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CHAPTER 3: INSTALLATION

469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL 3–25

The source computer/PLC/SCADA system should have similar transient protection devices

installed, either internally or externally, to ensure maximum reliability. Ground the shield at

one point only, as shown in the figure below, to avoid ground loops.

Correct polarity is also essential. The 469s must be wired with all the ‘+’ terminals

connected together and all the ‘–’ terminals connected together. Each relay must be daisy-

chained to the next one. Avoid star or stub connected configurations. The last device at

each end of the daisy chain should be terminated with a 120 Ω ¼-watt resistor in series

with a 1 nF capacitor across the ‘+’ and ‘–’ terminals. Observing these guidelines provides a

reliable communication system immune to system transients.

FIGURE 3–27: RS485 Communications Wiring

3.2.13 Dielectric Strength

It may be required to test a complete motor starter for dielectric strength (“flash” or “hipot”)

with the 469 installed. The 469 is rated for 1.9 kV AC for 1 second, or 1.6 kV AC for 1 minute

(per UL 508) isolation between relay contacts, CT inputs, VT inputs, trip coil supervision, and

the safety ground terminal G12. Some precautions are required to prevent damage to the

469 during these tests.

Filter networks and transient protection clamps are used between control power, trip coil

supervision, and the filter ground terminal G11. This is intended to filter out high voltage

transients, radio frequency interference (RFI), and electromagnetic interference (EMI). The

filter capacitors and transient suppressors may be damaged by continuous high voltage.

Disconnect the filter ground terminal G11 during testing of control power and trip coil

supervision. The CT inputs, VT inputs, and output relays do not require any special

precautions. Low voltage inputs (less than 30 V), RTDs, analog inputs, analog outputs,

digital inputs, and RS485 communication ports are not to be tested for dielectric strength

under any circumstance (see below).

GE 469 User Manual

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