FORM 150.44-NM4
45
YORK INTERNATIONAL
To program the Low-Limit Water Temperature (LOOT)
and the Control Range (CR), press the CHILLED LIQ-
UID TEMP/RANGE key. This display will first exhibit a
message that LEAVING WATER TEMP CONTROL
is selected and 3 seconds later automatically scroll to
the next display of LWT and CR. The cursor will stop at
the first digit of LWT. Key in the Low-Limit Water
Temperature (LWT) that is acceptable in the system.
See below:
The micro will accept a range of programmable values
from 10.0 - 70.0°F (See SWITCH 1, Page 28). If brine
or gylcol is used in the system, chilled liquid tempera-
tures below 40°F may be desired.
To program setpoints below 40°F, Dip Switch S1, Switch
#1 on the Microprocessor Board must be properly pro-
grammed. (See Page 28). If the switch is incorrect,
when setpoints below 40°F are entered as well as when
unacceptable values are entered, the following mes-
sage will be displayed:
After the Low-Limit Water Temperature (LWT) is keyed
in, the lower limit of the CR (Control Range) in the dis-
play message will automatically change to a value iden-
tical to the LWT. See below:
The cursor will advance to the final entry which is the
upper limit of the CR (Control Range). This value is
programmed for the highest leaving water temperature
which is acceptable in the system application. Typically
2°F above the Low-Limit Water Temperature is appro-
priate. The micro will accept a value 1° - 5°F above the
LWT for this value. 2°F above the LWT is the default
value.
Key in the upper limit of the CR and press the ENTER
key. Otherwise the new values will not be entered into
memory. After pressing the ENTER key, the display will
continue to show the LWT and Control Range mes-
sage until another key is pressed.
CAUTION: Too small of a CR selection will cause com-
pressor/loader cycling. If compressor cy-
cling occurs, leaving water temperature
may vary considerably as a result of a com-
pressor that cannot restart due to the
anti-recycle timer. To eliminate this, in-
crease the
D
T (temperature differential) of
the CR and/or program the anti-recycle
timer for a minimum of 300 seconds if it isnt
already programmed for 300 seconds.
NOTE: Whenever reprogramming the LWT & CR, keep
in mind that the desired leaving water temp. or
target, should be midpoint of the CR.
Normal pulldown loading is limited by a 30 sec. Ioading
timer between stages with loading occurring whenever
leaving water temperature is above the RATE CON-
TROL RANGE.
However, on start-up, loading will be limited to a maxi-
mum of 1 stage per minute for the first 3 minutes. The
loading timer will be increased by the micro to 150 sec.
when temperature falls to within the Rate Control Range
or the upper half of the Control Range (Between Tar-
get and High Limit of the CR).
The Rate Control software will prevent loading and will
cause unloading in the Rate Control Range or Control
Range if temperature drops faster than 2X the pro-
grammed Rate Sensitivity. This is to prevent overshoot.
In the lower half of the Control Range between the Low
Limit and the Target, Rate Control will cause unloading
if temperature falls faster than 1X the programmed Rate
Sensitivity. As before, this is to prevent overshoot.
Below the Control Range, unloading will be done at 20
sec. intervals until temperatures fall back into the Con-
trol Zone. Unloading is controlled by a 20 sec. timer
below the Control Zone as well as when Rate Control
calls for unloading.
Further details loading/unloading and Rate Control will
follow:
PROGRAMMING LEAVING WATER RATE CONTROL
Programmable RATE CONTROL is designed to limit
compressor/loader cycling thus saving energy and re-
ducing wear on mechanical components. It also re-
duces the possibility of overshoot. RATE CONTROL
will allow the micro to react to fast changes in water
temperature beyond normal responses dictated by leav-
ing water temperatures, the 150 sec. Ioading timer, and
the 20 sec. unloading temperature when temperatures
are in the Rate Control Range or the Control Range.
RATE CONTROL requires programming the tempera-
ture range (RATE CONTROL TEMP) above the CON-
TROL RANGE (CR) where rate control is desired.
L W T =
4 4 . 0
F
C R =
4 4 . 0
T O
4 6 . 0
F
Low-Limit Water Temperature (LWT)
O U T
O F
R A N G E
T R Y
A G A I N !
L W T =
4 4 . 0
F
C R =
4 4 . 0
T O
5 4 . 0
F
The lower limit of the CR will always
automatically equal LWT