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Operator Interface Display
Dryer energized; Master Switch Off
Dryer energized; Master Switch On
Status
Stand-by Selected
Auto Selected
Refrigerant (low-side) Suction
Pressures
Refrigerant (high-side) Head
Compressed air at inlet to dryer
Optional - Differential pressure across dryer
Temperatures
Optional - Compressed air at inlet to dryer
Optional - Lowest air temperature
Compressor Solid State Motor Protector Open
Compressor Solid State Motor
Protector Open (2nd Compressor)*
Motor Starter Protector Open
Motor Starter Protector Open (2nd Compressor)*
Low oil pressure
Low oil pressure (2nd Compressor)*
Low (low or suction) side refrigerant pressure
Faults
High (high or head) side refrigerant pressure
High evaporator air temperature
Optional - Low water pressure
(water-cooled models)
Optional - High differential pressure
Optional - Low evaporator air temperature
Optional - High condensate level (air-to-air drain)
Optional - High condensate level (air-to-
refrigerant drain
Optional - High condensate level (separator drain)
Optional - High inlet compressed air temperature
* 50 HP and larger
3.2 Operating Sequence
1. With master switch OFF (pushed in), turn disconnect
switch "DISC" to on. Control transformer "IT", and
crankcase heater "HTR", are energized. Power on light
(white) illuminates. "DRYER ENERGIZED" is indicated on
display. Disconnect switch "DISC" must be left on
except for maintenance reasons. Crankcase heater
"HTR" must be energized twenty-four (24) hours prior
to start up.
2. Pull master switch on.
a. Control circuitry is energized and "CONTROL
CIRCUIT ON" is indicated on display. If no fault
condition exists, motor starter coil is energized
and motor starter "M" closes starting compressor
motor "MTR". Display indicates "DRYER PUMPING
DOWN."
b. Compressor motor "MTR" continues the pump
down cycle until low side system pressure reaches
the low pressure cut-out point. At cut-out point,
the PLC de-energizes motor starter "M" coil.
Display indicates "STAND-BY"
8
Condition
Display Message
DRYER ENERGIZED
CONTROL CIRCUIT ON - Dryer will automatically pump
down ("DRYER PUMPING DOWN" indicated) followed
by "STAND-BY"
Dryer will pump down if suction pressure is high
(indicated by "DRYER PUMPING DOWN") followed by
"STAND-BY"
PREPARING TO RUN followed by
COMPRESSOR LOADING and 33%, 50%, 66%, 75%
83%, or 100%
SUCTION PRESSURE
HEAD PRESSURE
INLET AIR PRESSURE
AIR PRESSURE DROP
INLET AIR TEMP
LOWEST AIR TEMP
SSMP-1MTR
SSMP-2MTR
MTR STARTER - 1MTR
MTR STARTER - 2MTR
OIL PRESSURE -1 MTR
OIL PRESSURE - 2MTR
LOW REFRIG PRESS
HIGH REFRIG PRESS
HI EVAP AIR TEMP
LOW WATER PRESS
CHECK SEPARATOR
LOW EVAP AIR TEMP
DRAIN 1 HIGH LEVEL
DRAIN 2 HIGH LEVEL
DRAIN 3 HIGH LEVEL
INLET AIR TEMP
c. If low side system pressure rises to low pressure
set point, compressor starts and pump-down
repeats automatically.
3. Turn momentary Stand-by/Auto selector switch to
AUTO and release.
a. If no fault condition exists, motor starter "M" coil,
liquid valve solenoid "1SOL", and hot gas by-pass
valve solenoid "2SOL", are energized. Display
indicates "PREPARING TO RUN" followed by "COM-
PRESSOR LOADING."
b. As low side system pressure drops to unloader set
point(s), PLC output(s) energize solenoids(s) 3SOL
and 4SOL (35 HP and larger) which unload com-
pressor cylinder(s). As pressure rises above the
unloader set point(s), compressor will load in
reverse sequence. Percentage following "Com-
pressor Loading" indicates percentage of cylinders
loaded.
c. High temperature message will clear when the
process drops below "HTS" set point.
d. Compressor runs automatically unless a SSMP,
motor starter, low oil pressure, high head pressure,
or low suction pressure fault occurs.
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