INSULATION RESISTANCE TESTING AND TRACING
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- เผยแพร่เมื่อ 5 พ.ค. 2024
- Why do we test the insulation resistance of electrical circuits? After all, it’s just plastic, what can go wrong?
In this video we look at the reasons for testing electrical circuits, and then look at some established methods to carry out insulation resistance tests. How do we prepare for testing, what must we do to the circuits even before we begin.
And then we will look at the numbers involved. What is a good result, a pass; and what is a fail?
We will show you how to calculate parallel resistances to obtain an accurate value for the whole of the installation so that decisions can be made regarding the ongoing safety and reliability.
And if we do find problems on a circuit or within the installation, what can we do about it? So finally, we will introduce an excellent method for tracing insulation resistance faults in a circuit.
This video is number 106 on our TH-cam channel
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 TH-cam search bar.
Always work safely, electricity can be dangerous. If you are unsure, stop and seek advice.
This video is provided for guidance only. Every electrical situation is different, please check and ensure that you are applying this learning information to your own individual circumstances correctly and safely. If in doubt, stop and seek competent advice.
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A lot of people are learning a lot from you Dave. As always, these videos are an invaluable addition to the tool box. The time and effort you put in to assist others is above and beyond. Well done mate!
Thanks Gary, really appreciated. It's all about helping each other.
Dave.
@@learnelectrics4402 been great help...make is easy to understand
So interesting
What an amazing video broke the testing down into bite-size pieces and made it easy to understand thank you very much
Thanks for the comments, appreciated. I try and stick to one topic for each video. Thank you for watching. Dave.
Big thanks , not rushed and very well explained👍
Thanks Stuart, appreciated. Dave.
Great as usual Dave 👌 👏 👍
Thanks 👍 Your feedback is appreciated.
Just what I needed. Thankyou.
Glad it helped. Thanks for watching.
I love these videos, the 18th edition one has really helped. Thank you very much
Thanks Craig. The 14 part 18th Edition was well received. Have you been having at go at the latest on 18th Edition Questions. The last one before Xmas was published today. Good Luck. Dave.
@@learnelectrics4402 I will have a look at work tonight. I found the way you presented the 18th really easy to follow, and did much better on my mock exams. Thank you for the help.
Have a great Christmas and New year Sir 👍👍
Craig, this is the video with the new questions etc. I will create a new playlist over the holiday.
18th Edition Exam Question Help Session 3 on this link.
th-cam.com/video/AZ6wZRWxK_k/w-d-xo.html
Thanks for watching
Dave
You are doing a great job, thank you!
Thanks Sajad, great feedback. Dave.
Thanks so much Mr ward for such an educative lesson.
Thank you Godfrey, but its not Ward, This is LearnElectrics. Thanks for watching, Dave.
😂
Wow! This is video very informative and the best tutorial on the topic for me so far. I really appreciate it. Thanks for sharing it with us.
You're very welcome Daniel, thanks for watching.
Excellent description and methodology
Thank you Phillip and thanks for watching. Dave.
Following on from ring fault finding and ring circuit socket sequencing this is great 👍
Glad that you enjoyed it. Thanks for watching. Dave.
Excellent video again. Very helpful
Glad it was helpful, very much appreciated. Dave.
Another brilliant and informative video 👍
Glad you enjoyed it Robert. Thanks for watching, Dave.
I like your binary search method for locating the fault in a ring circuit. I‘ve been programming for the past 38 years (recently retired) and it’s a classic tool in computer science. I studied electricity up to pre-university but this teaches you almost no skills in house circuits. I’m finding your videos invaluable. Thanks for your work. Subscribed.
Thank you for the feedback, really appreciated. Thanks for watching. Dave.
@@learnelectrics4402Please what should be the duration of the test
Great video as usual.
Thanks again, and thank you for the feedback.
Hi Dave. The last time I waited in anticipation like this for the next episode of anything, was prison break many years ago. 🤣. Merry Xmas, God bless. 👍🏼
Thanks Kojak. I know what you mean. I'm trying my hardest and thanks for the support, really appreciated. Dave.
Really useful information. What a brilliant channel.
Glad you think so, lots more to come.
Fantastic video. Thank you
Glad you enjoyed it, thanks for watching. Dave.
Hi Dave!
Brilliant as usual!
Regards mg.
Many thanks Malachy. I really appreciate your comments. Dave.
Such great tips. Thank u.
Thanks for watching and supporting the channel. Lots more to come. Dave.
Great videos thank you very much for your efforts..
So nice of you to say so. Thanks for watching. Dave.
Brilliant video 👍
Thank you, appreciated comment. Dave.
I have never regreted subscribing to it...
Lots more to come Daniel.
