236
FORM 160.54-M1
ISSUE DATE: 10/25/2019
SECTION 27 - LARGE TONNAGE CHILLER (LTC) I/O BOARD 031-02895-000/001
JCI COMPANY CONFIDENTIAL
JOHNSON CONTROLS
AUTO DETECTION
Earlier vintage chillers use Analog I/O Board 371-
02514-000 for the ht gas bypass feature. This board
also connects to the COM3 serial port (J12). Since this
board uses different protocol than the 031-02895-xxx
board, the microboard must know which board is pres-
ent in order to be able to communicate with it.
The microboard determines which board is present by
the features that are enabled:
• If heat recovery and/or or head pressure control is
enabled, it knows the 031-02895-xxx board is pres-
ent and only the 031-02895-xxx board is polled.
• If only hot gas bypass is enabled, the microboard
automatically determines which board is present.
At boot-up, the microboard alternates between poll-
ing the 031-02895-xxx board and the 371-02514-
000 Board. Once a valid response is received from
one of these two boards, the communications will
continue to only poll that board type.
DIAGNOSTIC SCREEN
The DIAGNOSTIC Screen (See
), accessible from the MAIN DIAGNOSTICS
Screen, is used to analyze the analog and Digital inputs
and outputs. It is also used to manually control the digi-
tal outputs and set analog output voltages.
There are two versions of this screen available as follows:
Service Access level
The voltage value of each analog input at the board in-
put terminals/pins, as interpreted by the I/O Board and
transmitted to the microboard, is displayed as ANA-
LOG INPUTS.
The voltage value sent from the microboard to the I/O
board for analog output displays as ANALOG OUTPUTS.
The ON/OFF status of the Digital inputs and Digital
Outputs are indicated with an LED. It is illuminated
when the input or output is on; extinguished when it
is off.
Modbus communication error counters are displayed
as follows, along with the ability to reset the counters:
• ID faults – This is the number of packets received
with an incorrect subordinate ID.
• Checksum errors – This is the number of check-
sum errors encountered in communication.
• Error packets – This is the number of error pack-
ets received.
• Timeout Faults – Number of timeout faults en-
countered. A timeout is registered when no valid
response is received for a poll within two seconds.
SERVICE access level plus Microboard DIP Switch
In addition to the displays above, the following can be
performed.
The digital outputs can be individually turned on or off.
Use the SELECT DIGITAL OUTPUTS key to select
the desired output, then use the ENABLE and DIS-
ABLE keys to turn it on or off.
The analog outputs can be individually set to a desired
voltage value. Use the SELECT ANALOG OUTPUT
key to select the desired output, then use the numeric
keys to set it to the desired value.
FIGURE 91 -
I/O BOARD (031-02895-XXX)
LD14349