ISO IEC TR 29125:2010 pdf – Information technology – Telecommunications cabling requirements for remote powering of terminal equipment
ISO IEC TR 29125:2010 pdf – Information technology – Telecommunications cabling requirements for remote powering of terminal equipment.
9 Connecting hardware
Connecting hardware in channels used to support remote power applications shall have an appropriate current rating when mated. Connecting hardware contacts may deteriorate as a result of mating or unmating under electrical stress, leading to possible degradation of transmission characteristics. Manufacturers should be consulted regarding the number of mating and unmating cycles supported by connecting hardware while conveying the intended levels of electrical power.
The temporary removal of remote power should be considered before mating or unmating connecting hardware in a remotely powered channel. Consideration should also be given to any operational impact that loss of remote power may have, especially when a remote power source is shared by multiple end stations.
It Is preferable that remote powering is not present during mating or unmating of connecting hardware.
Intelligent powering systems such as IEEE 802.3 Power over Ethernet and Power over Ethernet-plus (IEEE 802.3at) automatically recognise compliant loads before applying the required level of remote power, thus eliminating electrical stress during connector mating.
IEEE 802.3 Power over Ethernet also defines optional features to remotely manage the provision of electrical power to each port via port power management which may be used to remove remote power from a particular channel prior to unmating connecto’s.
Port power management is therefore the preferred approach to reconfiguration of remotely powered cabling channels.
Installed cabling is not easy to change to support new applications with additional requirements. This annex otters some considerations that may be useful to provide remote power over existing installations of Class 0 or better balanced cabling. Consideration should be given to local heat dissipation conditions, for instance going through framed wall construction, through insulating material, etc.
A.2 Minimum cabling class
Class D or better balanced cabling is recommended for remote powering.
A.3 Bundle size and location
Cables with improved thermal characteristics may be configured Into larger bundles. The location of a cable bundle is also an important consideration. Conduits sealed at both ends typically retain more heat than open conduits leading to a higher temperature rise in the sealed conduit. If cables are installed In an open tray, the temperature rise will be lower than the temperature rise in conduits (sealed or unsealed) for the same bundle size.
A.4 Mitigation options
If an existing installation does not meet the current capacity in this Technical Report for a particular bundle size, the following mitigation options may be considered.
• Use only half the cables in a bundle for remote powering with the other half used for applications that do not need remote power.
• If ambient temperatures are high, consider adding air-conditioning or air-circulation over cabling segments that are exposed to high temperature.
• If possible, separate larger bundles into smaller bundles.
If it is not possible to implement any of the mitigation options listed above, and the number of data terminals requiring remote powering is significant, upgrade the installation using cables with improved thermal characteristics.
Additionally, when the number of data terminals requiring remote powering is significant, upgrade the installation using the appropriate installation procedures to keep the bundle size reasonably low (e.g. 24 cable count) to allow proper heat dissipation all along the channel, permanent link oc CP link.