Power Source Interruptions; System Grounding - Cisco Catalyst 6840 Series Hardware Installation Manual

Power Source Interruptions

Power Source Interruptions
Systems are especially sensitive to variations in voltage supplied by the AC power source. Overvoltage,
undervoltage, and transients (or spikes) can erase data from memory or even cause components to fail. To
protect against these types of problems, power cables should always be properly grounded. Also, place the
system on a dedicated power circuit (rather than sharing a circuit with other heavy electrical equipment). In
general, do not allow the system to share a circuit with any of the following:
• Copy machines
• Air conditioners
• Vacuum cleaners
• Space heaters
• Power tools
• Teletype machines
• Laser printers
• Facsimile machines
• Any other motorized equipment
Besides these appliances, the greatest threats to a system's power supply are surges or blackouts that are caused
by electrical storms. Whenever possible, turn off the system and peripherals, if any, and unplug them from
their power sources during thunderstorms. If a blackout occurs—even a temporary one—while the system is
turned on, turn off the system immediately and disconnect it from the electrical outlet. Leaving the system on
may cause problems when the power is restored; all other appliances left on in the area may create large
voltage spikes that may damage the system.

System Grounding

You must install a system ground as part of the chassis installation process. Chassis installations that rely only
on the AC third-prong ground are insufficient to adequately ground the systems.
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 install a system ground,
you reduce or prevent shock hazards, chances of equipment damage due to transients, and 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 ground.
Caution Installations that rely solely on system grounding that uses 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 ground.
The following table lists some general grounding practice guidelines.
Catalyst 6840-X Switch Series Hardware Installation Guide
26
Preparing for Installation