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. ruclips.net/channel/UCYaJQnpO4XAp0yCgqzMkmfA
you probably dont give a damn but does anyone know a method to get back into an instagram account?? I somehow forgot my login password. I appreciate any tips you can give me
@Dante Ameer thanks so much for your reply. I found the site on google and I'm in the hacking process now. Takes a while so I will get back to you later with my results.
I can't begin to tell you how grateful I am for these videos although I retrained 7 years ago as a older student know 53 they give me a much better understanding I am now confident enough to help some of the younger apprentices with issues or just show them your videos keep them coming matey 👍
Thanks Mark, brilliant feedback, makes our day. 53? Still got loads of life in you yet and yes, it is good to pass on knowledge to the younger electricians. Thanks again. Dave
@@learnelectrics4402 hi dave 👋today is Christmas day "so I'll bid you merry Christmas 🎅 "and a big thanks for your teaching videos " I've been in the building trade for nearly 40 years now? As a bricklayer ☠👻spent most of my time on sites 'but went self employed in 2000 ' I've learnt a little bit about electrics 'wired up a few sockets now and again? And normally had to get electrician to check it over ' 🤪but recently I came across your videos " and got interested in expanding my knowledge of electrics 'I've watched other videos of similar advice "but found yours the one that struck me the most ' its not elaborate or highly glifick "but some how it works for me?? Think it comes down to how someone can get a difficult scenario across ! I find your instruction easy to understand 😃I'm going to follow you deeper into this "and get more equated with this "wish you could of taught me years ago "🙈all the best my friend "have a good New-year 👍
You have saved the day once again mate. I was sweating over this theory on a training course and its a relief to now understand it. Thanks to your excellent communication skills. 👏
If i am not wrong, there is not even a channel like yours... It is helping me... Thank you for everything and may ALLAH(GOD) bless you... From Mozambique
Thanks Mohammed. Thanks for watching and I'm so glad the channel is helping. I have some very fond memories of my time in Africa. Beautiful country, amazing skies. Dave.
Thankyou described it in a easy to understand, in the past I have looked at books on electrics,and they made it sound so complicated, but with your explanation I got it straight away,once again thanks
Thanks a lot dude. Just about to complete my engineering apprenticeship and now wish to base my career from an electrical bias. These theories aren't so intimidating when broken down and structured as well as you have demonstrated here 👍👍 will be sure to watch more. Thanks again
Master your videos are superb. I'm not yet an electrical engineering student but I'm about to be, watching your videos is pretty good for a lost sheep. After tons of research this piece just made my day.
Thank you so much, your explanation is perfect. In class they gave us handouts stating the steps of finding the cable size with these Ib, In, Iz symbols, never understood the meaning of these symbols, and now that i viewed this well explained video everything became clear
Fantastic explanation really informative. Completed a domestic installers course with a well known training centre and this is great to keep my knowledge from rusting up. Great stuff and easier to understand.
Hi great video but ai am confused you say at 8:32 there are 2 entries for 32a when there are 9, & 6 of them meet the installation method 100.. am I missing something obvious this is a little old not as page 82 now.. your help here would be most appreciated.. Thanks
2 entries for that type of protective device. The OSG covers several devices, breakers, fuses etc. I will be re-vamping this video, this week to accord with the brown OSG and will take your comments into account for a better explanation.
Hi Dave, I recently completed and passed an excellent domestic electrician course at EC4U in Ditchling. Your video series is a superb “old-school” reinforcement of these key principles and in some cases has offered an even clearer explanation, or at least a different perspective on the same learning points. Being an older learner who has recently changed to the electrician career, this series has been brilliant. Thank you!
Thank you Mike for the very positive feedback. Our aim is to produce videos that tackle just one subject each week and they are based on all the questions and difficulties that electricians and learners have had over the years during the time that we ourselves have been working on the tools and as assessors and instructors. There are many more to come yet, keep watching and thanks again. Dave.
@@MS-Patriot2 does the domestic electrician couse fit your purpose, such as capable for you to do the minor electrical work ? Any comment to this course?
Nothing should change. Install conductors with sizes as if they were in a TN-C-S system. They still have to take overload currents. Its just that your measured ZS will be all over the place. Dave.
Thanks for all your vids, they’re a massively help for improvers like me working towards getting qualified! I have a quick question, not sure if you’ll see this: If a dedicated oven circuit has a 40A breaker on it, why are there sometimes cables on that circuit that are rated for less than 40A? Is it the case that if the smaller cable is on the load side of the fused isolator switch, then you’d take the rating factor of that fused isolator switch as your “In” in the formula? Apologies if that’s obvious, I’ve just got a little confused and can’t find a clear answer elsewhere. Thanks again!
Take a look at the link below about Zs. A single 13A socket on a cooker switch plate is acceptable. It is assumed that if something goes wrong with whatever is in the socket then it will go wrong big style and enough current will flow to trip the 40A breaker. Hope this helps, if you search for Zs on the LearnElectrics YT channel you will find over twenty videos about this subject. Good luck, its a great trade to be in. Dave. ruclips.net/video/HbWhzt4r644/видео.html
Thank you for explaining this better than the big book! It's quite a simple theory, made incredibly confusing and baffling by the wording in BS7671. I don't know why they don't just print the formula in BS7671 instead of the 3 bullet points.
Im training as an electrician and your videos are very helpful, i can see this calculation wiuld be good for an individual radial or ring say for a shower or cooker, how would this woek with lighting circit or socket? I am starting my NVQ level 2 in september so sorry if this is a basic question.
