Installing and Managing Power over Ethernet (PoE)
Power Shelf and PoE Port Guidelines
OmniSwitch 7700/7800 Hardware Users Guide
April 2005
page 3-9
Redundant Power Supply Configurations
Power supply redundancy is defined as having at least one power supply more than the minimum require-
ment (i.e., N+1). With redundancy, if a power supply is removed from the power shelf or fails unexpect-
edly, the remaining power supplies automatically take up the load without disrupting PoE support.
Use the table below to determine the minimum number of power supplies needed in a
redundant
PoE configuration
For example, a PoE configuration with 184 powered devices, each requiring 7.5 watts of power, uses a
total of 1380 watts. Because 2+1 power supplies support up to 1043 watts only, a configuration of 3+1 is
required for this application—i.e., four power supplies must be operating in the power shelf at all times.
Important.
Alcatel recommends that PoE-enabled switches with attached IP telephones should have oper-
ational power supply redundancy at all times for 911 emergency requirements. In addition, both the chas-
sis and the power shelf should be plugged into an Uninterruptible Power Source (UPS). Power supply
redundancy must also be enabled in the system software (see
“Setting PoE Redundancy Status” on
Power Supplies
Power
1+1
514 watts
2+1
1043 watts
3+1
1572 watts
