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MSC4000 - MSC15000 USER GUIDE
9.6
Diagnostic Code “E6” Shutdown on Low Suction PSI
If the suction pressure of the refrigeration system drops 20 psi (1.4 bar g) or lower it will break
contact through the low-pressure switch. This in turn breaks power to the refrigerant compressor
for protection.
To correct this: 1. Bypass the compressed air around the dryer. 2. Based on the size of the unit
you will have either manual resetting pressure switches, or a reset through the control panel by
pressing the mode selection button off then on again after 10 seconds. If the condition continues,
check the following probable causes:
A) Low Freon
Typically if the unit were low on freon you would see an “E3” code. However, if there was for
some reason a large loss of freon in short time this could result in a low-pressure cut out. This
condition is usually caused by a large leak due to a damaged refrigerant line.
1.
Some ways of determining a leak is to physically examine the unit for what may appear as
a puddle or spray of oil. Refrigerant carries the lubricant for the compressor and would
show up where the leak occurred. Another possible determining factor would be the
appearance of the refrigerant sight glass. It normally appears clear with a color moisture
indicator in the center. If the moisture indicator is yellow, chances are there is a leak in
the system. The best way to determine a leak is to contact a refrigeration service house.
They have the technology of a halide torch or electronic leak detectors.
B) Pressure Switch
If you are low on freon or freon pressure the low-pressure switch will be showing electrically
open. You can check the low-pressure switch for continuity to see if the switch is in fact open.
If it is closed you may have a control board problem. There is a possibility the pressure switch
may be faulty giving a false low-pressure indication. Again the best way to determine this is to
contact a refrigeration service house. With their gauges they can check the system pressure
and the settings of the pressure switch. The low-pressure switch is set to trip at 20 psi g (1.4
bar g). If you have an automatic resetting switch it will close again at 50 psi g (3.45 bar g).
C) Unloader Solenoid Failing to Open
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 marked “Unloader”, terminals 9
and 10. There should be a 120V output from this relay. If there is no 120V output,
replace the board.
3.
If the coil is functioning and the dew point continues to fall, or the unit shuts down
displaying an “E6”, the unloader solenoid is defective. The internals or the whole valve
should be replaced.
Remember the unloader must be check while the unit is operative and in the unloaded state.
The way this is determined is by the Power Saver Active light being illuminated.
D) Refrigerant restriction
If there should be a restriction in the refrigerant system this could cause a low-pressure
situation. The most common points of restriction are:
1. Faulty suction line solenoid
- If the suction line solenoid (1500 and up) were defective or
not functioning electronically, this could cause a restriction. When the Power Saver Active
light is off the suction line solenoid should be energized and fully open. To verify this
examine the following:
