GE Industrial Solutions GE ZENITH SERIES MDU - Manual (Page 30)

System Monitoring
GE Z ENITH C ONTROLS
MDU Owner’s Manual
601 S HILOH R OAD January 2013
Plano, TX 75074 Page 30
4.1.5. Contractor Connections
1. Printed Circuit Boards (PCB)
A low voltage control junction box shall not be included on this equipment. All Remote
Emergency Power Off, building alarms, output relays, communication ports and other
control wiring shall be terminated onto a Contractor Interface Board which is an integral
component within the MDU system itself.
Standard Interface Board
a. Remote Emergency Power Off interconnect positions
b. Four (4) Relay Contacts (NO contacts) rated 5 amps (summary alarm)
c. Four (4) Building alarm contacts rated 5 amps
d. Remote monitoring connection ports (ModBus RTU Protocol, RS-422/485)
Advanced Interface Board (optional)
a. Remote emergency power off interconnect positions
b. Eight (8) Relay Contacts (NO contacts) rated 5 amps (summary alarm)
c. Eight (8) Building alarm contacts rated 2 amps
d. Remote monitoring connection ports (ModBus RTU Protocol, RS-422/485)
e. Local monitoring of GE approved devices (ModBus RTU Protocol, RS-422/485)
Note: The Tx+ and Tx- are transmission points, and should be connected to the
receiver of the monitoring system. The Rx- and Rx+ are receiving points.
4.1.6. Communications
1. ModBus RTU
a. Hardware
The GE Zenith™ Series MDU monitor has a 4 or 2 wire plus ground, RS-422/RS-485
compatible interface. The communications parameters for the interface are 9600
baud, 8 bit, even parity, and 1 stop bit as standard with options for odd and no parity
and 2400, 4800 and 19200 baud. For (4) four wire all commands are sent to the
monitor on (1) one pair and all replies from the monitor are on the other pair. The pair
on which an M4 sends will be in a high impedance state until an M4 responds to a
command. For (2) two wire all commands are sent to a GE ZENITH™ SERIES and all
replies from a GE ZENITH™ SERIES are sent on the same pair. The pair will be in a high
impedance state until an M4 responds to a command. For (2) two wire
communications the transmit + and receive + must be jumped together as well as the
transmit - and receive -. You must also verify that the packet is complete before
another transmit is initiated. The interface is isolated.
b. Packets
The monitor never initiates communications, rather it responds to command packets
sent to it. Each command packet sent to the monitor has an address byte that
includes the address of the destination of that monitor. It does not respond to packets
addressed to “0”.