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NOTE: Operation below 0°F may cause nuisance low
pressure safety shutdowns. Occasional shut-
downs can usually be tolerated since the need for
sustained operation at these low temperatures is
unlikely and temperatures rarely stabilize for any
length of time below 0°F.
To program the LOW AMBIENT CUT-OUT, access the
password protected values as described previously. Key
in the desired low ambient cut-out and press the ENTER
key. The new value will be entered into memory and the
display will advance to the next user programmable value.
The micro will accept a range of programmable values
between 00.0 - 50.0°F for this cut-out, if Dip Switch #2 on
the Micro Logic Board is in the CLOSED position. In the
OPEN position, a fixed 25°F cut-out is recognized.
HIGH AMBIENT CUT-OUT
H I G H
A M B I E N T
C U T O U T
=
The HIGH AMBIENT CUT-OUT is selectable to establish
the chiller high ambient cut-out point. If the ambient rises
more than one degree above this point, the chiller will shut
down. Restart can occur when temperature drops more
than one degree F below the cut-out. This only applies to
outdoor air cooled chillers.
This cut-out is normally set at 130°F to allow operation to
the absolute maximum temperature capability of the
electro-mechanical components.
To program the OUTSIDE AIR TEMP HIGH CUTOUT,
access the password protected values as described
previously. Key in the desired high ambient cutout and
press the ENTER key. The new value will be entered into
memory and the display will advance to the next user
programmable value.
The micro will accept a range of programmable values
between 100.0 - 130.0°F for this cut-out.
DISCHARGE PRESSURE UNLOAD
D I S C H A R G E
U N L O A D
=
The DISCHARGE PRESSURE UNLOAD point is a
programmable limit to keep the system from faulting on
the high discharge pressure cut-out should a system
problem or chiller problem occur. A typical problem would
be dirty condenser coils. Pressure would rise and
90
T E M P
1 3 0 . 0 ° F
P R E S S U R E
3 6 0 . 0
P S I G
eventually cause the chiller to fault causing a total loss of
cooling. By unloading the compressors at high discharge
pressures, the chiller is allowed to continue to run
automatically at reduced capacity until the dirty
condenser coils can be attended to.
When the unload point is reached, the micro will
automatically totally unload the affected compressor.
Typical maximum programmed limits would be 375 PSIG
for air cooled chillers with a 395 or 405 PSIG high pressure
cut-out.
Reloading will occur when the discharge pressure drops
to 60 PSIG below the programmed unload pressure and
will increment loading one stage at a time as indicated by
the loading timers.
To program the DISCHARGE PRESSURE UNLOAD,
access the password protected values as described
previously. Key in the desired discharge pressure unload
value and press the ENTER key. The new value will be
entered into memory and the display will advance to the
next user programmable value.
The micro will accept a range of programmable values
between 200 - 390 PSIG (128 - 270 PSIG for R134a) for
the unload point.
AVERAGE CURRENT UNLOAD
A V E R A G E
C U R R E N T
U N L O A D
=
The AVERAGE CURRENT UNLOAD point is a
programmable limit designed to assure that the motor
current safety does not cause shutdown of the
compressor.
If motor current rises above the programmed motor
current unload point, the micro will automatically begin to
unload the affected compressor at 5 second intervals until
the current draw on the motor falls below the unload point.
This will assure that the motor operates under acceptable
conditions insuring maximum motor life. Reloading will
occur when the motor average current drops below 90%
of the programmed unload point.
This feature may also be used in instances where demand
limiting is required. By programming the unload point
below the % current drawn when the compressors are fully
loaded, the compressors will be prevented from fully
loading which reduces energy consumption.
To program the MOTOR CURRENT UNLOAD, key in the
desired value and press the ENTER key. The new value
will be entered into memory and the display will advance
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% F L A
YORK INTERNATIONAL
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