Insulation Resistance Test (Includes Line and Neutral Together to Earth and Between Live Conductors)
HTML-код
- Опубликовано: 5 май 2024
- Students training aid for testing insulation resistance of complete domestic dwelling. Demonstration shows how to set up your Megger MFT tester and 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 BS 7671 is 1 megohms for the whole instillation with further investigation when the reading falls below 2 megohms.
Also shows and explains the need to switch both 2 way switches into the other on position and repeat the insulation resistance test. Removing of all loads and leaving switches in the on position.
== 🕐 Time Stamps - Cut to the action 🕕 ==
00:00 - Insulation resistance test
00:34 - Continuity of CPC test leaving all circuits on and all loads removed
01:19 - Returning connections in the consumer unit to the correct torque settings
02:02 - BS 7671 states insulation resistance test is to be carried out between live conductors and live conductors to earth
03:22 - Setting up a Megger MFT tester to carryout insulation resistance test
04:21 - Insulation resistance test live conductors (line and neutral) together to earth
06:03 - Insulation resistance test between live conductors (line and neutral)
06:53 - Remember to operate 2 way and 2 way and intermediate switches and repeat the test again as stated in the On-Side Guide
🔵 AM2 or AM2S Insulation Resistance Testing of 2 Way and Intermediate Switching Using Guidance Notes 3 • Insulation Resistance ...
Videos are training aids for City and Guilds (C and G) and EAL courses Level 1, 2, 3 plus AM2, AM2S and AM2E.
You can follow me day by day on Facebook, Instagram and Twitter lookout for "GSH Electrical.
▶️ FACEBOOK / gshelectrical
▶️ INSTAGRAM / brihzmraygdtmjmdb9lunq...
▶️ TWITTER / gsh_electrical
▶️ TikTok vm.tiktok.com/ZMRBLFdhe/
#GSHElectrical #Electricaltrainingvideos #electrical #electricaltesting
Do YOU Know What Happens to a Circuits Insulation Resistance When the Circuit Length is Increased?
ruclips.net/video/Ml95TFpchmA/видео.html
Thanks for your time to make our study much easier and understandable.
Wish you all the best.
Thanks - working hard has its rewards 🦾. All the best Gaz
The same way as we do it here in Germany. With the exception you'll have to test three lines, and test them against each other in addition. Three-phase power supply (3x230/400 VAC) is the standard here, even in residential buildings.
Thanks for improving knowledge
Hi GSH, thank you for the video. Very helpful method to allow the collection of the combined reading
+David Roche
Thanks. Often missed in industry the testing of both live conductors together to earth. All the best and keep watching GSH Electrical
Is the old lead acceptable under GS38 as it has more of an exposed end?
+R P
Hi. The insulation resistance test is the third DEAD test and GS38 applies to live testing probs. All the best and thanks for watching GSH Electrical
Hi GSH, thank you for the video. Very helpful
absolutely spot on, straight to the point, very clear explanation, head and shoulders above my 2391-52 course leader's explanation.
Massive thanks for the amazing comment 👍🏻. Gaz
Thanks this is really help full!
Your lessons are really helpful
Very clear as always. I have just bought my self an IR tester for DIY electrical work I am doing (boo hiss!!!), and now I understand the procedure, cheers!
Really helpful. Appreciate the efforts put in to share this knowledge. Keep doing the good things.
Hi. Thanks for commenting and watching 👍.
Great video.Great teaching skills.Appreciate your work mate.
Thanks 👍
Hi GSH electrical, I'm currently studying a course online for electrical installation. I have to say I have learnt more from your videos then I have from reading from this course. Thank you for the brilliant videos 👍
Thanks for the great message Daniel - tons more content coming this year good luck with your studying 👍🏻. Gaz
Thank you.
Dear sir a most brilliant tweek.keep up the great work and videos.thankyou loads.
Thanks for the support and watching. Gaz 👍
Hi Gaz thanks for the excellent, clear and concise video on insulation testing. Please could you possibly do a video on board changing with tips and advice on getting it as neat as possible. Thanks.
Step by Step How to Connect up a 10 Way Wylex Dual RCD Consumers Unit (Fuse Box) By Luke Wichard ruclips.net/video/tyOiLAUlSpU/видео.html
This may help 👍.
