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11 - STANDARD MAINTENANCE
11.7.2 - Compressor rotation control
Correct compressor rotation is one of the most critical application
considerations. Reverse rotation, even for a very short duration,
damages the compressor and can even destroy it.
The reverse rotation protection scheme must be capable of
determining the direction of rotation and stopping the compressor
within one second. Reverse rotation is most likely to occur
whenever the wiring at the compressor terminals has been
modified.
To minimise the opportunity for reverse rotation, the following
procedure must be applied. Rewire the power cables to the
compressor terminal pin as originally wired. Apply a counter-torque
at the lower nut at the supply cable terminal during installation.
For replacement of the compressor, a low pressure switch is
included with the compressor. This low pressure switch should be
temporarily installed as a hard safety on the high pressure part of
the compressor. The purpose of this switch is to protect the
compressor against any wiring errors at the compressor terminal
pin. The electrical contact of the switch would be wired in series
with the high pressure switch. The switch will remain in place until
the compressor has been started and direction of rotation has
been verified; at this point, the switch will be removed.
The switch that has been selected for detecting reverse rotation
is Carrier part number HK01CB001. This switch opens the contacts
when the pressure falls below 7 kPa.
The switch is a manual reset type that can be reset after the
pressure has once again risen above 70 kPa. It is critical that the
switch be a manual reset type to preclude the compressor from
short cycling in the reverse direction.
11.8 - Frequency variator maintenance
ATTENTION: Before any intervention at the frequency variator,
ensure that the disconnect/isolator switch is open and that
no voltage is present (reminder: the capacitor discharge time
is approximately 20 minutes).
Only a well-qualified person is allowed to replace or modify
the components inside the frequency variator.
During periodic inspections, check the ventilation grilles at the
frequency variator door; ensure that they are not pierced, damaged
or obstructed.
Replace the fan, if a "replace fan" alert/warning is displayed in the
alarm list.
For any other alarm or problem at the frequency variator, contact
the Carrier service department.
The frequency variators do not require a dielectric test, even if
they are replaced parts: they are systematically checked before
delivery. Otherwise the filtering components installed in the
frequency variator can falsify the measurement and may even be
damaged.
If it is necessary to test the insulation of a component
(e.g. compressor, cables) the frequency variator must be
disconnected at the power circuit.
11.9 - High pressure safety loop periodic test
The aim of this periodic test is to check the settings of the high
pressure safety loop on one of the unit's refrigerant circuits and
check it is operating correctly. This procedure must be repeated
for each circuit.
11.9.1 - Complete safety loop test
The purpose of this periodic test is to verify the proper functioning
and setting of the high-pressure safety loop of a refrigerant circuit.
In order to reach the triggering pressure of the loop, the pressure
and temperature thresholds activating the discharge of the
compressor by the regulation system are raised.
This procedure must be repeated for each circuit of the unit.
1. Set up a calibrated pressure gauge on the high pressure part
of the circuit (compressor discharge)
2. Reset all activated alarms
3. Activate the HP test mode for the corresponding circuit via the
control interface.
Enable Quick Test Mode (Quick Test Menu> [ QCK_TEST ]
parameter active)
Activate the high pressure test for the desired circuit (Menu Quick
Test> parameter [HP_TEST] to 0 for circuit A or 1 for the B circuit.
The corresponding circuit starts to perform the HP test.
4. Getting Started Machine
5. For water-cooled units, stop the circulation of the secondary
circuit to the condenser in order to stop the condensation and
cause the increase in pressure (this operation is managed by
the control on air-cooled machines)
6. Record the trigger value
7. Check that both HPS were triggered
If both HPS have tripped, go to step 10
If only one of the HPS has tripped, go to step 8
8. Replace the triggered HPS with another system whose trigger
value is adequate .
Alternatively, an emergency stop button can be installed.
9. Repeat steps 2 to 6
10. Check if the trigger values are correct
The release values should be between -1 .5 /+0.5 bars of nominal
values indicated on the unit.
11. Reset all alarms
12. Reset all HPS
Note:
Access to the maintenance functions can be protected by a
password. Contact your dealer or the manufacturer's service
department for more information.
For step 8, the electrical disconnection of the triggered HPS
and its substitution must be performed in an environment
with live parts. All the procedures and authorization provided
for this type of intervention must be respected.
The type of connector must be WAGO 231-302 or equivalent.
29
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