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SECTION 7 – UNIT CONTROLS
plied power for the micro board +5V supply. 24VAC
is rectified, but not regulated, to provide unregulated
+30VDC to supply all of the digital inputs.
The I/O board contains one green "Power" LED to in-
dicate that the board is powered up and one red "Sta-
tus" LED to indicate by blinking that the processor
is operating. The I/O board also contains two sets of
Receiver/Transmit LED's, one for each available serial
communication port. The receive LED's are green, and
the Transmit LED's are red.
A jumper on the I/O board selects 4 to 20mA or 0 to
10VDC as the input type on the remote temperature
reset analog input.
TRANSFORMER
A 75VA, 120/240VAC, 50/60Hz transformer is pro-
vided to supply power to the Microprocessor Board,
which in turn rectifies, filters, and regulates as neces-
sary to supply power to the display, sensors, and trans-
ducers.
DISPLAY
The 40 Character Display (2 lines of 20 characters) is
a liquid crystal display used for displaying system pa-
rameters and operator messages.
When a key is pressed, such as the OPER DATA key,
system parameters will be displayed and will remain
on the display until another key is pressed. The system
parameters can be scrolled with the use of the ↑ (UP)
and ↓ (DOWN) arrow keys. The display will update all
information at a rate of about 1 a second.
Display Messages may show characters indicating
"greater than" (>) or "less than" (<). These characters
indicate the actual values are greater than or less than
the limit values which are being displayed.
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KEYPAD
The 12 button non-tactile keypad allows the user to
retrieve vitals system parameters such as system pres-
sures, temperatures, compressor running times and
starts, option information on the chiller, and system
setpoints. This data is useful for monitoring chiller op-
eration, diagnosing potential problems, troubleshoot-
ing, and commissioning the chiller.
It is essential the user become familiar with the use of the
keypad and display. This will allow the user to make full
use of the capabilities and diagnostic features available.
UNIT SWITCH
A unit ON/OFF switch is just underneath the keypad.
This switch allows the operator to turn the entire unit
OFF if desired. The switch must be placed in the ON
position for the chiller to operate.
BATTERY BACK-UP
The IPU II contains a Real Time Clock integrated cir-
cuit chip with an internal battery backup. The purpose
of this battery backup is to assure any programmed
values (setpoints, clock, cutouts, etc.) are not lost dur-
ing a power failure regardless of the time involved in a
power cut or shutdown period.
PROGRAMMING # OOF COMPRESSORS
The total number of compressors is programmable un-
der the PROGRAM key. Dual (2) system chillers can
have 4, 5, or 6 compressors.
FORM 150.72-ICOM6
ISSUE DATE: 12/29/2017
JOHNSON CONTROLS
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Troubleshooting
