Chapter 5 – Fault Tracing
ACS/ACH 400 Direct N2 Bus Interface 5-3
It is also possible that the time-out selection for
the drive is too short for the given installation.
The Metasys is not polling the drive within the
time-out delay time given in the parameter 5303
TIME-OUT TIME. If this is the case, increase
the time-out.
Intermittent off-line
occurrences
If drive parameters are changed from the
operator panel while the N2 interface is
communicating, the communication from the
drive may halt for short periods.
How to correct: If parameters need to be
adjusted while communication is operational,
set parameter 1602 PARAMETER LOCK to NO
SAVE position. When you have adjusted all
needed parameters, save your changes with
parameter 1607 PARAM. SAVE. Note that,
while saving, you may loose communication
from drive for a short period.
Metasys
Commissioning
Verify that the N2 Bus has been installed as
described in the “N2 Communications Bus
Manual” from Johnson Controls. Also verify that
all the commissioning steps are completed
according to this documentation. Go through
the Troubleshooting Procedures described in
the manual.
Summary
The problems described here cover the most
usual problems encountered when starting up
the N2 Bus. Intermittent problems might well be
caused by marginally loose connections, wear
on wires caused by equipment vibrations, or
especially through insufficient grounding and
shielding on both the devices and on the
communication cables.
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