Particular Notes On Safe Compressor And System Operation; Operation; Regular Tests; Maintenance - Bitzer CSH6553-35Y Instructions De Service

6.6.8 Particular notes on safe compressor and
system operation
Analysis show that compressor failures are most often
due to an inadmissible operating mode. This applies
especially to damage resulting from lack of lubrication:
• Function of the expansion valve – observe the manu-
facturer's notes!
– Position the temperature sensor correctly at the
suction gas line and fasten it.
– When using a liquid suction line heat exchanger:
Position the sensor as usual after the evaporator
and not after the heat exchanger.
– Ensure sufficiently high suction gas superheat,
while also taking into account the minimum dis-
charge gas temperatures.
– Stable operating mode under all operating and
load conditions (also part-load, summer/winter op-
eration).
– Solid liquid at the expansion valve inlet, during
ECO operation already before entering the liquid
subcooler.
• Avoid refrigerant migration from the high-pressure
side to the low-pressure side or into the compressor
during long shut-off periods!
– Always maintain oil heater operation when the
system is at standstill. This is valid for all applica-
tions.
When installing the system in zones where the
temperatures are low, it may be necessary to in-
sulate the oil separator. At compressor start, the
oil temperature, that is measured under the oil
sight glass, should be 15 .. 20 K above the ambi-
ent temperature.
– Automatic sequence change for systems with sev-
eral refrigerating circuits (approximately every 2
hours).
– Mount an additional check valve in the discharge
gas line if no temperature and pressure compens-
ation is reached even after long standstill times.
– If needed, mount a time and pressure-dependant
controlled pump down system or liquid separators
on the suction side – particularly for high refriger-
ant charges and/or when the evaporator may be-
come hotter than the suction gas line or the com-
pressor.
• For further information about pipe layout, see
manual SH-170.
SB-170-7
Information
In the case of refrigerants with low isentropic ex-
ponent (e.g. R507A), a heat exchanger between
the suction gas line and the liquid line may have
a positive effect on the system's operating mode
and coefficient of performance.
Arrange the temperature sensor of the expan-
sion valve as described above.

7 Operation

7.1 Regular tests

Check the system at regular intervals according to na-
tional regulations. Check the following points:
• Operating data, see chapter Compressor start, page
47.
• Oil supply, see chapter Compressor start, page 47.
• Safety and protection devices and all components
for compressor monitoring (check valves, discharge
gas temperature sensors, differential oil pressure
limiters, pressure limiters, etc.).
• Tight seat of electrical cable connections and
screwed joints.
• Screw tightening torques (see SW-100).
• Refrigerant charge.
• Tightness.
• Prepare data protocol.

8 Maintenance

8.1 Oil change

NOTICE
!
!
Damage to the compressor caused by degraded
ester oil.
Moisture is chemically bound to the ester oil and
cannot be removed by evacuation.
Proceed with extreme care:
Any penetration of air into the system and oil
drum must be avoided under all circumstances.
Use only oil drums in their original unopened
state!
The listed oils, (see chapter Application ranges, page
30), are characterised by their high degree of stability.
An oil change is generally not required when appropri-
ate suction-side fine filters are mounted or used. In
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