warning will occur if the Discharge Line Temperature Sensor
is not detected by the module.
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