There are standard sizes that we usually use for each type of circuit. The important thing is that the cable capacity MUST be equal to or greater than the fuse/breaker rating. I'll be doing a video on this soon. Stick with it, its a good trade to be in.
These are taken from the OSG (blue version). The brown version of the OSG will have different page numbers. Perhaps I should do another video for the brown books. Dave.
Well, you've found them now. Stick with it, it really is a good trade to be in. It's taken me around the world several times, worked in some fantastic places. Dave.
Thank you for the video. What is the difference between "rating" and load" in the table on page 64. Is this assuming diversity of 80% e.g. the shower is off for at least 12 minutes in every hour of use?
Load is the amount of current you put through a fuse. A kettle might put a load of 13A on the circuit. A table lamp might have a load of half an amp The rating of the breaker in the consumer unit might be 20A or 32A if a ring Hope this helps. Dave.
Seems easy enough as you explained in great detail, I am looking to install panel heaters in my flat, can these just be added to ring main or need a separate circuit, if a separate circuit then can I do myself to save money?
Consult the heater manufacturer's instructions. Some say that they can be plugged in, coming with a fitted plug is usually a good clue. Other heaters are recommended on their own circuit. Adding a new circuit assumes that you are competent and can notify the work to LABC afterwards. Only you will know if you can do this. If you are unsure, I would suggest using a REGISTERED electrician, but ask to look at his registration card (NAPIT, NICEIC etc) before giving him/her the job and before handing over any money. Tell them you want a Building Control certificate when the job is finished. And get three written quotes before making a decision.
Hi Dave, When you mention @3.23 "larger cable " "paying for extra copper that you do not need". Is this the only reason? Will a larger cable not affect anything else, only cost?
A larger cable will carry more current more easily and will not heat up at the same rate as smaller cable sizes, We can always install bigger cable and know that we will not have a problem, except perhaps with getting the cable into the terminal holes, 10mm shower cable will work for a lighting circuit but no way will it fit in the switch (an extreme example, sorry). So yes, that little section comes down to cost. Good question and thanks for watching. Dave.
@@learnelectrics4402 I believe a larger cable would actually be required in the *particular case* when the on-site installation runs for more than the calculated maximum cable length, right?
First of all I want to say thanks a lot for all Your excellent video. I would like to ask about 3 phase circuit how we can find out about Ib and cable size .
Thanks for watching, glad you found it useful. We will be posting a video soon on 3 phase cable sizes, lots of people asking for information. Good request. Dave.
@@learnelectrics4402apologies, not 32A I mean 30.43A. I was referring to the second you highlighted in the table. There’s a column that says “Load (A)” i wondered if that was the maximum load permitted, and if so, that is lower than the design current.
Thanks for your prompt reply. In your video, you said you choose 6mm cable is based on method 100 in 2nd row, but 3rd row also has method 100. So may I ask to explain more by based which Wiring Reg. , we should choose 6mm but not 10 mm cable? I have confusion to choose one between them. Thanks.
You need to look at all the information on each line. With 6mm cable the maximum cable length is 63 metres which is more than long enough for most domestic dwellings and this matches up with the rest of the information on the slide. If you install 10mm you can take the length to 105 metres. Hope this helps.
A 6mm cable (6 sq mm) is fine when the insulation stays the same and the shower remains at 7000 W. A 6mm cable is near the limit. The user may well fit a 8000 W shower when a 7000 W shower becomes unavailable on replacement by a plumber. Or the insulation is upgraded. On balance I would install a 10 mm (10 SQ mm) cable.
We have to show the method adopted by the Regs, which is the nearest size suitable. In this case 6mm is just big enough. I agree that in practice you may want to install 10mm cable. Thanks for the nice comments.
Thanks for your prompt reply. In your video, you said you choose 6mm cable is based on method 100 in 2nd row, but 3rd row also has method 100. So may I ask to explain more by based which Wiring Reg. , we should choose 6mm but not 10 mm cable? I have confusion to choose one between them. Thanks.
Love yr video's can you please make a video on two way lighting circuit and fault finding if the wire's mixed up on celling rose and the switch thankyou
We have lots of videos on all aspects of lighting on our website. Go to LearnElectrics.com and put lighting into the search box and you will get a list of all the videos about lighting and direct links to the videos. Hope this helps, thanks for watching. Have a look at lighting Differences on this link ruclips.net/video/NEjCXO_ZC5c/видео.html
Hi Thanks for good clips . I am a bit confused though When I calculate for 63 meter 6 mil cable the voltage drop will be 14 volts which is over the allowance voltage drop . example in this clip according to table 7.1 onsite guide (7.3*30.43*63)/1000=13.99voltage drop which is more than 11.5 volts allowance
Some of the pre-calculated tables take diversity, RCDs, and other factors into account. I will be revamping this video to the brown OSG later this week. Thanks for the input.
Thank you for the breakdown it always helps when it’s explained correctly. Please keep up the good work you have my full support. Regards Karamat Hussain
Yes Richard. Amazon is probably about your cheapest. The current 18th Edition is a blue book, BUT Amendment 2 is due to be issued very soon. Whether that is weeks or months we don't know. If you buy the blue OSG you may need to buy the new amendment 2 when that comes out. Current price for the On-site Guide is about £30 depending on what deals are on.
thank you so much for clear clips. can I ask you if we have 63 meter cable length and use voltage drop formula vd={(44/6)*63*32 }/1000 the result will come to 14.7 volts and because its greater than 5% allowance means 11.5 volts is it acceptable ?
