User manual

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2.12 Modbus Setup
Menu Location
Page
1
Modbus (RS485)
Advanced Setup > Set Modbus
74
Modbus has the capability to start and stop the genset and to transition
from OFF to AUTO to do this. Modbus should be disabled while
performing maintenance or repairs by unplugging the Modbus
connector.
GSC400 has a RS485 connection and supports the Modbus protocol. It is a
slave device and must be polled by a master. Modbus works in any mode
(SLEEP, menu system, OFF, AUTO, Running) so if it is connected properly it
should just work.
The Modbus port is not isolated. If you are running cable longer than 100ft,
running cable outside, or using existing cabling it is recommended you install a
RS485 isolator on the GSC400 end. Be careful of using old wiring / unknown
wiring as it can have significant resistance which can damage the GSC400.
Note that the connector on the GSC400 is a molex type (see Table 1 on page 16
for connector part number). The customer must use this connector or they can
purchase a premade harness from Dynagen: DWG1454. This connects to the
GSC400 Modbus and power and has 5 pigtails on the other end: +, -, Modbus
common, power, and ground. Power and ground can be used to power the
master device.
A RS485 twisted pair 120Ohm impedance shielded cable is required for Modbus
communications. 120Ohm resistors are required on either end of the Modbus
bus. Two possible options for cables are:
1. Beldin 9841 – one shielded twisted pair, 24AWG. Twisted pair can be
used for Modbus + and -. The drain wire can be used for Modbus
common.
2. Beldin 7895A – two shielded twisted pairs. 20AWG twisted pair for
Modbus + and -. 18AWG twisted pair for power and ground. Drain wire
can be used for Modbus common. This is the cable the Dynagen
DWG1454 accessory uses.
Older GSC400 units had a 100Ohm resistor between Modbus common and
battery -. This can cause problems. It is recommended that you run a wire from
Modbus common to battery - if this is the case. This is not an issue with the LSC
/ LXC revision units.