Combined Insulation Resistance Test Line and Neutral Together to Earth & Between Live Conductors
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- เผยแพร่เมื่อ 12 ม.ค. 2019
- BS7671 test results sheets only have two boxes for insulation resistance. Live conductor (line and neutral) to earth and between live conductors (line and neutral).
GARY....Megohms.... not Megaohms (site slang SORRY)
The lead we use to piggyback the test leads is not made by Megger (it’s an adapted Metrel test lead). However I have given Megger both a video and photographs of this setup which could result in them manufacturing one in the future.
Students training aid for testing insulation resistance of complete domestic dwelling. Demonstration shows how to set up your Megger MFT tester and how to carry out an insulation resistance test live conductors (line and neutral) to earth and between live conductors. Test voltage is 500V d.c. and the minimum acceptable value according to BS7671 is 1 megohms for the whole instillation with further investigation when the reading falls below 2 megohms.
Note the supply is isolated all loads have been removed and all switches are in the on position.
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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You make amazing videos. Thanks.
Hi. Thanks for the lovely comment 👍Gaz
Having to watch these vids Because my I’ve literally done about 4 hours in total in the workshop this year you guys are life savers
Thanks for the support 👍...
Another quality video, setting the standard from the get go. I love your approach I wish you had of been my tutor
Hi. Thanks for the lovely comment 👍Gaz
The reason I don't like this method is when testing the L+N to E you could have a bad reading on one circuit, a bad reading on a another circuit and so on - due to a fault being on the neutral (which you keep testing with each circuit on the same section) which could confuse some, means you then have to seperate and do the circuits seperately anyway, and means you've been constantly been sending 500v down all the neutrals on that section (I hope one would do a continuity between L & N first to ensure nothing has been missed such as an outdoor RCD socket hidden in a cupboard etc,). If I had a doller for every time I saw a perfect workshop demonstration that wouldn't work in the real world I'd be rich. That said, The video is well made and don't wish to discourage. I would just suggest the next video you do is an unedited one in a 1960's house with original wiring and several diy socket spurs between rooms & floors. I think it would be quite entertaining ;)
Gas turbine commissioning engineer here.
Just want to say that your videos are great, fantastic resource, and not just for electricians.
Wow thanks for that 👍🏻
You can test at 250v if there is electronic equipment which can’t be disconnected
You’ll still get false readings
Between line and neutral you would get false readings most likely but live conductors and earth should give you some better readings.
Yes
@@Baggiolyfulyes but it does'nt tell you if you have a fault between line and neutral!! You could power up thinking allis good then bang goes the MCB because you have a line to neutral fault!!
It would be nice to see some vids with fault finding on these circuits. Great video as always.
Another brilliant video Gaz can't wait to get started on my course
Hi. Thanks for the lovely comment 👍Gaz
Exellent video chaps.well done.
Nice video guys... down to earth and well explained.
Hi. Thanks for the lovely comment 👍Gaz
Another brilliant video keep up the good work.
Hi. Thanks for the lovely comment 👍Gaz
Fantastic channel, fantastic video broken down to appeal to the likes of myself who found the class room jargon a little too much to take in
Great way of IR testing the whole installation, usually done this way on initial verification of a new installation as you should expect an off the scale reading across all circuits. An older installation can also be tested this way but you're more likely to come across a latent defect with an individual circuit.
Yes but the test does not tell you if you have a fault between line and neutral
Informative thanks. Would the handheld probe with the test button of worked here?
Another great video loving the efixx channel too
Excellent well explained.
Thanks 👍🏻
Amazing..Thanks
if you link the bus bar to the neutral bar and put the mcbs in the on postion and the rccb in the off postion how does that damage the rccb
Very interesting 👍👍👍👍👍
Thanks
If there are spotlights in the apartment do we remove them as well? let's say we got 15 spotlights do we remove them?
Where can I purchase a decent piggy back lead ?
Hi CJR. They are just metrel test leads and they allow you to piggyback them 👍. Thanks for the message and I look forward to your video using them 👍. Gaz
Hi guys! Loving the 2019 content really running away with it already I see.
Any chance you could prospectively do a video on the methods of safe isolation and disconnection with regards to incoming supply/ meter tails.
As a learner I’d really like some more insight into this area. For example to show what to do if one was to relocate a consumers unit etc as I understand not all incoming supplies have isolation points.
