JOHNSON CONTROLS
100
FORM 150.27-NM1
ISSUE DATE: 09/30/2015
SECTION 7 – UNIT CONTROLS
The on-board power supply converts 24VAC from
75VA, 120/24VAC 50/60Hz UL listed class 2 power
transformer to +12V, +5V and +3.3V using switching
and linear voltage regulators located on the I/O and
IPU II boards. These voltages are used to operate inte-
grated circuitry on the board. The 40 Character Display
and unit sensors (transducers and temp sensors) are
supplied power for the microprocessor board +5V sup-
ply. 24V AC is rectified, but not regulated, to provide
unreg30VDC to supply all of the digital inputs.
The IPU II board contains one green “Power” LED to
indicate 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 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 4-20mA or 0-10VDC
as the input type on the remote temperature reset ana-
log input.
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.
Display
The 40 Character Display (2 lines of 20 characters) is
a liquid crystal display used for displaying system pa-
rameters and operator messages.
The display in conjunction with the keypad, allows the
operator to display system operating parameters as well
as access programmed information already in memory.
The display has a lighted background for night viewing
and for viewing in direct sunlight.
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.
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.
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.
Transformer
A 75VA, 120/24VAC 50/60Hz transformer is provided
to supply power to the microprocessor board, which
in turn rectifies, filters, and regulates as necessary to
supply power to the display, sensors, and transducers.
Programming # of Compressors
The total number of compressors is programmable un-
der the PROGRAM key. Chillers can have 4 or 6 com-
pressors.
