TR 42.7 is basically a cabling related organization, where the cable manufacturers are definitely under represented - compared to the connector manufacturers.
Furthermore the cable heating touches a field way out of TIA 42.7's competence area, and these are code related issues.
What we have to come up with is a scaling up of the difference between operating and ambient temperature, and we will have to ensure that this will be reflected in the relevant codes to make it legally viable.. Operating and ambient temperature were assumed to be equal in the past, but even under PoE (and here I have to make an apology for the negligence of myself and ISO/IEC JTC1/SC25 WG3, because we did not see and did not correctly evaluate the implications of even transmitting a current of 0.175 A over the data grade cables at that time) and especially under PoEP conditions these difference will have to be revised and possibilities will have to be evaluated for installation practices to eventually alleviate the conditions on this difference which will have to be imposed due to the number of cables in the bundles and the number of current loaded cables in this bundle - which was estimated by members of the PoEP task force to be close to 100%.
As I do not see any comprehensive representation of the north American cable manufacturing industry and as I have serious doubts about the competence of the TIA TR47.7 group to consider the heating problems of cables, I have to suggest to wait for the results of the ISO/IEC JTC1/SC25 - ; ISO/IEC JTC1/SC25 WG3 - and the IEC SC 46C WG7 meetings with the confirmation of IEC TC46, before taking any further steps.
I wrote a test procedure for assessing the heating problem of cables, and published also to all relevant standards committees. So far I did not see it yet on the reflector of IEEE though, despite the fact that I send it in the the chair of the PoEP task force quite a time ago and additionally I contacted as well Mr. D. Law.
I saw some tests carried out according to this procedure, and I saw also some test with a slightly modified test configuration, where the error assessment render the test nearly useless, by looping the cables at the ends without properly isolating them. Furthermore the ambient temperature has not been kept absolutely constant as required for any thermodynamical analysis. To adjust the results afterwards according to the measured ambient temperature does not take into account the time dependent heat transfer.
I shoiuld like to remind that this problematic has to be reflected in the nationally relevant codes, and that an absolute rigurus test method and procedure has to be maintained. Any short-cut in this sense jeopardizes our efforts in this direction !
Kind regards to all of you
Jo Walling
Chair of the UL-CSA Harmonization Committee for UL 444/CSA 22.2 No.214-02
Canadian head of delegation to ISO/IEC JTC1/SC25; IEC TC 46; IEC SC 46C and IEC SC48B
Wael Diab wrote:
Dear IEEE 802.3at Task Force Members,At our last meeting, the group requested another informal joint session with TR42 to discuss cabling related issues. TR42 has graciously agreed to host this informal session on Tuesday, October 3rd from 7.30pm to 9.30pm in Portland, OR. Below is the note that Val sent to the TR42.7 reflector. The note and attached document has additional details on the venue and the TR42.7 agenda.RegardsWael--
Wael William Diab
Director of Marketing, Broadcom
Secretary, IEEE 802.3 CSMA/CD Working Group (Ethernet)
From: Valerie_Rybinski@xxxxxxxxxx [mailto:Valerie_Rybinski@xxxxxxxxxx]
Sent: Thursday, August 10, 2006 2:47 PM
To: tr427@xxxxxxxxxxx
Cc: Wael Diab; Mike_McCormack@xxxxxx; hvcongdon@xxxxxxxxxxxxxxxxxxx; bjensen@xxxxxxxxxx
Subject: Notice of Joint IEEE 802.3at/TR-42.7 Task Group Meeting in Portland, OR
Hi Folks:
Please find TR-42.7's meeting agenda for October 3 - 4 in Portland, OR attached below.
In addition, individuals interested in studies related to PoE Plus issues such as temperature rise versus current in cabling and maximum current carrying capacity are encouraged to attend a joint 802.3at/TR-42.7 session that is scheduled for 7:30 - 9:30pm on Tuesday, October 3rd. The goal is to follow-up on our last meeting and see if there are any things that TIA can do to help accelerate the discussions on current capacity versus heat. Also, a few IEEE 802.3at committee members had some additional questions for TIA members that they would like to review. An informal agenda will be proposed at the start of the session and it can be amended as appropriate by the attendees on Tuesday evening.
It is the intent to keep this session informal so we can keep the information between both groups flowing as opposed to waiting for liaison letters after each group's meeting cycle. By the way, feedback received indicated that the exchange at the last joint session in Mystic, CT was great and went a long way in helping both groups better understand each other's needs.
Thanks for your interest - Val
