Hardy HI 1769-FC - Manual (Page 61)

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Chapter 7
B1 - Guidelines for Instabilities on Formerly Operating Systems
(Cont’d)
B1 Electrical
B1.1
Physical Grounding -
All common equipment share a common ground point.
Keep the ground cable length to earth ground as short as possible.
Install a new ground rod if the cable length is excessive.
B1.2
Cable -
Cuts or breaks in the load cell insulation allow moisture to wick into the
cable and load points. This can setup stray capacitance charges and allow
ground currents to exist. This could create a highly intermittent situation.
B1.3
Vessel, Fill and discharge piping -
Ground all to a common point to eliminate electrical differences in potential
and static build-up.
B1.4
Load Cells -
Ground straps must be installed to provide a direct discharge path to ground
around the load points.
B1.5
Cable Routing -
Separate high voltage sources and cables form low voltage signal cables.
Stay a minimum of 14 inches from magnetic fields and VFD controls.
Avoid parallel high voltage and signal cable runs.
B1.6
Cable Shielding -
Ground low voltage cable shields only at the controller end.
Grounding both cable ends produce ground currents.
Verify, with and ohm meter, the shield is only grounded at the weight controller.
Disconnect the shield at the controller and check for an open circuit between ground
and shield. Reconnect the shield to ground and confirm a proper ground path from
the IT Junction box to the controller.
Verify the shield is not connected to ground at the IT Junction Box.
Load cell shields only pass thru the IT Junction boxes and are not connected
ground at that point.
B1.7 Weight Controller - Common AC ground and Chassis grounds.
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B