this video continues on a series of videos i've been producing on the two plate method the two
plate method is where the supply is taken directly to the switch and in this installation we've come
from the consumer unit and we've taken our line our neutral and our CPC directly into the switch
unlike when we do the three plate method which is done on the channel where we take that supplied
directly to the lighting points we've expressed in other videos why we would do it it reduces the
number of cables for LED downlights in this series of videos we've done the one way circuit the
two way and two way intermediate explaining those connections so this video carries on to test that
circuit so we've got two way switch intermediate switch and a two way switch controlling these
LED downlights using the two plate method we're going to carry out the continuity CPC the polarity
and insulation resistance test in this video to prove that this circuit is working before we can
energize it the next stage is to set up our megger MFT tester so we'll go and do that and then we're
getting nice and close and you can see me test this circuit we're going to use our megger MFT in
order to measure the continuity of the CPC and we know from previous videos that we're measuring the
resistance therefore we need to go round to here where the omega symbol is because we're measuring
it in ohms our instrument comes on we saw in a previous video as well how i made this lead up
that meant that i could get to the furthest point of this circuit where they've got LED downlights
and also showed you in the previous video how to fit the easy fit connectors from Collingwood
we're going to be using the red and green leads for a line in our CPC and we're going to need to
make sure we connect them correctly in the top of our instrument so we're going to use the red and
green sections it doesn't matter which way around they go but we always like them to go the correct
way around for colour matching but these leads themselves obviously offer resistance so we need
to make sure we remove the resistance of those leads so i'm just going to link these two together
with this piece of copper here so if i just wedge that into position i can remove the resistance of
the lead so we currently got it at 0.09 there's a test button on either side doesn't matter which
one i press press it once and now we have zero remember on the Megger MFT tester if it's flashing
zero it's actually less than zero so we're now ready to carry out our continuity of CPC tester
our lighting points and include the polarity check in other words we're gonna operate those switches
we know from previous videos in the series we're going to have to link together the
line conductor and the CPC together now i used to use a crocodile clip and link for that connection
but we found that crocodile clip started getting a bit high resistant so i'm going to just do
a simple process of undoing my line conductor and just popping it into the earth bar it doesn't
matter where i go in the earth bar remember it's a solid brass bar that means that the CPC and the
line conductor are linked together there in the earth bar and not using that separate link that
i've shown in previous videos we would expect to get our highest reading for continuity CPC in a
radial circuit at the furthest point and this light fitting here is the furthest point on the
circuit however we're going to need to prove that this one comes on and off as part of our polarity
check as well as the other LED downlights in the area so we will check here as well
however we will always record the highest reading we achieve for our continuity CPC wherever that
is in circuit but we know logically it should be the end of a radial circuit because that's the
maximum amount of cable and if you come in nice and closely you can also do a visual polarity
check where you're checking the l the earth symbol and the neutral are connected correctly in here
so it's a nice little touch so you can do a visual polarity just going to pull this connector out and
insert my test lead adapter now the readings are going to jump around a little bit on here okay so
we're going to pick a reading so we've got it nice and frozen there at what have we got 1.17 ohms
the circuit is closed in other words the switches are in the on position so it wouldn't matter where
i went in circuit to turn it off so if i go to the first switch down here and i operate that switch
we should see the reading change to infinity so in other words now i've got an open circuit
i can go to any switch on the circuit i should get it to come back on we'll go to the
intermediate switch in the middle operate that switch and i now have a reading of 1.2 ohms go
to the next switch so we're going to operate our third switching circuit our two way switch
and again we can see it's gone off so we've got an infinite reading
and then we go back to any switch should come back on i've got a reading now of 0.71
go back to my first two way switch and then the circuit we can see is now again
open circuit so it's gone off it doesn't matter which way to operate now it should come back on
and i'll let it settle down of all the rings i've got there i need to remember the highest one even
though it might not be at the moment the height is ridden in circuit because we've got a test
the other lighting point and the switches so this is the other lighting point next
so we've tested to the furthest point on this radial circuit and proved that we've
got a CPC there but you need to prove the CPC is every point in circuit we got a reading of 1.2
ohms now we've got to remember that reading because if that reading
we find a higher one that will be the one we recorded however logically because we're going
to have less cable in when we check at this point you expect our reading for R1 plus R2
the continuity reading to fall so let's move it across to the next LED downlight and connect it
and we can see at the minute that we have no reading so in other words we have an open circuit
so we're required to press a switch if i go back to that first two way switch and operate it
i have a reading it's going to move around a little bit let's go with 0.62 of an ohm
i operate my intermediate switch we can see that it's now gone to open circuit so it's
not actually in the on position now so we've got no reading we go back to my two way switch
operate the switch i get a reading of 0.71 of an ohm operator switch the intermediate switch
we go to open circuit and let's do it on the final switching position let's operate the last
two way switch and we have a reading of 0.3 ohms so we've still got our highest reading
at the the first test that we did of 1.2 ohms but we now need to check at each of the light switches
that they also have a CPC i've removed the lead that i used to get to the furthest point of the
LEDs and gone back to my traditional probes again using the red and green sections in the
top of the MFT tester again we'll just confirm that they are zeroed before starting the test
there are zeroed so we can now test the CPC as each of the light switches
so we need to prove the CPC is also here remember we've said it many times this could
be changed from metal exposed conductive part that would need connecting to the CPC
so one of our probes goes on to the earth terminal one of them picks up our line conductor
press nice and firm we have a reading of 0.27 of an ohm we'll move to the next switch
into our intermediate switch we make our connection for our circuit protective conductor
we pick up a line connection press nice and firmly my reading settles down i've got 0.06 of an ohm
onto our final two way switch pick up our circuit protective conductor
pick up our line connection and we have a read in there again of 0.06 of an ohm
so we've got our highest reading for our continuity CPC as 1.2 ohms which we're going
to record under that box heading R1 plus R2 we confirm that the switch is turned on the lighting
