SECTION 10 – MAINTENANCE
BACnet and Modbus Communications
Chiller data that can be read and modified using
specific BACnet or Modbus Register Addresses; and
the data associated with the addresses, is outlined in the
following description:
ANALOG WRITE POINTS
This data can be read and modified using a BACnet or
Modbus network connection. The Modbus Register
Address for these points is 1025 + AV #.
BINARY WRITE POINTS
This data can be read and modified using a BACnet or
Modbus network connection. The Modbus Register
Address for these points is 1537 + BV #.
ANALOG READ ONLY POINTS
This data can be read using a BACnet or Modbus
network connection and can NOT be modified using
this connection. The Modbus Register Address for these
points is 513 + AI #.
BINARY MONITOR ONLY POINTS
This data can be read using a BACnet or Modbus
network connection and can NOT be modified using
this connection. The Modbus Register Address for these
points is 1281 + BI #.
Refer to Table 31 for complete list of BACnet and
Modbus registers.
The latest data map information is
listed on the Johnson Controls Equip-
ment Integration website.
194
Communications Data Map Notes:
(See Table 31)
1. IPU II based units are configured for Native BACnet
MS/TP and Modbus RTU communications.
Microgateway or E-Link not required for these
two communication protocols.
2. BACnet Object Types: 0= Analog In, 1 =
Analog Out, 2= Analog Value, 3= Bina-
ry In, 4 = Binary Output, 5= Binary Value,
8= Device, 15 = Alarm Notification (0 -127 are
reserved ASHRAE Objects).
3. WC= Inches of water column; CFM = Cubic Feet
per Minute; FPM = Feet per Minute: PSI = Lbs
per square inch; Pa = Pascals; kPa = Kilopascals;
PPM = Part per Million; kJ/kg = Kilojoules per
Kilogram.
4. Water Cooled Scroll units use the same firmware
as Air Cooled Scroll units, ignoring Fan Control.
FORM 150.72-NM3 (1020)
ISSUE DATE 10/05/2020
JOHNSON CONTROLS