Enterasys Networks BL-89710ENT, BL-89720ENT, BL-89520ENT Powering Up, Power Sensing Considerations

Powering Up

Powering Up

Simply plug one end of the power cord into the unit, and the other end into a grounded AC power source. Units are typically connected to a power strip or other power outlet that may be cycled on and off. An uninterruptible power supply may also be used.

Check to make sure each module installed displays a green Power LED (see Figure 2-4). Verify that any module that does not display a green LED is properly seated in the chassis backplane.

Power Sensing Considerations

The Mid-Span IEEE 802.3af PoE modules look for a 25K resistance in the sense phase, but can have trouble properly sensing the class resistor value when the powered device has any ground connection. This is especially true when some ground currents may exist such as from a motor or a fluorescent ballast. If the mount results even in a large capacitance to ground, it may cause the mid-span module to reject the load as a short.

For best consistent results regardless of local electrical conditions, the physical mounting of the PoE clients should be electrically insulated from ground. The use of an insulated bracket and nylon washers/screws may be necessary.

For example, make sure that

•the PoE client is not mounted with a metal bracket and screws to the metal drop ceiling structural grid, or

•the fluorescent light fixtures are not connected to the junction box through flexible metal conduit.

If problems exist, refer to the troubleshooting checklist in Chapter 3, Troubleshooting.

If you require assistance, contact Enterasys Networks using one of the methods described in “Getting Help” on page x.

Mid-Span Power Hub 20-Port and 10-Port User’s Guide 2-5