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FORM 150.66-NM3
ISSUE DATE: 09/25/2020
When in leaving chilled liquid temperature control,
the microprocessor will attempt to control the leaving
water temperature within the temperature range of the
setpoint plus or minus the range. In the above example,
control will be in the range of 43 - 47°F.
Return Chilled Liquid Control
S E T P O I N T
=
R A N G E
=
In return chilled liquid control, the range no longer has
a plus or minus X.X °F, but only a plus X.X °F RANGE
setpoint. This indicates that the setpoint is not centered
within the RANGE but could be described as the bot-
tom of the control range. A listing of the limits and the
programmable values for the COOLING SETPOINTS
are shown in Table 15.
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
microprocessor will turn all compressors off at setpoint
and will turn compressors on as return chilled liquid
temperature rises. All compressors will be on at set-
point plus the range. If the range equals the tempera-
ture drop across the evaporator when fully loaded, the
leaving chilled liquid temperature will remain near
the setpoint plus or minus 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.
Remote Setpoint Control
Pressing the COOLING SETPOINTS key a second
time will display the remote setpoint and cooling range.
This display automatically updates about every 2 sec-
onds. Notice that these setpoints are not "locally" pro-
grammable, but are controlled by a remote device such
as an ISN control, remote reset option board, or remote
PWM signal. These setpoints would only be valid if the
unit was operating in the REMOTE mode.
The following messages illustrate both leaving chilled
liquid control and return chilled liquid control respec-
tively.
JOHNSON CONTROLS
4 5 . 0
° F
+ 1 0 . 0 ° F
R E M
S E T P
R A N G E
=
(leaving chilled liquid control)
R E M
S E T P
R A N G E
(return chilled liquid control)
The low limit, high limit, and default values for the
keys under "SETPOINTS" are listed in table 15.
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.
M A X
E M S - P W M
T E M P
R E S E T
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). The PWM
signal may be applied directly on these terminals from
an Energy Management System or from the Tempera-
ture Reset Option Board. See page 143 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
allows one start/stop time per day. The schedule can
be programmed Monday through Sunday with an al-
ternate 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 pro-
grammed" 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 fol-
lowing display.
M O N
S T A R T
S T O P
SECTION 7 - UNIT CONTROLS
=
4 4 . 0 ° F
+ / - 2 . 0 ° F
=
4 4 . 0 ° F
=
+ 1 0 . 0 ° F
R E M O T E
=
+ 2 0 ° F
=
0 0 : 0 0
A M
=
0 0 : 0 0
A M
117
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