ADIABATIC EQUATIONS 18th Edition Training BS7671
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- čas přidán 26. 07. 2024
- Adiabatic Equations are an essential part of confirming safety in an electrical installation.
During an earth fault there will be massive fault currents flowing, several hundred amps and if the earth cable or CPC has not been correctly specified there is the danger of over-heating and damage to the cable.
This video explains the danger and covers the three types of adiabatic checks that we can make to ensure the safety of the installation and its occupants.
We cover the calculations in an in-depth, step by step, way so that learning can become internalised and properly understood.
There will always be questions on adiabatics in the 18th Edition exam and we cover the types of questions that are most often asked. For everybody else, this will act as a good refresher for forgotten knowledge.
This video is the fourth part of our help series on the 18th Edition of the Wiring Regulations and No.60 on our CZcams channel where we have videos on a wide range of electrical topics.
This video is made for Amendment 1 of the 18th Edition Wiring Regulations:BS7671
Page numbers and references are specific to the BLUE Wiring Regulations book.
This Amendment 1 video will help with your learning for Amendment 2 exams but be aware that none of the page numbers will match.
Amendment 2 videos can be accessed on CZcams by searching for
LearnElectrics Amendment 2
To see a full list of all our LearnElectrics videos, click on the link below. / @learnelectrics4402
You can also view all our videos by typing LearnElectrics all one word into the CZcams search bar.
SEE ALL - To view a list of all our LearnElectrics videos, click on the link below.
There are many videos on many electrical topics including Installation, Part P, 18th Edition, Testing, Certification, Lighting, Sockets, Ring Circuits and much more.
czcams.com/channels/YaJQnpO4XAp0yCgqzMkmfA.html
Great job - thanks.
This is the best explanation I've ever seen, I can't thank you enough
Glad I could help. Lots more to come. Dave.
You've really made this so much easier for me to understand all of these equations, thank you so much.
Thank you. Yes, equations are often a tricky one unless explained in stages. Hopefully it works. Dave.
Absolutely the best and most systematic channel for learning electrics! Thank you very much for your work and knowledge!
Thanks for watching.
If you go to LearnElectrics.com and put Amendment 2 into the search bar, you will get a list and direct links to all the Amendment 2 help, questions and answers videos for the latest exams. Thanks for watching. Dave.
Hi, one if the best channels and have helped me out in tye past 2 years.
Thanks for the feedback. This video is on Amendment 1 of the Regs, the blue book. If you are revising for the amendment 2 exam, the brown Regs book then go to LearnElectrics.com and put Amendment 2 in the search box. You will get a list of direct links to the Amendment 2 videos. Good luck, Dave.
I would like to thank you sir, thanks to your videos i was able to pass the exam with 85 percent, im not even from an electrical background.
Excellent. Well done. It was your efforts that got you that pass and if the videos helped a little, then great. kepp learning, its a great trade.
Wow amazing explanation, better than any of the other videos I’ve watched. Keep up the great work 😃
Thank you Imran. Lots more to come. Dave.
Struggled with this in the classroom, this video helped immensely, thanks
Brilliant Graham, so glad they help. Thanks for supporting the channel. Tell your classmates, they might need help too. Dave.
Appreciate all the videos, your effort is making a difference. Thank you .
Thanks Chris, so glad you find them useful and thanks for watching. Dave.
Brilliant, clear, concise and relevant. Thanks
Thanks for the positive feedback. Appreciated.
Your videos are helping me out massively. Thanks
Glad to hear it, thanks for watching. Lots more to come and lots on the website.
Brilliant educational channel, keep up the great work.
Thanks, will do, thanks for watching. Lots more to come. Dave.
Another great lecture from the one and only learning channel...this channel should be recommended in every college
Fantastic feedback. Spread the word Dennis, really appreciate your comments. Dave.
Thank you for your contribution and explain this topic which is the most simple and easy way I have ever seen.
Thanks Muhammed, great comments. Dave.
Excellent learning resources. Was introduced to this concept by my site supervisor.
Great stuff Mattias. Try to learn a little something every day - it works. Lots more learning videos on the way, spread the word - it all helps - and thanks.
Dave.
Your videos are amazing, this one especially was very good and made simple what otherwise many find too complicated
Thank you Nadeem, great comments. Yes, adiabatics is a guaranteed question and it's not that complicated if explained correctly. Thanks again, keep watching, some good videos coming up.