Thanks for watching and commenting. Gaz
Thank you for posting this video. Hopefully should help me to pass my AM2 next week! Liked and Subscribed!
Hi thanks. All the best with AM2 Gaz 👍
Am2 is now Am2s the only difference is you now have to bend metal conduit
This video has been some help.
Great videos !!, best on you tube by far. Where can i get the short crocs leads you use for shorting out the the test probes?
Remember 500v dc is the maximum test voltage for a 230v installation. In reality 250v makes more sense, much less likely to damage sensitive equipment. I know it should be disconnected but in the real world its very easy to miss stuff.
Been a spark for ages this is good time saving idea.
Bit like a gobal test but good time saving idea
Hi Gary great video again , Just a note maybe I find doing a lead check with the Megger with a short , set the voltage to s minimum is 250 v it save the battery's
Well done, Thank you
Thanks for watching and the great comment 👍🏻
Top class!
Thanks
Thank you for the video. Very clear instructions.
Just wondering if i do IR testing in real house for c20 power circuit. Do i have to unplug all the equipment for that circuit inside the house in order to do Ir testing 500v? Wouldn’t it be too much time? Any quick way you can suggest would be great? Thank you
Hi, great video, thank you for sharing 🙏 If there are fused spurs, should the appliance (eg washing machine) be disconnected before applying test or should the spur switch be switched off or fuse removed?
Hello. Thank you for the upload. On the eurotester, you use four probes that are short circuited into an "octopus", why is that not the case here?
Great video thanks
Thanks for commenting 👍
I enjoy all presentations more , I depend on them
Thanks for the support and watching 👍🏻
Hi, I have a question about insulation resistance on ring circuuts since the focus is mostly done on radial circuits. When carrying out the insulation resistance test on a ring circuut, shall one test on only one end of the L and N cables? Or can one link the LL and NN and test across them? Thanks again
Great video 👍
Thanks for watching 👍🏻
Great video. Would you be able to explain the best way to test both individual circuits and the whole installation where there are ONLY single pole RCBOs (neutral fly-lead, no earth fly-lead) installed where the manufacturers instructions state that "all connections to the device must be removed prior to conducting insulation resistance tests".
Hi. Thanks for the great massage I will add your video request to my list 👍 all the best GSH Electrical
Do we have to considered the resistance of the Test Lead, while doing IR or Earth Test or even Soil Resistance Test? Thereafter minus resistance of the Test Lead in order to get the accurate test results?
Great video, very informative and helpful. If you are testing a normal house say and the lighting downstairs is one circuit ,do you remove every downlight lamp from the fitting in order to get a true reading?
Hi you should do however on an EICR often the insulation resistance isn’t carry out between Line and Neutral as all loads cannot be removed. On a new installation the loads wouldn’t be fitted so this test can be carried out. Thanks for commenting and watching. Gaz
for lighting circuit do I need to remove strip lamps or lower the voltage ?
So easy on a test rig. Try it in a school or office block or factory floor with 150 luminaires connected and F.C.U.’s with neons multiple items of equipment out of reach or above false ceilings. There’s only so much you can put down as limitation.
I get the unplug and leave switched on etc but what about fused spurs. Ie say a washing machine. What do I need to do for them. Leave switches off or pull fuse or take front off and physical disconnect.
Can you please please help. I know sensitive circuits need to be tested at 250v. Would you say you do insulation resistance at 250v for garden sensors
, cooker circuits, smoke alarms etc ?
Does every installation have a double pole isolation switch for doing the IR test ?
What would be your solution when testing a 40-circuit panel feeding to various lighting and power branch circuits with dimmers, bulbs, smoke detectors, etc on the branch circuit? It can't be reasonable to hunt through the entire building looking for these devices to connect.
I was taught in college to test each wire of the live to mcb and just clamp.it to the neutral bar without a strapper then the earth to neutral and then the earth to live. What's the difference now ? Is it because of split boards?
Do you have to test every cable at every point in the circuit you are testing, or just at the distribution board?
Thank you very much for this informative video, can you please help to find an example of this table shown in 2.20. I really wonder how such an installation report looks like in full.
nice sir
Hi, How can you get IR on the DB supply cable from supplh meter if its live and cannot be isolated?