Can you explain the digital scale on a multimeter for measuring resistance? The only thing I can find is a old vid from perkies talking about ohms scale?! Many thanks do you have an e mail I like to talk about the course I’m doing !
Fantastic video again thank you, if you were installing a domestic cooker circuit for a 16.5kw cooker and induction hob (very large i know) how would you go about that? Would you install a 16mm cable that would be able to handle the full maximum load of 67amps or with diversity included would say a 10mm cable would be sufficient? Installation method ref method c no insulation and 8 meters of cable for the circuit Sometimes these scenarios confuse me a little and i don’t feel 100% confident with selecting the correct size cable. Any help would be greatly appreciated thank you
Thank you for watching and the great comment. We have a video that will show you how to calculate diversity for your cooker. The example in the video is for a 7kW cooker, just change the necessary numbers. Cheers, Dave. To view the video, DIVERSITY and MAXIMUM DEMAND, click on the link below ruclips.net/video/TV2IZtmydm4/видео.html
Hi Dave, another excellent video, we all thank you for all you are doing. I'm confused about the choice of cable size. On the chart on page 72 I see many entries with a rating of 32A that fit with the 100 installation method, why did you say there is only one? Also, do you know where in the book we could find the installation methods? Again, thanks for what you are doing.
You will find installation methods begin on page 433 of the Wiring Regs book. If it is flat profile twin and earth we choose the nearest size cable equal to or greater than 32A which is 6mm. See Table 4D5 on page 456. Hope this helps. Dave.
Hey Dave just a quick question if the shower is taking 30amps on a 32 breaker but the cable rating is 34 so is that mean the shower is taking 34amps? Which will trip the breaker?
The cable can take up to 34 amps but the actual current in the cable depends on the load. A 1 amp bedroom lamp pulls the same current through a 10mm cable as it does for a 1mm cable - about 1 amp
@@learnelectrics4402alright thank you so if an appliance was taking 45amps and let’s say you wanted to use a 6mm cable what breaker size would you choose a 45 or 50?
No, as long as it is less than 32A load its ok. A 32A breaker will not trip at 32A, it will be many amps greater than that. 32A is its working current 7 days a week, 24 hours a day.
I have some questions, if I calculated the design current to be 102 A and I need to choose a circuit breaker, as you said that the circuit breaker needs to be bigger than the design current, can I choose 125A, 150 A, 200A circuit breaker? what is the difference? Is it appropriate to choose the 200A like the bigger the better? Just cut out the cost issues and focus on the safety of the system.
No, bigger is not safer. Ideally you need the same size or the next size up that doesn't exceed the design current. We want to fuse as close as we can to the design current for safety.
The Regs are for the UK only. But I used the same data when I worked in France as many devices are BS EN approved. I should check with a local electrician in the country of your choice before relying on them.
These are the recommended loadings in the On-Site Guide. Iz is the symbol chosen by the IET. We mere mortals get no say in it. Why do we use I for amps or current is another question that we are often asked. Thanks for watching. Dave.
@@learnelectrics4402 can use only 26A for 32A breaker is on site guide instruction 7:46 , it is exceed than 30.43A 7:15 of design current in your video.
I think it’s worth mentioning that when you’re calculating your design current, if it is a 3 phase system you would put root 3 at the bottom of the fraction and if you have a power factor you would put Cos(power factor) at the bottom of the fraction aswell
@@learnelectrics4402Thanks for the reply, can I clarify something in the video you linked? It states the equation Ib ≤ In ≤ Iz, however the summary text states that Iz must in fact be greater than In. Just wondering, as the formula implies that selecting a breaker rated the same as the CCC of the cable is fine. So would a 10amp breaker be fine for a cable that can only carry 10 amps, for example?
I’m confused, on page 72 for cable sizes you say there’s only one that matches the reference method 100, but there’s actually two? 32 amp 6mm and below it 32amp 10mm? Also is there another chart that goes higher than 40A on page 64 ?
The two 100 references are for different cable lengths - 63 metres and 105 metres. A longer run will need 10mm cable. Fuses/breakers above 40 amps look at pages 61/62/63 in the Wiring Regs. That's a good point, perhaps I should do a definitive list for all fuses/breakers and put it on the website. food for thought. Thanks. Dave.
@@learnelectrics4402 i mean 3 to 5 depending on load. What you suggest is simple but load can vary so i am still searching what is the rule of thumb for such factor. Ideally i would also not use factor of 3 to 5 but i have seen in some videos.
for mcb type b, 3-5 factor is considered for short circuit protection, but what is the factor for overload protection, should the breaker size should be 1.25 time max load current? if we see characterisitc, that is where thermal trip will occur but how much time will that trip regarding design. cable size current rating consider only overloading conditions but short circuit does not damage the cable i guess because that is where breaker trips. but the cable size should not have rating of 3-5 time for mcb type b breaker? i hope you understand what i mean`?
Really useful videos for someone learning the trade. With regards to choosing the cable size, I'm just a bit confused, could you also choose the 10/4 mm too seeing as it also allows 100 as the installation method?
Definitely not ok. Every shower should be on its own circuit. Putting three showers on one breaker will contravene the Wiring Regulations, contravene the Building Regulations, contravene the Electricity at Work Regulations and contravene the Health and Safety at Work Act. That's just for starters, you will also invalidate any trade insurance you have and any professional indemnity insurance and invalidate the buildings insurance.
