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. th-cam.com/channels/YaJQnpO4XAp0yCgqzMkmfA.html
That's great Jimmy, thank you very much. Apprentices and new starters especially will learn a lot from these videos. We try to keep it as one topic, one video. We really appreciate what you are doing for us and thanks again. Dave.
i am dyslexic and for years i was looking for someone like you that knows how to explain electrics , can you do more videos regarding the test EAM exam thank you
Thank you Joanne. I'm really happy that our videos suit your learning style. There are lots more videos being planned including the 18th Edition exam help every Thursday. Keep learning, its a good trade to be in. Good luck. Dave.
if you have a length of single core cable,like conduit wire,can you messure from each end or got use 2 wires ,for flow and return ,and can you cut a 1 meter length of wire ,and messure it ,if it is not in the guide tables,so make your own guide ,like if you had a strange size cable ,or not solid cable ,like car wiring ,soft flexi cables ,love these vids,you make it interesting and fun ,jump in the back of the van with the megger ,do experiments,also can you do ir test on bare cables,check for ok,to use ,on off cuts,dead testing ,did once have roll new cable ,and circuit keep tripping rcd,turns out the cable was faulty ,short inside ,had rewire new cable and was good then ,but never seen new bad cables before ,caught me out
Yes, you can make your own tables for "strange" sizes. Use the tables in Guidance Note 3 Appendix B and you will be able to work out sizes like 1.25mm, 8mm and so on. Some sparkies will continuity test and IR test a new roll. There is always a little bit of cable to get to on the inside of the cardboard roll. And yes, I once lost a whole days work for a damaged cable just 5 metres from the end of a 90 metre run. Thanks for watching. Dave.
Is there a formula for measuring the lenght of a ring circuit using R1 & R2 and dividing by the resistifity of the cable...I was thing make it into one big radial from the fuse board....would that work...or there is formula we can use
That's an easy one Dennis. I'm assuming standard UK 32A Socket Ring in Twin and Earth 2.5 Phase/Neutral and 1.5 Earth. You must use R1+R2 not Zs. *** Length of circuit cables is R1+R2 multiplied by 205 *** This will give you the length to within a metre. Good question, you keep testing me. Perhaps I will do a video on this in the future. Keep watching mate and spread the word. Dave.
Hi Jimmy, there are no tables for this in BS7671 that's why the video mentions Table B1 in GN3 - Guidance Note 3 Inspection and Testing. Hope this helps.
I am going over your videos again Dave, as they are so good and my memory and retention is so bad. I have just noticed an error in your slides at 2'12" and wonder if anyone else has picked up on it? The picture depicts 2.5mm2 T&E as Class 2 when it only becomes that above 2.5mm2 and in reality is Class 1 solid core copper conductor. Nit picking but thought I would mention it. I am still a Huge fan of your work nonetheless.
Thanks Olly. The picture was only used as an example to show that the T/E sheath contained different size conductors. You guys are too good for me. Keep watching. Dave.
Is it the same for a ring circuit because the cable is 2.5mm and got two legs to the ring say you got a reading of 0.34 ohms for r1+r2 still the same maths to work out the length
Yes, because you are removing the cables from the CU so they become one length of copper for resistance test. Then you can apply the maths as per the video to determine the actual length . Thanks for watching.
So basically say I had a ring circuit that’s 50m long into a b32 So I do my ring continuity test on it and I get a reading of L-L 0.14 N-N 0.14 Cpc-Cpc 0.23 R1+R2 0.09 Does that mean the to work out length of cable it would be (0.09 x 1000)/19.51 = 4.61m for the whole circuit or would that be for each cable so overall length of cable would be 4.61x2 Because when doing the calculations the cable seems very short for the overall length of the run on the circuit
I know this is old but, how do they get 19.51mΩ in the onsite guide? I tried using 1.77x 10e-8 (@ 20°) for both the radius of 2.5mm (r=1.784) and 1.5mm (r=1.382) in my calculations. eg for 2.5mm² ; 1.77x10e-8 x 1÷π(1.784x10e-3)²
Just use table B1 in Guidance Note 3 . 2.5 plus 1.5 as in twin and earth is just the milliohms for 2.5 added to the milliohms for 1.5. Hope this helps.
Probably wont answer this question but could u help me out with this question: Find the csa of a single copper cable 500m long, which carries a current of 2.5 amperes and has a volt drop of 3.58 volts. Take the resistivity of copper to be 1.72 x 10-8 ohm/metre.
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.
th-cam.com/channels/YaJQnpO4XAp0yCgqzMkmfA.html
Calculating a cable's length by measuring it's resistance - that's some electrician magic right there. Thank you very much Dave.
The black art Orestis. Thanks for watching, appreciated. Dave.
The value of these videos cannot be underestimated,
Fantastic feedback. Thank you. Dave.
I will recommend your site to the apprentices and anyone who is learning electrics
That's great Jimmy, thank you very much. Apprentices and new starters especially will learn a lot from these videos. We try to keep it as one topic, one video. We really appreciate what you are doing for us and thanks again. Dave.
I am learning quite a lot. One of the best youtube electrician course. please keep producing more videos.
That's the plan Abreham. I will keep making videos if you keep watching. Thanks for your support. Dave.
Thank you for an understandable and excellent presentation. Well done
Thank you for the positive comment. Dave
i am dyslexic and for years i was looking for someone like you that knows how to explain electrics , can you do more videos regarding the test EAM exam thank you
Thank you Joanne. I'm really happy that our videos suit your learning style. There are lots more videos being planned including the 18th Edition exam help every Thursday.