Great video. Very informative. Just a quick question. How do you perform the IR test on a circuit which has lighting loads connected to it.? Is there a way to still conduct the test? I watched some vids and they said that testing the insulation by linking the neutral and line to earth is the way to do it.
Yes link live and netrual linked to earth sometimes you just cant get access because of having to get up high to the lights and access etc.
Note on certifcate that you only tested
L/N TO CPC
On a new fresh install you would do a full test but on a periodic tou would only do the above unless client said different then you would agree that and charge accordingly !!!
@@bramcoteelectrical1088 would you then leave L-L test blank on the certificate
If you have an MEN link between neutral and earth do you have to remove that before you run these tests
Hi there, only just watched this video now as I have my AM2 in 2 weeks time, would they say anything if I was to do the same with the crocodile clip whilst testing? Doesn’t seem right 🤣great way of testing tho! Makes things so much easier! Really helping me these videos!
How’d u get on with your AM2 mate and u got any tips? Got mine sometime this year not to sure wen tho cos of COVID lol
Excellent vid, what was the need to repeat the test for the 2 way switches??
To test the strappers in the 2way circuit
As at the time of test you would only be testing the common and say L1
By flicking the switch your testing Common and L2 etc
Nice GS38 probe
Hi gsh, thanks for the awesome video. Let’s say you can’t take out all the loads of a lighting circuit but you want to still see if IR integrity is lost between live conductors. Do you short active and neutral together and go between the pair to earth? Thanks.
Thanks for the kind words... yes you can 🦾. Gaz
@@GSHElectrical legend 💪🏻
@@GSHElectrical I don't understand - if you short Line & Neutral together and test to Earth, how does that prove IR integrity between the Live conductors? You've shorted them together!
That is why I don't do that one I simply can't see the sense.
If we leave something plug in into socket when testing is in progress, the test results will be the same ? Or will be something wrong with the results?
When you test between live and neutral you have other neutral wires also connected to the bar. How is this ok ?
Liked the wee crock link Gary
Thanks 👍👍
I have 2 neutral wires burned at the busbar . My electrician installed the panel 15 years ago and it is only now I noticed as I was installing a new MCB for a Camera system ..... Yes yes I know I'm not supposed to be in there if I'm not qualified before all the spark heads start slatting me ! I have fair knowledge of electrical circuits and would only work at something that I'm confident in installing and straightforward.
Each MCB is independent and don't have any shared neutrals. I did check the neutrals for a loose connection as arcing was my first thought.
They seem all good but the busbar itself is slightly corroded .. the screws being the worst . I have now installed a new wire and bent the ends for better contact ( Original sparky had the two neutrals in one screw , not sure if that makes a difference )
Could slight corrosion cause this and if so why did the rest of them not do this ?
The wire is 1.5 mm solid, Goes to the first led light and onto the next 7 lights at a distance of 30 metres ( 60 watt each )
Again I'm not a sparky ! If I have to pay for someone I will but I like learning the cause and solution of such problems !
Hi Gaz.... Could your method ( using the link wire) be used with RCBO's? I ask because of the neutral connection through the RCBO.
Hi. Great question. Sitting drinks wine I think you are correct... remember to have the RCBO in the off position (electronic device). Thanks for watching GSH Electrical
Does not work with pme. Disconnect earth from met?
Hi,
Can you explain how to do an IR test from somewhere other than the CCU.
Like, when the ring final circuit is being split, how you test at the "halfway" point to confirm which side has the lower reading?
Also, can it be done at ceiling roses/switches etc
Hi. Breaking circuits down is an essential part of fault finding. In your case to discover a section of a circuit with a low IR 👍. Thanks for commenting and watching GSH Electrical
@@GSHElectrical Definitely. How would you complete an IR test at a socket though? Just test on the wires once removed from the socket outlet?
Hi. Instead of that crocodile clip. Cant U just use 3rd neutral cable? Coming out from meeger tester? I
Can you still carry this test out if using only rcbo's?
Also on the test form you talk about live - live and live - earth (being l+n+e) so would you write down the result for l+n+e in both boxes ?
Thanks
Hi. Only ever write down results of tests you carryout as you are signing the paperwork.
Hi Gaz
If you're doing an initial verification, would you need to bother testing with Line and Neutral connected together or is that more for if you're testing an older installation and its impractical to remove every single bit of kit throughout the house?
