POWER OVER ETHERNET – 18th EDITION AMENDMENT 4 – WHAT IS IT – WITH EXAM QUESTIONS AND WORKED ANSWERS

Added: 2026-05-26

[00:00:01]In this Learn Electrics video, we will look at some more of the changes to the 18th edition of the Wiring Regulations book and BS 7671.

[00:00:12]So, what are the changes and what is this new section?

[00:00:17]With Amendment 4 of the Wiring Regulations, we find new sections, new regulations, and new exam questions.

[00:00:26]And the introduction of a new section in part 7, special installations or locations.

[00:00:32]This new section is called Power over Ethernet and is abbreviated to PoE and is numbered section 716.

[00:00:43]You will find this new section on pages 330 and 331.

[00:00:49]A very short section, but because it is new to the regulations and because it is an emerging technology and rapidly becoming more widespread, do expect to have a question or two on section 716 in the 18th edition Amendment 4 exams.

[00:01:09]Before we look at the new section proper, let's make sure that we have a little understanding of what Power over Ethernet is.

[00:01:17]This is just a very, very basic introduction.

[00:01:21]A more detailed description will be in a following video.

[00:01:25]Power over Ethernet is the sending of both data and DC power down the same Ethernet cable, allowing you to run equipment like security cameras, access points, and phones without a separate power supply or mains outlets at the point of use.

[00:01:44]The relevant standards define how much power can be pushed along the wire, how it is standardized, and how many pairs of cables are used.

[00:01:54]So, PoE is data plus DC power all on one Cat 5e or Cat 6 cable.

[00:02:03]This power is delivered from a PSE or power sourcing equipment to a PD or powered device.

[00:02:14]There are currently four types of PoE standards depending on how many watts of power will be sent along the conductors and the table below shows these.

[00:02:25]Type one is simply called PoE and the table shows how many watts can be passed along the conductors.

[00:02:34]Type two is called PoE plus and types three and four are PoE plus plus.

[00:02:42]Why so many pluses?

[00:02:44]We started out with just a simple PoE but then what was being demanded of new PoE equipment as demands grew meant that the technology had to advance for some installations.

[00:02:58]This became PoE plus.

[00:03:02]Then the inevitable happened.

[00:03:04]Technology moved on another step and PoE plus just wasn't enough for all the new stuff. So, another improvement in capabilities and PoE plus plus was born.

[00:03:17]The voltages on all the cables is in the extra low voltage range between 48 volts and 57 volts DC.

[00:03:26]Remember that the DC extra low voltage band has a range of 0 to 120 volts ripple free DC.

[00:03:35]Unlike the AC band which is between 0 and 50 volts AC.

[00:03:41]PSE, as mentioned on the previous slide, is power sourcing equipment. The thing that provides the power.

[00:03:49]Whilst PD or powered device is a thing that is being powered.

[00:03:56]Some examples of what we might use PoE for are shown in the yellow box on this slide.

[00:04:02]We've expanded the entry for IoT or Internet of Things as shown in the lavender box.

[00:04:09]These are just a few examples. The list will be almost endless as more uses and applications are added on a regular and ever-increasing basis.

[00:04:20]This drawing shows the basic idea of sending power down the twisted pairs that are used for data transmission.

[00:04:28]To ensure that we don't overload the conductors and to avoid any unbalancing in the cables, both conductors of a certain pair are used to send the current to the powered device and both conductors of another pair are used to return the current from the PD.

[00:04:47]A short list of some of the uses to which we put the ability to send power over Ethernet are shown here.

[00:04:54]Again, not exhaustive. There really are so many uses for this technology.

[00:05:01]That was a very brief overview for those amongst us that have not come across power over Ethernet before.

[00:05:08]Now, we will have a few exam-style questions just on power over Ethernet as per section 716.

[00:05:16]In truth, there are very few questions that can be created for this section, but I want you to look at the pages to get a visual overview of this new section rather than just skipping over the two pages.

[00:05:31]So, let's get started.

[00:05:34]Question number one asks us, in a power over Ethernet installation for protection against electric shock, one of the protective measures to be applied is and there are four possible answers shown and only one is the correct answer for this question.

[00:05:51]Pause the video, make your choice, and then check the answer on the next slides.

[00:05:57]Look for the keywords in the question, specific words relating to the question.

[00:06:02]They will help you to narrow down your search and to find the correct answer more quickly.

