JOHNSON CONTROLS
90
FORM 150.62-NM6 (103)
When in leaving chilled liquid temperature control, the
micro will attempt to control the leaving water tempera-
ture within the temperature range of the setpoint + or
- the range. In the above example, 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 indicates that the
setpoint is not centered within the RANGE but could be
described as the bottom of the control range. A listing of
the limits and the programmable values for the COOL-
ING SETPOINTS are shown in Table 20.
The SETPOINT and RANGE displays just described
were based on LOCAL control. If the unit was pro-
grammed for REMOTE control (under the OPTIONS
key), the above programmed 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 temperature
rises. All compressors will be on at setpoint + the range.
If the range equals the temperature drop across the
evaporator when fully loaded, the leaving chilled liquid
temperature will remain near the setpoint + or - a few
degrees as the chiller loads and unloads according to
return chilled liquid temperature.
Both LEAVING and RETURN control are described in
detail under the section on CAPACITY CONTROL.
Pressing the COOLING SETPOINTS key a second time
will display the remote setpoint and cooling range. This
display automatically updates about every 2 seconds.
Notice that these setpoints are not “locally” program-
mable, 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 REMOTE mode.
The messages below illustrate both leaving chilled liquid
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 20.
Pressing the COOLING SETPOINTS a third time will
bring up the display that allows the Maximum EMS-PWM
Temperature Reset to be programmed. This message
is shown below.
The Temp Reset value is the maximum allowable reset
of the temperature setpoint. The setpoint can be reset
upwards by the use of a contact closure on the PWM
Temp Reset input (CTB1 terminals 13 - 20). See the
section on Operating Controls for a detailed explanation
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 setpoint, 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 alternate
holiday schedule available. If no start/stop times are
programmed, the unit will run on demand, providing the
chiller is not shut off on a unit or system shutdown. The
daily schedule is considered “not programmed” when
the times in the schedule are all zeros (00:00 AM).
To set the schedule, press the SCHEDULE/ADVANCE
DAY key. The display will immediately show the following
display.
The line under the 0 is the cursor. If the value is wrong,
it may be changed by using 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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