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Fujitsu FO20R Series Installation Instructions Manual page 41

Variable speed r-410a heat pump outdoor units
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8.0 ACTIVE SYSTEM PROTECTION FEATURES
If there are 3 low pressure faults in the same call
for cooling or during 120 minutes of continuous
heating operation, the VSODC will lock the
compressor out and flash a 21L fault code and
the Digital Control Center will display a Low
Refrigerant Pressure Lockout fault on the screen.
If the outdoor ambient is below -10°F [-23°C] in the
heating mode when the lockout occurs, the control
will automatically reset when the outdoor ambient
rises to -10°F [-23°C]. If the outdoor ambient is
above -10°F [-23°C], a manual reset is required
for the VSODU to exit the compressor lock-out
mode and clear the fault. This is accomplished
by disconnecting the electrical power to both the
indoor and outdoor units for 1 minute and then
reconnecting power.
NOTE: If the system experiences a low
refrigerant pressure lock-out, the system
should be evaluated to determine the cause
for the low pressure condition and corrective
action taken to eliminate the cause. Possible
causes include low refrigerant charge, failed
indoor blower motor, dirty return air filter, or
a dirty indoor coil in the cooling mode or low
refrigerant charge, a failed outdoor motor, or a
dirty outdoor coil in the heating mode.
8.7 Compressor Shut-
Down Sequence for
High or Low Refrigerant
Pressure Fault
1.
The compressor is commanded to operate at
zero (0) RPM for a minimum of 5 minutes.
2.
The outdoor EXV will be directed to completely
close for a period of 5 minutes and will then
open up completely.
3.
The outdoor fan motor will continue to operate
during the 5 minute compressor off delay.
4.
The VSODC and Digital Control Center will
display the applicable fault code.
5.
If after 5 minutes cooling or heating demand
persists and the pressure has reached reset
conditions, normal system operation will
resume and the fault codes will be cleared
from the VSODC and Digital Control Center
displays.
6.
If after 5 minutes cooling or heating demand
persists and the pressure has not reached
reset conditions, the outdoor fan motor will be
shut down. Once the pressure reaches reset
conditions after the 5 minute delay, normal
system operation will resume.
8.8 Overcurrent and
Current Imbalance
If the compressor current exceeds an acceptable
level for the compressor or inverter, the inverter
will reduce the compressor speed to allow the
current to return to an acceptable level. If there
is a current imbalance between the compressor
3-phase windings, the inverter will shut the
compressor down for 5 minutes and will lock the
compressor out if there are 3 faults within a single
call for operation.
8.9 Compressor
Operation Outside
Envelope
If the inverter detects that the compressor
motor torque exceeds an acceptable level for
the compressor, the inverter will reduce the
compressor speed to keep the torque at an
acceptable level.
8.10 Over and Under
Voltage
If the supply voltage or internal DC voltage is not
within an acceptable operating range, the inverter
will shut the compressor off until the voltage
returns to an acceptable level.
8.11 Inverter Over
Temperature
If the internal inverter temperature sensors detect
excessive temperatures within the inverter, the
inverter will reduce the speed of the compressor or
shut the compressor down until the temperatures
drop to an acceptable level. The compressor will
be locked out if there are 3 faults within a single
call for operation.
8.12 Controls and
Communication
Malfunction
If the controls senses a malfunction within the
control system or communications or if system
model data is not available, the controls will act
to shut the system down to prevent the system
from operating at a condition that could harm
components.
41

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