Great video yet again. Any chance you can do a video on fault finding on ballasts and also led drivers please as common problem and hard to test due to small terminals on drivers/ballasts. Thanks
Certainly something to think about Alan. I've put it on the list and will definitely think about doing this one. Thanks for watching. Dave.
@@learnelectrics4402 a lk
Thank you for your efforts, this is high quality content. Your visual diagrams are also an excellent aid. Subscribed.
- also i’d like to ask, if testing between L+N and Earth, how would you locate the neutral for that circuit as shown on 14:21
If you have put the Line into the Neutral bar, it will not matter about identifying the exact neutral. They are all connected together, BUT, current will only flow down the correct neutral, the neutral that has the probe on it at the other end. Hope this helps.
@@learnelectrics4402 Many Thanks, looking forward to the next videos!
Great video. How do you test the single phase DOL starter motor . Do you disconnect coil conductors ?
For winding continuity disconnect the windings - after making a drawing or taking a photo. Thanks for the support. Dave.
Thanks for this. it keeps me ontop of my professsion. I passed my 2391-52 C & G after learning from this channel. Guys, continue subscribing to this educative channel please.
Quick question: What are the test a Solar PV Electrician should carry out of intallating a Solar PV system? Ze, IR etc ?
That would be a good topic for a video, I've put it on the list.. Great idea. Thanks for watching and keep spreading the word.
Great video
Thank you Dibbo, great support, really appreciated. Happy New Year. Dave.
Great video 📹 👍 👏 👌
Thank you for the positive comment and thanks for watching. Dave.
Thanks Dave
My pleasure David, I appreciate your support. Dave.
I’ve been chucked into testing and EICRs before I feel I’m ready. I’m pretty good I think but I like to be more cautious. But £ needs to come in.
The IR issues I seem to have always seems to be lighting.
Things like smokes, drivers, transformers, dimmers etc all seem to cause essentially misleading results… which you have just mentioned in the video… I’d be dead keen to understand why in more detail…
Make sure you are testing at the correct test voltages, see the video below.
Where possible, test on a naked circuit, all devices, lamps etc. removed.
replace dimmers with a normal switch for the test, remove transformers or use a L+N to E test.
th-cam.com/video/Kly-q-DShxA/w-d-xo.html
Thank you
You're welcome Prabhdeep, thank you.
Thanks man
You're welcome and thanks for watching. Dave.
Hi Dave. I love your videos. Very helpful. Im a bit confused over the reciprocal method in your video 2391 Assessment practise 1 and the reciprocal method in this video. They look different, one is using little r1 and the second one is using big R1. The use of rn is also confusing me between the two formulas. Please help. Many thanks, Craig
Craig, have a look at this video, it explains the differences.
th-cam.com/video/9DLgM8wM5xo/w-d-xo.html
Once you understand that little r is the resistance of a piece of copper of certain length and size and cannot change But big R is the effective resistance depending on if it is radial or ring and can be different depending on how connected.
Dave.
Thanks Dave
thank you
You're very welcome. Thanks for watching.
Brilliant video dave. Just a question. When joining line and neutral together and testing to earth which i see alot of people do nowdays to avoid having to dissconnect loads.
Only problem i see with this test is that it will not tell you if you have a line to neutral fault!! Would i be correct in saying that? So if you power up your relying on the fact that there is no line to neutral fault. If there was obviously MCB will trip as it is a short circuit
You are right. The book advises that we should only link L&N if there is a load that cannot be disconnected. And yes, it has become a common sight on site. This sort of short cut only saves perhaps 2 or 3 minutes, and folk spend much more than that texting their mates. The sequence of tests is there for a reason. Glad to know that you follow them. Thanks for your comments. Dave.
Hi Dave, wonderful content. So if i was carrying out an insulation test for sockets for example, would i just replace usb sockets with standard ones but can leave bulbs and fire alarm connected for as im only testing for sockets and vice versa? Thanks
Whichever MCB the circuits are on should have susceptible devices removed. Thanks for watching. Dave.
@@learnelectrics4402 thanks for clarifying Dave.
Can you IR test and entire board of its populated solely with rcbos? I’m guessing not but worth asking? Thanks
You can test the whole board. Remember that with current regs you should test the cables only at 500 volts first then with components etc at just 250 volts. Always make sure that manufacturer's instructions permit IR testing as some require precautions to avoid damage to electronic parts.
Thanks for the video. I've watched several videos on this topic and understand the basics. I realise that pushing 500V through L and N in connected loads etc could cause damage. What I don't understand is why if we test separately with 500V L to E and N to E and we get >200MOhms for both does that not suggest that L to N is ok?
Good question and JUST FOR YOU, I've put a short post on the LearnElectrics website explaining this. Log in to LearnElectrics dot com and there is a search box on the right hand side, half way down.
