Swapped Wires
If the communication wires are swapped (terminal A on one
drive is connected to terminal B on another):
• The value of 5306 EFB OK MESSAGES does not
advance .
• The values of 5307 EFB CRC ERRORS and 5308 EFB
UART ERRORS are advancing .
To correct:
Check that the EIA-485 lines are not swapped .
Fault 28 – Serial 1 Err
If the drive's control panel shows fault code 28 "SERIAL 1
ERR", check for either of the following:
• The master system is down . To correct, resolve problem
with master system .
• The communication connection is bad . To correct, check
communication connection at the drive .
• The time-out selection for the drive is too short for the
given installation . The master is not polling the drive
within the specified time-out delay.
To correct:
Increase the time set by parameter 3019 COMM FAULT TIME,
page
53 .
OM 1190-1 • MD4 VFD
Fault 31 – EFB1
For BACnet: If the drive's control panel shows fault code 31
"EFB1", the drive has aninvalid Device Object Instance ID . To
correct, use parameters 5311 and 5317 and establish a unique
drive ID that is in the range 1 to 4,194,303 .
Faults 31...33 – EFB1...EFB3
Except as noted above, these three EFB fault codes (listed for
the drive in "Diagnostics" in the ACH550 User's Manual, fault
codes 31...33) are not used .
Intermittent Off-line Occurrences
The problems described above are the most common
problems encountered with MD4 serial communication .
Intermittent problems might also be caused by:
• Marginally loose connections,
• Wear on wires caused by equipment vibrations,
• Insufficient grounding and shielding on both the devices
and on the communication cables .
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