new neighbors yeah yeah which makes it a little bit darker fierce we're gonna do the insulation
resistance test of a lighting circuit yeah there's lots of things as an agenda well consider yeah
this is not a simple lighting circuit by any means this is fairly complex we've got a couple
of light fittings on here we've got some delicate components that we need be careful about and we've
also got intermediate switching thrown into the mixer as well which is going to add to our are
testing quite a lot so what sort of things we're gonna have to be careful of Gaz very specifically
as the insulation resistance tested going to pass five into volts DC through the circuit we're gonna
have to be careful as always to make sure the RCCB in this case which is in our consumer unit is in
the off position yeah but I've also got an issue at the moment with Joe yeah absolutely because
in here this has got an electronic ballast which means that there's delicate electronic components
in here yeah if we were to pass 500 volts across the line and neutral terminals of this we would
potentially fry those so we do need to exercise a little bit of caution when we carry out that test
also as we've moved towards AM2 AM2S regardless how the 2 way or 2 way and intermediate circus
wide in conduit or in PVC twin CPC they said to us and went to the Luton centre though there's
some things they'd like us to do in our training yeah well we've left this job we've come back to
it and whenever a period of time we've left it and we've got a one way switch controlling our
for us and life in but we've also got 2 way an intermediate switching down this side are they
on well this is the point we don't know now so when we did our continuity of CPC test normally
what we do is we would leave the switch is in the on position we would we know then we've got
every scrap of cable being tested and we know all we've got to do is put the two way switches
into the other on position however because now we don't know whether this is off or on we don't
know whether we're testing every scrap of cable or not so how are we gonna get over that Gaz
what was what's the the guidance that we need to follow on this what are we working to when
we're at the AM2 test Center he said for ease of them to standardize their practice they work from
guidance notes 3 and guidance notes 3 says where there's two way or two way intermediate switching
and you're carrying out an insulation resistance test you will carry out the test and operate each
switch individually repeating the test after each switch has been thrown it is a little bit longer
but let's standardize that practices we're all working towards that AM2 or AM2S absolutely okay
yeah that way when we walk into the AM2 - or to test or AM2S test Center we're crushing there
and we know exactly what we've got to do we're not going to be thrown off by you know someone
saying what about this two way switch and we'll know that's the next step on this test so what
we do is we bring the camera in and show you what we've done in fluorescent light fitting to remove
the electronic ballast yeah will reiterate the fact that we've turned the RCCB off and we'll
just look at these switches before we carry out the insulation resistance test let's do it so Joe
looking inside the fluorescent light fitting and I can see you've disconnected the conductor for
me can you explain what's happened there so what we've done is we've disconnected the switching
line out of the light fitting itself so what's happening now is when we do our installation
resistance test we're not going to be connecting 500 volts across the line and the neutral terminal
that connects onto the electronic ballast so what that's going to do is it's basically going to make
sure that we test the entire circuit but it's also going to keep our piece of kit here safe
from harm it's not going to get damaged we could have disconnected the neutrals if we so desired
but in this case because we've only got the one line conductor to going into the switching line
terminal it makes sense that that was the one that we took out and just put it into a little
connector block now the other thing just to bear in mind what we're going to do here is
we're going to box this back up because of course it's when we screw fronts on when we box stuff up
that's when we the electrician are most likely to cause a fault when we measure our insulation
resistance so we'll box this back up before we do the test thank you Joe so John the mains end
here and we can see is important that before we carry the insulation resistance test that were
connected to the external earth source so we've actually got our earthing conductor connected
to an MET and we pan up to the consumer unit joe we've reiterated a point in the introduction that
the RCCB needs to be in which position the RCCB needs to be switched off and again that's because
this contains delicate components which could be damaged by the 500 volts DC current now we're
going to pass across this and we also expect our learners to leave the circuit breakers off because
remember when you probe on to the top terminals character insulation resistance test he doesn't
realize where this going out and help me through the circuit or down absolutely nothing through
here and I can cause damage on this side if we're not careful so again for AM2 and AM2S make
sure that all electronic components are either disconnected or turned off in this case so what
we're looking at here we've got our one way switch that is controlling our fluorescent light and here
we've left this switch in the on position so we know that switched on which means when we carry
out our insulation resistance test we're testing the permanent line conductor that comes down to
the switch but we're also testing the return switch line conductor as well which means that
we've covered every scrap of insulation that is on that bit of the circuit so Joe we have panned
around to our two way and intermediate section of the switching we understand they're very
close together in this training simulation but the test itself is still going to be exactly the same
as it would be an industry can you confirm whether we're on or off at the moment Joe well this is the
challenge we've got because we should stepped away from the installation and then we've come back