Type in P114 in the search box and it will take you directly to the post about why we test all three conductor permutations. Hope this helps. and please leave a comment here on this TH-cam video if it does. It may help others.
Thanks for the support. Happy to help. Dave
Why would it? L and N could be touching each other but not via E, no?
Pl show the video for 3 phase system.most od people are working in industry.make short one .one subject per video
Thanks for watching, appreciated.
Hi Dave,
When using the reciprocal method, if there was 6 circuits, would 1 to 5 be added resistances as per the example and the 6th circuit would be the RN. Is this correct.
Kind regards
Craig
Just keep making reciprocals Craig. The Rn means ANY NUMBER of Reciprocals.. You can have 4, 16, 200 its up to you. Just keep dividing into one and add them all up at the end. Hope this helps. Dave.
@@learnelectrics4402 Thanks Dave that's great
You're welcome Craig. Keep learning, it's a good trade.
@@learnelectrics4402 it certainly is, I work in industrial on the docks with the big cranes. But I also did a full apprenticeship, but got made redundant 1 month before my AM2.
I have a great shift pattern that can allow me to further learn. I was thinking domestic installer route just to tide me over on my days off and go for AM2. What do you think Dave ?
Hello Dave, When the insulation resistance for one circuit is 1 Mega ohm , it will pass. But, of course the parallel resistance for whole installation would be less than one and a fail. So considering the amount 1M ohm in the standard as a pass looks weird.
I did a quick look at BS7671 and on site guide, The 1M ohm for every circuit was in both of them. But I couldn't see and find the 2M ohm for overall system. Do you remember the source?
I do yes. Electricians Guide to the Building Regulations. Section 6.3.6 should find it. Thanks for watching, thanks for supporting the channel, appreciated. Dave.
Yes, I agree it looks odd. But it does say, "below 2Mohm should be investigated".
Dave.
If the mft gives a reading more then the reader can count, how to you do the parallel resistance calculation as you don't have the actual amount? It will just say something like above 200 M ohms. BTW that you, your videos helped me pass my 18th edition
Haider, don't worry about that. As long as each circuit is over 2M you are ok. If you have say 10 circuits and all are above 200M, then the parallel will be 20M. And great news on your 18th exam. keep learning, its a good trade to be in.
what other things can cause low resistance readings? can damp, moisture, loose connection and corrosion in a socket for example cause a low resistance reading on the whole circuit? Also if your lighting circuit has been wired with junction box in ceiling somewhere, thus meaning only Switch Line, Neutral and CPC at light fitting,,,, you cannot split anything to test IR like this can you?
There are so many variables, this is where experience comes into its own. Brilliant feedback, Thanks for watching, appreciated. Dave.
@@learnelectrics4402 Only for example? maybe you have come across this yourself?
sir just asking..what is the normal and minimum insulation level for 440V,220V and 110V system?
hoping for your answer..thank u
Most 220/400 volt cables have at least 600V insulation, a lot use 1000V. If you use approved electrical wholesalers they will tell you what the rating is for the cables they sell.
If required insulation for 1 circuit is more than 1 Mohm , adding 2 such circuits will make overall insulation resistance 0.5 M ohm making the insulation test fail ? Can you please elaborate on this. thank you.
Kalum, at the consumer unit all the individual circuits are in parallel to each other. parallel circuits always have a combined resistance value that is smaller than the smallest individual circuit. Hope this helps.
👍👍
Thank you Mike. Appreciate the thumbs up.
Please what should be the test duration
Your test meter will set the duration automatically and turn the voltage off at the end of the test.
Hello Dear, timer 10:43 should + not equal thanks.
Yes, good that you worked it out, thanks. Dave.
What I don’t understand is on an insulation test you expect a high ohm reading, but on a continuity test on the same circuit you’d expect a low/within the length limit reading.
Continuity is testing the copper conductor. Insulation tests are checking the pvc insulation. Hope this helps. Dave.
@@learnelectrics4402 Thanks Dave, But you’re still testing the copper conductors on the insulation test. I can’t understand how it works out such a high ohm reading on insulation resistance.
@@Jim804you're testing how much leakage current is produced by the test, not how much current flows in the conductors.
LE also has a video explaining that the IR test produces a 'charge' in each conductor, which the meter then measures, although I don't quite understand that one!
🙏🙏
Thank you, appreciated.Lots more to come. Dave.
Why is the test done at 500V DC and not 500VAC ?
Something the boffins decided. I've never questioned it because all the meters are set to 500V DC anyway. Thanks for watching. Dave
Dont forget there could be an amplifier in the loft
Exactly, tracing circuits is an important part of our job. Thanks for watching. Dave.
🤓
Thanks for watching, appreciated. Dave.
Thanks Dave
Thanks for watching. Dave.