[00:06:09]Here's a little help for when you are searching. In an exam, where are you going to find the power over Ethernet section? Because you won't remember the page number, and flicking through the book in the hope of finding it by luck is useless.

[00:06:24]After all, you only have an average of 2 minutes per question.

[00:06:29]Instead, we can find it through the contents page, page three of the book.

[00:06:34]This is quick and proven.

[00:06:37]If we look in part seven, special installations or locations, on page three, we will find power over Ethernet listed as section 716, and scanning along to the right will give you the first page number for it, page 330.

[00:06:55]There are only two pages to look at in section 716, and we can quickly locate the regulation that we need. It is regulation 716.410.3.3 under general requirements heading on page 330.

[00:07:13]Read the wording, and we can see that SELV is mentioned in the regulation, and that it also appears as a possible answer.

[00:07:22]None of the other choices match, so the answer must be answer C, SELV, separated extra low voltage.

[00:07:32]Question number two is next.

[00:07:34]In a PoE system, one of the below listed cable categories shall be used for for distribution of DC power and must comply with BS EN 50173-1.

[00:07:49]What is the cable category?

[00:07:52]Pause the video and look for the keywords in the question. They will be there.

[00:07:57]Attempt an answer and choose just one of the possible answers shown.

[00:08:03]The keywords for this question are shown in the blue boxes and we find the cable categories are shown under types of wiring system in regulation 716.521.101 on page 331 along with the other keywords ICT cables and BS EN 50173-1.

[00:08:31]So, choose answer C, category five.

[00:08:36]And question three asks, in a PoE installation, the connecting hardware used for data cables for the distribution of DC power shall be able to support a continuous operating current per contact of what?

[00:08:53]As before, pause the video and find the answer.

[00:08:58]All the questions in the power over Ethernet section should be easy to find as you only need to look at two pages.

[00:09:06]Finding the keywords will help. They are shown in the red boxes.

[00:09:11]Looking at regulation 716.526.101 on page 331 gives us our answer.

[00:09:23]A continuous operating current of 750 milliamps per contact and answer B is the correct choice.

[00:09:32]Question four is about protective measures and asks, which protective measure is particularly suitable where functional equipotential bonding is used as an EMC mitigation measure in a power over Ethernet scenario?

[00:09:49]Again, four possible answers. Pause the video, determine the keywords, and find an answer.

[00:09:58]The answer is choice A, PELV or protected extra-low voltage.

[00:10:04]Look at note three within regulation 716.414.1.1 on page 330.

[00:10:14]In note number three, we can see the appropriate part of the regulation highlighted in red.

[00:10:21]Finally, question number five. And the question asks, "When considering the current-carrying capacities of cables in a PoE system, the load current or design current in any conductor shall not exceed what?"

[00:10:37]Pause the video, identify the keywords, and find the answer.

[00:10:43]You should choose answer D, 750 milliamps. You should remember this one. We've already had 750 milliamps for connectors, and now we have 750 milliamps for conductors.

[00:10:57]And of course, we know that they should be the same maximum current. Why should they be different?

[00:11:04]If you found the keywords, then you should quickly find the correct regulation and the right answer.

[00:11:12]Let's have one last question, only partially related to section 716.

[00:11:18]In fact, it's related to the whole of the book.

[00:11:22]Why does one of the regulations in section 716 end in a dot 201, yet five regulations end in {dot} 101.

[00:11:34]And there are many more instances in the book where regulations end in {dot} 101 and {dot} 201.

[00:11:42]What does it mean?

[00:11:44]Can you find the answer before looking at the next slide?

[00:11:48]Pause the video and have a go.

[00:11:51]And here, at the bottom of page 20 of the regulations book, is our answer.

[00:11:57]The {dot} 101 numbers indicate references to Europe-wide CENELEC harmonization documents.

[00:12:06]The {dot} 201 numbers are references to UK only regulations.

[00:12:12]Just a little something to keep at the back of your mental toolbox.

[00:12:17]I hope that you found this short video useful and that it helps in your studies towards the exam.

[00:12:23]Or maybe you already have the qualification and you're just updating your professional knowledge of the changes in Amendment 4 in order to remain compliant.

[00:12:33]If you already have any 18th Edition qualification, there is no requirement to reset the exam or to attend any refresher or update courses.

[00:12:44]But, you are expected to make yourself aware of the changes and new additions to Amendment 4.

[00:12:51]Something that we will cover in these Learn Electric videos.

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