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11.1.6 Evaporator freeze…
a compressor killer !!
The temperature at the evaporator surface is conditio-
ned by three main parameters:
g
The compressor suction pressure (set by the co
pressor)
g
The flow of refrigerant in the evaporator
(set by the Thermal eXpansion Valve-TXV)
g
The air flow rate through
the evaporator fins
Evaporator freezing
If one of these parameters differs from the autho-
rised limits, freezing may occur and may disable the
refrigerant changing from liquid to gas.
A massive return of liquid refrigerant to the suc-
tion port jeopardises the compressor.
11.1.7 How to avoid
the evaporator freezing
Evaporator freezing can be avoided by the system
itself, as well as good practices during the A/C loop
servicing.
Controlling the suction level
g
The suction pressure can be controlled only on
variable capacity compressors
Monitoring the evaporator temperature
g
In fixed-cylinder compressors, the suction
pressure cannot be adjusted. The compressor
must be stopped when its temperature ap-
proaches 0°C to prevent the evaporator from
freezing.
Good practices:
g
A restricted filter-drier, a low refrigerant charge or a
faulty Thermal eXpansion Valve can lead to evapo-
rator freezing.
g
A restricted air flow through the evaporator (cabin
air filter or blower issue) can lead to freezing as
well.
A yearly maintenance preserves the A/C loop per-
formances.
Air inlet, cabin air filter, and blower performances
are some of the fundamental points to be checked
during servicing
How does the system manages the freezing of the
evaporator?
This depends on the compressor technology, and
can be achieved by:
11. The components
of the A/C Loop
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