Thanks in advance
Hi. The video was to provoke the debate as BS7671 only has 2 boxes for installation resistance 🤔. Thanks for commenting Gaz
On the lighting circuit containing two way or two way and intermediate switches would you not need to operate switches *one at a time* as it states in GN3?
👍
smacznykonsek
ruclips.net/video/9AjyWl_2bds/видео.html
@@GSHElectrical Thank you for your response and for the link! I must have watched this one very recently as I am currently revising for my AM2 exam tomorrow.
I wanted to add my thought on the topic of the discussion that you are provoking on this video regarding the two boxes for IR on schedule of test results form.
Looking at IR testsing of three-phase 4-core power cable guidance in GN3, table 2.3 says that the lowest value obtained from tests between live conductors (Test 1 to 4) is recorded as 'between live conductors' and for Test 5 and 6 again the lowest value of these tests is recorded as 'between live conductors and earth'. Maybe the same principle can be then applied to single phase circuits where the lowest value from testing L to E and N to E would be recorded as 'between live conductor and earth'? And then any reading below 20 mega ohms would be investigated as required. Just my thoughts!
And yes, all of your videos I watched so far have been great help!
@@GSHElectrical I stand corrected. Even at the beginning of this video presentation you mention that light switches were left in "on" position ;)
On a side note, I was thinking about it now and concluded that with two way or two way and intermediate switches (no matter how many) with any connection method for those we only really need to operate the first switch (nearest to the supply) and perform two tests - in that way we will have both strapper "sets" tested including the switch line going all the way to the load. Please correct me if I am wrong? And, again, this is just me sharing my thoughts.
Thanks GSH Sir,very helpful video,how much price insulation tester.
Hi. They range in price but about £600-800 thanks for watching Gaz
Sir i am INDIAN ,wher are you from☺
Hi Gaz. Loving the video. 5 star mate. However, do we need to remove all load/components. I.e. washing machine, cooker etc? Or just lamps and infrareds?
Links
Do you have to remove. Loads. Like washers cookers
Of course, otherwise you'll be pushing insulation testing current directly into the appliance
All loads if you cant do that then put a limitation and state your minky tested Live + Netrual to cpc (earth)
Would you only carry out the L+N to E test if there are loads connected. For example, an EICR where it's impractical to remove loads.
L to N would cause damage to sensitive equipment right?
Hi. Thats correct. Thanks for the question GSH Electrical 👍
Hi. However the paperwork in BS7671 only has 2 boxes for insulation resistance and this was a video showing away of doing the combined test L/N to E for an initial inspection. Thanks again GSH
I was just looking at that second board how would you run say a garage board. Would you connect it into the main board or use those Henley connection blocks inbetween the main income terminals
Will depend how you design the distribution circuit.
4 years later......Henley block to Isolator near main DB....or connect into main board..up to you.Depends if there is room or not
HI GSH, Just a question - you mention the removal of sensitive electronics. If we were at a stage where a cooker had been weird into the cooker switch would we need to remove this before the test? or would we do the test with the switch turned off?
Ideally you would remove the load and have the switch ON so you test the full length of the cable in circuit 👍🏻. Gaz
Ideally you would remove the load and have the switch ON so you test the full length of the cable in circuit 👍🏻. Gaz
Hi Gaz, you said the minimum resistance of the whole installation must be at least 1Megohm, if less than 2Megohm should be further investigated. Correct me if I'm wrong but the latter, shouldn't that be any circuit that is less than 2Megohm should be investigated rather than the whole installation that is less than 2megohms?
Steve Tang agreed. Thanks for the message. Gaz
Alot of low readings are due to lead cable or water on conductors or a common one is forgetting to take lamps out lol done that....
Surely, if you do the test this way a dead short in either the earth or neutral will be impossible to find. Doing it the way we were taught way back in college allows you to split your results to find insulation resistance failure in 2 potentially faulty conductors out of 3.
Hi. The test paperwork for the IET has only two boxes for recording installation resistance between live conductors and live conductors to earth hence the video. These videos are designed to provoke discussions within my classroom as it has with you. The readings can still be carried out as you have stated but the installation resistance test between live conductors together to Earth is required to be measures and recorded according to the IET model forms. This reading will not necessarily be the same as the individual tests you have stated as you will have two parallel conductors line and neutral tested to Earth in my example the measurement if often less than L/E N/E tests. If L/E was 4M ohms and N/E was 4M ohms live conductors to earth would be 2M ohms. Thanks for watching and commenting GSH Electrical.