point so we can tick our polarity box we're now expected to do our insulation resistance test
so i'm going to need to drop my line conductor back out the earth bar and return it to the
required torque setting and in this case it is 2.3 newton meters of torque so as i've clicked through
there i know i've returned the torque setting to that line conductor in the top of this Crabtree
Starbreaker six amps rated to the required torque setting on the channel i've shown videos on how
to set up a torque screwdriver and the importance of using it so just to remember to return that to
the required torque setting we're now ready to get our covers on and our loads removed in order that
we can carry out our insulation resistance test next we're now going to carry out the insulation
resistance test on our circuits we've put all the covers back on we've also removed the sensitive
loads in this case being the LED downlights we don't want to start passing 500 volts DC through
those because they could be damaged also we've got to be thinking now about the switch positions we
don't know whether they're on or off and this is really crucial at AM2 AM2S and AM2E when you're
carrying out your insulation resistance test on your lighting circuit that could possibly be
two way intermediate you must follow the next procedure when carrying out the test so we're
going to test from with inside the consumer unit we're going to test with the breaker off and the
RCCB off because the RCCB also contains electronic components we're going to carry out the test
between line neutral and CPC do those three tests then what we've got to do is come back into the
installation operate the first switch repeat all three tests again operate the second switch repeat
all three tests again operate the third switch and re-test for a final time meaning actually
on the lighting circuit you're going to carry out the insulation resistance test four times
and it's really important that you remember that when you're doing that end point assessment
as part of your AM2 AM2S or AM2E so we're next inside the consumer unit carry out the insulation
resistance test and then we'll be operating the switches and repeating the test again
we're going to need to set our megger MFT up to do the installation resistance test we've got the
megohms scales here sometimes with the megohm scale we need to set it to 500 volts 500 volts
DC and we need to check that these leads actually are good so in this case we're going to bring them
together and expect to get a dead short one here so we bring the two leads together connect them
and then we have to press and hold our test button and we expect to get a dead short if
one of the leads had broken and they can sometimes break at this point here without you noticing it
it's no different than being broken here so if we do imagine we had a broken lead let's remove those
apart and we did our test we've actually got a reading greater than the machine can read greater
than 999 megohms or megohms however you want to say it so that would be a false reading that
we'd think was brilliant so it's always important that you just bring your leads together before you
carry out this test press your test button and just confirm you've got a dead short so they're
connected together leads are in good shape let's carry out the insulation resistance test next
so ready to our insulation resistance test our RCCB is in the off position our circuit breakers
in the off position we're going to do it from the top of our breaker and our neutral and earth
bars there is no correct sequence and it's not even a Gary sequence so we're going to go in any
order we like connect onto the earth bar and i'm going to test between the earth bar and neutral
i'm going to press my test button on my instrument and i get a read in
greater than machine can read remember the smallest acceptable value of insulation resistance
is one megohm but we'd expect a very very high reading for a brand new installation next i'm
gonna test between my line and my earth connection so i'm a CPC in my earth bar so there we go so
that's between line and CPC greater than the machine can read just going to take my crocodile
clip move it across to the neutral bar and test between the neutral bar and the line connection
and again greater than the machine can read now you might think that's it
the insulation resistance test is done but for AM2 AM2S AM2E your endpoint practical assessment for
anything with two way or two way intermediate switching of a lighting circuit you need to
operate your switches according to Guidance Notes three so in our installation here we don't know
whether our circuit was on or off so what you do is you tested the board as we've done you walk
out into the installation and you operate a switch so we've operated this switch here we go back into
our board and we do all three again once we've done that we will come out and operate this switch
do all three again and then we'll do this switch and do all three again so effectively
you're going to do the insulation resistance test on this circuit four times that means
that we will prove that all elements of the switching and strappers were at some point
in circuit and check for insulation resistance testing so we've operated this switch we come
back into our board and we test again the three sets as we go through so we can see the reading
we now go between the earth and neutral bars once again greater than the machine can read
we move it across we connect our line connection and our CPC
and again we're very happy with these readings we come back into our installation we operated
this switch first time so we come to this switch now operate the switch
we come back to our consumer unit and we go through all three once again
there we go move across we test again
and we need to move the crocodile clip across to our earth bar
test between that and our line connection and we can see again greater than machine can read
we leave the consumer unit we come back into the installation we've operated this switch
we've operated this switch so we're now required to operate this one here
and now we can go back and test for the final time
meaning we've actually carried out the insulation resistance test four times
so reading greater than the machine can read move it across test again
and then finally we move across into here we test for our last time
we have taken a lot of readings there they were all the same so it's nice and easy to record it
on our test paperwork and i like it as plus 999 for this instrument rather than using the greater
than symbol it's up to you what you want to put in but that's our insulation resistance test carried
out now and we've carried it out with our switches and then we operated them as per guidance note 3
and as you will be required of your endpoint assessment so that's the installation resistance
test finished that's completed this mini series of looking at the two plate method so we did one-way
two-way and two-way intermediate and we tested all of those circuits and this is
a common method on-site taking the feed to the switch where there's loads of led down lights
and there are other videos on the channel to help you with wiring diagrams with it in situ
i'm actually in a modern property where i show you the connections at the lighting point as i
change over light fillings and how they'd use the two plate method so i recommend you check
out those videos if you haven't already seen them we're likely to go on from this series to look at
doing the safe isolation where you've got two way intermediate and only one cable at the lighting
point because again that will help you with AM2 and AM2S we will also look at maybe some other
connections that can be made for LED downlights but for this video and this mini series on two
plate method that's the last video in this series and as always i hope this video has been some help