Do you Know Which Conductors Need to be Connected During the Insulation Resistance Test?
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- เผยแพร่เมื่อ 9 มิ.ย. 2024
- In this video we look at the conductors that must be in place and connected before you can correctly carryout the third dead test insulation resistance. I use both a test rig and BS 7671 On-Site Guide to demonstrate how this dead test needs to be carried out to conform with the Wiring Regulations.
Do you link live conductors (line and neutral) together and test them to the protective conductor? The 2 videos links below show you 2 different techniques for linking live conductors together during the insulation resistant test.
🔵 Insulation Resistance Test (Includes Line and Neutral Together to Earth and Between Live Conductors) • Insulation Resistance ...
🔵 Combined Insulation Resistance Test Line and Neutral Together to Earth & Between Live Conductors • Combined Insulation Re...
🕐 Time Stamps - Cut to the action 🕕
00:00 - Insulation resistance test
00:25 - Remove all loads
00:43 - Some conductors are missing
01:05 - Test rig
01:23 - Disconnect SPD's
01:33 - RCBO's and an AFDD
01:47 - Electronics
02:37 - Combined neutral and earth
02:42 - Sheath of the supply cable
02:58 - MET
03:35 - On-Site Guide
04:06 - Test sequence
04:37 - Continuity method 1
05:06 - Continuity method 2
05:24 - Stage 1 of the continuity of a ring final circuit
05:35 - Stage 2 of the continuity of a ring final circuit
05:45 - Stage 3 of the continuity of a ring final circuit
05:58 - Insulation resistance test
06:38 - Covers should be on
07:28 - Linking live conductors together to earth
08:11 - Must be connect to the source earth and protective bonding
08:35 - Carrying out the insulation resistance test
Videos are training aids for City and Guilds (C and G) and EAL courses Level 1, 2, 3 plus AM2, AM2S and AM2E.
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it's great to see the relation of practical and literature to back it up. Cheers Gazza
Thanks for watching 👍🏻
Excellent video Gaz, it's helpful as always.👍🏼 You explain these procedures with great detail & passion. Thank you for taking the time.😊
Thanks for the great comment and taking the time to watch. Gaz 👍🏻
Thanks Gary and your videos have always my helper.
Keep up the great work.
Thanks
Experienced that recently, cpc connected got under 1 M ohm disconnected 200 M ohm wasn’t tripping the RCD though. Great video 👍
The text in the Onsite Guide is very subjective ,'Test between the live conductors (line and neutral) and the circuit protective conductors at the distribution board Figure 10.3.3(iii) illustrates neutral to earth only.' My interpretation is that it means testing between line and cpc , then between neutral and cpc . By stating that the illustration shows neutral to earth ONLY then it certainly suggests that there is a line to earth test that is not illustrated. If you read on to the Three Phase test, then it specifically describes all live conductors 'together' tested to earth. No sign of the word ‘together' with the single phase test. Another puzzler, GN3 states that for a new installation then an insulation resistance value of 20 MΩ and not 2MΩ should be investigated. Still not sure if this is a misprint as I can find absolutely no reference to this anywhere else .
Makes me twitch every time you touch copper! I do eicr's exclusively and teach everyone I work with to treat all parts of an installation that could potentially be live, as live, regardless as to whether they've checked or it not. If you treat all potentially live components as live you can never get a shock. Better safe than dead! It's not often I get the chance to work on a board with the main switch off!
"Neutral" can the devil in disguise if full care isn't excercised. In a mares nest of wiring found in some consumer units, it could be easy to remove the live conductor and its associated neutral but accidentally identify and remove the wrong neutral. That removed neutral could then become live when someone activates the circuit associated with that neutral. The borrowed neutral scenario springs to mind here.
Another good video. Installations are changing as well as the protective devices. Wish this content was available when I first came out my time
Thanks for the great comment and watching. Gaz 👍🏻
Thanks for this helpful information.
Hopefully you can do a video on test car charging unit
8:10
Testing phase-earth and neutral-earth separately will achieve effectively the same result in the end as joining phase to neutral and testing to earth, so when it says "live conductors to earth" it make no difference really if that's separate or together.