to it and actually it's been some days in reality since we've done that we now have no idea if these
switches have been tampered with if someone's press them and operated them so we simply don't
know if this circuit is now in the on or off position it wouldn't be wise as the electrician
now to come back into the installation start doing his continuity or CPC combined with the
polarity test just to prove their back on would it it wouldn't be sensible you'd have to start taking
a circuit apart again and also it's not time efficient you can be disconnecting the circuit
doing the test that you've already done and then reconnecting it it's not a very very sensible
option so what we'll do is we'll follow the advice given to us in guidance note 3 by operating this
which is one at a time repeating the tests and that way we can be confident we've tested every
scrap of insulation that's covering the copper conductors on this circuit and we know that's
expected at AM2 and AM2S as well so standardized best practice critical point that you know that's
going into our test folks so Joe we're at the consumer unit now all the covers have been
returned all our loads have been removed we know a one way switch is in the on position we're only
sure about the two-way and intermediate switching positions so we're ready to start the insulation
resistance test according to guidance notes 3 can you say out the tester for me please Joe
yeah absolutely first I'm gonna do is check that the tester and the leads are in no way damaged
to make sure there's no cracks in the housing make sure there's no insulation missing split
or damaged on the leads there once we're happy that the equipment is fit for purpose we're going
to select our voltage range now we are testing a 230 volt circuit and according to BS 7671 we
need to test this at 500 volts so we've set this to 500 volts DC so now when we press the test
button we will be applying 500 volts DC across the ends of these two probes so we just need
to make sure at this point that we're a little bit careful because while this isn't enough of
a supply to do a serious injury it still hurts if you get 500 volts from one of these kits across
you so we'll avoid that so what we'll do first of all is we'll just make sure that the meter
is working so we're not zeroing our leads here but all we're doing is just making sure that the leads
are functional so there we go so we've got a very very low reading and then if we disconnect we get
a very very high reading so we're really happy there that the instrument is working that the
leads are continuous as I say that wasn't zeroing the leads we were expecting to get a value in the
mega ohm or millions of ohms range which means that any small amount of resistance within these
leads is not going to affect the overall reading so we've got the meter set up what we'll do now is
we'll proceed to test the circuit okay Joe already carry out the test and you're going to try as hard
as you can to stay out of the way the camera as you connect on to carry out the sequence please
for the insulation resistance test remembering there is no particular order in which to probe
onto as long as we cover all three conductors during the test okay so we'll make a start then
we're going to test between as you say all three combinations of conductors so I'm going to start
off by testing between a line and so we'll clip on to the earth bar there so we're gonna be testing
between line and CPC obviously that's the CPC so we will connect onto that terminal there now what
you always want to make sure of when you're doing this test is that you're actually making contact
between the metal work of the terminal and the actual tip of the probe because sometimes this
PVC can actually stop you from making contact it can kind of sit on the head of the screws always
like to just make sure I'm actually touching the metal work of the terminal and if we just slide
that out of the way and press the test button we should get a reading there so we can see
we're getting a reading of 999 mega ohms it has a little greater than symbol there but we could
just put a plus 999 mega ohms in the test result box I like to leave my clip onto the earth bar
there so we'll test now between CPC and neutral and again we should get a nice high reading again
greater than 999 mega ohms and then finally we've got one more test today which is between line and
neutral so we'll clip onto the neutral bar there and put our probe carefully into that hole press
the test button and once again we're getting great than 999 mega ohms so that's our first round of
insulation resistance testing done so Joe the first round of insulation resistance testing on
this lighting circuit however because we have to way and intermediate switching I think you don't
have to walk onto the installation and do what for me so we're going to have to do now is follow
the guidance that we're given in guidance note 3 Gardens note three states that where we've got to
way or two way and intermediate switching we have to operate the switches one at a time and then
repeat the tests now again we could kind of argue the validity of doing some of these things we're
going to test between neutral and CPC in line and neutral every time we operate a switch again
potentially in this circuit the neutral might not go anywhere near these two way intermediate
switches however in a different installation we may well be running the neutral next to those
conductors so for what we're going to do here in order to ensure that we hit every test that
we need to do we're going to make sure that we carry out all 3 combinations of test every time we
operate one of the switches so let's get started so we'll operate the first of our switches and
then we'll repeat the three insulation resistance tests so Joe walked out into the installation
operate the switch and is now returned back to the consumer unit remembering the supplies not
connected to the consumer unit as the tails were disconnected and the meters end and we're going to
subject the circuit to the tests once again so as we did before I'm gonna clip onto the earth
bar here test between line and CPC so we clip on there carry out the test and once again we get
in greater than 999 mega ohms leaving that clip on there we're now going to test between neutral
and CPC once again we're getting greater than 999 mega ohms and then we're going to move that on to
