Extreme Networks 8720 Hardware Installation Manual page 34

UPS (Uninterruptible Power Supply) Requirements
•
Restart equipment after a long power outage.
•
Display the voltage currently on the line.
•
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
a Suitable UPS Transition Time
Note
We recommend that you 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, we
recommend that you 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 transition times vary between UPS models and implementations, but shorter
transition times are preferred. For Extreme Networks stacking products, we
recommend a UPS transition time of 20 milliseconds or less to ensure optimum
performance and minimize service interruptions.
For high-availability and fault-tolerant installations in which the switches use
redundant power supply units (PSUs), we recommend that each PSU in a switch be
connected to a different UPS and that each UPS be 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 different UPS units.)
34 Extreme 8720 Switch Hardware Installation Guide
on page 34 .)
Preparing for the Installation
Providing
UPS transfer time .