NEC EXPRESS800 - Manual (Page 27)

Planning Your Site 2-11
Grounding Requirements
The system rack must have a dedicated ground attached to the power
distribution panel.
The ground wire must have an earth resistance of 100 ohms or less and
depending on your local electrical code, a thickness of 38 mm
2 or more.
A grounding cable (12 gauge) that attaches the rack to frame (earth) ground
must be used.
For safety reasons, ground connections are necessary for both power distribution
systems and air conditioners.
If it happens that the ground to the server and the safety ground must be shared,
branch it near the grounding electrode.
If a building structure such as a steel frame is used as a grounding electrode, use
the main structural member closest to the building foundation.