Data center grounding is designed to not meet code but exceed it. Code minimum design is for life safety and not necessarily for critical equipment installations.
There are various codes and standards relative to grounding, lightning protection and sensitive equipment grounding. Code is a requirement whereas standards are recommendations. They are listed below.
Many equipment vendors will not warranty equipment unless the installation meets code as well as many of the equipment standards.
1. FIPS PUBS 94, 1983, Guideline on Electrical Power for ADP Installations, 1983 (USA Federal Information Processing Standards Publications) (Standard)
2. ANSI/IEEE 1100, Recommended Practice for Powering and Grounding Electronic Equipment (Standard)
3. National Fire Protection Assoc. (NFPA) 70 – National Electrical Code (NEC) (Code)
4. National Fire Protection Assoc. (NFPA) 780 - Standard for the Installation of Lightning Protection Systems (Standard)
5. EIA / TIA 607 - Commercial Building Grounding and Bonding Requirements for Telecommunications (Standard)
6. ATIS 0600318, Electrical Protection Applied to Telecommunications Network Plant at Entrances to Customer Structures or Buildings (Standard)
7. ATIS-0600313, Electrical Protection for Telecommunications Central Offices and Similar Type Facilities (Standard)
8. EN 50310, Application of Equipotential Bonding and Earthing in Buildings with Information Technology Equipment (Standard)
9. MIL-HDBK-419A, Grounding, Bonding, and Shielding for Electronic Equipments and Facilities Basic Theory (Standard)
10. ANSI/IEEE C2, National Electrical Safety Code (NESC) (Code)
11. ANSI/ATIS 0600333, Grounding and Bonding of Telecommunications Equipment (Standard)
Many equipment vendors will not warranty equipment unless the installation meets code as well as many of the equipment standards.
Data center equipment can be subject to power quality issues that include over and under voltages as well as spikes due to utility system issues or internal building operations; lightning activity; electrical noise (typically Common Mode); electromagnetic interference (EMI) and radio frequency interference (RFI). Adequate grounding systems minimize or eliminate most of these issues.
We do not recommend that the lightning protection system utilize the building steel columns as down conductors for the protection system.
Data center grounding requires the bonding of all ground references to a common equipotential plane. This starts with the Signal Reference Grid (SRG) inside the data center. In accordance with FIPS 94, “A signal reference structure (SRS) should be employed as the basic means of achieving a high-frequency common ground reference for all equipment within a contiguous area. A properly designed and installed SRS effectively equalizes ground potential over a broad range of frequencies from dc through the megahertz range.”
SRG is also credited with the following benefits:
1. Equipment communication interference reduction
2. Equipment damage prevention
3. Noise discharge path
4. Electrostatic discharge (ESD) protection
The below is from the IEEE Emerald Book, Powering and Grounding Sensitive Electronic Equipment, IEEE Std 1100-1992, IEEE, NY, 1995, p. 216 and it confirms the need of equipotential grounding across the facility:
"It is important to ensure that low-impedance grounding and bonding connections exist among the telephone and data equipment, the ac power system's electrical safety-grounding system, and the building grounding electrode system. This recommendation is in addition to any made grounding electrodes, such as the lightning ground ring. Failure to observe any part of this grounding requirement may result in hazardous potential being developed between the telephone (data) equipment and other grounded items that personnel may be near or might simultaneously contact."
This requirement applies to the building, the utility service and all emergency /standby power sources for the site.
Dedicated down conductors are best practice for data center lightning protection.
Lightning protection, as indicated in NFPA 780, should be provided. NFPA 780 is a standard and not a code. The standard allows for protection of various types of facilities. Good data center engineering practice is to provide an equipotential grounding ring around the facility, while connecting all external equipment serving the facility to that equipotential ring. This would include the utility transformers, generators, service equipment, metallic water piping etc. We do not recommend that the lightning protection system utilize the building steel columns as down conductors for the protection system. Potential for elevated voltages due to lightning strikes would be expected and these will be detrimental to data center equipment operation. Dedicated down conductors are best practice for data center lightning protection.
Many lightning protection design guides as well as the Lightning Protection Institute recommend a grounding electrode ring for the lightning protection system as indicated below from Golde, Lightning, Academic Press, NY, 1977, vol. 2, chapter 19 by H. Baatz, Stuttgart, Germany, p. 611:
"Equalization of potentials should be effected for all metallic installations. For lightning protection of a structure it is of greater importance than the earthing resistance...The best way for equalization of potentials utilizes a suitable earthing system in the form of a ring or foundation earth. The down conductors are bonded to such a ring earth; additional earth electrodes may be unnecessary…"
The lightning protection system requires annual maintenance/testing/verification to maintain the UL Master Label. Conductors and connections to the system need to be accessible to permit this verification.