JOHNSON CONTROLS
104
SECTION 7 - OPERATION
Form 201.28-NM1.1
Issue date: 08/06/2021
default value when programming numeric values. For
key has no function.
-
ways between the same displays on different systems.
while viewing the system #1 suction pressure moves the
display to system #2 suction pressure.
opposite direction. The arrow keys also allow fast
scrolling through data under keys such as HISTORY
by enabling the operator to move between subgroups
of data such as Unit, System, and VSD data.
Keypad data entry mode
For numeric programmable items, the data entry mode
is entered by pressing any of the number keys, the deci-
mal point key, or the +/- key. When the data entry mode
is entered, the data from the key press will be entered
and the cursor will appear under the position where the
data is being entered.
For non-numeric programmable items, data entry
keys. When the data entry mode is entered, the cursor
will appear under the first position of the non-numeric
string. The programmable choice may be changed by
To exit the data entry mode and store the programmed
value, the (ENTER) key must be pressed. When
the (ENTER) key is pressed, the cursor will disappear.
The data entry mode may also be exited by pressing
the X (CANCEL) key. The programmed data will be
returned to its original value when the X (CANCEL)
key is pressed.
When the data entry mode is exited, the cursor will
disappear. If any other key is pressed while in the
Data Entry Mode, the following display will appear
for 2 seconds indicating the user must choose between
accepting or canceling the change:
XXXXXXXXXXX PRESS TO ACCEPT VALUE OR
X TO CANCEL DATA ENTRY
If the (ENTER) key was pressed from the data en-
try mode and the numeric value entered was out of
range, the following message will appear for 2 seconds
followed by the original data display.
XXXXXXXXXXX OUT OF RANGE TRY AGAIN!
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Display
The 80 character (2 lines of 40 characters per line)
display is a Liquid Crystal Display (LCD) used for
displaying unit parameters, system parameters, and
operator messages. The display has an LED backlight
background for night viewing and is viewable in direct
sunlight.
Anti-recycle timer
On power-up of the control panel, the anti-recycle tim-
er for each system will be set to 120 seconds and must
time out before a compressor is allowed to start.
Whenever a system starts, the anti-recycle timer for all
systems will be set to 120 seconds and will count down
from the time the motor starts. The timer must time out
before another compressor is allowed to start.
Whenever a system shuts down, the anti-recycle timer
for that system will be set to 120 seconds. The timer
must time out before the system is allowed to restart.
Evaporator pump control
The evaporator pump dry contacts are energized when
any of the following conditions are true:
• If a Low Leaving Chilled Liquid Fault occurs.
• Whenever a compressor is running.
• The Daily Schedule is ON and the UNIT switch
is ON.
Even if one of above is true, the pump will not run if
the panel has been powered up for less than 30 seconds
or if the pump has run in the last 30 seconds to prevent
pump motor overheating.
Evaporator heater control
The evaporator heater and suction valve actuator are
both controlled by ambient air temperature when the
system is idle. If no systems are running and the ambi-
ent temperature drops below 4.4C (40
is turned ON and the suction valve is closed. If no
systems are running and the temperature rises above
7.245
opened. Whenever a system is running, the evaporator
heater is turned OFF and the suction will be open. Both
evaporator heater outputs will always be tuned ON and
OFF together. An under voltage condition will keep the
heater OFF until full voltage is restored to the system.
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