so building up a series of videos using the two plate method remember the two plate method
where we take the line neutral connection to the switch and then we go from the switch to
the actual lighting points remember it makes it easier when we fit in recessed
down lights in this case LED ones we went on we looked at one way we extended that to two way
and we looked at the connections on the two way lighting circuit using the two plate method
so in this video presentation we're going to go on and carry out our continuity of CPC test
including polarity at the same time and follow it with insulation resistance i've got my Megger MFT
tester ready to go i've also made a new lead to adapt the ability to connect to these easy fit
connectors the video i did with Joe Joe was a little bit struggling to get onto the pins so
i've made a new lead in order to make that part of the testing process a little easier we're going to
bring the camera in nice and close and see where i'm making my connections within the consumer unit
without using a link and where am i putting my probes at the switches and have a look at this
new uh test adapting lead that i've made let's bring the camera in so for the continuity CPC test
i'm going to take my line conductor at the top of my six amp type B circuit breaker and put it into
my earth bar effectively linking together the line and CPC in some of my earlier video presentations
i did this with a crocodile clip and link however we've said in other videos that we've done is
that's becoming a little bit highly resistive and causing a few issues with the actual test results
so we'll just take that one and push it into the earth bar it doesn't matter where we go in the
earth bar it's a solid brass bar so it doesn't matter which of these terminations we go into
we've actually connected the line conductor and CPC together within the consumer unit so
now we're ready to test it the switches and the lighting points on this circuit
so my Megger MFT i'm going to set it to the ohm scale this is the orange section here so we can
rotate it around to the ohm scale the instrument comes on and we're going to use the red and green
sections in the top of the instrument as always it doesn't matter if the green lead goes in the red
and the red lead goes into green but historically we always put red in red and green and green
in order to carry out this continuity test and we're going to see if our leads are also zeroed
by connecting them together like so small amount of resistance offered by the leads
so we'll just put those there we now press the test button the test button again and we
can see now they are connected together but our resistance is now zero i'm gonna swap these over
for my probe tips
like so okay and i'm ready to go into here i'm gonna connect it into the common
in here wouldn't matter you might have to order the switches but i always like
to go into the common and obviously my earth terminal at the back when my CPC is connected
so i'm going to clip onto the common and onto there i get a reading of
naught point one two ohms so that was on the common connection and the CPC at the back
i'll go across to here again i'm gonna connect into the common into the bottom
of the switch and onto the CPC terminal here and i get a reading of when it comes down
i've got 0.21 so 0.21 being my highest reading at the moment i now need to check actually
at the lighting points themselves and this is where my new adapter will come into play next
so i've got an easy fit connector here from Collingwood and this is the section here
that i make my terminations with my PVC PVC twin and CPC cable and Joe struggled a little bit to
get onto these terminals to prove that we had our connections to these points so what i've done is
i've made up a test lead with actually one of the other ends of the easy fit connector on
i've probed into my red and green section at the top of my instrument and i'll now just need to
remove the resistance of this i've made myself a little link to link between the conductors
and you can see already with zero those out so i'll just link those together a small piece of
copper if you were doing loads of these easy fit connectors every week what an easy way now it is
going to be to get on to the end of that point in order to prove continuity CPC and polarity at my
lighting points we'll do that next so i've got my homemade easy fit connector end ready to test to
each of the lighting points we're going to operate the switches to prove polarity and then we're
going to record the highest reading of what we get at this lighting point if it's higher than the
reading that we got the actual light switches we expect it to be because obviously the cable went
down to the switch through the switching sequence and back to the lights so you'd expect the highest
reading to be up here however we always know we record the highest reading wherever it is
let's go for the first lighting point unclip the actual light itself
clip in my homemade connector push it into place i have absolutely no reading whatsoever that's
suggesting that the switches are probably in the off position so we go to the first switch
the circuit is now on we need to remember the highest of these readings 1.28 so if it goes off
circuit comes back on we've got slightly more of the switching circuit in so we've
got slightly higher reading so that's the one we need to remember so one point it'll settle down
seven seven goes off comes back on we've got a slightly lower reading now so the readings
we got there we remember the highest one and we moved to the next lighting point just to
point out for those people who are pretty clever about this with the amount of cabling circuit
the switches that we use at college very rarely have a current and voltage passing through which
would create a spark every time you open close a switch which cleans the contacts of these switches
which makes a better electrical connection these are often left in boxes for a year before
they're reused so we do see the readings keep changing because those switches for the first
time in almost 12 months get operated i say to my learners go through the sequence a few times
and get it so the switch has been made and break and and then pick a reading when you go
through your sequence of your highest reading and that's what they end up doing but that's
