Grounding; Chassis Ground Lug - Emerson FB3000 Instruction Manual

2.5

Grounding

There are four separate and distinct ground references within the FB3000 architecture. The chassis
ground lug (also known as Protective Earth or PE), internal system bus ground, isolated ground,
and the 24V loop ground (for modules that support loop power).
2.5.1

Chassis Ground Lug

The RTU includes a chassis ground lug to the left of the power supply modules. In CSA documents,
this may be called the Protective earthing (PE) conductor. The chassis ground lug provides a path
to earth ground for electrical safety, static discharge, and stray voltage from a lightning strike.
CAUTION
DANGER TO PERSONNEL AND EQUIPMENT
Do not use the chassis ground lug for a direct connection to a lightning arrestor/lightning rod.
The chassis ground lug is completely isolated from the isolated, signal, and loop power ground
terminals on I/O modules, or from the 24V loop power ground terminal on some I/O modules. To
prevent noise and equipment damage, you should keep these grounds separate from the chassis
ground.
Figure 2-5. Chassis Ground Lug Location (8-slot left, 4-slot right)
Once you have installed the unit, run a ground wire (14 AWG protective conductor) between the
chassis ground lug and a known good earth ground.
Use stranded copper wire to earth ground and keep the length as short as possible.
Clamp or braze the ground wire to the ground bed conductor (typically a stranded copper AWG
0000 cable installed vertically or horizontally).
Run the ground wire so that any routing bend in the cable has a minimum radius of 30.48 cm (12
inches) below ground and 20.32 cm (8 inches) above ground.
Note
If your installation includes multiple chassis, you must individually ground each chassis.
For more information on grounding or if your installation uses cathodic protection, refer to
Considerations for Equipment Installation, Grounding, and Wiring
Installation
Emerson FB3000 RTU Instruction Manual
(D301452X012).
D301851X012
October 2022
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