York YCAS 0138EB, Installation Operation & Maintenance

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JOHNSON CONTROLS
temperatures. If operation is occasionally needed below
1°F (-17°C), the cutout should be set at 00.0°F. This will
allow operation at any temperature, as the micro will only
recognize temperatures above 1°F (-17°C). Temperatures
below 1°F (-17°C) will not be displayed.
To program the Low Ambient Cutout, key in the required
setting and press the Enter key to store the value into
memory and scroll to the next display.
Operation below 1°F (‑17°C) may
occasionally cause nuisance low
pressure safety shutdowns. This will
generally not cause a problem provided
ambient temperature is not expected to
be below 1°F (‑17°C) for more than a
short time.
Low Leaving Liquid Temperature CutOut
The Low Leaving Liquid Temperature Cutout protects
the evaporator from damage due to ice build up caused
by operation below the chilled liquid freezing point.
If the leaving chilled liquid temperature (water or glycol)
drops below the cutout point, the chiller will shut down.
The chiller will restart automatically when temperature
rises more than 4°F (2°C) above the cutout point and
cooling demand exists.
If the Dip Switch on the microprocessor board is set
for “Water Cooling” (see Section 3.7, page 142) the
cutout is automatically set at 36°F (2°C) and cannot be
reprogrammed. If the Switch is set for “Brine Cooling”
(glycol) the cutout can be programmed between 08.0 -
36.0°F (-13 through -2°C). The cutout should normally
be set to 4°F (2°C) below the setpoint minus the range,
i.e. 34°F (setpoint) – 2°F (range) - 4°F = 28°F (see
Section 6, page 153).
To program the Leaving Liquid Temperature Cutout, key
in the required setting and press the Enter key to store the
value into memory and scroll to the next display.
High Motor Current Unload Point
The Motor Current Unload point is used to avoid a
high motor current safety shutdown by unloading a
compressor, if current draw approaches the maximum
set to the saturated refrigerant pressure equivalent to
18°F (10°C) below the lowest temperature of the pro-
grammed chilled liquid Control Range (Section 6). This
programmable value is password protected.
To program the Suction Pressure Cutout, key in the re-
quired setting and press the Enter key to store the value
into memory and scroll the next display.
High Ambient Temperature Cutout
The High Ambient Cutout is used to select the ambient
temperature above which the chiller may not operate.
If the ambient temperature rises 1°F (1°C) above this
point, the chiller will shut down. Restart will occur
automatically, when temperature falls more than 1°F
(1°C) below the cutout and cooling demand is present.
This cutout is normally set at 130°F (54°C) to allow op-
eration to the absolute maximum temperature capability
of the electromechanical components; however, values
between 100.0 - 130.0°F (38 - 54°C) are accepted. This
programmable value is password protected.
To program the High Ambient Cutout, key in the re-
quired setting and press the Enter key to store the value
into memory and scroll to the next display.
Low Ambient Temperature Cutout
The Low Ambient Cutout is used to select the ambient
temperature below which the chiller may not operate.
If the ambient temperature falls 1°F (1°C) below this
point, the chiller will shut down. Restart will occur
automatically, when temperature rises more than 1°F
(1°C) above the cutout and cooling demand is present
(see also Section 2.5 page 135). This programmable
value is password protected.
If the SW1 Dip Switch on the Microprocessor Board
is set for “Standard Ambient Control” (see Section
3.7) the low ambient cutout is set at 25°F (-4°C) and is
NOT programmable. If the Dip Switch is set for “Low
Ambient Control”, programming of the cutout between
00.0 - 50.0°F (8 - 10°C) is allowed. This allows higher
values than 25° F (-4°C) to be programmed to shut
down the chiller when other cooling methods become
operational. Values below 25°F (-4°C) can be used
for applications requiring chiller operation at lower
H I G H A M B I E N T T E M P
C U T O U T = 1 3 0 . 0 ° F
L O W A M B I E N T T E M P
C U T O U T = 2 5 . 0 ° F
L E A V I N G L I Q U I D T E M P
C U T O U T = 3 6 . 0 ° F
H I G H M O T O R C U R R E N T
U N L O A D = 1 0 5 % F L A
Micro Panel Contents