54
YORK INTERNATIONAL
The LEAVING WATER TEMP CUT-OUT protects the
chiller from an evaporator freeze-up should the chilled
liquid temp drop below the freeze point. This situation
could occur under low flow conditions or if the micro panel
SETPOINT values are improperly programmed. Anytime
the leaving chilled liquid temperature (water or glycol)
drops to the cut-out point, the chiller will shut down.
Restart will occur when temperature rises above the
cut-out if the anti-recycle timers are satisfied.
For chilled water applications (comfort cooling, SW1
OPEN), the cut-out is automatically set at 36.0°F. This
covers applications where leaving water temperatures are
not designed to go below 40.0°F. If chilled liquid (glycol)
temperatures are required below 40°F, the cutout should
be programmed for 4°F below the desired leaving chilled
liquid temperature.
To program the LEAVING WATER TEMP CUT-OUT the
BRINE & PROCESS MODE (SW1 CLOSED) must be
selected, key in the desired value and press the ENTER
key. The new value will be entered into memory and the
display will advance to the next programmable limit.
The micro will accept a range of programmable values
between 08.0° - 36.0°F for this cut-out.
SUCTION PRESSURE CUT-OUT
The SUCTION PRESSURE CUT-OUT protects the chiller
from an evaporator freeze-up should the system attempt
to run with a low refrigerant charge. Anytime the suction
pressure drops below the cut-out point, the system will
shut down.
NOTE: There are some exceptions, where suction pres-
sure is permitted to temporarily drop below the
cut-out point. Details are outlined in the SYS-
TEM SAFETIES section.
For chilled water applications, the cut-out should be set
at 44 PSIG. If glycol or brine is utilized with leaving water
temperature designs below 40°F, the cut-out should be
adjusted according to concentration. A rule-of-thumb
cut-out design is to drop the cut-out 1 PSIG below 44
PSIG for every degree of leaving glycol below 40°F. In
other words, 30° glycol requires a 34 PSIG suction pres-
sure cut-out.
To program the SUCTION PRESSURE CUT-OUT, key in
the desired value and press the ENTER key. The new
value will be entered into memory and the display will
advance to the next programmable limit.
The micro will accept a range of programmable values
between 20-70 PSIG for this cut-out. In the COMFORT
COOLING MODE (SW1 OPEN), the cut-out is adjustable
from 44-70 PSIG. In the BRINE & PROCESS MODE (SW1
CLOSED), the cut-out is adjustable from 20-70 PSIG.
RATE SENSITIVITY
The RATE SENSITIVITY establishes the rate of change
of return or leaving water temperature where the micro
will over-ride the normal 30-150 seconds per stage load-
ing rate which is based on error between setpoint and
actual temperature.
The RATE SENSITIVITY is active when the leaving chilled
liquid temperature is in the RATE CONTROL TEMP RANGE.
In this range, if water temperature is dropping faster than
the RATE SENSITIVITY setting, the micro will not load any
more stages because water temperature is dropping quickly.
This provides demand limiting and reduces loader/compres-
sor cycling and overshoot. If quick response is needed,
RATE SENSITIVITY can be programmed accordingly. When
temperatures are in the RATE CONTROL TEMP RANGE,
loading will occur in intervals according to both rate of water
temperature change and error in water temperature versus
setpoint. This will override the typical 30-150 seconds per
stage based on error in setpoint versus actual water tem-
peratures. If water temperature is dropping faster than the
RATE SENSITIVITY, no further loading will result and in some
cases, the chiller will unload to slow temperature drop.
RATE SENSITIVITY is also active in the CONTROL RANGE
in RETURN OR LEAVING WATER CONTROL. Further load-
ing will not occur if water temperature is dropping too fast
regardless of whether temperature calls for further loading.
Typically this value should be programmed for 5.0°F.
Additional details of programming this control will be dis-
cussed in the SELECTION OF RETURN OR LEAVING
CHILLED LIQUID CONTROL Section (Page 57).
NUMBER OF LOAD STEPS
The number of steps of loading must be programmed to
assure proper loading sequence and temperature con-
trol. This is done at the factory, but should be checked
against the table below:
S U C T I O N
P R E S S U R E
C U T O U T
=
4 4
P S I G
R A T E
S E N S I T I V I T Y
=
5 . 0
F / M I N .
N U M B E R
O F
L O A D
S T E P S
= 0 5 ( E N T E R
5 , 7
O R
1 0 )
J45
J55
J56
J66
J67
J77
J88
J99
Standard
5
5
7
7
7
7
10
10
Steps Steps Steps Steps Steps Steps Steps Steps
Optional
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
NOTE: Optional unloading is not available. Hot Gas
Bypass (Loadminder) should not be counted for
programming purposes.
The YCW/YCR J56 must be programmed for 7
steps; however, it is only capable of 6 steps of
unloading since the 4 cyl. compressor has a
single unloading solenoid.
Program the number of steps as required. If 5 or 7 steps is
programmed, the 0 key (05 or 07) must be pressed first.
Summary of Contents for YCWJ45EE0
Page 29: ...FORM 150 24 NM27 YORK INTERNATIONAL 29 CONTROL CIRCUIT With I O Expansion Board LD02106...
Page 30: ...30 YORK INTERNATIONAL FIG 9 SYSTEM WIRING...
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Page 36: ...36 YORK INTERNATIONAL MICROPANEL CONNECTION DIAGRAM With I O Expansion Board LD02107...
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