Hi. You would find the neutral earth fault when testing between live conductors (L/N) together to earth. Then the circuit would be spit down for find the faulty (low resistance) circuit(s). Thanks again GSH Electrical
Can I ask a couple of questions: 1. What if you have an installation with load of down lights, do you have to get step ladders and remove them all for the test? 2. One thing that I am confused by, is that, if the main neutral is ultimately connected to earth back at the supply transformer, why would you not get a zero or close to zero reading when you measure between neutral and earth in the consumer unit if you were making three tests rather than the combined neutral and live to earth test? Just for my understanding. Thanks.
The main switch is locked in the off position so the neutral will not be making a connection to the earth unless there is a fault in the system which is what you are testing for.
So Gary, for EICRs I got into the habit of doing the test of Lines-Earth only siting my reasons. According to BS 7671 I’m supposed to fulfil both tests, the other one being Line-Line. My question is, do I have to remove all those lamps in the downlight fittings? Which is what I’ll have to do. I’m not asking the question in a negative way as I am in a pursuit of excellence, hence the reason why I watch your videos.
Hi. BS7671 test results page only has 2 boxes for insulation resistance testing Live/Earth and Live/Live remember live conductors are line and neutral. Napit and NIC test paperwork have 3 boxes. On an EICR you possibly won’t be able to remove all loads so a test between Live conductors cannot be carried out. Thanks for commenting and watching Gaz 👍
GSH Electrical
You’re on point. I actually fill out the NIC forms and haven’t looked at a BS7671 model form for an age. Having had a thought, by testing first off, Live-Live, and that being satisfactory then testing afterwards Lives-Earth and that too being satisfactory you need not test, Live-Earth and Neutral-Earth. I noticed too on the BS7671 model form that the field for the amount of points is not present. Again, you see, I’ve only been filling out the NIC forms.
Question: For insulation resistance testing, what are you NOT testing when leaving the switch(es) of a socket, in the ‘off’ position?
@@abdulseaforth6930 if you leave sockets switched off you will not be testing the end contacts of the socket points hence you must leave it on
Great explanation!! Quick question. How do you do an insulation resistance test when impractical to remove all lamps, sensors, electronic equipment ? Is it allow to perform the test only between L-E , N-E?
Hi. Test with Line and Neutral together to Earth... if you cannot remove the loads never test between Line and Neutral👍. Thanks for commenting and watching Gaz
@@GSHElectrical Thank you very much for your prompt answer. Best regards
just test at 250
@@GSHElectrical Hi, if you are testing Line and Neutral together to Earth does that mean the 500v DC current is not going through any loads and bypasses it and goes out through the Earth cable? If you have for example fixed downlights connected on the lighting circuit does the 500 volts not passthrough the lamp?
Best regards and thanks.
@@joshstrom2791 so if I get
So performing an IR test this way is acceptable if rcbo's are present?
Guidance note 3 states tou need to do a gobal test.
I failed my am2 as I didnt do a gobal test I was testing individually lol.
Passed on 2nd try many moons ago
.
@@bramcoteelectrical1088 yeah true although for circuits protected by sensitive devices you can do an individual IR test or link them out to complete a global test
Hi Gaz, just one more question - if you was to test an old installation for insulation resistance and it was below the minimum 1megaOhm what would be the action to take?
Further investigation. Breakdown the circuits and try and find the part(s) if the installation that are brewing down the readings
Also an interesting video 👇🏻
ruclips.net/video/Ml95TFpchmA/видео.html
@@GSHElectrical Thank you very much - That other video was definitely worth the watch!!
Hi .what values you got from the test and the values should be at least how many Megaohms?
Greater than 1Mohm
the mega meter was readfing 999 but on the result sheet you wrote +299 ?
Depends on megger but yes if meeger tests to 999 you put greater than >999
If it's the older style megger you put >299
when the insulation resistance values measured between the neutral terminal and the earth terminal at a consumer unit are below 0.5 Mega Ohm. How do safety precaution to do the troubleshooting?