This video is just about single phase 230 volt circuits Zeeshan. We are making a video for 3 phase cable sizes very soon. Thanks for watching and thanks for asking. Dave.
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.
ruclips.net/channel/UCYaJQnpO4XAp0yCgqzMkmfA
you probably dont give a damn but does anyone know a method to get back into an instagram account??
I somehow forgot my login password. I appreciate any tips you can give me
@Alejandro Lian Instablaster =)
@Dante Ameer thanks so much for your reply. I found the site on google and I'm in the hacking process now.
Takes a while so I will get back to you later with my results.
@Dante Ameer It worked and I now got access to my account again. Im so happy!
Thank you so much you saved my ass :D
@Alejandro Lian glad I could help =)
9 times out of 10, yt influencers give out incorrect information. This guy does NOT.. Excellent stuff sir . Sub from me
Thanks for the sub, really appreciated. Dave.
When you fully understand something it is easy to explain said Isacc Newton. Your explanation was simple and complete. Thanks
Thank you Chris. We really appreciate this feedback.
Dave
I can't begin to tell you how grateful I am for these videos although I retrained 7 years ago as a older student know 53 they give me a much better understanding I am now confident enough to help some of the younger apprentices with issues or just show them your videos keep them coming matey 👍
Thanks Mark, brilliant feedback, makes our day. 53? Still got loads of life in you yet and yes, it is good to pass on knowledge to the younger electricians. Thanks again. Dave
Mark, Your just a young man, Im 66 and still going strong so dont worry about age mate.
@@angelofranklin1 66 that's excellent I just noticed I put 53 don't know why because I'm 55 🤣 tell me I'm going be OK 🤣
Finally someone has explained the actual calculation of what we were trying to learn 👏
Thanks for the great comment. Lots more videos to come, including more calculations. Dave.
@@learnelectrics4402 hi dave 👋today is Christmas day "so I'll bid you merry Christmas 🎅 "and a big thanks for your teaching videos " I've been in the building trade for nearly 40 years now? As a bricklayer ☠👻spent most of my time on sites 'but went self employed in 2000 ' I've learnt a little bit about electrics 'wired up a few sockets now and again? And normally had to get electrician to check it over ' 🤪but recently I came across your videos " and got interested in expanding my knowledge of electrics 'I've watched other videos of similar advice "but found yours the one that struck me the most ' its not elaborate or highly glifick "but some how it works for me?? Think it comes down to how someone can get a difficult scenario across ! I find your instruction easy to understand 😃I'm going to follow you deeper into this "and get more equated with this "wish you could of taught me years ago "🙈all the best my friend "have a good New-year 👍
You have saved the day once again mate.
I was sweating over this theory on a training course and its a relief to now understand it. Thanks to your excellent communication skills. 👏
Glad we could help John, spread the word. Dave.
Yes, I completly agree. Easy to follow through.
If i am not wrong, there is not even a channel like yours...
It is helping me...
Thank you for everything and may ALLAH(GOD) bless you...
From Mozambique
Thanks Mohammed. Thanks for watching and I'm so glad the channel is helping. I have some very fond memories of my time in Africa. Beautiful country, amazing skies. Dave.
Thankyou described it in a easy to understand, in the past I have looked at books on electrics,and they made it sound so complicated, but with your explanation I got it straight away,once again thanks
Glad you liked it. Keep watching James. Thanks Dave.
Thanks a lot dude. Just about to complete my engineering apprenticeship and now wish to base my career from an electrical bias. These theories aren't so intimidating when broken down and structured as well as you have demonstrated here 👍👍 will be sure to watch more. Thanks again
Thanks for the feedback. There is access to over 200 videos on the website LearnElectrics.com Dave.
Thanks once again for well presented technical material in the subject of electrical calculations
Kindly keep them coming
Thanks
Thank you, I will, lots more to come. Thanks for watching. Dave.
i learnt more from you than from my 2 years at the college... keep the excellent work up
Thanks, will do Imran. That's fantastic feedback. Dave.
Master your videos are superb. I'm not yet an electrical engineering student but I'm about to be, watching your videos is pretty good for a lost sheep. After tons of research this piece just made my day.
Thanks Matthew, good luck with your studies. Thanks for watching and keep learning. Dave.
Excellent video. I learned a lot about choosing the correct wire size and fuse to be used.
Thanks. If the video helped then its done its job. Dave.
Thank you for this video, something what i thought id never get my head around made it very easy by watching this. once again thank you
Great to hear that Jess. If the video helped, its done its job. Dave.
Thank you so much, your explanation is perfect. In class they gave us handouts stating the steps of finding the cable size with these Ib, In, Iz symbols, never understood the meaning of these symbols, and now that i viewed this well explained video everything became clear
So glad that it helped. Tell the rest of your class mates about us, it makes it all worthwhile to keep making more videos. Dave.
Very easy to understand. Great video. Cheers
Glad it helped, thanks for watching.
Dear your explanation was so simple and it is delivering your experience. thanks ......
Thank you. Great feedback, appreciated. Dave.
Fantastic explanation really informative. Completed a domestic installers course with a well known training centre and this is great to keep my knowledge from rusting up. Great stuff and easier to understand.
Thanks Robert, really appreciate the good comments. Dave.
Great video, very well explained, clear and to the point. Thank you very much
Glad you enjoyed it, thanks for the support.
It's very important idea and concept about Electrical Engineering
Thanks for watching. Appreciated. Dave.
