Parts and Service
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IM 743-7 • MICROTECH II CHILLER UNIT CONTROLLER
Parts and Service
Troubleshooting
Follow these general procedures if you can control the
MicroTech II chiller unit controller from the keypad/display, but
are not able to communicate with the unit from the network:
General
→
Confirm that the communication module is inserted
properly (see
Installation
section).
→ Verify the unit controller is set up to communicate
Modbus using the keypad/display. Refer to the
Network
Configuration
section or the MicroTech II Chiller Unit
Controller OM (
Reference Documents
) for details.
Network Parameters
→
Verify that the Network Address of the communication
module (slave) is unique in the network. In contrast, the
Baud Rate must match the other slave devices on the
network.
→
Make sure there are no duplicate devices on the
network and that Network Address and Baud Rate are
set correctly as shown in
Table 2.
Network wiring
If performance is unsatisfactory or network is experiencing
issues such as noise or slow transmission:
→
Confirm that the shield is landed at only one point in
the trunk.
→
Be aware that the recommended network topology is
daisy-chain (no T-Taps or ring layout).
→
Verify that network wiring does not exceed 4000
ft total distance limit (without repeaters) at 19200 bps
baud.
→
Verify that polarity is maintained.
→
Check that there are end-of-line termination resistors
(120 Ω) at the first and last device on the trunk. This is
required by the EIA-485 specification.
→
Verify that the network trunk avoids strong sources of
electromagnetic interference (EMI).
→
Note that the two-wire bus is
not
interchangeable and
must be connected correctly.
→
Verify that the network trunk is not located near a DC
load switch (relay).
Network Performance
→
If network traffic is slow, communication is
intermittent, or the trunk is experiencing “noise,” it
may be necessary to use a network protocol analyzer
or oscilloscope to determine the source of poor
performance.
→
Confirm power is applied to the unit controller.
Contact the Daikin Applied Controls Customer Support group
at 866-462-7829 for additional assistance, if necessary.
Parts
Table 3: Replacement Parts List
Description
Part Number
MicroTech II Modbus Communication Module kit
Kit includes: Modbus communication module (RS-485
serial network board), network connector, and IM 743
350147402
Network connector
Wago
330803003
Phoenix (shown in
Figure 12
)
910108485
Figure 12: Phoenix Network Connector
To find your local parts office, visit
www.DaikinApplied.com
or
call 800-37PARTS (800-377-2787
