More grounding noise is sensed when there is not an equipotential plane between the computer and other grounded metal.
To eliminate such noise, the computer shall be grounded with a radial system that clears the ground system of ground loops. Ground loops produce paths for circulation of the ground currents, and these currents create unwanted electrical noise that causes computers to malfunction.
Grounding for a computer shall be installed in accordance with Article 250. The grounding electrode conductor at the service equipment or subfed transformer shall be connected to all exposed non-current- carrying parts of the computer enclosure. The equipment grounding conductor is used to provide this function of grounding to the enclosure of the computer.
Note: An information technology equipment room is defined in 645.2 and 645.4.
HIGH-FREQUENCY REFERENCE GRID
645.15
A high-frequency reference grid system shall be permitted to be connected to a computer grounding point. A single ground point shall be grounded radially and tied to a high-frequency reference grid for computer equipment. The computer shall be grounded by the grid at the same ground point. The grounding electrode is then grounded to the computer ground point. This type of grounding scheme is installed to help minimize electrical noise and complies with the rules and regulations of the NEC.
The power conductors, grounds, and grounded (neutral) conductor shall be installed in the same conduit or cable except for the reference grid ground; if need be, it shall be permitted to be routed away from these circuit conductors.
