Signal Reference Grid

A Signal Reference Grid (SRG) is a means to reduce high-frequency impedance (also called noise) so that a device or outlet has the lowest impedance path to earth ground. This grid has multiple paths to ground to ensure that grounding loops do not develop.

The SRG should be designed for the data center. This provides an equal potential plane of reference over a broad band of frequencies through the use of a network of low-impedance conductors installed throughout the facility. The following figure shows part of an SRG in a blueprint detail.

Figure 7-3. Blueprint Plan of a Signal Reference Grid

Recommended Practices

The following is a list of recommended practices for an SRG. This information should be well understood by the electrical engineer/contractor but should be used only as a reference because electrical codes in your area might be subject to different requirements.

1. Follow applicable codes and standards for safe grounding.

   There is no conflict between safe grounding for people and effective high-frequency grounding for sensitive electronic equipment.

2. Install equipment ground bus.

   Use sized 10" long, 1/4" thick, 4" high on 4" insulators. Bond via exothermic weld with #2 AWG bare copper to grounding ring.

3. Provide exothermic weld or other code compiant connection between intersecting ground grid connectors.

4. Provide grounding/bonding for raised floor pedestal system in data center as follows :

   Install #4 AWG bare copper for MFG (raised floor pedestal) grid. Bond to every other raised floor pedestal.

5. Route #3/0 from equipment grounding bus bar to grounding bus bar in main electrical room.

   Make sure that you have a path to earth ground.

6. Bond HVAC units to perimeter ground or medium frequency ground loop via #6CU conductor.

7. Keep data and power cables on or near SRG.

   All data and power cables should lay on or be very close to the SRG.

8. Complete documentation.

   Documentation should be complete in all details, including the proper grounding and bonding of heating, ventilation , and air-conditioning equipment, piping, raceways, and similar items. The responsible engineer should not expect the installers to complete the design.