Cisco Systems 4948E-F manual Environment Electromagnetic Grounding Recommendations

Chapter 2 Preparing for Installation

System Grounding

Proper grounding practices ensure that the buildings and the installed equipment within them have low-impedance connections and low-voltage differentials between chassis. When you include NEBS-compliant system grounds, you reduce or prevent shock hazards, greatly reduce the chances of equipment damage due to transients, and substantially reduce the potential for data corruption.

Without proper and complete system grounding, you run the risk of increased component damage due to ESD. Additionally, you have a greatly increased chance of data corruption, system lockup and frequent system reboot situations by not using a system (NEBS compliant) ground.

Caution Installations that rely solely on system grounding using only an AC third-prong ground run a substantially greater risk of equipment problems and data corruption than those installations that use both the AC third-prong ground and a properly installed system (NEBS compliant) ground.

Table 2-1lists some general grounding practice guidelines.

Table 2-1	Grounding Practice Guidelines
Environment		Electromagnetic	Grounding Recommendations
		Noise Severity Level
Commercial building is		High	All lightning protection devices must be
subjected to direct lightning			installed in strict accordance with
strikes.			manufacturer recommendations. Conductors
For example, some places in the			carrying lightning current should be spaced
			away from power and data lines in
United States, such as Florida,
			accordance with applicable
are subject to more lightning
			recommendations and codes. Best grounding
strikes than other areas.
			practices must be closely followed.
Commercial building is located		High	Grounding best practices must be closely
in an area where lightning storms			followed.
frequently occur but is not
subject to direct lightning
strikes.
Commercial building contains a		Medium to High	Grounding best practices must be closely
mix of information technology			followed.
equipment and industrial
equipment, such as welding.
Existing commercial building is		Medium	Grounding best practices must be closely
not subject to natural			followed. Determine source and cause of
environmental noise or			noise if possible, and mitigate as closely as
man-made industrial noise. This			possible at the noise source or reduce
building contains a standard			coupling from the noise source to the victim
office environment. This			equipment.
installation has a history of
malfunction due to
electromagnetic noise.

Catalyst 4948E and Catalyst 4948E-F Switch Installation Guide

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