YORK INTERNATIONAL
84
FORM 150.62-NM7 (103)
When in leaving chilled liquid temperature control, the
mi cro will at tempt to control the leaving water tem per a-
ture with in the tem per a ture range of the setpoint + or
- the range. In the above ex am ple, control will be in the
range of 43 - 47°F.
RETURN CHILLED LIQUID CONTROL
Notice that the range no longer has a +/- X.X °F, but
only a + X.X °F RANGE setpoint. This in di cates that the
set point is not centered within the RANGE but could be
described as the bottom of the control range. A list ing of
the limits and the pro gram ma ble values for the COOL-
ING SETPOINTS are shown in Table 19.
The SETPOINT and RANGE displays just de scribed
were based on LOCAL control. If the unit was pro-
grammed for REMOTE control (under the OP TIONS
key), the above pro grammed setpoints would have no
effect.
When in return chilled liquid temperature control, the
micro will turn all compressors off at setpoint and will
turn compressors on as return chilled liquid tem per a ture
ris es. All compressors will be on at setpoint + the range.
If the range equals the temperature drop across the
evap o ra tor when fully loaded, the leaving chilled liq uid
tem per a ture will remain near the setpoint + or - a few
degrees as the chiller loads and unloads according to
return chilled liquid temperature.
Both LEAV ING and RE TURN control are described in
de tail under the section on CAPACITY CONTROL.
Pressing the COOLING SETPOINTS key a second time
will display the remote setpoint and cooling range. This
display au to mat i cal ly updates about every 2 seconds.
Notice that these setpoints are not “locally” pro gram -
ma ble, but are controlled by a remote device such as
an ISN control. These setpoints would only be valid if
the unit was operating in the RE MOTE mode.
The messages below illustrate both leaving chilled liq uid
control and return chilled liquid control respectively.
(leaving chilled liquid control)
R E M S E T P = 4 4 . 0 ° F
R A N G E = + / - 2 . 0 ° F
R E M S E T P = 4 4 . 0 ° F
R A N G E = + 1 0 . 0 ° F
M A X E M S - P W M R E M O T E
T E M P R E S E T = + 2 0 ° F
S E T P O I N T = 4 5 . 0 ° F
R A N G E = + 2 . 0 ° F
Unit Controls
(return chilled liquid control)
The low limit, high limit, and default values for the keys
under “SETPOINTS” are listed in Table 19.
Pressing the COOLING SETPOINTS a third time will
bring up the display that allows the Max i mum EMS-PWM
Temperature Reset to be pro grammed. This mes sage
is shown below.
The Temp Reset value is the maximum al low able reset
of the temperature setpoint. The set point can be reset
up wards by the use of a contact closure on the PWM
Temp Reset input (CTB1 ter mi nals 13 - 20). See the
section on Operating Con trols for a detailed ex pla na tion
of this feature.
As with the other setpoints, the Up Arrow and Down
Arrow keys are used to change the Temp Reset value.
After using the UP and DOWN ARROWS to adjust to the
desired set point, the ENTER/ADV key must be pressed
to enter this number into memory.
SCHEDULE/ADVANCE DAY key
The SCHEDULE is a seven day daily schedule that al-
lows one start/stop time per day. The schedule can be
programmed Monday through Sunday with an al ter nate
holiday schedule avail able. If no start/stop times are
pro grammed, the unit will run on demand, pro vid ing the
chill er is not shut off on a unit or sys tem shutdown. The
daily schedule is con sid ered “not programmed” when
the times in the sched ule are all zeros (00:00 AM).
To set the schedule, press the SCHED ULE/AD VANCE
DAY key. The display will im me di ate ly show the fol low ing
display.
The line under the 0
is the cursor. If the value is wrong,
it may be changed by us ing the UP and DOWN arrow
keys until correct. Pressing the ENTER/ADV key will
enter the times and then move the cursor to the minute
M O N S T A R T = 0 0 : 0 0 A M
S T O P = 0 0 : 0 0 A M
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