FORM 150.60-NM3
37
YORK INTERNATIONAL
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 (gly-
col) temperatures are required below 40°F, the cut-out
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 sys-
tem 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 °F 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 adjust-
able 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 override 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 CONROL
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 tem-
perature is dropping quickly. This provides demand limit-
ing and reduces loader/compressor cycling and over-
shoot. 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 tem-
perature 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
temperatures. If water temperature is dropping faster
than the RATE SENSITIVITY, no further loading will re-
sult 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 loading 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 for programming this control will
be discussed in the SELECTION OF RETURN OR
LEAVING CHILLED LIQUID CONTROL Section (Page
40).
NUMBER OF LOAD STEPS
The number of steps 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:
Standard unloading requires programming for 5 steps.
Optional unloading is not available.
NOTE: Hot Gas Bypass (Loadminder) should not be
counted for programming purposes.
Program the number of steps for 5 steps. The 0 key
(05) must be pressed first.
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
= 1 0 ( E N T E R
5 , 7
O R
1 0 )
STANDARD
Z88EE8 J44HE8 J54HE8 J55HE8 J65HE8
5 STEPS 5 STEPS 5 STEPS 5 STEPS 5 STEPS
Summary of Contents for YCAJ44HE8
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Page 17: ...FORM 150 60 NM3 17 YORK INTERNATIONAL FIG 5 ELEMENTARY DIAGRAM Cont d LD02166...
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Page 21: ...FORM 150 60 NM3 21 YORK INTERNATIONAL FIG 7 CONNECTION DIAGRAM Cont d LD02172...