Keep learning, its a good trade to be in. Good luck. Dave.
Yes I'm dyslexic too, learn electrics and John ward have been really helpful..
Hi you are very good teaching I never ever seen please do more video to more learn thank you
Lots more videos are coming. Thank you. 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 helpful Daniel, thanks for the support.
Really appreciate your videos. Thank you.
Thanks so much for the comments and thanks for watching. Dave.
Very useful
Much appreciated reply.
if you have a length of single core cable,like conduit wire,can you messure from each end or got use 2 wires ,for flow and return ,and can you cut a 1 meter length of wire ,and messure it ,if it is not in the guide tables,so make your own guide ,like if you had a strange size cable ,or not solid cable ,like car wiring ,soft flexi cables ,love these vids,you make it interesting and fun ,jump in the back of the van with the megger ,do experiments,also can you do ir test on bare cables,check for ok,to use ,on off cuts,dead testing ,did once have roll new cable ,and circuit keep tripping rcd,turns out the cable was faulty ,short inside ,had rewire new cable and was good then ,but never seen new bad cables before ,caught me out
Yes, you can make your own tables for "strange" sizes. Use the tables in Guidance Note 3 Appendix B and you will be able to work out sizes like 1.25mm, 8mm and so on. Some sparkies will continuity test and IR test a new roll. There is always a little bit of cable to get to on the inside of the cardboard roll. And yes, I once lost a whole days work for a damaged cable just 5 metres from the end of a 90 metre run. Thanks for watching. Dave.
Cheers mate 👍🏻 good vid.
Thanks for the feedback Robert, appreciated. Dave.
Fantastic explanation tha k you so much
Thanks for the positive comments Chris, appreciated. Dave.
Great❤❤❤
Happy to help, lots more to come.
Thanks alot
Happy to help, thanks for watching. Dave.
You're amazing.
Thanks, appreciated comments. Dave.
Please keep more videos 🤌🤌👌🙏🙏🙏🙏
Thanks for watching Kanta. Lots more videos to come.
Is there a formula for measuring the lenght of a ring circuit using R1 & R2 and dividing by the resistifity of the cable...I was thing make it into one big radial from the fuse board....would that work...or there is formula we can use
That's an easy one Dennis.
I'm assuming standard UK 32A Socket Ring in Twin and Earth 2.5 Phase/Neutral and 1.5 Earth. You must use R1+R2 not Zs.
*** Length of circuit cables is R1+R2 multiplied by 205 ***
This will give you the length to within a metre.
Good question, you keep testing me. Perhaps I will do a video on this in the future.
Keep watching mate and spread the word. Dave.
@@learnelectrics4402 lol...ur the mentor I have been search for
My pleasure.
Sir and how can we measure the length installed fire rated cable
You would need to know the milli-ohms per metre resistance for the cable and then use the formulas shown in the video. Thanks for your comments. Dave.
what table is it in BS7671 please?
Hi Jimmy, there are no tables for this in BS7671 that's why the video mentions Table B1 in GN3 - Guidance Note 3 Inspection and Testing. Hope this helps.
@@learnelectrics4402 Thanks,was just going through it then looking for it,lol
Happy to help JImmy, anytime.
I am going over your videos again Dave, as they are so good and my memory and retention is so bad. I have just noticed an error in your slides at 2'12" and wonder if anyone else has picked up on it? The picture depicts 2.5mm2 T&E as Class 2 when it only becomes that above 2.5mm2 and in reality is Class 1 solid core copper conductor. Nit picking but thought I would mention it. I am still a Huge fan of your work nonetheless.
Thanks Olly. The picture was only used as an example to show that the T/E sheath contained different size conductors. You guys are too good for me. Keep watching. Dave.
Is it the same for a ring circuit because the cable is 2.5mm and got two legs to the ring say you got a reading of 0.34 ohms for r1+r2 still the same maths to work out the length
Yes, because you are removing the cables from the CU so they become one length of copper for resistance test. Then you can apply the maths as per the video to determine the actual length .
Thanks for watching.
So basically say I had a ring circuit that’s 50m long into a b32
So I do my ring continuity test on it and I get a reading of
L-L 0.14
N-N 0.14
Cpc-Cpc 0.23
R1+R2 0.09
Does that mean the to work out length of cable it would be (0.09 x 1000)/19.51 = 4.61m for the whole circuit or would that be for each cable so overall length of cable would be 4.61x2
Because when doing the calculations the cable seems very short for the overall length of the run on the circuit
I know this is old but, how do they get 19.51mΩ in the onsite guide?
I tried using 1.77x 10e-8 (@ 20°) for both the radius of 2.5mm (r=1.784) and 1.5mm (r=1.382) in my calculations.
eg for 2.5mm² ; 1.77x10e-8 x 1÷π(1.784x10e-3)²
Just use table B1 in Guidance Note 3 . 2.5 plus 1.5 as in twin and earth is just the milliohms for 2.5 added to the milliohms for 1.5. Hope this helps.
Probably wont answer this question but could u help me out with this question:
Find the csa of a single copper cable 500m long, which carries a current of 2.5 amperes and has a volt drop of 3.58 volts. Take the resistivity of copper to be 1.72 x 10-8 ohm/metre.
Probably 16mm cable. Top of my head 15.3 thereabouts.
If its just one way, that might be 10mm cable. I was basing 16 on there and back. Do you have a formula.