44
YORK INTERNATIONAL
The next item which will require programming is the
RATE SENSITIVITY. The RATE SENSITIVITY is a
means of overriding the loading/unloading timers when
water temperatures are in the RATE CONTROL RANGE
or the CONTROL RANGE. This allows the micro to react
to abrupt downward changes in leaving or return water
temperatures. The ability to respond to rate of change
variations in water temperatures gives the micro antici-
pation capabilities to reduce the possibility of over-
shoot in leaving water temperature.
In demand limiting applications, to avoid cycling or to
avoid overshoot, RATE SENSITIVITY should be low. This
allows the micro to go into rate control to prevent loading
whenever water temperatures drop faster than the pro-
grammed RATE SENSITIVITY. Rate Control can go into
effect whenever water temperatures are in RATE CON-
TROL RANGE or the CONTROL RANGE. For these ap-
plications, a 3° - 5°F/min. RATE SENSITIVITY is recom-
mended. This may be needed for small water loops.
However, if problems arise where the chiller does not
load and pull temperature down, select 5.0° F/min.
NOTE: Too small of a RATE SENSITIVlTY value se-
lection may prevent loading due to varying flows
or if the water system allows a slug of cold water
to enter which falsely fools the micro into think-
ing the RATE SENSlTIVlTY has been ex-
ceeded, preventing loading and allowing leaving
water temperature to rise above the desired
temperature.
For normal comfort cooling, batch, or process applica-
tions, select a high RATE SENSITIVITY of 5°F/min. Be-
fore RATE CONTROL can go into effect, the water tem-
perature would have to change at a very high rate to ex-
ceed the RATE SENSITIVITY value programmed. This
will assure normal loading will occur. 5° F/min. also
works well in comfort cooling applications.
If unsure of
a RATE SENSITIVITY selection, use 5°F/min.
To program the RATE SENSITIVITY, first press the
PROGRAM key. Repetitively press the ENTER key until
the display below appears.
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 user programmable limit.
The micro will accept a range of programmable values
between 0.5° - 5.0°F/min.
PROGRAMMING LEAVING WATER CONTROL
Chilled Liquid Temp/Range
When the CHILLED LIQUID TEMP/RANGE key is
pressed, the following message will be displayed for 3
seconds indicating Dip Switch S1, Switch #4 on the Mi-
croprocessor Board is programmed properly:
If this message is incorrect, see the SELECTION OF
RETURN OR LEAVING CHILLED LIQUID CONTROL
Section (Page 40) for instructions to reprogram the Mi-
croprocessor Dip Switch S1, Switch #4.
The display will then scroll to a second message & hold:
This message will display the Low-Limit Water Tempera-
ture (LWT) and the Control Range (CR). In the sample
above, the LWT is 44.0° F and the CR is 44° - 46° F.
The Control Range (CR) is the variation in leaving water
temperature which is acceptable in the system applica-
tion. As long as leaving water temperature stays be-
tween the low limit and midpoint of the Control Range
(CR), the Microprocessor will consider the temperature
acceptable and will not initiate any loading/unloading re-
action unless Rate Control requires. The Low-Limit
Water Temperature (LWT) is the minimum acceptable
leaving water temperature in the Control Range (CR), not
the actual user desired leaving water temperature
setpoint.
The desired leaving water temperature is known as the
Target temperature which is the temperature the micro
will attempt to control to. The Target temperature is not
programmable, but it is always the midpoint of the Con-
trol Range (CR). Example: A control range of 44° - 46°F
will have a Target Temp of 45°F. which should equal the
desired system leaving water temperature. As men-
tioned before, the micro will be satisfied with a leaving
temperature between 44° - 45° F unless the rate control
is exceeded. The microprocessors rate control is de-
signed to be less responsive in the upper half of the Con-
trol Range (i.e. 45° - 46°F) than in the lower half (i.e. 44°
- 45° F). This is to prevent overshoot.
To program the Low-Limit Water Temperature (LWT) and
the Control Range (CR), press the CHILLED LIQUID
R A T E
S E N S I T I V I T Y
=
5 . 0
F / M I N
L W T =
4 4 . 0
F
C R =
4 4 . 0
T O
4 6 . 0
F
L E A V I N G
W A T E R
T E M P
C O N T R O L
Summary of Contents for YCAJ44HE8
Page 16: ...16 YORK INTERNATIONAL WIRING DIAGRAMS LD02165 FIG 5 ELEMENTARY DIAGRAM...
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Page 20: ...20 YORK INTERNATIONAL CONNECTION DIAGRAM ELECTRICAL BOX FIG 7 CONNECTION DIAGRAM LD02171...
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