Much appreciated if you could help assist with this. 👍🏻
Regards
Dan
Hi. Thanks for the kind words and watching
Will this playlist help
th-cam.com/play/PL2Ea5r9gxUUeC9ehdfVWwQCgAedptsRla.html
Thanks Gaz
Thanks Gaz, much obliged.
Would you disconnect the bonding at the pipes? Otherwise the pipes become live?
Great video as always. You had a few problems securing your blue clip, could you show us a result if the clip had not made connection.
Hi. Thanks for the comment and watching.... the results would have been +999 megohms. All the best Gaz 👍
What if you can’t take the light bulbs out? Would you just put it as a limitation?
Hi Gaz, thanks for another great video. One question, on a new DB install with new and existing circuits..(existing circuit test L/N to earth only) would an IR test from neutral bar and earth bar damage any of the existing sensitive equipment?
Hi, the IR test will only damage electronic equipment if 500v DC is passed down L and N and not L and N together to E. thanks for commenting. Gaz 👍
GSH Electrical thanks for the speedy reply.. and on a Saturday too.. legend 🙏🏼
Always wondered, if this is the case why do people every test at 250 because of 'sensitive loads'
@@GSHElectrical that’s why there is no point having the RCDs and MCBs in the of position.
Wow
Would you be able to explain why GN3 tells us to make sure the CPC is left connected to the earth bar? I usually IR final circuits individually and don't see an iisue with testing L&N to CPC with all conductors out of the board. Thanks
I thinks its because you have to include all earth fault paths possible.
Amazing videos, thankyou.
Can you please send me a link on where I could obtain the adapted metrel leads. Thanks.
Thanks for watching 👍
Something like this
m.ebay.co.uk/itm/Metrel-TEK119-Three-Wire-Test-Lead-Set-S2038/153650885245?ul_ref=rover.ebay.com/rover/1/710-53481-19255-0/1?ff3=2&pub=5575376664&toolid=10001&campid=5338268676&customid=Cj0KCQiAl5zwBRCTARIsAIrukdMpsC5F2BwjZ7CPzDez1y6Na8Ou3TCPjl8tAGnAhqbQ6n4huNn0maIaAkvSEALw_wcB&lgeo=1&item=153650885245&srcrot=710-53481-19255-0&rvr_id=2237776744865&rvr_ts=4dd43f8216f0ad3045700392ffbb21c4&_mwBanner=1&_rdt=1&ul_noapp=true&pageci=a4d435cd-0cf6-492c-9c4e-fc815102524a
All the best Gaz
@@GSHElectrical Thanks for the swift reply Gaz. I followed the link, the issue I found with the leads is they are attached to a plug, which i believe is the mertel plug. The one in your video has a crocodile clip on one end and the other end has the tester piggyback.
Do i need to make an adjustment to the leads. Please can you advise further
Excellent video that is a great tip with the cables which I will be using for my upcoming assessment, obviously with a new installation there shouldn't be any cable not tested but it would be great if you could do a video doing once loads have been applied for instance a hardwired oven off an fcu or where there are multiple downlights and neons. People seem to say that if you do it the way you have there and connect R1 and RN together and test to earth it won't damage sensitive equipment is this correct?
Finally what do you do in regards to smoke/heat alarms with RF bases? For example the aico rf because even if you take the alarm off the voltage would still be passing through the base?
Thanks again for the clear informative video
Hi. Many thanks for taking the time to comment in such detail. More videos to follow so hopefully we can cover some of the points you raised👍 Gaz
@@GSHElectrical that would be great thank you, your vids are really helpful.
When testing with voltage sensitive equipment connected, you have two options, you either test with live conductors together to earth as Gary done in the first part of the test or you disconnect one of the live conductors at the load and put in a terminal block.
@@alvina69 thanks alvina, what would you do in regards to alarm bases that are rf (they say don't IR the bases cause they are sensitive too, without clarification I would disconnect and put the cables in a wago connector so it bridges the rest of the circuit but wanted to know thats ok to do incase my assessor asks me to do an IR test on the lighting circuit
Robert Melbourne If you had say 3 RF bases connected in series, I would disconnect the line conductors at bases 1 and 2 using a connector as a temporary bypass, disconnect the line conductor at base 3 and terminate into a connector temporarily for the purpose of IR testing. It doesn’t matter if the neutrals are still connected at the bases, as you’ve in effect created an open circuit and the equipment can’t be damaged whilst IR testing. Remember this is a dead test so safe isolation must be observed at all times.
