HP ProCurve 6400cl Series Management And Configuration Manual page 225

Note
Power Over Ethernet (PoE) Operation for the Series 5300xl Switches
with 20 watts of PoE power remaining available on a module, you can connect
one new PD without losing power to any currently connected PDs on that
module. If that PD draws only 3 watts, then 17 watts remain available and you
can connect at least one more PD to that module without interrupting power
to any other PoE devices connected to the same module. If the next PD you
connect draws 5 watts, then only 12 watts remain unused. With only 12 unused
watts available, if you then connect yet another PD to a higher-priority PoE
port, then the lowest-priority port on the module loses PoE power and remains
unpowered until the module once again has 15.4 or more watts available. (For
information on power priority, refer to "Power Priority Operation" on page 11-
8.)
Disconnecting a PD from a PoE port causes the module to stop providing PoE
power to that port and makes the power available to any other PoE ports on
the module that have PDs connected and waiting for power. If the PD demand
for power on a module becomes greater than the PoE power available on the
module, then the module transfers power from its lower-priority ports to its
higher-priority ports. (Ports not currently providing power to PDs are not
affected.)
15.4 watts of available power is required for an xl PoE module on a switch to
begin delivering power to a port, such as when a newly connected PD is
detected or when power is released from higher-priority ports. Depending on
power demands, lower-priority ports on a module with high PoE power
demand may occasionally lose power due to the demands of higher-priority
ports on the same module. (Refer to "Power Priority Operation" on page 11-8.)
Table 11-1. xl PoE Module Maximum Power Allocations
Power-Sourcing
Equipment (PSE) Load on
the EPS
One xl PoE Module Only
Two PSE Devices (Two xl
PoE Modules, or one xl PoE
Module and One HP
ProCurve PoE Stackable
Switch)
1
If an HP ProCurve EPS device is supplying PoE power to two PSE devices, then both PSE
devices receive 204 watts. If an HP ProCurve EPS device is delivering PoE power to only one
PSE device, then that device receives 408 watts.
Power to PoE PoE Power Available for
Module from Module
1
External EPS
408 Watts Maximum (15.4 W) available to all ports on the
module.
204 Watts Depending on the power demand from the PDs,
lower priority ports may not be provisioned.
Refer to "Calculating the Maximum Load for an
xl PoE Module" on page 11-21.
General PoE Operation
the xl PoE (J8161A)
11-7