DSP-OHMNI Instruction Manual I-GARD
25
A complete test of the system can be accomplished with the connection of a resistive fault between one
of the three lines and ground at a location downstream of one of the Feeder current sensors. This simple
test will identify the integrity of sensor, Feeder Module circuits, connections, communications, System
Module operation, DDR2 resistor OHMNI-PM resistor and Pulsing without causing a Trip to occur on any of
the breakers. The only thing it will not test is the priority of the double-fault trip process. For this two such
resistors would be required, with resistor value low enough to provide more than the 100A trip current.
NEVER USE A PIECE OF WIRE TO CREATE A TEST FAULT. IT IS POSSIBLE THAT THE PROTECTION MAY NOT
BE OPERATIONAL DUE TO MIS-WIRING OR OTHER PROBLEMS AND CANNOT CLEAR THE FAULT CURRENT
RESULTING IN A SERIOUS ARCING SITUATION WHICH MAY SEVERELY DAMAGE THE EQUIPMENT AND CAUSE
INJURY OR DEATH.
12 SERVICE
For assistance in installation, setup or testing please call I-Gard toll free
at 1-888-737-4787 ( 1-888-RESISTR)
There are no user-serviceable parts in the DSP, therefore all service should be referred to qualified factory
representatives, other than direct replacement of entire Modules to I-Gard. Please visit the I-Gard website
for information regarding field service representatives in your area. (www.i-gard.com)
NOTE: Please ensure that proper authorisation is obtained from I-Gard before returning the equipment.
13 COMMUNICATIONS
Installation
To allow communications to a remote terminal or network, a 4-wire RS-485 communications jack is
provided at the rear of the DSP-DM Display Module. The 5-pin connector supplied has screw terminals
and allows disconnection without breaking the RS-485 daisy chain. A ground connection is supplied for
grounding the shield of the 4-wire cable. The protocol supported is MODBUS RTU. The baud rate can be
changed in the DSP-DM set-up to 4800, 9600 or 19200 as desired. The frame set-up is 8 bit, No Parity
and 1 Stop Bit. The I/D number for the DSP-DM must be entered in the set-up within the range of 1 to 32.
Cable should be standard 4-wire with two twisted-pairs ideally, and a grounding shield for emc protection.
The shield of the cable between nodes should not be continuously grounded, but each section of cable
should be grounded at GND pin of J3. When installing cable, avoid star connections and make connections
flow from node to node. Cable length of 1-2 kilometres or more should be easily accommodated.
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