York Millennium YCAJ150, Установка, эксплуатация и обслуживание, Страница: 46 / 116

46 YORK INTERNATIONAL
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 (4.4 - 20°C) 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 (303.3 kPa). If glycol or brine is utilized with
leaving water temperature designs below 40°F (4.4°C),
the cut-out should be adjusted according to concentra-
tion. A rule-of-thumb cut-out design is to drop the cut-
out 1 PSIG (6.9 kPa) below 44 PSIG (303.4 kPa) for
every degree of leaving glycol below 40°F (4.4°C). In other
words, 30°F (-1.1°C) glycol requires a 34 PSIG (234.4
kPa) suction pressure 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 the next programmable limit.
The micro will accept a range of programmable values be-
tween 20 - 70 PSIG (137.9 - 482.6 kPa) for this cut-out. In
the COMFORT COOLING MODE (SW1 OPEN), the cut-
out is adjustable from 44 - 70 PSIG (303.4 - 482.6 kPa). In
the BRINE & PROCESS MODE (SWI CLOSED), the cut-
out is adjustable from 20 - 70 PSIG (137.9 - 482.6 kPa).
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 re-
duces loader/compressor cycling and overshoot. If quick
response is needed, RATE SENSITIVITY can be pro-
grammed 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 over-
ride the typical 30 - 150 seconds per stage based on error
in setpoint versus actual water temperatures. If water tem-
perature 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 loading will not occur if water temperature is drop-
ping too fast regardless of whether temperature calls for
further loading.
Typically this value should be programmed for 5.0°F
(2.7°C). Additional details of programming this control
will be discussed in the SELECTION OF RETURN OR
LEAVING CHILLED LIQUID CONTROL Section (Page
50).
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:
Standard unloading requires programming for “5” steps.
Optional unloading requires “7” or “10” step selection.
The YCAJ190 will actually operate only 8 of 10 steps
since one compressor is a 6 cylinder with only two un-
loading solenoids.
Optional unloading requires a 2nd Relay Output Board.
No compressor changes are required.
NOTE: Hot Gas Bypass (Loadminder) should not be
counted as a load step for programming pur-
poses.
Program the number of steps as required. If 5 or 7 steps
is programmed, the “0” key (05 or 07) 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 )
J150 J160 J180 J190 J200 J220 J230
STD. 5 STEPS 5 STEPS 5 STEPS 5 STEPS 5 STEPS 5 STEPS 5 STEPS
OPT. 7 STEPS 7 STEPS 7 STEPS 8 STEPS 10 STEPS 10 STEPS 10 STEPS