Hi. You need to break the circuits down and test them individually to find the circuit(s) causing the overall insulation resistance to be blow 2Mohms. Then investigate that circuit(s)... thanks for commenting and watching GSH Electrical
GSH Electrical thank you 😊
How we can test a ring circuit for insulation resistance
The same way you do any other final circuit 👍
Which brand is the IR tester? I need one like that.
Meggar
What if you have led intergrate lights which you cant remove? How to perform test
Test between line and neutral together to Earth (only) 👍
😊
Which Megger did you use?
1711 thanks. Gaz 🦾
Keep doing these videos there are very helpful
How would you test all live conductors to earth on a three phase installation using your method?
Hi great question. Ideally you would be linking at the disconnect tails as shown in many testing text books (as if you can do that when the supply is connected). I came up with this solution for a single phase installation as I was constantly ask by learners how to over come this issue. I will have a think but industry gives no guidance have you got a solution.?
It requires a 'comboined' test? 2:36
Hi. The schedule of test results in BS7671 only has two boxes for insulation resistance between live conductors and live conductors to earth. I did the video to show away that could be used to link live conductors and then test to earth. I couldn’t find any guidance on how this test could be preformed other than testing from the tails (not possible). All the best and thanks for watching GSH Electrical
Easy on a test board, how about showing us how to do it with 50+ led fixed lights, neon FCU and inaccessible white goods etc.
To do the tests at maximum efficiency you would disconnect all led lights. (Either live or neutral at each light and join them in a connector), remove all lamps from other lights. As for the white goods, pull the machines out and disconnect, any neons have to be removed from the circuit (disconnect switch spur and join cables to complete circuit to the end of line etc etc)
Theres no quick fix.
Painstaking: Yes
Time consuming: Yes
Always possible: No
Bill accordingly: Most definitely
You sign your name to something, you better be sure you've covered your ass.
Put something down in the limitations 😂. Real world. No like in this video 👍
Then charge £80 for the EICR
It’s for college students lad
@@Jay369😊
GS38 says 4mm max probe length - Monday's session. I'm pretty sure the "older probe" is more than 4mm...
Hi. Max 4mm preferably 2mm preferably spring loaded as stated in GS 38 👍. Gaz
Insulation resistance testing is a dead test (below the 50v limitation complying to GS38) so in this test you do not need to comply.
Nathan Claxton it actually states used to measure or deliver voltages over 50vac or 100vdc and in this case, your delivering a voltage of 500vdc so they need to apply
There’s always one wise ass know it all. Shut up @Gareth Evans
@@seanmac2384 you are correct coz it can still cause an involuntary movement from the shock of the testers 250v+ voltages
Are these probes not against the regs
It’s not a live test… no requirements for GS38 probes during dead testing👍🏻
What is the duration for Insulation Resistance Test. In some places where i worked, the IR Test was carried with a duration of 1 min for each circuit base on the length. Correct me if i am wrong. Thx
Test until meter stable readings
What is the main reason for this test
To check the conductor insulation isn’t breaking down 👍🏻
What if low voltage transformer connected to lighting circuit and it serving fan in bathroom. What voltage test to use and between which conductors ? Thanks
Hi if loads are still in circuit and cannot be removed test only between live conductors (line and neutral) together to earth. Thanks Gaz
Im an electrician in canada and we never do this kind of testing
Thanks for commenting and watching GSH Electrical 👍
Same in Oz. Nothing like this. I have been in the UK seven years now.
Gaz. Why do u have to move the Clip in the neutral bar when u tested the next circuit??
It's not a knock at all just wondering since the entire neutral terminal is one unit electrically speaking so any where on there would yield the same reading.
Also does your college do test n inspection courses for àn installation sparky who wants to upgrade?? Ta
@@carlmarquardt994 Because the RCD's are in the off position thus isolating the two neutral bars on the left from the main one.
@@carlmarquardt994 the neutral bar is split into 3 separate blocks if u look closer
carl marquardt This particular unit has 3 segregated neutral bars to achieve separation of circuits. Integrity. The individual circuit neutrals from the 3 split positions are electrically isolated.
hi there what if its not greater than 999 what we need to look for?
When testing individual circuits are you not reading the cumulative parallel insulation resistances or faults from all of the connected neutrals to their associated and other grouped CPCs? Wouldn't you need to disconnect the Neutral for the circuit being tested?
