Re: [8023-POEP] List of questions regarding cabling and connector s
Steve-
You are not correct for all cases, and therefore not for the worst
case.
The worst case is 2 ports on a 802.3af PSE switch feeding a single 4 pair
cable that is then terminated to two RJ-45s on a single outlet plate.
Each outlet then goes to a separate PD.
This is a permissible configuration under ISO/IEC 11801 although it is
not conformant to TIA.
This configuration was discussed in the meeting and is the basis of Jo's
calculation.
I hope this helps.
Geoff
At 12:30 PM 9/14/2005 , Steve Robbins wrote:
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Regarding the issue of cable
heating, I have a concern about Jo Wallings analysis. In his
supporting document, "walling_2_0905.pdf" the last sentence in
the second paragraph states "...under the assumption that all pairs
in all cables are energized with the same current."
This is a valid assumption for
PoE Plus, since it appears very likely that we'll use a 4-pair
system. But Jo's assumption is invalid for 802.3af since only half
of the pairs are carrying current.
So I think Jo overestimated the
heat dissipation in the cables (for 802.3af) by a factor of
2.