so we're back at our two plate method rig we've got our one way lighting circuit installed and
you've seen over a series of videos i've explained the connections in the switch and
the connections at the lighting point and then we changed it over to the easy fit connectors
from Collingwood so the first test joe being continuity CPC we're going to measure all the
readings at all the points i'm recording which one we're going to be recording the highest point
again don't get confused and think you record the end point is the highest value you record
but i've got a little bit of issue now because i've got these easy fit connectors can you
explain how i'm going to make my connection for that continuity test yeah absolutely so
you might look at this and think well the end of the circuit is on this fitting here because this
is after the connector however this is a double insulated fitting so there's no CPC connection
to this it doesn't have an earth connection so what we're going to be looking at is we're going
to be looking at testing uh within here so we're going to test in here and in here because we test
at every point we do so in order to do that i think the best way of doing that is simply to
unplug the led light fitting because we're going to have to do that anyway when we do our
installation resistance desktop and then test across the pins which we'll be able to access
on the end there okay so we're going to test the light switch we're going to test that lighting
point 1 lighting point 2 recording the highest reading and we're also going to include our
polarity test at the same time so obviously we're going to operate the switch so it's a little bit
different than what we've seen before when we hit our basic one-way lighting circuit for two reasons
we've got the two plate method and we'll now introduce led lights i think if we bring the
camera in next let's see how we're going to perform the first test continuity CPC and polarity
so a little bit different from my early videos i've done on GS38 electrical i've started now
actually putting the line conductor into the earth bar where the CPC is connected it doesn't
matter which of the terminations it goes in but that actually physically links the two together
rather than using my crocodile clip and link because we've had some issues with the
resistance of that and removing it and obviously the clip itself is starting to become unreliable
this is a more reliable connection where i've got the line conductor in the bar with the CPC
we're now ready to set up our test instrument to carry out the continuity test so joe we're
about to set up our Megger MFT to carry out the continuity of CPC test can you do that set up
for us please absolutely first things first let's get the leads in the right place so we've got here
our L1 and L2 terminals so that's where we're going to connect our leads up and of course we
like to get the colours matching because otherwise Joe's ocd gets triggered so let's have a look at
this then so we're going to set it to measure a low ohm setting so we're going to measure low ohms
turn it to the orange setting on this Megger MFT let it do its initial warm-up and then you can see
that it's looking for it now it's important to remember with this type of tester it's testing all
the time so it's currently trying to test what the resistance of the air between these two probes are
we're going to zero the leads before we do anything so we're going to clip these together and
notice i'm using the fixed jaw connected to the fixed jaw because what that does is it gives us
the most reliable connection and instead of putting them across each other i'm going to
put them long ways like that and that allows you the best contact across the greatest surface area
now interestingly on the multi-function test now it's showing that we've got less than zero ohms
that's because this has maybe been zeroed with a different set of leads or something like that
so then we press the test button which in this case is the zeroing button
and you'll notice the little zero symbol here has gone so 0.13 ohms is the resistance of the leads
with this connection so i'll just make sure that's nice and tight there so we've got 0.14 if i now
press the test button again you can see we're now at zero it's not saying less than zero so
we're ready to start testing we've got the little zero symbol there and we can ready to do the test
so we've connected together the line and CPC within the consumer unit we're down at the first
switch and in this case the only switch and we're going to test between the line conductor and the
CPC we're not going to operate the switch at this stage we're just going to prove that we have a CPC
at the actual lighting point itself joe just remind me do i need a CPC down here at this point
because this is all plastic the CPC is technically not required at the moment however it's best
practice to take a CPC to every point in the installation because at some point in the future
this may well be changed for a metal clad version okay making it an exposed conductive
part okay brilliant let's carry out the test then okay so we're just going to connect across the
CPC connection in the back there and the line connection in the front okay and we have a
reading of when it settles down of zero point one eight okay 0.18 very good and of course if
at this stage you haven't got a reading it may be that your switch is off or perhaps you're
on the the wrong side of the uh switch itself uh with the switch in the off position so it might
just be worth if you're not reading that should really be the first thing that you think about
checking okay so the easiest thing is for me is just to drop down into the other hole and then
obviously pick up the other brown conductor in order to do the test so we're doing another switch
well that's the first one we've now got to go to every lighting point in circuit we've only got two
of all the reasons we get joe which one will record we'll be recording the highest reading
don't just go to the end of the circuit and presume that'll be the highest reading sometimes
there's t's and things that you can't see behind the scenes okay so let's go to the line point next
after testing the light switch we come up to the easy fit connectors these would normally be in the