Is that your daughter? She must be about 2 years old now - lovely photo - be proud. Dave.
@@learnelectrics4402 thanks, yes she'l be 3 soon, I had my first NAPIT assessment visit today, passed :) , your videos helped me in refreshing my knowledge
Thank you!! very well explained you are an excellent teacher 👍🏻👏🏻👏🏻
Well thanks, a great compliment and appreciated. Glad you enjoyed it. Dave.
Thanx you so much for these videos, if I could give you a thousands like , I would, plz carry on with the content, I’ve learnt so much from you sir
So nice of you to say that. Great feedback and appreciated. Dave.
A better and much easier way!?
Easier just to use the actual given figures without squaring them all then take the square root of the answer? No immense sizes to work with, less buttons to press on the calculator, so less chance of making a mistake. e.g. in example No.1 in the video: 115x4 divided by 650 equals 0.70769. Just hit the x2 (x squared) button on this answer and you get the correct answer of 0.5. I appreciate that you probably need to know the equation with all of the huge squared numbers in it for exam purposes, but in reality you still get the correct answer using this simpler technique. PS I am subscribed to this channel because it is by far the best teaching channel on CZcams so thank you for all your excellent videos.
Yes, but in the exams, they expect you to calculate the answer. Thanks for watching.
Thank you for your best explanation.
Thanks for the positive feedback, appreciated. Dave.
Excellent Vid Dave thank you.
You are very welcome Angelo. Thanks for your support. Dave.
Excellent !
I am an elect. for 35 years & wish I had this in college!
So we’ll explained!!
Regards m.
Thank you Malachy, really appreciate your comments. Lots more to come. Dave.
Excellent, as always
Thanks David. Some good videos on the way.
Great Video. Very well explained.
Thank you Syraj, appreciated.
Another very useful video. Your teaching method assumes nothing, and I like that. You even explain what the square of a number is - a lot of lecturers would just assume that the student knows that.
Thanks for that, appreciated.
Brilliant explanation .
Glad you liked it Pasquale, and thanks for watching.
You do the best teaching on here regarding the 18th Edition
Super feedback. Thanks so much. Don't try and remember all the regulations in the book, just learn how to use it. That is the secret between pass and fail. Good luck.
@@learnelectrics4402 thank you I think had I watched your videos for longer I would have passed. I got 55% on test so failed but I literally just turned up for the exam and did not even look at the book until 1 day before. 🙃 I'm going to watch all your videos from start till end this time. As opposed to spending 5hrs watching other videos on here which didn't teach as much as yours did in just a 10 to 15 min video. I'm still struggling to read the tables though. Sure I messed up a few regarding zs which should be easy to amend and on top of this I know for sure I got 0 questions correct regarding formulas. The tutor said I done well considering I didn't even do the 3 day course I was supposed to. 2 weeks till next exam and I've now bought the book and will go through your videos. Hopefully this time I pass 🙏🏾😊
Seriously, watch all the videos, pause them and do all the examples that are in them. The videos will show you how to find information which is what the exam is about. Like an A to Z for a town. If you can understand the index and how to read the A to Z you will find the street. Each video tells you how many questions are in each section. Remember that parts 4 and 5 have about 15 questions each - 50% of the exam, so make sure that you are good at finding info in them. And make sure that you can use table of tables at the back of the book. Finally, good luck. Dave.
@@learnelectrics4402 Thanks Dave
Best teacher !!!
Thank you. Thanks for watching.
I've tried understanding this method but with no avail. watching this video has made it a breeze. Another great video, thanks Dave.
I've seen many, many people struggle with this over the years.
Stick with me buddy, we'll get there. Dave.
@@learnelectrics4402 will do Dave. Will you be doing any videos on the practice side, like the dead test sequence etc and fault finding. Thanks
Definitely will be doing very soon. Keep watching and thanks for your support.
Great video mate👍🏻
Thank you. Much appreciated feedback. Dave
Amazing sir
Legend is legend 🙌
Legend. I've got some reputation to keep up now. Thanks Akash. Take care. Dave.
I have looked at all of the teaching out there … this is very good no ego involved fantastic I am on a course and if it wasn’t for these clips I would not have a chance … wish I could contact this man to explane my situation! May I request a description of the ohms scale and how to apply to a multimeter I have only found from the past from a company called perkys metres good but could do with clarity …. Many thanks!!!!
Thanks for the request, I think I know what you need and it's now on the list for a future video. Thanks for watching. Dave.