Wow! This is very informative, thanks for sharing it with us. It worth it and the best tutorial on the topic for me...dl
Glad it was useful.
@@learnelectrics4402I am here again
First video I see from your channel, amazing 👏. Thank you for your content sir.
Keep watching, lots more to come. Thanks for the comments. Dave.
Hi great video but ai am confused you say at 8:32 there are 2 entries for 32a when there are 9, & 6 of them meet the installation method 100.. am I missing something obvious this is a little old not as page 82 now.. your help here would be most appreciated.. Thanks
2 entries for that type of protective device. The OSG covers several devices, breakers, fuses etc. I will be re-vamping this video, this week to accord with the brown OSG and will take your comments into account for a better explanation.
Its great the way you simplify it by using that box method,really helpful.
Thanks Marc, appreciated comments. Dave.
Thanks Dave, your a Legend loving all of your video
Have a great Christmas & take care
Thanks Johnny, thanks for the support and have a great Xmas yourself. Dave.
Thank you so much for these valuable videos. Much appreciated 🙏
Glad you like them Aleko. Thanks for watching.
Hi Dave, I recently completed and passed an excellent domestic electrician course at EC4U in Ditchling. Your video series is a superb “old-school” reinforcement of these key principles and in some cases has offered an even clearer explanation, or at least a different perspective on the same learning points. Being an older learner who has recently changed to the electrician career, this series has been brilliant. Thank you!
Thank you Mike for the very positive feedback. Our aim is to produce videos that tackle just one subject each week and they are based on all the questions and difficulties that electricians and learners have had over the years during the time that we ourselves have been working on the tools and as assessors and instructors. There are many more to come yet, keep watching and thanks again. Dave.
Mike.
How about the Domestic Electrician course in EC4U? I also want to join it.
@@hingninwong yes, look them up on google. The website is easy to navigate. Good luck!
@@MS-Patriot2
does the domestic electrician couse fit your purpose, such as capable for you to do the minor electrical work ? Any comment to this course?
Fantastic video. What would change in the calculations if it was on a tt system. ?
Nothing should change. Install conductors with sizes as if they were in a TN-C-S system. They still have to take overload currents. Its just that your measured ZS will be all over the place. Dave.
Thanks for all your vids, they’re a massively help for improvers like me working towards getting qualified!
I have a quick question, not sure if you’ll see this:
If a dedicated oven circuit has a 40A breaker on it, why are there sometimes cables on that circuit that are rated for less than 40A? Is it the case that if the smaller cable is on the load side of the fused isolator switch, then you’d take the rating factor of that fused isolator switch as your “In” in the formula? Apologies if that’s obvious, I’ve just got a little confused and can’t find a clear answer elsewhere. Thanks again!
Take a look at the link below about Zs. A single 13A socket on a cooker switch plate is acceptable. It is assumed that if something goes wrong with whatever is in the socket then it will go wrong big style and enough current will flow to trip the 40A breaker. Hope this helps, if you search for Zs on the LearnElectrics YT channel you will find over twenty videos about this subject. Good luck, its a great trade to be in. Dave.
ruclips.net/video/HbWhzt4r644/видео.html
@@learnelectrics4402 Great stuff! Big props for replying to comments on vids that are years old, you're a massive help mate!
Very clear and easy to understand 👌
Great. That's exactly what we wanted to achieve. Thanks for watching. Dave.
Again very well explained. totally at ease with the way you explain things. very well done
Thanks Iqbal, great comments.
Thanks useful video. For the video of playing at 8:57, may I ask why not choose cable size of 10mm/4mm?
See above.
What a video, great at explaining and making things more clear and easier to understand! Bravo!
Thank you so much David. We really appreciate your positive comments. Dave.
A fantastic help. Thanks for the video!
You're welcome. Thanks for the support.
Thankyou really clear and easy to understand
Glad it was helpful Paul. Thanks for watching.
Thank you for explaining this better than the big book! It's quite a simple theory, made incredibly confusing and baffling by the wording in BS7671. I don't know why they don't just print the formula in BS7671 instead of the 3 bullet points.
Unfortunately we have no control over how the boffins lay out the book. Glad it helped. Dave.
Im training as an electrician and your videos are very helpful, i can see this calculation wiuld be good for an individual radial or ring say for a shower or cooker, how would this woek with lighting circit or socket? I am starting my NVQ level 2 in september so sorry if this is a basic question.
There are standard sizes that we usually use for each type of circuit. The important thing is that the cable capacity MUST be equal to or greater than the fuse/breaker rating. I'll be doing a video on this soon. Stick with it, its a good trade to be in.
hello Sir can I ask what book you use for the tables amd charts you used in the video? thank you in advance
These are taken from the OSG (blue version). The brown version of the OSG will have different page numbers. Perhaps I should do another video for the brown books. Dave.
I've done 3 years of evening college, honestly wish I'd come across your videos first.
Well, you've found them now. Stick with it, it really is a good trade to be in. It's taken me around the world several times, worked in some fantastic places. Dave.
Love the video, the way it is explained is brilliant, grateful of the videos👍
Thanks for the really positive feedback. We try our best. Lots more to follow. Dave.
Thank you for the video. What is the difference between "rating" and load" in the table on page 64. Is this assuming diversity of 80% e.g. the shower is off for at least 12 minutes in every hour of use?
Load is the amount of current you put through a fuse. A kettle might put a load of 13A on the circuit.
A table lamp might have a load of half an amp
The rating of the breaker in the consumer unit might be 20A or 32A if a ring
Hope this helps. Dave.