ceiling we've got our led down lighters let's just confirm again we can clearly see on the side there
the symbol for double insulated even though it's metallic the CPC is not required at this point
therefore we're going to test at the easy fit connectors themselves joe do you want to do
that for us absolutely so it's just a matter of pushing down this little plastic spring there
and that just pulls apart really nice and easily you can also see through the plastic you can see
which terminals are aiming for so we've got our line connection here and our CPC here
so we're just going to connect across those so make our connections really nice and firm
and we've got a zero oh just slipped off there joe a little bit just a little bit
i've got a reading of 0.18 if i operate the switch
we're getting full scale deflection and we're back on again so we've left
so 0.18 if you'd like to do the second one for us absolutely so by flicking that switch there
Gary what have we actually proved by that well we're proving that the line conductor opens and
closes now the breaks and makes it within the circuit itself we know that we've connected the
line conductor and consume it to the CPC and this is all part of the polarity test we've also done
a visual polarity up here by confirming the line conductor and CPC we can also see the neutral so
that's all part of the polarity test absolutely making sure that that line conductor is being
switched and we're not switching the neutral it's very important 0.21 operate the switch
and again we're going to leave it in the on position remember in the highest of all our
readings remember on a very small rig we don't get very large readings so we left it on because which
test are we going to carry out next joe so next we're going to carry out our insulation resistance
so we've reconnected the line conductor into the top of the 6 amp type B circuit breaker
we've confirmed its torque settings as we're mimicking a domestic installation we've got RCD
protection offering additional protection rate at 30 milliamps it could be 30 milliamps or below
however Joe with the cover back on the switch and the switch left in the on position there's still
some precautions for insulation resistance testing absolutely so inside our LED light fittings here
there's some fairly delicate electronics two things could happen number one we'll get a false
reading we're gonna do our insulation resistance across line and neutral and also we could damage
the inlets of this and we don't want to do that when we're pumping 500 volts for it what we could
do on electrical installation condition reports is actually carry out the insulation resistance
test first of all look what voltage before we up into the 500 so we could attempt it 250 volts to
start with and if it's clear at that point then we could think about going to the 500 that's in
situations where you're not sure if you've left a load connected or something like that
and that's something that perhaps Marcus is going to explore in further videos you can
watch on Marcus which is in his fault finding and testing section on a playlist within
GSH electrical nice and easy for us i think we can see the light fittings are connected joe how easy
is it going to disconnect them from the circuit well i'm going to have to go inside here i'm going
to have to open up the junction box i'm going to have to undo the connections and i'm going to have
to think well i want to redo those i'm going to end up damaging those delicate stranded conductors
or how about we just disconnect those connectors like that just nice and simple so we've now
disconnected the sense of electronic components within the led fitting as always we've left the
RCCB off because we know that's got sensitive electronic components in it for my learners and
joe's learners we also leave the breaker off even though we know there's no sensitive electronics
because the test actually goes out and through the circuit but it'll also go down so if we left
this on the circuit could have 500 volts through here the insulation resistance could be across
the bottom of the RCCB is the electronics at the top joe or the electronics at the bottom we don't
know we don't know so we always say to leave that off and we're just going to carry out the
standard insulation resistance test from in here remembering the important part of this part of the
video is that we've disconnected the sensitive electronic components within the LEDs and the
RCCB's we're going to bring the camera in joe you happy with that absolutely bring the camera
in and we'll just see what we can do in here when we carry out the insulation resistance test
so can you set up please Megger MFT in order to carry out the insulation resistance test please
absolutely so we're going to change this now to our 500 volt setting so we're going to change
that so when we press the test button it's going to inject 500 volts DC into the electrical system
now a couple of things just to note at this point the tester stops testing all the time because we
wouldn't want to have phone revolts across the ends of these probes without that being under our
control that could lead to a bit of an accident and also it's worth noting at this stage that
there are times when your test leads may snap down here internally so it may be that the flexible
copper inside there can give way over time because obviously we know our leads get a fair
bit of abuse in the workplace and what tends to happen is you don't notice until you pull that out
and you've lost your connection so at this stage it's always a good idea just to quickly check that
your tester is working as you'd expect it to so if we press the test button we get a phenomenally
high reading there because we're testing the resistance of the air between our two probes there
and then it's a good idea just to connect them together to make sure that your leads are doing
their job the test is working properly and when we do this now we should get a very very low reading
just slipped off there trying again so we should get a very very low reading
very nice so that just helps us to see that we're going to get the readings that
we should be getting because obviously when we do the test and we get a huge number greater than 999
mega ohms we're assuming that that's because the insulation is doing its job in the installation
but what we don't want to happen is for this to have snapped inside here