Do you have an e mail address please ? Thanks michael
Amazing lecture. thank you
Thank you Omar, glad you liked it. Some great videos coming up soon. Dave.
@@learnelectrics4402 I can not wait.
Great video Dave, I'm loving the maths, but I did struggle at school with maths 😜 and was not keen 👍
Thanks for the good comments Andy. Maths is a good subject if it's shown to you properly. Stay with it, lots more to come. All about Zs and 80% rules on Monday (a bit of maths) and Voltage Drop calculations on Thursday (more maths). Dave.
Hi it very good you are very experienced teacher do more Adiabatic Equations
Thank you. Yes, more videos with electrical calculations are being planned.
Nice one mate..
Thank you Amri, appreciate your comments. Dave.
Thank you 👍
You're very welcome Royston. Lots more to come. Dave.
@@learnelectrics4402 very helpful, gonna do my C & G next week so looking forward 👍
Good luck. Dave.
These tutorials are great. Its a shame the narration is based on page numbers that are now basically all incorrect, but the page you need is usually somewhere nearby
This video is for Amendment 1 of the Regs, the BLUE book as shown on the first slide. If you are sitting the Amendment 2 exam, the brown book then go to LearnElectrics.com and put Amendment 2 into the search box. You will get a list of links to videos and questions on 18th Edition Amendment 2. Dave.
Thanks
You're very welcome Mark, thanks for the feedback.
Another great video,
With regards to specifically calculating main earthing conductor size, and some of the problems encountered.
Where the main service fuse rating and type is unknown (both with regards to rating and bs1361/bs88) should we assume worst a case scenario of 100/80A?
Would the minimum main equipotential bonding sizes have an impact on calculating and selecting the minimum size of main earthing conductor, when using the adiabatic equation? Depending if the bonding was connected at the cutout position or at the met inside the consumer unit would, for instance if the adiabatic suggested a 6mm main earthing conductor was adequate, would this be overruled by the minimum size of bonding requirements (10mm)?
Lastly could you clarify the time “t” that should be entered into the equation, when say a bs1361 (or a bs88) fuse is used in the service head as the tripping curves for this fuse isn’t in the 18th edition?
Thanks 🙏 👍
Thanks for the feedback. This video is specifically styled on the adiabatic equations as asked in the 18th Edition exam. The exam setters assume that the service head components and the wiring before the consumer unit is correctly selected by the DNO. Questions in the exam will only be on what happens from the consumer unit.
A new main earth should be 16mm and new main bonds 10mm. We have a video soon on earthing and bonding. look out for that one.
For the t = time question, have a look at this video for time about final and distribution circuits.
czcams.com/video/Jsqx7b9VdyM/video.html
Brilliant
Thanks Keith, appreciated.
If you set calculator to maths mode then press the two squares one above the other, this splits the calculation, then press the down to do the lower calculation. Press = it will look like what you have on screen,then press S-D and it will calculate the second calculation. You can use up / down arrow to go back or forward.
Or you can do it without the need to go all the way to S-D
Thanks for the input, appreciated.
3:18 in the New Edition of BS7671 (big brown book) the pages are 98 and 200.
Thanks for the input Andrew, there is an Amendment 2 video on the channel that includes this, but a good reminder for me to update this one. Thanks. Dave.
excellent video thanks ! why K factor is different for both cables 115 and 143 any specific reason ?
Thanks for the great comment. The k factor is different because cables can be made from different materials, different construction methods, different plastics, lots of reasons.
Hope this helps and don't worry about it, in the 18th exam they will tell you what k is.
Hi This really helped me with understanding the Equations. i was wondering if you will be updating your videos to be inline with the BS7671:2018 Amendment 2:2022 as im studying this edition and the tables are obviously in different locations.
Already being done Matty. In CZcams put in - LearnElectrics Amendment 2 - to see them or go to LearnElectrics.com where they are all listed and watchable. Thanks. Dave.
Hi dave.. Just have a question about the commercial lighting circuit cable is it 1.5mm or 2.5mm to be comply?
Thanx alot
Whichever is the most appropriate cable size. Caravans and exhibitions will have increased minimum cable sizes for cables but this adiabatics video is just about choosing the correct size earth or cpc to answer the exam questions. Hope this helps.
Hello Dave, could you please explain how the 650 amps of fault current in the example is calculated? Thank you.
