Parker Airtek MSC Series, Руководство пользователя, Страница: 38 / 47

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MSC4000 - MSC15000 USER GUIDE
D) Expansion Valve Stuck Closed
Test by applying heat (hair dryer) to TXV sensing bulb located just after the flood level control
for about 30-45 seconds. This should cause the unit to flood back and lower the super heat.
To check this, take a temperature reading on the suction accumulator, it should be extremely
cold, if it is not, your expansion valve is stuck closed. Your suction accumulator normally
shows a level based on temperature of being 1/3 to 1/2 full.
9.4 Diagnostic Code “E4” Shutdown on Freeze Protection
Freezing is defined as the point at which the actual dew point falls to 20ºF (-7ºC) or lower. If this
condition occurs and lasts for ten minutes, an “E4” will display and the dryer will shut down. This
will prevent the unit from freezing.
Most importantly it will save the evaporator from developing a leak due to expansion of moisture,
which may be present within the evaporator tubing.
The probable cause of this problem is the unloader valve failing to open in some matter. To
further diagnose the cause of this failure and to check operation, turn the unit off then on
again after 15 seconds using the Load/Unload mode. This will clear the diagnostic code and
cause the unit to operate again. When the dew point falls below the dew point set point the
Power Saver Active light should come on and the following items should be checked:
1. You need to first check the coil of the unloader valve to ensure that it is functioning. The
easiest way to verify if the coil is energized is to take a screwdriver and touch it to the screw
or post on the top of the coil. If the coil is energized there will be a magnetic field pulling the
metal to the screw or post. If the Power Saver Active light is on and there is no magnetic pull,
the coil is not functioning.
2. If you have determined the coil is not functioning there are two things you must check. Test
the coil electrically for continuity to ensure it is not shorted. If it is shorted replace the coil.
If the coil is not shorted you need to check the K3 relay on the back of the control board
marked “Unloader”, terminals 9 and 10. There should be a 120V output from this relay. If
there is not, replace the board.
3.
If the coil is functioning and the dew point continues to fall, the unloader solenoid is defective.
The internals or the whole valve should be replaced.
Remember all of this must be checked while the unit is operative and in the unloaded state.
The way this is determined is by the Power Saver Active light being illuminated.
9.5 Diagnostic Code “E5” High Dew Point Shutdown
If the actual dew point on the digital control board reads 40ºF (4ºC) higher than the dew point set
point for 10 minutes, the dryer will shut down and a diagnostic code of “E5”.
The probable causes for this condition are the unloader solenoid sticking open, or a weak or
defective compressor.
The dryer can be reset by pressing the mode selection button to turn the unit off, and then
pressing it again will turn the unit back on. If the dew point does not fail check the following:
A) Unloader valve stuck open
1. You first need to determine if the unloader valve is functioning properly. When the dryer
is refrigerating and the Power Saver Active light is off, the unloader valve should be de-
energized and closed. It is unlikely that the coil is shorted closed but not impossible. You
can check the solenoid electrically to see if it is getting an electric signal. Another way
to see if the coil is energized is to take a screwdriver or something metal and touch it to
the screw or post on the top of the coil. When the coil is energized there is a magnetic
field produced which will pull the metal object to the screw post. If it is, the coil may be
shorted closed, causing the digital control board to give a constant electric signal from the
K3 relay affixed to the back of the board. If this is the case replace the control board, and
the coil.