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David,I can see that the liaison from IEC has caused some interesting discussion amongst PoE experts (and myself), however I think that we are being asked to comment on what may well be design flaws in specific products and I do not think that is a healthy discussion within 802.3.
I suggest that we should send a reply along the following lines: ==========================================The problems described in your liaison spurred some vigorous discussion amongst our task force members regarding possible causes for the damage that you describe. However the members are not aware of any similar reports that might indicate a systemic problem with 802.3 compliant equipment. It is the opinion of the members of IEEE P802.3at Task Force that the standard allows product manufacturers to build reliable and interoperable equipment that will meet the requirements for supplying power over Ethernet in many environments. However, the standard does not define how a manufacturer must build the product to ensure reliability or how an installer should ensure that the media is suitable for correct operation within the standard. We suggest that you should work with the equipment manufacturers involved to determine whether the failure is the result of a systemic problem with the standard and whether a specific amendment may be required.
With respect to the bit error rate performance of 802.3 links when power is being supplied over the same link, the members of IEEE P802.3at Task Force believe that a compliant system supplying power over an 802.3 link will not perturb the channel sufficiently to degrade the performance of the underlying link. However, it is the responsibility of the product manufacturer to ensure that noise introduced by the load does not couple to the link and violate the power over Ethernet specifications or the channel specifications required for the link. Similarly it is the responsibility of the system installer that the channel characteristics are met in the presence of environmental noise.
=========================================== Hugh. David Law wrote:
All,The IEEE 802.3 Working Group has received a liaison letter from IEC TC65/SC65C/JWG10, Industrial process measurement, control and automation/Industrial networks with respect to Power over Ethernet performance in industrial environments. I just wanted to inform you that I intend to delegate the generation of a draft response to the IEEE P802.3at DTE Power Enhancements Task Force during the plenary week in July. The draft response will be consider and then voted upon at the closing IEEE 802.3 Working Group plenary as part of the IEEE P802.3at closing report. You therefore may wish to review the letter prior to the meeting, the letter can be accessed at the URL [ http://www.ieee802.org/3/minutes/jul09/0709_IEC_SC65C_JWG10_to_802_3.pdf ].Best regards, David Law IEEE 802.3 Working Group Chair