You're not putting a voltage across any potential loads (and even if you were, testers are so current limited you'd be very unlucky to damage anything as the voltage won't rise to its nominal 500V+) so you're not going to cause any issues.
The worst case scenario would be a 1Mohm IR between phase and earth up to a switch that's open (which it shouldn't be, but it can be awkward with contactors etc.) that just scrapes a pass. Then a 1Mohm IR from after the switch through the load and neutral referenced to earth. So both legs scrape through but the combined reading wouldn't. But that's a very similar argument as to whether you test the entire installation in one go or each circuit individually. Are 10 circuits each with a 5Mohm IR OK? They would be in isolation but wouldn't be if you tested them as a board.
I'd say that if you were only just scraping a pass on each leg of a circuit then you're probably wanting to work out why.
As for disconnecting from RCBOs, some manufacturers specifically say "our double pole RCBO is great, you don't have to disconnect the leads to do IR testing" which is handy.
Nice
JW. Did a video were he tested a smoke alarm at 250 500 and 1000 volts, and guess what ? The smoke alarm was fine and continued to work as intended.
Only last week Nick Bundy put up a video we’re he tested A LED lamp and driver at 250 500 and yes a1000 volts, and the LEDs were fine and worked as intended after each test . So in my opinion both JW And Nick Bundy have expelled the miff that electronic equipment can or could be damaged by a 500v insulation resistance test .
But I have to agree we should remove such equipment from circuit. To avoid misleading test readings.
The problem here could be that after the inspection is complete the client magically finds things that are no longer working. Guess whose fault that is going to be if they were included in the test procedure! Confiming they are working before carrying out testing could take longer than simply removing them.
Perhaps I'm just a pessemist. :(
Great video again gaz...in the feild I always first test at 250v then the 500v later.I've blown a boiler controller before. 🙄
I will be following this video up in the future 👍🏻. Thanks for watching and commenting
Please explain the effect of external cpc and bonding effects result of test cpc to live conductors.
Great videos. I’d just like to ask, when you mention Tresham College: is that Tresham College in Kettering?
The electrical team work out of Corby and Wellingborough 👍🏻
Why do you have to have all the earthing and bonding connected when you do the insulation resistance test thought it was just like IR testing a pyro or 2.5 or 1.5 radial there is no earthing connected then can you explain the reason
Trouble is all my lighting circuits are Quinetic based which makes it really hard to IR test. I did test but how would you test in those circumstances?
Thanks for this Gaz, I think there's a lack of YT content relating to the testing of modern RCBO/SPD configured DBs which this addresses. I prefer taking conductors out to IR, you just never know. No more global IR though. :(
I wasn't taught, as far as i can remember, about having the earth in place and struggle to work out its importance of you could expand on that please.
I will follow this video up at some point Olly 👍🏻
Very important to keep the protective conductor connected to earth , if a neutral was nailed to a water pipe for example this fault would go undetected
As far as I know it’s to flag up problems with stuff like steel stud work being in contact with damaged live conductors.
So by measuring the insulation resistance of a circuit with all the other earthing, protective and bonding conductors connected you will identify any issues where a deterioration in insulation resistance has occurred with respect to that circuit and other parts of the installation for example a water pipe or similarly other earthed parts of the installation due to a parallel path that has now developed due to the poor insulation resistance. This is important as a significant enough deterioration in insulation resistance can lead to a dangerous potential to occur on that other service or conductive part that won’t necessarily be high enough to trip a protective device. It can still be high enough though to present a significant danger to users of the installation.
Hi Gaz, similar age to you , with 30 odd year's experience..now going for the 2392-10 ... traditionally? Wouldn't we had disconnected the relevant CPC for said circuit, for insulation testing? otherwise, isn't their the potential to " false readings?" With all the other CPC's connected? Also noticed in other vids, you done IR direct to bars with all other N ,and CPC's connected, cheers Andy
Yes, but what is the reason for the main earthing conductor and bonding conductors being in place during IR testing? Surely without them connected you still get a true reading for a particular set of circuit conductors
The “Why” would have been really helpful here as it gives a better understanding of why the test should be carried out in this way and what issues it helps identify.
