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this point, the chiller will shutdown. 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
operation to the absolute maximum temperature capa-
bility of the electromechanical components; however,
values between 100 and 130°F (37.8 and 54.4°C) are
acceptable.
Low Ambient Temperature Cutout:
L O W
A M B I E N T
C U T O U T
=
The low ambient temperature 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 shutdown. Restart will
occur automatically, when temperature rises more than
1°F (1°C) above the cutout and cooling demand is
present.
If the Dip Switch (S1) on the AMB board is set for
'STANDARD AMBIENT CONTROL' the low ambi-
ent temperature cutout is set at 25°F (-4°C) and is not
programmable.
If the Dip Switch (S1) on the AMB board is set for
'LOW AMBIENT CONTROL', programming of the
cutout between 0.0° and 50° F (-17.8°C and 10°C) is
allowed. This allows higher values than 25°F (-3.9°C)
to be programmed to shutdown the chiller when other
cooling methods become operational. Values below
25°F (-3.9°C) can be used for applications requiring
chiller operation at lower temperatures.
Low Leaving Liquid Temperature Cutout:
L E A V I N G
L I Q U I D
C U T O U T
=
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 gly-
col) drops below the cutout point, the chiller will shut-
down. The chiller will restart automatically when tem-
perature rises more than 36°F (2°C) above the cutout
point and cooling demand exists.
If the Dip Switch (S1) on the AMB board is set for
'WATER' cooling mode, the cutout is automatically
set at 36°F (2.2°C) and cannot be reprogrammed.
YORK INTERNATIONAL
T E M P
3 9 ° F
T E M P
3 6 ° F
If the Dip Switch (S1) on the AMB board is set for 'GLY-
COL' (Brine) cooling mode, the cutout can be pro-
grammed between 8°F and 36°F (-13.3°C and -2.2°C).
The cutout should normally be set to 4°F (2°C) below
the setpoint minus the range, i.e. 32°F (setpoint) -1°F
(range) -20°F = -40°F [0°C (setpoint) - 1°C (range) -
2°C = -3°C].
High Motor Current Unload Point:
H I G H
M O T O R
U N L O A D
=
1 0 0 %
The motor current unload point is used to avoid a high
motor current safety shutdown by unloading a com-
pressor, if current draw approaches the maximum limit
cutout value. The chiller can then continue to run auto-
matically at reduced capacity until the cause of the ex-
cessive current is resolved.
The microprocessor will accept between 30 - 105% for
the unload point. The motor current safety will shut
the compressor down whenever current exceeds 115%.
If the programmable limit is set between 100% and
105% of full load current, this safety will protect against
excessive current causing compressor shutdown due
to extremely high ambient, high chilled liquid tempera-
ture, and condenser malfunction caused by dirt or fan
problems.
If the programmable limit is set below 100% of full
load current, this feature can be used for 'demand lim-
iting'. This is important when demand limiting is criti-
cal due to power requirements or limitations in the
building.
For the first 60 seconds of operation, the unloading
safety is disabled. After this time, if motor current ex-
ceeds the programmed limit, slide valve current will
be slowly reduced until the motor current drops below
the programmed limit. Additional loading will take
place when motor current drops below 90% of the pro-
grammed threshold.
Typically, this point should be set at 100% for maxi-
mum motor protection, programming for 100% is ad-
visable. When programming values below 100% use
of a leading '0' is required, e.g. 085%.
Anti-Recycle Time:
A N T I
R E C Y C L E
=
6 0 0
S E C S
FORM 201.25-NM1 (302)
C U R R E N T
F L A
T I M E R
71
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