38
YORK INTERNATIONAL
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/compressor
cycling and overshoot. If quick response is needed, RATE
SENSITIVITY can be programmed accordingly. When tem-
peratures are in the RATE CONTROL TEMP RANGE, load-
ing 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 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.
Additional details of programming this control will be dis-
cussed in the SELECTION OF RETURN OR LEAVING
CHILLED LIQUID CONTROL Section (Page 41).
NUMBER OF LOAD STEPS
The number of steps of loading must be programmed to
assure proper loading sequence and temperature con
done at the factory, but should be checked against the
tables below:
Optional unloading requires a 2nd Relay Output Board.
No compressor changes are required.
NOTE: Hot Gas Bypass (Loadminder) should not be
counted as a step for programming purposes.
Program as required. If 5 or 7 steps is programmed, the “0”
key (05 or 07) must be pressed first.
60HZ
Z88DR6 J44DR6 J44HT6 J54ES6 J55HT8 J65HT8 J66MT8
Standard 5 Steps 5 Steps 5 Steps 5 Steps 5 Steps 5 Steps 5 Steps
Optional
N/A
N/A
N/A
N/A
N/A
N/A
N/A
50HZ
J44DR7 J55DR7 J55HT7 J65ES7 J66HT9 J76HT9 J77MT9
Standard 5 Steps 5 Steps 5 Steps 5 Steps 5 Steps 5 Steps 5 Steps
Optional
N/A
N/A
N/A
N/A
7 Steps 7 Steps 7 Steps
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 adjust-
able from 44-70 PSIG. In the BRINE & PROCESS MODE
(SW1 CLOSED), the cut-out is adjustable from 20-70
PSIG.
RATE SENSITIVITY
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 )
