7 Fault Conditions, Messages and Causes
The variable speed drive is featuring Modbus registers
reflecting the exact operating conditions of the system:
•
Normal Operation Status (reg. 40121 and 40122),
the system operates without limitations.
•
Derating Status (reg. 40123 and 40124), the
system cannot operate at the quested capacity.
•
Safe Mode Status (reg. 40125 and 40126), the
system has encountered a condition that has
made operation unsafe, e.g. loss of communi-
cation with the EEV controller or a sensor signal.
In Safe Mode, the drive is running a constant
speed of 2400 RPM until the problem is resolved
and then automatically resumes normal
operation.
•
Alarm Status (Fault) (reg. 40127 and 40128), the
system has encountered a severe exceptional
condition and the compressor has been stopped.
The alarm bit remains logic “one” for at least 120
s and the system will afterwards attempt to
return to normal operation when the bit becomes
logic “zero”. In some cases (see individual alarms),
the drive goes into a trip lock condition. To
restart the system, it is necessary to cycle power
to the drive or perform a reboot (register 40135).
A reset alone does not clear this condition!
The statuses are expressed by individual sticky bits, which
are set logic “1” as long as the particular status is present,
see the following detailed explanations.
Normal Status (reg. 40121 and 40122):
Bit 0, Compressor Running
Whenever the compressor is running, this bit will be set.
This is independent of control mode, speed or other
operation conditions.
Bit 3, Crankcase heating
The crankcase heater is active; the drive injects a DC
voltage into the compressor motor.
Bit 4, Control Start-up
The system is performing a start-up sequence, e.g. for
proper oil distribution and is not (yet) following the
required speed reference. During start-up, the compressor
runs at 2400 RPM for 60 s and then returns to the
requested speed.
Bit 5, Control Oil Return
The system has been running at less than 2400 RPM for 30
minutes and is automatically performing an oil return
sequence. The thermo controller will ignore the requested
reference and runs the compressor at 2400 RPM for 60 s to
distribute oil in the system and then returns to normal
operation.
Bit 6, Restart time
When the compressor is stopped, but system still powered
on, the restart timer is activated. The restart timer will not
allow the compressor to restart before 60 s after it was
stopped.
Bit 28, Derating Active
The system is in a derating condition, read the Derating
Status register for more information.
Bit 29, Safe Mode Active
The system is in a Safe Mode condition, read the Safe
Mode Status register for more information.
Bit 30, Alarm Active
The system is in an Alarm condition, read the Alarm Status
register for more information.
Bit 31, Alarm Trip Lock Active
The system is in an Alarm Trip Lock condition, read the
Alarm Status register for more information.
Derating status (reg. 40123 and 40124):
Bit 0, Derating - Drive Temperature High
The temperature measured in the drive’s power electronics
has reached a critical level and the drive cannot maintain
full capacity output. Therefore the drive slows the
compressor down until the temperature is no longer
critical. When temperatures have normalized the drive
attempts to return to normal operation.
Bit 2, Derating - Suction Pressure Low
The suction pressure (P0) has reached a critical low value.
To make the suction pressure recover, the drive has slowed
down the compressor. When the pressure has normalized
the drive will attempt to return to normal operation.
Bit 4, Derating - Condenser Pressure Low
The condenser pressure (Pc) has reached a critical low
value. To increase the condenser pressure, the drive has
slowed down the condenser fan speed. When the pressure
has normalized the drive will attempt to return to normal
operation. This function is only available in AC mode and
system configurations with condenser fan control.
Bit 5, Derating - Condenser Pressure High
The condenser pressure (Pc) has reached a critical high
value. To decrease the condenser pressure, the drive has
slowed down the compressor. When the pressure has
normalized the drive will attempt to return to normal
operation.
Bit 6, Derating – Output Power Limit
The supply voltage has dropped below 208 V or an
extreme operating condition, e.g. high condensing
pressure has activated the derating function limiting the
output power of the drive. The drive returns to normal
operation when the supply voltage has recovered or
operating conditions have normalized.
Fault Conditions, Messages ...
VLT
®
Inverter Scroll CDS 801 Operating Instructions
44
MG10V402 - VLT
®
is a registered Danfoss trademark
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