the neutral bar and we're going to test between neutral and line and again we're getting greater
than 999 mega ohms so that's the second round of testing completed after we've operated the
first switch so now we're going to go and we're going to operate the second of our two way and
intermediate switching so we'll operate a switch and then we'll carry out the three tests once more
so as you're watching this and Joe is carrying out all three again what we've got to remember
is that we're not trying to eliminate doing parts of the test remembering things like neutrals are
often taken to switches in domestic dwellings if the wiring for this circuit was in conduit
it uses a different wiring method and often the conductors can pass the neutral conductor so
we're leaving all three to be tested in each of the sequences so once again we've done all three
tests there and all three tests were greater than 999 mega ohms so now we'll operate the
third of our 2 way and intermediate switches and will carry out the three tests once more
test between line and CPC now just a small point to note here it's very good practice
when you're carrying out this test to release the test button before you remove your probe from the
terminal now the reason for that is that you've got quite long runs potentially of twin and CPC
cable and this can actually start to act a little bit like a capacitor and because we're passing a
DC current into our circuit it can actually charge it up with some potential discharge of electricity
and if you've charged it up removed your probes and then you touch across what is assumed to be
a dead circuit you can actually get a little shock off there the same as you would offer
capacitor probably not enough to do any serious harm but certainly enough to make you jump and
that could obviously lead on to further things so we it's best practice when we do the test
put the probe on to the terminal press the test button and then if you release the test button
the current will actually discharge back through the meter again quite safely meaning that you
don't have that capacity of effect going on so now we'll just carry out the last of our three tests
another point I'd say for your AM2 or AM2S is also you wouldn't want to be holding the button
and anyway near the ends of the leads if the instructor was to see you pass 500 volts yourself
he would suggest you're not working safely and would fail you that element of the test as well
so that's all three tests done and we've operated all three switches so we've carried out all our
installation resistance testing now at this point is very important that we go back into our circuit
and we reconnect any of those sensitive loads that we disconnected the first time around so
when we power the circuit up we've got this back up and running again and operational now at this
point we might get people saying well if you've taken the lid off and then put it back on again
you'd need to carry out the insulation resistance test again obviously we'd get stuck in an endless
loop there and that's just going to be pointless we've taken every precaution that we can and we've
carried out the test into the most extreme point that we possibly can do at this point we've got
to be satisfied with the results that we've got so we're completely insulation resistance test of
our lighting circuit yep our lighting circuit had 2 way and intermediate switching and we approach
it differently than I had done in any of my other video presentations what's thinking behind that
Joe the thinking behind that is that we want to make sure when you're going to carry out your
AM2 or your AM2S you have the information you need in order to pass that particular qualification for
me carrying out insulation resistance testing has one purpose and that is to make sure that
the resistance of the insulation covering all of those conductors is doing its job to that
end you need to make sure that you have tested every section of insulation carrying out the way
we did in Gary's previous video we'll achieve that carrying it out the way we did in this video we'll
also achieve that however the way that we've done it in this video is according to the instruction
in guidance note 3 which we believe is a standard that is used in the AM2 and AM2S test centres in
order to produce some standardization that the Assessors can work to is a conversation you can
have with him I think or her the the person doing your examination is that you can suggest the way
you'd like to do maybe it's the way that we've originally done it or you can suggest perhaps
the way in guidance notes three I think another conversation between the two you suggest you know
what you're doing any of them straighten your understanding and your knowledge again of the
purpose of the test so if you're thinking about what you're doing and you're carrying it out in
a way that doesn't even of the resistance of the insulation then you've carried out that
test correctly however if you're approaching AM2 or your AM2S really we need to be thinking about
what does guidance notes 3 tell us to do and we know from BS7671 the smallest acceptable value
of insulation resistances is 1 megaohm however goes if you were a new installation what value
would you be looking for ideally looking to guidance notes 3 if that's what they using
at the AM2 or AM2S centers it says here that a brand new circuit which we've installed and you
will do on a AM2 or AM2S must have an insulation resistance above 20 mega ohms because at 20 mega
ohms you've got to do further investigation that stage we know BS7671 says under normal
installations when the whole installations insulation resistance falls below two mega
ohms then we obviously going to carry out further investigation so their key points I think to be
demonstrating to your examiner that you know again you've got that range of knowledge of the answers
you're not just firing back one answer you're actually giving a considered answer that shows
knowledge across various different documents we're also going to do the same similar test when we do
a conduit exercise on where you know we're gonna have 2 way switch it on there and we'll repeat
both processes again we'll go to those videos so we're trying our hardest to add some AM2 and
AM2S stuff in and I think time to say sure it we shall we hope this video has been some help