7.1.4. VLT HVAC Parameter Settings for Modbus Communication
The following parameters apply to the RS-485 interface (FC-port):
Parameter Num-
ber
Parameter name
Function
8-30
Protocol
Select the application protocol to run on the
RS-485 interface
8-31
Address
Set the node address. Note: The address range
depends on the protocol selected in par. 8-30
8-32
Baud Rate
Set the baud rate. Note: The default baud rate
depends on the protocol selected in par. 8-30
8-33
PC port parity/Stop
bits
Set the parity and number of stop bits. Note: The
default selection depends on the protocol selec-
ted in par. 8-30
8-35
Min. response delay Specify a minimum delay time between receiving
a request and transmitting a response. This can
be used for overcoming modem turnaround de-
lays.
8-36
Max. response delay Specify a maximum delay time between trans-
mitting a request and receiving a response.
8-37
Max. inter-char delay Specify a maximum delay time between two re-
ceived bytes to ensure timeout if transmission is
interrupted.
7.1.5. EMC Precautions
The following EMC precautions are recommended in order to achieve interference-free operation
of the RS-485 network.
NB!
Relevant national and local reg-
ulations, for example regarding
protective earth connection,
must be observed. The RS-485
communication cable must be
kept away from motor and
brake resistor cables to avoid
coupling of high frequency noise
from one cable to another. Nor-
mally a distance of 200 mm (8
inches) is sufficient, but keeping
the greatest possible distance
between the cables is generally
recommended, especially where
cables run in parallel over long
distances. When crossing is un-
avoidable, the RS-485 cable
must cross motor and brake re-
sistor cables at an angle of 90
degrees.
VLT
®
HVAC Drive Design Guide
7. RS-485 Installation and Set-up
MG.11.B2.02 - VLT
®
is a registered Danfoss trademark
123
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