just a good point for you that settle down to a lot lower reading but we've probably got less
of the switching circuit in it's the highest reading when we see it that we have to record
let's change adapters now i'm going to leave it disconnected for the insulation resistance test
so let's put the adapter into the second lighting point
and we remember the highest reading if it's higher than what we got in the first stage
operate the switch goes off comes back on goes off let's go back on
okay and of all those readings we get we're going to record the highest reading
under the box heading r1 plus r2 r1 being the resistance of the line conductor added to r2
the resistance of the CPC we've operated the switches we know we've got the line conductor
connected here which would be in the breaker so polarity proves that we switch and fuse in the
line conductor we can tick that box and we can now move towards our insulation resistance test
we've already got our loads removed so our lighting points are out
our covers need to go back on in order to perform the insulation resistance test next
so we need to pop the line conductor back into the top of the breaker we would need to return
these terminations to the required torque setting unfortunately one of our torque screwdrivers out
at the moment and the other one i'm struggling to find but the learners when i'm teaching them know
that they've got to get that torque screwdriver and return this to the required torque setting
so just because i'm nipping this one back into position doesn't mean that that's correct that
termination needs returning to the required torque setting i know these two were already done this
rig is ready to go so remember for my learners the torque setting here it's very important that
we get that back to the right torque setting we're done with the switches are on or off let's presume
we're doing something for AM2 or AM2S they like you do the insulation resistance test this way
in early video presentations i did i'll always leave the switches on and then i operate both
switches and do the installation resistance test again AM2 and AM2S likes you to do the
test once operate switch do test again operate and switch to the test again to effectively do
the installation resistance three times meaning that you have done it in the on position it's
uh in the on-site guide guidance notes three etcetera so let's stick with that method let's
turn our instrument to the red scale on a Megger MFT to 500 volts DC i've still got my probes in
uh back to the original set and this time i've got a crocodile clip and a probe ready to go
so we're going to do the test i'll try and stay out the way as best as i can but i'll be talking
you through where my terminations are going no order particularly so earth bar for me first
top of the breaker nice and firmly pressed press the test button and we get a reading
greater than the machine can read greater than 999 mega ohms
so i'm going to take my probe now i'm going to the neutral bar so i'm now testing between the
earth and neutral bars press and hold greater than machine can be greater than 999 mega ohms
and now i'm going to go on to the neutral bar which always falls off on camera
hope it doesn't today and on to the top of the line connection press the test button again
okay and that's the test done for the first time return out a few points for my learners they'll
always remember to keep the breaker and the RCCB in the off position the RCCB has electronic
components in could be affected by the 500 volts we've disconnected the LED down lights again
electronic components in order that we don't want to damage those so they're disconnected
and we've done the test once we walk out now into the installation and we go to the first of
the two way switches and change its position and we repeat the test again so earth bar
top of the breaker firmly connected press and hold we've gone to the neutral bar press and hold
and we move that onto the neutral bar hopefully it won't fall off oh there you go pulls off make
sure it's firmly connected and see the problem because i'm trying to keep my hands out of the way
hold it this time and on to the top of the line so between the neutral bar and line connection
press and hold greater than machine can read we could leave them on there we're going to
imagine we've walked out into the installation so let's take those off we walk out into the
installation we've already operated this switch once we operate the other switch
this means that we've confirmed that we've got the strappers in circuit in order to carry out the
insulation resistance we walk back to the consumer unit and we repeat all three again so earth bar
and line greater than 999 mega ohms neutral bar
greater than 999 mega ohms i'm sure someone's already corrected the word
mega and the uh below uh comments box we're on in position between the neutral and line connection
and there we go the minimum insulation resistance test is one mega ohm uh however
further investigation required at two it does send guidance notes three for a brand new installation
it shouldn't be less than 20 mega ohms so all three of those my learners are fully aware
of they're also aware of the fact that the earthen conductor has to be connected within the tails
obviously the line of neutral don't matter but the earthing conductor needs to be connected to
the supply source of earth so let's just recap them so we've done the continuity CPC and polarity
test first we followed it by the insulation resistance test we've made sure that our sensitive
electronic equipment within our RCCB is in the off position we also keep the breaker off because the
voltage would go underneath and across the bottom of the RCCB so there's no electronic components
in the circuit breaker but there is in the RCCB we've operated the switches repeated the tests
we'll do three times we'll remove the sensitive electronic equipment in the LED down lights
and we can record those readings now so that's the two plate method testing two way switching
when we've got uh in this case led downloaders in circuit we'll go on in the next video we'll
extend the two way circuit into two way and intermediate we'll look at the connections for
that video and we'll follow it in a video after that where we actually carry out the testing for
two-way and intermediate circuit testing as well so as always i hope this video has been some help
you