Installation Guide

• Provide alarms on certain error conditions.
• Provide short-circuit protection.
Selecting a UPS
To determine UPS requirements for your switch, answer these questions:
• What are the amperage requirements?
• What is the longest potential time period that the UPS would be required to supply backup power?
• Where will the UPS be installed?
• What is the maximum transition time that the installation will allow? (See Providing a Suitable UPS
Transition Time on page 178.)
Note
Use a UPS that provides online protection.
Calculating Volt-Amperage Requirements
To determine the size of UPS that you need:
1. Locate the voltage and amperage requirements for each piece of equipment.
These numbers are usually found on a sticker on the back or bottom of your equipment.
2. Multiply the numbers together to get Volt-Amperes (VA):
VA = Volts x Amperes
3. Add the VA from all the pieces of equipment together to find the total VA requirement.
To determine the minimum volt-amperage requirements for your UPS, add 30% to the total.
Providing a Suitable UPS Transition Time
UPS transition time is the time required for the UPS to change from providing AC power derived from
the utility (or mains) supply to providing AC power derived from the battery backup. UPS transition
time is sometimes called UPS transfer time.
UPS transition times vary between UPS models and implementations, but shorter transition times are
preferred. For Extreme Networks stacking products, a UPS transition time of 20 milliseconds or less
ensures optimum performance and minimizes service interruptions.
For high-availability and fault-tolerant installations in which the switches use redundant power supply
units (PSUs), ensure that each PSU in a switch is connected to a dierent UPS and that each UPS is
powered by an independent AC supply. This will prevent service interruptions when a power source is
lost, or when a UPS unit fails. (Note that a single, appropriately sized UPS can power PSUs in multiple
switches. The recommendation is simply that for any given switch, the two PSUs should be connected
to dierent UPS units.)
DC Power Requirements
This system should be installed in a DC-I battery return configuration.
In a DC-I configuration, the battery return conductor should be connected directly to the central oce
power return bus, and not to the equipment frame or the grounding means of the equipment.
DC Power Requirements
Site Preparation
178 ExtremeSwitching Hardware Installation Guide