It all revolves around ohms law. The 650A was selected because many houses have a PFC of about that. Take a look at this video, it will help.
czcams.com/video/xtDId-g7GjU/video.html
Another curious question...wouldnt the earth conductor already be install in order to carry out a fault current test...or its a short circuit fault test we should do
Zs tests include R2 which is the cpc or earth. You use the Adiabatic to make sure its the right size for the PFC.
Thank you so much for these lessons they are proving invaluable and so much easier to absorb than the course content I have. I am a little confused by the calculation in example 1 for time though? The limiting temperature is given as being 70 degrees, but table 43.1 giving the k value of 115 is an initial temperature of 70 degrees and a final temperature of 160 degrees, could you perhaps explain why the initial temperature is the limiting value when it appears that the cable could go as high as 160 degrees please? I am not doubting you for a minute, I would just like to understand. Thank you very much.
The cables we use have an upper limit of 70C in order that they match up to requirements for Zs. At 70C the conductor resistance will be at the permitted maximum for the tables in part 4 of the Regs. Hopefully we are starting off at a lower temp. How long will it take the cable toi teach 70C from the starting temp with this amount of fault current. If it takes longer than 0.4 seconds in final circuits, then all is ok.
Take a look at this video on Zs.
czcams.com/video/ihD-NO-7G5Y/video.html
@@learnelectrics4402 Thank you for taking the time to reply, I think I asked the wrong question really! I realise that 70C is the maximum temperature for thermoplastic, so was confused when the table has 70C as the initial temperature, when as you say, you would hope the starting temperature is considerably lower, and it then shows the final temperature as 160/140 degrees, but what does this figure refer to? Your video on Zs answered another of my questions on why I kept seeing the 0.8 factor in formulae, but it was never explained in my course! Thank you again for your channel, it is of huge benefit to people like myself.
Hey I’ve got my theory exam next Friday. We just found out today. Does this playlist cover everything.
It covers a lot. Can't say it will cover everything but if you can work your way through the playlist and understand that every question will always give clues where to look for the answer, then yes. But will it cover every possible question, no. But if you follow the method you will be helping yourself tremendously. Viewers that have followed this playlist have come back with test results of 95% and even 100%. Good luck. Dave.
These videos are fantastic, thank you.
I’m having trouble working through a design project to work out the cpc size for a ring final for an extension. Hopefully someone can help (please!)? Hopefully what follows is clear? The ring final length is quite short at 24 metres of 2.5/1.5 TCE, which gives me an R1+R2 of 0.14 ohms (calculated as (19.51 x 24 x 1.2)/1000 all divided by 4). When I add this to my Ze of 0.22 I have a Zs of 0.36 and this works through to an I pfc of (230 x 1.1)/0.36 = 253/0.36 = 703 A. My 32A MCB will operate rapidly as the I pfc exceeds 160A. Should I take t as 0.4 seconds or take it as 0.1 seconds, which is the lowest value I can get from table Table 3A4? If I take t as being 0.4 seconds as guided in the video and k = 115, then working through the adiabatic equation tells me I need a cpc greater than 3.86 mm. If I take t = 0.1 seconds my cpc still needs to be 1.93 mm, but I have 1.5 mm. However, if I keep t as 0.1 seconds and cunningly add extra cable length into the calculations to make it, say, 45m I can increase my R1=R2, and thus my Zs, which will decrease my pfc and reduce my required cpc size, S, to less than 1.5mm. (As an aside, could this apparent quirk of circuit design be the reason why I sometimes find yards and yards of apparently surplus live circuit cable in lofts and voids in some houses?). If I don’t want increase my cable size, is the approach of lengthening the cable acceptable? Any help or constructive comments welcome - TY.
The Regs require that the final circuit disconnects in less than 0.4 seconds. If the manufacturer has designed a breaker to operate in 0.1 seconds then that satisfies YOUR 0.4 second requirement. Hope this helps.
@@learnelectrics4402 , thank you - it does. 👍
Hi great learning channel, do you have any examples of using steel armour as a earth with copper conductors? And also using the amount of strands needed to meet disconnection time.
I have seen it ie k1/k2 x s but unsure.
Thank you
Regards..
Generally accepted that properly terminated steel strands can be used as an earth path. Many sparkies also attach a separate earth conductor to the outside of the SWA as well. Thanks for watching. Dave.
@LEARN ELECTRICS
Yes ok thank you for your reply Dave much appreciated 👍
Hi, in response to the answer to the question in the last video, why should I be looking at table 41.4 and not 41.2. Both have Fuse system C with BS 88-3. I understand that 41.4 has 5 second disconnection time, but how am I supposed to know to look here?