You made it simple for us...
Great feedback, appreciated. Dave.
I've been looking for this for a long time now. Well explained, thanks a lot.
Great Pabor, glad it was helpful. Lots more to come, check out our other 50 plus videos.
Thank you so much for the lesson. It was so easy for me to understand the way you explained.
Brilliant. That's exactly the feedback that we want. One video, one topic, made easy.
Lots more videos on the way. Dave.
you're the great explainer.
The great explainer, sounds like a song. Thanks for the great feedback, really appreciated. Thanks for watching. Dave.
Seems easy enough as you explained in great detail, I am looking to install panel heaters in my flat, can these just be added to ring main or need a separate circuit, if a separate circuit then can I do myself to save money?
Consult the heater manufacturer's instructions. Some say that they can be plugged in, coming with a fitted plug is usually a good clue. Other heaters are recommended on their own circuit.
Adding a new circuit assumes that you are competent and can notify the work to LABC afterwards. Only you will know if you can do this. If you are unsure, I would suggest using a REGISTERED electrician, but ask to look at his registration card (NAPIT, NICEIC etc) before giving him/her the job and before handing over any money. Tell them you want a Building Control certificate when the job is finished. And get three written quotes before making a decision.
@@learnelectrics4402 thanks, the heater doesn't come with a plug, needs wired in to a fused switch
❤fabulous video ❤
Glad you enjoyed it, appreciated.
another great video, i did miss the normal couple practise questions you put in though.
This is an older video, before I started doing that. Thanks for watching. Dave.
Hi Dave, When you mention @3.23 "larger cable " "paying for extra copper that you do not need". Is this the only reason? Will a larger cable not affect anything else, only cost?
A larger cable will carry more current more easily and will not heat up at the same rate as smaller cable sizes, We can always install bigger cable and know that we will not have a problem, except perhaps with getting the cable into the terminal holes, 10mm shower cable will work for a lighting circuit but no way will it fit in the switch (an extreme example, sorry). So yes, that little section comes down to cost. Good question and thanks for watching. Dave.
@@learnelectrics4402 I believe a larger cable would actually be required in the *particular case* when the on-site installation runs for more than the calculated maximum cable length, right?
Thankyou for your amazing video.
Glad you enjoyed it, thanks for watching.
You are very welcome. Thank you.
First of all I want to say thanks a lot for all
Your excellent video. I would like to ask about 3 phase circuit how we can find out about Ib and cable size .
Thanks for watching, glad you found it useful.
We will be posting a video soon on 3 phase cable sizes, lots of people asking for information. Good request. Dave.
Ref method 100 @ 8:00. The maximum load is 26A but our design current is 32A. Wouldn’t you use the one below?
Have another look at the video. Max load is almost 31 amps. Thanks for watching, Dave.
@@learnelectrics4402apologies, not 32A I mean 30.43A. I was referring to the second you highlighted in the table. There’s a column that says “Load (A)” i wondered if that was the maximum load permitted, and if so, that is lower than the design current.
Again an excellent video and thank for the great explanations.
Thank you. Glad that you are finding them useful. Dave.
Thanks for your prompt reply. In your video, you said you choose 6mm cable is based on method 100 in 2nd row, but 3rd row also has method 100. So may I ask to explain more by based which Wiring Reg. , we should choose 6mm but not 10 mm cable? I have confusion to choose one between them. Thanks.
You need to look at all the information on each line. With 6mm cable the maximum cable length is 63 metres which is more than long enough for most domestic dwellings and this matches up with the rest of the information on the slide. If you install 10mm you can take the length to 105 metres. Hope this helps.
@@learnelectrics4402
Yes, i got it that based on the length of cable for the house dwelling in this case. Thanks.
A 6mm cable (6 sq mm) is fine when the insulation stays the same and the shower remains at 7000 W. A 6mm cable is near the limit. The user may well fit a 8000 W shower when a 7000 W shower becomes unavailable on replacement by a plumber. Or the insulation is upgraded. On balance I would install a 10 mm (10 SQ mm) cable.
Hi Dave, very well explained thank you.
Thanks Angelo. Thanks for watching.
Thanks useful video. For the video of playing at 8:57, may I ask why not choose cable size of 10mm/4mm? (3rd row data)
We have to show the method adopted by the Regs, which is the nearest size suitable. In this case 6mm is just big enough. I agree that in practice you may want to install 10mm cable.
Thanks for the nice comments.
Thanks for your prompt reply. In your video, you said you choose 6mm cable is based on method 100 in 2nd row, but 3rd row also has method 100. So may I ask to explain more by based which Wiring Reg. , we should choose 6mm but not 10 mm cable? I have confusion to choose one between them. Thanks.
Love yr video's can you please make a video on two way lighting circuit and fault finding if the wire's mixed up on celling rose and the switch thankyou
We have lots of videos on all aspects of lighting on our website.
Go to LearnElectrics.com and put lighting into the search box and you will get a list of all the videos about lighting and direct links to the videos.
Hope this helps, thanks for watching.
Have a look at lighting Differences on this link
ruclips.net/video/NEjCXO_ZC5c/видео.html
Really really good video, thanks,
Glad you liked it. Thanks for watching. Dave.
Hi
Thanks for good clips . I am a bit confused though When I calculate for 63 meter 6 mil cable the voltage drop will be 14 volts which is over the allowance voltage drop . example in this clip according to table 7.1 onsite guide
(7.3*30.43*63)/1000=13.99voltage drop which is more than 11.5 volts allowance
Some of the pre-calculated tables take diversity, RCDs, and other factors into account. I will be revamping this video to the brown OSG later this week. Thanks for the input.
