It will depend upon what the amount of power is that each device requires. The AVERAGE power per port cannot exceed 7.65 watts per port to get all 48 ports delivering PoE power. But do you really need 48 ports of PoE power? Are you using any of the SFP/MGBIC uplink ports? If you are, then you lose one of the 10/100/1000 ports for every SFP uplink port used since these ports are "combo" ports (in other words the switch is truly a 48 port switch - it is not a 52 port switch (48 port 10/100/1000 switch with 4 1Gb SFP uplinks)) So do you need PoE power on 48 or 47 or 46 ports?
PoE works as follows on the B3. If an attached device advertises itself as a Class 3 device (requires 15.4 watts) of power, the switch checks to see if it has the 15.4 watts available. If it does, it provides the power. The B3 monitors the port to see what the actual power draw of the device is. If the device only draws 8.0 watts of power, the switch will return 7.4 watts of power (15.4 minus 8.0) to the central PoE pool so it can be distributed to other ports. In this way, many more Class 3 devices can be powered than permanently allocating 15.4 watts (the maximum possible power draw) to each port. For example, let's look at a VoIP phone that requires 8.0 watts of power. It will advertise itself as a Class 3 device since it requires more power than Class 2 which is 7.0 watts. If the switch permanently allocated the maximum 15.4 watts of power for each 8.0 watt VoIP phone, it could only power up 24 devices (375 watts divided by 15.4 watts which is equal to 24.35). But by monitoring the actual draw and returning unused power to the central pool, that same 375 watt PoE switch could power 45 8.0 watt VoIP phones ((375 watts minus 15.4 watts (for the last device that can be powered up) divided by 8.0 watts) Viewed a different way 44 8.0 watt VoIP phones would require 352 watts of power (8.0 watts times 44 device) which would leave 23 watts of power in the pool (375 watts minus 352 watts) which is enough power to power up one more Class 3 device for a total of 45. I hope this helps answer your question. Karl F Pieper Product Manager - Fixed Switching Enterasys Networks Office: 978-684-1445 Cell: 978-886-9868 Email: [email protected] -----Original Message----- From: Gavade, Prashant [mailto:[email protected]] Sent: Wednesday, May 19, 2010 1:00 AM To: Enterasys Customer Mailing List Subject: [enterasys] POE Switch Dear All, I am looking for connecting 48 POE phones to B3G124 48P switch. According to datasheet B3G124 48P switch supports 375 watts per switch with up to 15.4 watts per port. If my poe phone is supporting Class C then, can I connect these all for 48 ports? Can we control the power level of on each port? Class Measured current (mA) Maximum PD power (W) 3 25 to 34 6.49 to 12.95 Best Regards, Prashant Gavade --- To unsubscribe from enterasys, send email to [email protected] with the body: unsubscribe enterasys [email protected] --- To unsubscribe from enterasys, send email to [email protected] with the body: unsubscribe enterasys [email protected]
