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MSC4000 - MSC15000 USER GUIDE
WARNING!
If the refrigerant has been seriously contaminated with water, you probably won’t be
able to dry it with dryers and certainly not vacuum. Best to do solvent cleanup on the evaporator
and suction accumulator or replace the evaporator. A flooded shell holds a lot of water and is
difficult to clean effectively.
8.2
Refrigerant Control Valves
Expansion valves:
The superheat (+15ºF) (-9ºC) that the valve controls is created in the control
evaporator or suction line heat exchanger. There is liquid or zero superheat tat the main
evaporator outlet to facilitate oil return and keep the shell flooded. If there is superheat at the
main evaporator outlet or if the suction line to the compressor is warm to the hand, 1) check the
charge. If the sight glass is full, 2) the TXV may be defective or the liquid line is blocked. The TXV
superheat adjustment is not critical.
Parker Airtek uses standard type valves that can be found in wholesale houses anywhere. When
replacing or repairing them, remember these points:
Don’t use any TCLE Alco valves. TCLE valves are too slow.
•
Use cross-ambient “C” or liquid “L” charges. Do not use any pressure limiting or all-purpose
“W” charges.
•
We recommend that you increase the superheat setting of the new valve about 5ºF (-15ºC)
from the factory setting. Turning the stem 2 turns in is about right.
•
Position the sensing bulb of the new valve just where the old one was. It is crucial that the
suction line be clean and the bulb well insulated.
8.3
Solenoid Valves
The suction solenoid valve rarely causes any trouble because the pressure difference across it is
never great. Unloader solenoids operate with greater differentials and so are more likely to fail.
Parker Airtek uses valves with a rated life of more than two million operations. When they finally
wear out, the usual symptom is failure to close. The valves can usually be restored by installing a
diaphragm repair kit available from Parker Airtek or the valve’s local distributor.
8.4
Drains
The draining of water from the separator is the most crucial part of the whole process. A
complaint of “There’s more water in the air now than there was before the dryer was installed” is
usually a drain problem.
Parker Airtek has a float-operated drain. Operate the drain manually; push to test. Check the float
switch, board or solenoid valve if not.
In the case of the tier drain (Drain Master) not working you can power the valve with a 115 V test
to decide which component is bad.
8.5
Electronic Controls
A dew point temperature controller is used on the Dual Mode Dryers. The controller operates
the unloader solenoid, opening it to stop refrigeration if the sensed temperature goes below the
controller setting, usually 35ºF (2ºC). The suction solenoid is closed during unloading.
This temperature is sensed by a sensing probe inserted in one of the evaporator tubes. When air
passes over the probe, the air temperature controls the dew point normally. When there is little
or no airflow, the controller sees the evaporator temperature, and is able to prevent it from going
below freezing. The operation of the dew point controller is really simple. All it does is switch
back and forth between opening the suction line solenoid and closing the unloader and vice versa.
A malfunction of the control system can be suspected if:
1.
The suction pressure won’t fail when the dew point is above the set point. You
can suspect the unloader solenoid isn’t closing due to a bad diaphragm.