Thank you for the breakdown it always helps when it’s explained correctly. Please keep up the good work you have my full support. Regards Karamat Hussain
Thank you so much Karamat.
Great comments.
Dave.
Well done again...
Thank you, thanks for watching. Dave.
Love it! Thank you once more
Thanks for watching.
Thanks for sharing it with us
My pleasure Daniel. Thanks for watching.
I'm glad to get ur channel sir,10Q
Glad that you lie the channel Aeneas. Lots more good videos to come. Dave.
NOT , I'M NOT LIE U. I swear.
Thank you for your excellent video.
Great comments. Appreciated.
Can I purchase a copy of the on site book in paper version as I find it hard reading from screens
Yes Richard. Amazon is probably about your cheapest. The current 18th Edition is a blue book, BUT Amendment 2 is due to be issued very soon. Whether that is weeks or months we don't know. If you buy the blue OSG you may need to buy the new amendment 2 when that comes out. Current price for the On-site Guide is about £30 depending on what deals are on.
thank you so much for clear clips. can I ask you if we have 63 meter cable length and use voltage drop formula vd={(44/6)*63*32 }/1000 the result will come to 14.7 volts and because its greater than 5% allowance means 11.5 volts is it acceptable ?
A 14.7 volt drop isn't acceptable as its above the values in the Regs. You would need a bigger cable size. Dave.
Can you explain the digital scale on a multimeter for measuring resistance? The only thing I can find is a old vid from perkies talking about ohms scale?! Many thanks do you have an e mail I like to talk about the course I’m doing !
Thanks, I've put this on the to do list of videos. Dave.
Very good explanation
Nice comments, thank you. Dave.
Fantastic video again thank you, if you were installing a domestic cooker circuit for a 16.5kw cooker and induction hob (very large i know) how would you go about that?
Would you install a 16mm cable that would be able to handle the full maximum load of 67amps or with diversity included would say a 10mm cable would be sufficient?
Installation method ref method c no insulation and 8 meters of cable for the circuit
Sometimes these scenarios confuse me a little and i don’t feel 100% confident with selecting the correct size cable.
Any help would be greatly appreciated thank you
Thank you for watching and the great comment.
We have a video that will show you how to calculate diversity for your cooker.
The example in the video is for a 7kW cooker, just change the necessary numbers.
Cheers, Dave.
To view the video, DIVERSITY and MAXIMUM DEMAND, click on the link below
ruclips.net/video/TV2IZtmydm4/видео.html
@@learnelectrics4402 thank you very much your videos are extremely well presented and helpful keep up the great work
Thanks again. Happy to help. Dave.
Hi Dave, another excellent video, we all thank you for all you are doing. I'm confused about the choice of cable size. On the chart on page 72 I see many entries with a rating of 32A that fit with the 100 installation method, why did you say there is only one?
Also, do you know where in the book we could find the installation methods? Again, thanks for what you are doing.
You will find installation methods begin on page 433 of the Wiring Regs book.
If it is flat profile twin and earth we choose the nearest size cable equal to or greater than 32A which is 6mm. See Table 4D5 on page 456. Hope this helps. Dave.
Great information
Thanks for watching, appreciated.
Hey Dave just a quick question if the shower is taking 30amps on a 32 breaker but the cable rating is 34 so is that mean the shower is taking 34amps? Which will trip the breaker?
The cable can take up to 34 amps but the actual current in the cable depends on the load.
A 1 amp bedroom lamp pulls the same current through a 10mm cable as it does for a 1mm cable - about 1 amp
@@learnelectrics4402alright thank you so if an appliance was taking 45amps and let’s say you wanted to use a 6mm cable what breaker size would you choose a 45 or 50?
Onsite Guide video at 8:17, The Chart gives Breaker 32A with Load as 26A, but your Ib = 30.43, shouldn't you choose a bigger size Breaker?
No, as long as it is less than 32A load its ok. A 32A breaker will not trip at 32A, it will be many amps greater than that. 32A is its working current 7 days a week, 24 hours a day.
I have some questions, if I calculated the design current to be 102 A and I need to choose a circuit breaker, as you said that the circuit breaker needs to be bigger than the design current, can I choose 125A, 150 A, 200A circuit breaker? what is the difference? Is it appropriate to choose the 200A like the bigger the better? Just cut out the cost issues and focus on the safety of the system.
Thank you in advance for valuable lessons!
No, bigger is not safer. Ideally you need the same size or the next size up that doesn't exceed the design current. We want to fuse as close as we can to the design current for safety.
You are very welcome.
Is this an alternative method to using the 18th Edition BBB and using the design current x length of cable x mv/A/m x any grouping factors?
This video is about Ib In Iz. Condition factors are covered in a different video.
Thanks for watching. Dave.
Do these tables are valid only for UK or for the whole of Europe?
The Regs are for the UK only. But I used the same data when I worked in France as many devices are BS EN approved. I should check with a local electrician in the country of your choice before relying on them.
Great ,subscribed.
Thank you Stephen, much appreciated. Dave.
Just wow this video is gold
We're glad you like it. keep watching, more to follow. Dave
but will this table be inside the regs A32:2022 book ?
Not that exact table, that is my own table to show you ta simple relationship. Thanks for watching. Dave.