Would you test live and neutral combined to earth if there was sensitve loads on the circuit that can't be removed. Will this stop them from getting damaged at 500v
The potential difference between L and N would be zero so no damage.
What if you cant remove a sensitive load i e in commercial settings..
Hi, where do you get the L& N linked test lead can't find anywhere
Yes I would greatly appreciate if you could give product details please. Great videos keep up the great work 💪
Is it not just good practice to test everything separately? It’s just something I’ve always done I do miss the old test sheets with the extra column for this
You would yes, but you have to factor in real world scenarios. Your not always going to have access to all loads in a domestic property ie bedrooms or sockets you can’t get to. Test the circuits you can and then the ones you can’t you just have to notify on the test sheet to cover your back
Fantastic video Guy’s as always.
But I do think it is a bit contradictory as Gaz when connecting the leads to the tester you said we ignore the blue as this is not a live test? Well technically it is a live test if you think i’am wrong touch the ends of the probes , secondly it’s a two lead test and in a previous video you demonstrate how to do the LN -E by use a link between the red probe and the neutral bar .
Piggybacking the green test lead is normally done for ZS on a TNC-S earthing system, or you would use the three leads and connect the green and blue onto the main earth. But I have to say piggybacking the red and green leads is a good idea?
Also the idea of the IR test damaging things like RCDs and smoke alarms is a myth JW did a video were he IR tests a smoke alarm At 250v 500v and at 1000v and the smoke alarm was fine and working as normal. Nick Bundy also did a video were he IR tests a selection of LED lights again at 250 500 and 1000v and yes they were all fine and continued to work as normal . However I believe that if we were to pass 500vDC down a circuit with a TV plugged in then it properly will damage the TV ? .
Fantastic video as always Gaz and Joe 👍👍👍👍❤️
HI GAZ , so in the old system we carried out 3 insulation tests L-E N-E and L-N does this now mean there are four insulation tests the fourth being live conductors to earth ? many thanks mark
Mark Brookes hi, your Choice is to do 3 tests or 2 tests. Conventionally we would do Line to N, Line to PE and N to PE however the paperwork from BS7671 only has 2 boxes to record your results so which ones do you record. The 2 boxes are Live to PE (line and neutral together to earth) and between live conductors (line and neutral) hence the video. Hope this helps. Gaz 🦾
@@GSHElectrical thanks Gaz, I'm going for my Am2, so I'm being an anorak. As long as it's a safe installation is the important point. The fly lead method in another one of your videos also looks good. I'm a bit surprised that the megger mft1741 hasn't got the correct leads to do this test straight out of the box. Having said that, it's a great tester. Thanks again
@@GSHElectrical I think this may be a misinterpretation of the model paperwork in BS7671:2018. In the companion IET GN3 (2.6.7) it does seem to allude to doing the 'traditional' 3 tests L-N, L-E & N-E. The combined LN - E is only for when vulnerable equipment can't be reasonably disconnected. IET GN3:2018 (pg128 note 19) does go on to state, 'enter the minimum value recorded....for each of the various configurations'. I suspect the reduced IR boxes in the model paperwork is to allow for additional IR test voltage and AFDD columns.
Thought I'd add my thoughts as I find your videos a great teaching aid and really appreciate the time and effort you put in.
So it’s not a good idea to leave mcbs on so 500v can pass through buzzbar and test all circuits on one rcd at a time. Can it affect the rcd even though it’s off?
Hi. We always go topside of the MCB with the MCB off as I don’t know if the electronics in the RCCB are in the top or the bottom of the device. Also this technique works with RCBO’s and that’s where Industry is going 👍. Thanks for commenting Gaz
GSH Electrical yeah it’s something I never thought about really . Think I might have to change how I do it . Haven’t had any problem with damaging an rcd yet (as far as I can see anyway) . Guess it will only take slightly longer to do.
Hi. Great video as always!! Can you or anyone else point me in the right direction of where to get one of those test leads from please?
Hi. They are matrel testing leads. All the best Gaz 👍
I thought you had to remove the incoming neutral beform you performed it
Hi guys. Where did you get that combined lead from?
