46
YORK INTERNATIONAL
TEMP/RANGE key. This display will first exhibit a mes-
sage that “LEAVING WATER TEMP CONTROL” is se-
lected 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 Tempera-
ture (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 29). If brine
or glycol 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 29). If the switch is incorrect, when
setpoints below 40°F are entered as well as when unac-
ceptable values are entered, the following message 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 pro-
grammed for the highest leaving water temperature which
is acceptable in the system application. Typically 2°F
above the Low-Limit Water Temperature is appropriate.
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 message
until another key is pressed.
CAUTION: Too small of a CR selection will cause com-
pressor/loader cycling. If compressor cycling
occurs, leaving water temperature may vary
considerably as a result of a compressor
that cannot restart due to the anti-recycle
timer. To eliminate this, increase the
∆
T (tem-
perature differential) of the CR and/or pro-
gram the anti-recycle timer for a minimum
of 300 seconds if it isn’t 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. loading
timer between stages with loading occurring whenever
leaving water temperature is above the RATE CONTROL
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 Target
and High Limit of the CR).
The Rate Control software may prevent loading or cause
unloading in the Rate Control Range or Control Range if
temperature drops faster than 2X the programmed 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 be-
low 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 com-
pressor/loader cycling thus saving energy and reducing
wear on mechanical components. It also reduces the
possibility of “overshoot”. RATE CONTROL will allow the
micro to react to fast changes in water temperature be-
yond normal responses dictated by leaving water tem-
peratures, the 150 sec. loading timer, and the 20 sec.
unloading temperature when temperatures are in the Rate
Control Range or the Control Range.
L W T =
4 4 . 0
F
C R =
4 4 . 0
T O
4 6 . 0
F
O U T
O F
R A N G E
T R Y
A G A I N !
Low-Limit Water Temperature (LWT)
The lower limit of the CR will
always automatically equal LWT
L W T =
4 4 . 0
F
C R =
4 4 . 0
T O
4 6 . 0
F