and for us to get that really high reading no matter what's happening so this is the first
time in a long while we're having two people doing this so i'm behind the camera joe so i can tell
whether your hands are blocking the view because everyone says to me i can't see what you're doing
okay then so insulation resistance testing then so what we're going to do is we're going to test
all combinations of conductors so we've got three conductors which gives us three tests
so what we're going to do in this case is first of all i'm going to test between line and neutral so
in doing this obviously getting onto the neutral bar is really really nice and easy we've got no
problem there and putting this probe here into the top of the circuit breaker is normally fine
but again a little bit of an issue here you just need to be careful of because we've got
quite short tips here as you'd expect them to be what can happen is that sometimes the end of the
probe doesn't quite make the contact with the metal but the plastic bit kind of sits on the
edge of the screw kind of gap so it sort of it feels like you're pressing in really hard but
it's not actually making contact so it's a good idea just to make sure that you are actually got
the tip of your probe onto the metal work of there otherwise again you'll get a really high reading
which is what we want but it won't be because you're making a connection so let's test away
so greater than the machine can read so we would record plus 999 mega ohms joe so it's
a fantastic reading happy days right so now we'll go and we'll do line and CPC so again
making a good connection inside our line terminal there and we'll go on to the earth bar up here
again greater than nine nine nine mega ohms now that's mega or mega or meg oh well Joe you just uh
did you do the next test just have that discussion yeah i i don't really think it matters that much
but people will comment so i normally say mega roams i'm sure i'm sure there's going to be some
comments popping up at this point in the video now and now we'll test between neutral and CPC
having said that of course always happy to be corrected if we do make a mistake
greater than nine nine nine mega ohms okay
for that so i'm gonna say greater than nine nine nine meg over scary okay
there's no Gary order for this um there's no joe order for this we just got a test between
all three we've only got one circuit again check out other videos on the channel where we've got
multiple circuits and how you carry out an insulator resistance test when you have more than
one circuit in play just remind us for an existing installation what the smallest acceptable value of
insulation resistance is joe so the smallest acceptable value is one mega ohm okay and we
require further investigation with the overall insulation resistance of the circuits fall below
two mega ohms and we have to do for a brand new circuit according to guidance notes three have
a reading that is greater than 20 mega ohms for brand new installation we've done that with this
one we've got greater than the machine can read greater than nine nine nine and you're going to
say mega ohms this time let's keep it fresh okay so we're going to go okay thank you just
one more point before we finish uh it's critical if you're doing this in a real world installation
when you do your insulation resistance test the regulations require that you have your main
thing conductor connected so we want to make sure that that's in place obviously we're in
a simulated environment here so we don't have that conductor installed but when you go out
and do this in the real world potentially when you do this in an exam you want to make sure
that you've got that conductor in place and that doesn't mean we have to have the line in neutral
it's just the earthing conductor connected to the external earth source good point joe so raise some
interesting points there if nothing else that i still say mega homes and you sometimes say
okay i like to flick between the two yeah so that's some comments we're having on the channel
so let's reiterate some of those points obviously we've disconnected the sense of electronic
equipment joe and for us at this stage we're going to reconnect those because our learners don't do
at this stage any of the live testing so would you like to put those back in how easy it is again to
reconnect absolutely and again what an absolute fantastic idea this is so the fact that you can
do your testing really nice and thoroughly get all the readings you need but you're not causing
yourself an immense amount of hassle in terms of disconnecting and reconnecting those fittings
and i love the fact they're clear so you can do a visual polarity check insulation resistance
test we clearly said again the one conductor that must be connected from the tails to the external
source is the earthen conductor remember AM2 and AM2S that might be something you need to reiterate
and make sure is in place our switches are left in which position for this test so for the insulation
resistance let's leave them in the on position because that means that then we're testing every
scrap of insulation as far as we can inside the circuit we've completed three tests in
this video we've done the continuity CPC recorded under the box heading R1 plus R2 R1 standing for
the resistance of the line conductor and R2 the resistance of the CPC and that's what we measured
and we record the highest of our readings for that we also completed the polarity test what
we put in the player box show we just put a tick i'll put a tick in the player box and for this
one we're going to record all three readings for our insulation resistance test and they were all
greater than the machine can read and Gary likes to put plus rather than the greater than sign
because often my students put it the wrong way around okay so i like prefer plus so that's all
the things we've covered in this video we're going to go on in the next video to change it to two way
so we'll look at the connections for a two-way circuit when we've taken the feed to the switch
the two plate method and then hopefully joe will join us again and we can redo the testing
in that video just need to say the last thing joe what we're going to say we hope this video
has been some help need some help really on my own leave me hanging