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38 TRG-TRC005-EN
notes
period five
Accessories
Moisture-Indicating Sight Glass
A moisture-indicating sight glass is installed in the liquid line, upstream of
the expansion valve, and permits the operator to observe the condition of the
refrigerant prior to entering the expansion valve. The value of the sight glass is
in its moisture indication ability—the sight glass should not be used to
determine system refrigerant charge or subcooling. Actual temperature and
pressure measurements are required to determine proper charge and
subcooling.
With the sight glass installed directly ahead of the expansion valve, it can also
be used to detect the presence of bubbles in the liquid line. This would indicate
that some of the liquid refrigerant has flashed into vapor upstream of the
expansion valve. Since the expansion valve is designed to control the flow of
liquid refrigerant only, the presence of refrigerant vapor results in a reduction in
the quantity of liquid refrigerant being fed to the evaporator. There are many
potential causes of liquid refrigerant flashing. The sight glass can alert the
operator to the condition.
Moisture-Indicating Sight Glass
sight
sight
glass
glass
expansion
expansion
valve
valve
liquid line
liquid line
Figure 55