Simply connecting the green power ground to the appropriate terminal at the sign, outline lighting, or skeleton lighting isn’t sufficient. In addition, you must ensure all the metal equipment of these systems are bonded to the equipment grounding conductor (EGC). So, if you have a metal junction box, bond it to an EGC.
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Grounding and Bonding of Electric Signs and Outline Lighting
Do you know when to use an equipment grounding conductor?