19. July 2022

5 Min read

    Contents

      Written by Matthias Gerber

      Market Manager Local Area Networks

      Avoid overheating

      Wherever current flows, heat is generated by the line resistance. With Power over Ethernet (PoE), up to 90 watts now flow over the cables of the local data network. With the four-pair 4PPoE variant, this is how much current can be provided to power terminal equipment of the Internet of Things (IoT).

      This potential warming forces planners and installers to pay particular attention to the choice of cables, the link lengths, and the installation and underlying conditions. They must prevent cables from becoming too hot and thus interfering with data transmission. Please also refer to my blog of February 3, 2022, and our PoE site.

      What are remote power categories?

      The standardization committees have taken up the issue. They want to ensure that those responsible plan building cabling in a PoE-compatible manner. To this end, more attention must be paid to currents, ambient conditions, lengths, and safety factors.

      For this reason, the installation standards were adapted in 2020: EN 50174-2 for Europe and the globally applicable ISO/IEC 14763-2.

      What is referred to as the remote power categories RP1 to RP3 were introduced. They provide project managers with additional guidelines and requirements when designing PoE installations.

      Less current, more administrative work

      The RP1 remote power category is still relatively easy to implement. The focus here is primarily on PoE applications in the low and medium power range with an average installed power of up to 30W.

      There is no extra effort for planners and installers and it is sufficient to install appropriate signs at the outset.

      But prior to the connection of another PoE device, those responsible must check whether the current complies with the RP1 limit during the entire lifespan of the building.

      The result: simple initial installation with no PoE planning. Later in operation: laborious administration and control of connected PoE devices.

       

       

      More effort, more tables

      If planners want future-proof cabling from the outset, category RP3 is planned. Although this category is a real challenge for planners, it makes life much easier for building operators.

      • The first challenge is determining the cable’s temperature increase for a specific section of the cabling. The installation standards offer guidelines and simplified tables to help with this. But it is rather difficult to always find the right parameters in these tables.
      • The second challenge is to combine the different conditions along the cabling link to create an average overall temperature. There are sections where the temperature in the cable bundle is higher, and there are «colder» sections.
      • The average temperature determines the length of the cabling link that can be used for data transmission. If it could get too «hot», the distance must be shortened. The standards offer additional tables here as planning aids.

      The result: tedious PoE planning, hard-to-understand tables, and a high risk of errors.

      An easier way

      R&M helps planners with the PoE Calculator. The new version V3 contains the remote power categories and allows cabling to be modeled more precisely than is possible with the standard tables.

      With the help of this tool, planners can get closer to the real conditions of their PoE project. For example, they can enter the type of installation cable actually intended and thus take their own specifications into account.

      For up to three segments of a planned PoE cabling link, the cable types, bundle thicknesses, and ambient air temperatures can be specified and further parameters can be chosen. The PoE Calculator immediately shows the expected temperatures within the cable bundle of a segment. It also derives the maximum permitted link length from the data.

      The PoE Calculator V3 from R&M makes it possible to play with different cable types, bundle sizes, channel cross-sections, and other parameters. This lets you plan the optimal solution for the PoE project in just a few clicks.

      Proof for customers

      In addition, the PoE Calculator V3 from R&M documents the planning details used for a particular PoE project. This gives building operators the assurance that appropriate planning has been carried out and that the installation complies with the specifications and conditions of the agreed remote power categories.

      R&M has added the remote power categories to the R&Mfreenet warranty system. The documentation from the PoE Calculator is used to list the underlying conditions used for the applicable categories in the warranty certificate and to show them to the customer.

      Correctly planned and installed R&Mfreenet cabling automatically meets the requirements of category RP1. Based on the documentation from the PoE Calculator and the results of the measurements for formal acceptance, it can be confirmed that an installation meets the requirements for the higher categories RP2 or RP3.

      This is how R&M supports PoE planning comprehensively. And that’s not all.

      R&M has developed a solution for the quick and easy detection of PoE on a connection. The R&M PoE Indicator is a dust cover flap with an integrated PoE display in the form of an LED. Regardless of the PoE application type, it shows whether current is present and whether the connection can be used with PoE. The PoE Indicator fits into every RJ45 jack.