Hi. Thanks for commenting and watching. The insulation resistance of the whole installation must be great than 1 M ohm. If you measure individual circuits to have 200 M ohm, 100 M ohm, 50 M ohm and 2 M ohm the overall insulation resistance would be less than 2 M ohms as the circuits are in parallel. Hence you should test with all circuits connect or you would have to calculate the total insulation resistance from all the individual ones.
This link might help ruclips.net/video/MLTM-OJE0Lo/видео.html
All the best GSH Electrical
Understood when testing the whole installation, but at 4:54 you're talking about testing an individual circuit and the neutral is attached... I was under the impression it had to be removed for the single circuit test.
Please electrical dead test in hindi
Thanks once again for another great video. Couldn't help but notice that after you'd done the first part of the testing and went on to throw the switches of the two way lights that the switches were, in fact, in the off position.
As i understand it, when the toggles are in the same position (i.e. both up or both down), the circuit is, in fact, off.
To be ON, the switches should be in the opposite positions, i.e. one up and one down.
I know I'm perhaps being a little pedantic, and you are certainly infinitely more knowledgeable than me, and ALSO that it'd be a moot point if an intermediate switch was thrown into the mix (intermediate switches are ON in either position; they just allow the current to pass through to one of the other two way switches), but that's good practice, isn't it?
Anyway, that's what I noticed.
Hi. Are you saying that 2 way switches cannot both be down and the circuit off and likewise the other way around.....
GSH Electrical
Hiya. Sorry I've not made myself too clear.
No. I am saying that for the circuit to be ON, one should be up and one should be down.
When they are either both up, or both down, that in that configuration the circuit is OFF.
So, let's say that if they are both up (as in the first part of your test), and then both down (as in the second part of your test), are the strappers between the two switches being tested as they should be?
Hi. The 2 way switches need to be on during the first IR test let’s say both down. When I operate one switch (up) circuit would be off so I need to operate the other switch (up) on this means the other strapper is now in circuit and can be tested during the second IR. thanks Gaz
GSH Electrical
I guess what I'm saying is... are you sure that it was ON in the first test? Because if it was OFF, and you switched both switches, it would still be OFF for the second test.
And as I understand it, one presses a switch down (i.e. the bottom of the switch) to complete the circuit and turn the light fixture ON, but both switches were in the (assumed) OFF position for the first part of the test.
Why do you connect Live and Neutral together???!!
Isn't,
1. Live to Neutral,
2. Live to Earth,
3. Earth to Neutral,
Enough for insulation resistance???
This video may help 👍🏻
Do YOU Know What Happens to a Circuits Insulation Resistance When the Circuit Length is Increased?
ruclips.net/video/Ml95TFpchmA/видео.html
Are you suggesting that by testing live conductors to earth individually as opposed to combined is wrong???
Hi. Great question. The insulation resistance test of live conductors (L and N) together to earth will give an overall insulation resistance lower than the individual L/E and N/E. The model forms for BS7671 only have two boxes for single phase insulation resistance. Hope this helps (currently shopping with the wife). Thanks GSH Electrical
If you had 5 Mohms L/E and 10 Mohms N/E which one would you record... because if you tested live conductors together to earth would get a reading less than 5 Mohms...
Appreciate the reply GSK. Surely by testing between live conductors to earth combined or individually though is preference. After all if a result above 1M was found combined the next steps would be to then split them and test separately. I get for a periodic etc then combined or at 250v due to loads. Just seems like your stating it's WRONG. Am I missing something??
Sorry less than
Testing between live conductors to earth will always give you a lower reading than L/E and N/E. BS7671 paperwork requires the results for between live conductors and live conductors to earth to be recorded. I understand that LIM’s will be applicable on periodic inspections. All the best GSH Electrical
Why is machine set to dc
Hi this may help www.quora.com/Why-is-DC-voltage-applied-in-an-insulation-resistance-test.
We are measuring resistance. All the best this Sunday Gaz
But this test does not detect a fault between line and neutral!!
this wouldn't work on rcbos, they would throw out the readings as would certain mcbs.
also if you have a neutral to earth fault on any of the combined readings that would be your reading.
Bring on more RCBOs with switched neutrals
@@GSHElectrical I actually came across some last year...I can't remember the brand but I think they were just around £16 a pop