Have a look at this video, it explains it all - click on the following link
czcams.com/channels/YaJQnpO4XAp0yCgqzMkmfA.html
Also, next weeks video is about exactly what you have asked as well.
Thanks for watching, it does all make sense in the end. Dave.
@@learnelectrics4402 Hi dave. Ive got my 18th edition test coming soon. To revise/prepare, should I be watching these videos or your newer ones on amendment 2?
Hi - can you adiabatic a bonding conductor? If you can what fault current would you use would it be your PEFC ? Thanks
We wouldn't use a bonding conductor as part of the earth fault path. have a look at this video on testing bonding cables.
czcams.com/video/wYsYBE-MXzQ/video.html
Thank you for your explanation. would also like to know how to determine the fault current for applying the equation in P92 and 196 in real life,?
There are no equations on those pages in my books. However, the equations shown in the video are exactly the ones we use in real life and the examples shown are exactly as we would use them. watch the video again and have a practice at them yourself, they will soon make sense. Thanks for watching. Dave.
I really liked the explanation for this, really helped. But what was the answers at the end?
You're supposed to tell me. A & D. Thanks for watching, appreciated. Dave.
In the given questions, the maximum fault current was given. But in real life I think we need to calculate it and I think cause we need the maximum, so we must consider it at the beginning of a final circuit, ignoring R1 and R2. 230/Ze is my guess for maximum fault current.
Or if we are on site we can check it with multi function tester at the consumer unit. Am I right?
On site you can use a meter, but this video is to help you to pass the exam when you are dealing with just theoretical data. Thanks for watching. Dave.
Hi if applying this formula and we end up with 1.6mm ( as an example ) on a 2.5/1.5 twin and earth , do we need to change cable size ?
For the assessments and exams, they expect you to follow the book to the letter.
If your calculation says 1.6mm for the earth, then you must choose the next size up from 1.5mm which is 2.5mm. You must not go down in cable size.
Hi Dave, Just a thought based on your excellent way of teaching. Is there a chance you could run a course on the City and guilds 2396 possible? I'm sure you will get a lot of students wanting to listen to you.
Angelo, thanks for your confidence but I stopped face to face teaching during the Covid problems and decided that I would just pass on my knowledge through CZcams.
However, doing help videos on C&G 2396 is an idea worth considering. You would still need to attend a 2396 course though, otherwise you will not be able to take the exams and get the qualification. Worth thinking about. Thanks. Keep watching. Dave.
Hi Dave just an update, I have taken your advice and booked the 2396 course now for this coming November with Napit in Bristol. Would like to thank you again for all your contributions and good advice thank you.
It seems that we don't use adiabatic equations for phase or neutral conductor and just use the table of on site guide. We can infer that they have considered it in the table and in case of short circuit they will remain safe? I guess the reason is, considering the fact that cpc size is smaller or equal to phase and neutral, when cpc pass the test, the others pass too.
The adiabatic equation is for CPC and earth selection. Dave.
I take it this is not for the actual cpc in the 'twin &earth' cable? its for the main earth conductor connected to MET?
Yes it is. Regulation 543.1.1 The cross-sectional area of every protective conductor, other than a protective bonding conductor ...
Good question and thanks for watching. Dave.
Hi.First Thank you very much for your effort and great job to show how to learn book.
I'm confused with question from Part 3 with answer in part 4.
Answer B Zs is 1.6 Table 41.4
I found answer in table 41.2 Zs 0.91.Both answer can be correct or not ? Why take 41.4 is correct and not table 41.2.What is different as in question is nothing about table for 0.4 or 0.5 s.
Please could explain to me.Perhaps I lost something.
Thank you so much.
Are you looking at a final circuit at 0.4 seconds or a distribution circuit at 5 seconds. You need to be on the correct table. Re-read the question, it is a common mistake that lots of people make and the exam setters know this. Hope this helps.
@@learnelectrics4402 Hi Sir.
After your answer I understood.DISTRIBUTION this is a clue 😀
Thank you so much for your quick response and one again thank you for your effort to make all these lessons.
Best Regards.
Rob.
Glad to have helped. Dave.
Hi great video thanks!! But at 14.30 why do we assume 0.4 for a final circuit ?