I can't find it anywhere. Thanks
Hi it’s a metrel lead 👍🏻
I thought it's a Megger lead. Thanks again
So could u leave the loads in, smokes .Lamps.. dimmers.. neon switches.. usb sockets etc and do a joint - live conductors to earth test .. or is this bad practice ??
Hi. Remember this is a new installation and not an EICR... my learners are working towards AM2 or AM2s and all circuits need testing 👍. Thanks for commenting and watching Gaz
On an EICR technically yes, but it depends on what you’ve agreed with the client, they may want test results between line and neutral, in which case you’d have to disconnect/bypass all loads and voltage sensitive equipment.
What if the house has a load of downlights, do you still have to remove all of them for the test?
Yes you do. But to do this in a real customer installation is impractical, would take too long and also risk damage to the ceilings. You should test to the switch if you can then note this as a limitation on the report. Likewise for other loads, like items plugged into sockets that cannot practically be removed like washing machines or fridges or big heavy television stands that are blocking the socket outlet. Testing on a purpose make mock up like this is easy - Doing it in the real world is a pain in the whatsit!
Forgive my ignorance but the second test L to N was already verified during the first test wasn’t it? -Line to n&e
All very well, but when you are doing EICRs its impractical to disconnect all the loads, and thus you need to test at 250V
its acceptable now from the new ammendment 2 on the 18th edition but im pretty sure if their are no records of it ever being tested at 500v then its not acceptable to do it at 250v. Im also sure even at 500v beetween lives and earths no damage would be caused its only beetween the lines at 500v it could possibly damage equipment. PLEASE CORRECT ME IF I AM WRONG DO NOT BITE MY HEAD OFF.
👍🏼👍🏼
please which machine are you using
Megger MFT
Why hasn’t a board manufacturer designed a board with a better test point for the neutral and earth bars, the crocodile clip are forever jumping off.
Great point 👍Gaz
GSH Electrical Perhaps something like the linking bar that usually connects two earth bars, but deep enough that your crocodile clip can bite onto it without detaching itself.
Can anyone tell me if you test live to earth at 250v and then 250v neutral to earth will it damage equipment????
Nominal single phase AC voltage is 230 volts so doing the test at 250 volts DC will not damage connected equipment. Often during EICR’s this test is carried out at 250 volts DC. Thanks for watching and commenting. Gaz 👍
@@GSHElectrical thanks for responding mate that's exactly what I thought doing any line conductor to earth at 250v should be fine even 250v live to neutral shouldn't damage equipment but I wouldnt do it just to cover my arse.
How about IR testing on a live install. Much better, quicker and tests installation as a whole working unit.
it is but what if you have a installation with all rcbos that could be damaged from the 500v you couldnt just clip onto the bushbar as it will be going throught the rcbo
Gaz✅
Hi Gaz is the link lead called a piggyback lead or is there a technical name lol
Shaun Beard Multi contact test lead, try uk.rs-online.com
EBay.......type in search Piggy back test leads
Can we test
L N
L E
N E
Saperitly
Great question the paperwork provided by the NICEIC and Napit have more boxes for installation resistance testing (as per your questions). All the best Gaz
You keep saying Live conductors ... surly you mean Line conductors. Live suggests you test with the power turned on!!!
Line and Neutral when talked about together are live conductors
@@GSHElectrical not so! Live means hot. Which means current is going through it. The correct way is to address the wires as there name not there state!
@@martingregson7136 I suggest checking BS7671 definitions before incorrectly criticising others in the future.
@@davemyers77 Yes I have!
@@davemyers77 And it states. "Line conductor. A conductor of an AC system for the transmission of electrical energy other than a neutral conductor a PEN conductor. The term also means the equivalent conductor of a DC system unless otherwise specified in the regulations.
Live conductor is the same as live part: and it's States. A conductor or conductive part intended to be energised in normal used including a neutral conductor but not by convention not a pen conductor
You could have at least made some mistake lol. So we can see the faults of the reading not greater then 999
'Carry out' is an idiom that is being over used in this presentation. More use of words such as perform, demonstrate, show, do please.
Other than that irritation, it is an informative, beneficial presentation.
hi gaz, is that mcb not on a rcd going out to the garage or have I got it wrong..If so how is the cable going outside supplying the garage protected under all faulty conditions? thanks.