So if you carry out the test with the cpc disconnected, your are right in that it will reveal any issues of low or failing insulation resistance between the other conductors and the cpc in that circuits cabling.
What it won’t show you though, is if there are any issues with regards to the insulation resistance of that circuits cabling and the rest of the installation. As a circuit will often pass through a building in contact with other circuits, services and various extraneous conductive parts it has the potential to interact with any of them if the cable is damaged or the insulation has deteriorated.
So by measuring the insulation resistance of a circuit with all the other earthing, protective and bonding conductors connected you will identify any issues where a deterioration in insulation resistance has occurred with respect to that circuit and other parts of the installation for example a water pipe or similarly other earthed parts of the installation due to a parallel path that has now developed due to the poor insulation resistance. This is important as a significant enough deterioration in insulation resistance can lead to a dangerous potential to occur on that other service or conductive part that won’t necessarily be high enough to trip a protective device. It can still be high enough though to present a significant danger to users of the installation.
The actual procedure takes not more than a minute. But pre planning consumes many hours so as to make sure the one minute is error free. Pre planing is mostly detective work for finding hidden devices!
Test line and neutral together to earth is unlikely to damage any sensitive electronic equipment that includes RCBOs AFDDs and SPDS as there is no pertential difference
Follow up video made today 👍🏻
The one problem is with SPD that you cannot test them to make sure for main 100A Switch will trip in Disconection time Like an RCD
Test procedure to make sure the main Switch will trip
Would somebody like to explain why the CPC remains connected during IR testing. Something the guy in the video didn't bother to do.
This may be a minor thing/I may be thinking too much about it. But IR is stated as a test on the Minor works. It crosses my mind that repetitive connecting and disconnecting of conductor may eventually cause metal fatigue on the copper. I appreciate that in new installs we aim to leave ample slack, which allows you to re-strip, but certainly in older installs there often isn't enough there to re-strip your conductor. It always worries me working on older boards that the conductor copper may be lookingna bit worn out due to having been removed for testing several times.
Forgive me if I’m getting the wrong idea, but surely during a initial verification you should be testing between L-N, L-E and N-E separately as the circuit is not energised or have loads installed. The purpose of combined LN-E was a limitation on an EICR as loads couldn’t be disconnected?
Also, if installing a new circuit to an existing live board, the neutral for the circuit under test should be disconnected from the neutral bar (shown as connected in OSG) as you don’t want 500V going to live components up the neutral bar?
Thanks for all your amazing work!!
I will do another video at some point covering your comment… Note - the longer the circuit the lower the insulation resistance even if it is so small the instrument won’t register it… so linking live conductors together to earth gives you longer conductors when testing and therefore a lower reading the L to E and N to E…
All the best Gaz
@@GSHElectrical Would linking LN and testing to earth pickup IR faults between L and N, I thought it was treating them as one conductor and any faults between the two would be cancelled out as it’s just looking to faults to earth?
@@jongurney correct. L/N to cpc testing cannot determine a L/N insulation fault. Imho it is the usual easy test on an existing installation to establish whether the RCD is likely to trip due to an earth fault from either L or N insulation failure.
Or as I was told once, “it’s on an RCD, if it holds, it’s a pass”.
😳😳😳😳
Pretty much all brands of test schedules just have enough room for [live-live][live-earth] ,but I've come across many inspectors, on an EICR will just put 'LIM' for BOTH columns??? This is poor practice in my opinion as you should always be able to get an IR reading for one or both ,otherwise you can't possibly have an understanding of the extent of the circuit under test.
Thanks for taking the time to comment and watching 👍🏻
Line and neutral are both live conductors so that answers your first point about it saying live conductor in your book but the neutral is connected. And you didn't explain why the earth needs to be connected, you just stated that that's what the book say, not a very good explanation. If you're just wanting to test the IR of a single circuit it's totally irrelevant if the earth is connected, if you just want to prove a cable is ok then there's no reason any of it needs connecting to the DB at all.
Didnt leave my cpcs in on am2.
Well thats going to be a fail :(
Let’s hope not
@@GSHElectrical Argh failed on my metal conduit. 20mm out of spec. Passed everything else.
Roll on the resit!.