It's the figure quoted in the Regs. If we can disconnect a final circuit in less than 0.4 seconds then a normal healthy adult should survive the electric shock. In reality, most modern MCBs can disconnect in 0.1 seconds.
@@learnelectrics4402 thanks for the reply, what about 5s disconnection times for circuits exceeding the rated currents for 0.4? Do we not need to know the circuit specifics to work out the disconnection time?
Again they are industry recognised figures in the Regs. The 18th Exam is based on these figures and they give you all the info you need in the exam to be able to answer the question. Take a look at this video Zs Where do the figures come from.
czcams.com/video/IjpJK1eJLzw/video.html
It's becoming a bit complicated, let me check it with you, master🙂, First we calculate the load current in design process, then we select the correct protective device or simply MCB for it. Then the next process is choosing the correct cable size, we use a table of on site guide to choose the correct cable size with attention to cable installing methods. Now we have the correct size of phase and neutral, but we need to calculate the csa of cpc. For this holy purpose we use adiabatic equations or simply use the third method with the table. Then we use guidance note 3 to calculate R1+R2 to calculate the maximum cable size based on Zs,max . Also we calculate maximum length based on permitted voltage drop. the minimum of these two lengths would be the maximum length. Is my understanding correct?
Sounds good. It might seem a long process but taking one step at a time in the correct order is the way to go. Dave.
👍👍👍
Thanks Chris, appreciated.
At 20:47 of the the vid, 60898 32 B is 650amp fault current Bs7671 Fig3A4 gives 160A fault current for 0.1-5sec??
where did you get the conductor 70 c until 0.5 seconds please??
Andy, that is what the equation has just worked out for you. We entered data relevant to thermoplastic cable and the equation tells us that at 650 amps it will take half a second to reach 70C. We know the breaker will operate in less than that so the cable will not overheat.
The 70C?. Regs book. Page 522 Table of Tables. look for a table that says
--- Maximum operating temperatures for types of cable insulation ---
Go to that page and you will see the max Temps for different cables.
This table also comes up as an exam question.
Hope this helps. Dave.
@@learnelectrics4402 Yes I see but can I ask where do you get the 650A fault current for the 32A type B 60898? Fig3A4 gives 160A fault current for 0.1-5sec?? Sorry 5:59 video time.Were all the fault currents in the slides examples ?
160 amps minimum. In this case we just chose a fault current of 650 amps which is a typical domestic fault current. We could jus as easily have substituted this with 500 amps or 800 amps. Anything above 160 amps for these examples. Not every house will have the same fault currents. Is this making sense.
@@learnelectrics4402 The Adiabatic Equations make sense, But Fig 3A4 page 370 regs says 32A type B 60898 = 160 fault current ?
That 160 amps is the current to cause it to trip effectively but it can just as easily be 600 amps or 800 amps. Anything above 160.
The 160 amps is a minimum not a maximum. We are talking about "excessive" fault currents causing the earth cable to heat up before the breaker or fuse trips.
You haven’t shown or explained how to obtain the fault currents, this is key for these calculations & different for each formula.
The fault currents are also different for poly phase circuits.
For anyone not aware earth fault current is worked by dividing your nominal voltage to earth by the Zs of the circuit.
For poly phase short circuit current you divide the line - line voltage by Zn of entire circuit, or line to earth voltage divided by Zn x square root of three.
For single phase it’s nominal voltage divided by Zn only.
Thanks for watching.
@@learnelectrics4402 is the above correct? When using the formula for t on a 3 phase circuit is the fault current 400/R1+Rn? Thanks.
in example no.1, i keep getting the answer 0.5008284, this is the same as 0.5. what am i doing wrong?
0.5 is correct. There's nothing wrong with your answer, just round up or down to avoid too many decimal places.
Where do the fault current values come from ?
The fault currents in the questions are plucked out of the air just to make a question. They are, however, values that you might expect to see. Thanks for watching, keep learning. Dave.
👍🏽
Thank you Jason. Appreciated. Dave.
Earth conductor =16,
Size of conductor =2.5
Thanks for watching, appreciated.
The formula for t is in page 98 not 92. & there are no tables on 93! What are you on about? You must have the northerners wiring regulations, softy southern wnker regs are different.
If you are using the BROWN book then of course you will get different page numbers. This video quite clearly says it relates to the BLUE book. Go to LearnElectrics.com and put Amendment 2 into the search box and you will get all the Northern videos for the BROWN book, with questions and answers. Hope this helps, Dave.