1) 7:46 Maximum load just 26A for 32A breaker, is this selection wrong ? 2) "Iz" cable rating, what is "z" stand for ?
These are the recommended loadings in the On-Site Guide. Iz is the symbol chosen by the IET. We mere mortals get no say in it.
Why do we use I for amps or current is another question that we are often asked.
Thanks for watching. Dave.
@@learnelectrics4402 can use only 26A for 32A breaker is on site guide instruction 7:46 , it is exceed than 30.43A 7:15 of design current in your video.
I think it’s worth mentioning that when you’re calculating your design current, if it is a 3 phase system you would put root 3 at the bottom of the fraction and if you have a power factor you would put Cos(power factor) at the bottom of the fraction aswell
Excellent information, thanks for contributing. Dave.
For Showers/Heaters shouldnt the RCD be 10mA in BS7671 18th instead of 30mA?
30mA is the recommended RCD. You can fit 10mA if you wish but you may find you get nuisance tripping,
This says In must be equal to or less than Iz - so in theory a length of 1.5mm flex is fine on a 16a MCB, given that they’re both rated for 16 amps?
Thanks for watching, appreciated. Have a look at this video. Dave.
ruclips.net/video/VtTUkUpQ-Rc/видео.html
@@learnelectrics4402Thanks for the reply, can I clarify something in the video you linked?
It states the equation Ib ≤ In ≤ Iz, however the summary text states that Iz must in fact be greater than In.
Just wondering, as the formula implies that selecting a breaker rated the same as the CCC of the cable is fine. So would a 10amp breaker be fine for a cable that can only carry 10 amps, for example?
Morning is possible to get on side guide?
Thank you for watching.
I’m confused, on page 72 for cable sizes you say there’s only one that matches the reference method 100, but there’s actually two? 32 amp 6mm and below it 32amp 10mm?
Also is there another chart that goes higher than 40A on page 64 ?
The two 100 references are for different cable lengths - 63 metres and 105 metres. A longer run will need 10mm cable. Fuses/breakers above 40 amps look at pages 61/62/63 in the Wiring Regs. That's a good point, perhaps I should do a definitive list for all fuses/breakers and put it on the website. food for thought. Thanks. Dave.
Hi Dave, could you do a similar video for three phase?
Definitely planned. Watch this space. Dave.
Boss explanation this is.
Thank you Jake. Appreciated. Dave.
sir some people use a factor 3x5 times load current to calculate breaker size?
I've not heard of that, a factor of 15 seems excessive.
@@learnelectrics4402 i mean 3 to 5 depending on load. What you suggest is simple but load can vary so i am still searching what is the rule of thumb for such factor. Ideally i would also not use factor of 3 to 5 but i have seen in some videos.
for mcb type b, 3-5 factor is considered for short circuit protection, but what is the factor for overload protection, should the breaker size should be 1.25 time max load current? if we see characterisitc, that is where thermal trip will occur but how much time will that trip regarding design. cable size current rating consider only overloading conditions but short circuit does not damage the cable i guess because that is where breaker trips. but the cable size should not have rating of 3-5 time for mcb type b breaker? i hope you understand what i mean`?
Really useful videos for someone learning the trade.
With regards to choosing the cable size, I'm just a bit confused, could you also choose the 10/4 mm too seeing as it also allows 100 as the installation method?
You can always go up in cable size, the difficulty might be in getting the conductors to fit in the accessory. Thanks for watching. Dave.
@@learnelectrics4402 Ah, I get it....thanks for answering
Hi - when you say IN must be the same or just above IB, how do we quantify or calculate 'just above' ?
If Ib is 9.9A then you want a 10A breaker. If you put a 40A breaker in circuit that is too big.
You sis not mention factors like Ca for ambient temperature Cg for grouping ?
That's part of another video. Thanks for watching. Dave.
But you selected 32a breaker, that's maximum allowable current is 26amps, is it correct?
A ring circuit will have a 32A breaker and 2.5 cable because there are two parallel cables. Good question, thanks for watching. Dave.
Thanks for help
Always happy to help Reza, it makes the world go round. Dave.
Anyone know the correct onsite guide table numbers for the new brown book ?
Use pages 3,4,5 of the OSG to find what you are looking for as the tables are spread throughout the book. thanks for watching. Dave.
Hi, how do you know which reference method to choose?
Have a look at our video on Reference Methods on the link below.
ruclips.net/video/nD8FFMPJfgM/видео.html
@@learnelectrics4402 thank you very much 🙏
What if 3 shower is installed for single 32amp circuit breaker? Will it be ok?or do we need to recalculate
Definitely not ok. Every shower should be on its own circuit. Putting three showers on one breaker will contravene the Wiring Regulations, contravene the Building Regulations, contravene the Electricity at Work Regulations and contravene the Health and Safety at Work Act. That's just for starters, you will also invalidate any trade insurance you have and any professional indemnity insurance and invalidate the buildings insurance.
Hi, why not using Power Factor in Current calculation?
These are the basic single phase calculations. We cover three phase power factor in another video.
Thanks for watching.
Dave.
Would a 40 amp circuit breaker be too much over the requirement for this shower installation ?
Generally 9kW shower is 40A, 7kW shower is 32A.
Thank you for fast response, very clear videos
You are very welcome Gerry. Lots more to come.
Can this formula work for three phase 440 V?
This video is just about single phase 230 volt circuits Zeeshan. We are making a video for 3 phase cable sizes very soon. Thanks for watching and thanks for asking. Dave.