so in this video presentation we're going to look at the continuity of CPC polarity and insulation
resistance test of our level one PVC conduit exercise we've got an exercise here which uses
a one way switch controlling a light fitting is the first time these Learners have done plastic
conduit and we're reintroducing the process of carrying out those early dead tests so it's really
important for me that we prove the CPC gets to the exposed conductive part of the box the exposed
conductive part of the actual frame that holds the switch as well as the CPC connections within the
actual accessory we'll also prove the CPC gets up to the plastic light fitting in case it's changed
in the future to a metallic one so this video we're going to carry out the continuity of CPC
and include the polarity test at the same time and then follow with the insulation resistance
test of our level one plastic conduit lighting circuit so unlike earlier video presentations
where I actually just linked with a solid link to crocodile Clips at the end the line conductor to
the earth bar where the CPC is connected later videos have gone on now and I've actually run
move the line conductor altogether out of the top of the six amp type B circuit breaker for this
circuit and actually screwed into the earth bar itself so there's a sort of a permanent connection
between the two what we were finding was those crocodile clips kept getting a bit of a high
resistive reading for us so I've linked those two together but this time I'm linking them by putting
them actually in the earth bar so the CPC and line conductor are linked together just to recap
for our learners remember this lighting circuit because the way it's installed didn't need an RCD
rate of 30 milliamps and below however we know our domestic line circuits that we would have worked
on before this when we're using PVC PVC twin and CPC cables absolutely needed RCD protecting this
has just got it so it doesn't hurt to have the RCD protection but just remember there's some of
the discussions we've had in the classroom so the link's in place line and CPC are linked together
we're going to go to our switch first we're going to prove the CPC gets to there and then we've got
to a light and fit in and prove the CPC gets to there and actually will prove the polarity that
we switch and fuse within the line conductor so let's set up our Megger MFT in order to measure
the continuity of the CPC test that means we're measuring the resistance of the conductor so we
need to move it around to the orange scale which is for the ohms so we're going to measure this
in ohms we measuring resistance and we need to insert our leads doesn't matter which colours
we use we generally use the the red and green ones and again it doesn't make a difference
that we use the correct slots in the top we can use the red one and the green one historically
we'll put the red in red and green and green but those are the two we ignore the blue one at this
stage we'll get back to that one we're on the level three apprenticeship so let's put those in
like so and I'm going to change it over to the crocodile clips in order to remove
the resistance of the leads remember the leads have copper in them and therefore
these leads will offer resistance in circuit so maximum surface area to maximum surface area
flashing zero doesn't mean zero means it's below zero press the test button once have a reading
test button again we've now got a stationary zero means we've moved the resistance of these leads
we're ready to do the test so I'm going to attempt to talk you through as well as show you it might
not be as easy to show you as it is to listen to what I'm saying so I'm going to connect into the
common of the switch this brown conductor here being the permanent line from the consumer unit
the other brown out of L1 is the switching line to the light so I'm going to use the common and
I'm going to connect to the earth terminal the frame the earth terminal and the box in order
to prove that all connected to the CPC I'll try and keep my hands out the way so I'm in common
and if we get enough pressure I'm onto the earth terminal at the same time
so we'll go with 0.2 yeah 0.2 of an ohm come off and now I'm going to go back into common
and for me I'm going to use the hole here where their threads were for one of the screws and I
get one settles down 0.23 so that was using the hole here because it's got nice and clean inside
where the threads are so you have a really good connection if you go into the back of the actual
plate you have to scratch some of it away in order to get down to the bright steel so when common and
that threaded section there so we're now going to the common of the back box so common here and
into the back box it's gone to the earth terminal reading of 0.24 and then we're going to go again
to the threaded area here of the screw and we get 0.24 again two five yep as it settles down
so we've got to remember the highest reading there so I've got 0.2 let's go with five 0.25 of an ohm
proving the CPC got to the front plate CPC got to here CPC got to here but he got to the box
as well Gary it's really important the frame is earth and the box is earthed and we don't
just prove it on the actual CPC terminals we're now going to go up to the light we're going to
operate the switch when we're up there as well as part polarity test I'm going to prove there is a
CPC also connected to the light next so I've pulled the camera back a little bit further
so again you're gonna have to listen to what I'm doing the reason I've done that is I want to see
the operator switch the full scale deflections the instrument and I'll talk you through where
I'm probing on here so we're probably into the line and CPC in the actual fit in itself or tries
best I can it's going to be really tricky to do so if I go line and I go CPC first of all in here
let's see if we have a reader we have no reading whatsoever okay so you can start
panicking or you can think is it the switch in the the off position so let's operate the switch
let's go back up again let's go on to the CPC and then on to the line itself and we have a
reading of 0.2 let's go with 0.27 so we had no reading start with operate the switch we have a
reading so if we repeat the process if we operate switch again we should now form we have no reading
and we don't repeat the process again operate the switch back onto the line and CPC up here
and we should finally got a reading we have of all the readings we get we record the highest one of
those readings in the box heading R1 plus R2 under the continuity test we then can tick the polarity
box proving that we switch and fuse in the line conductor the switch was connected in the line
conductor and we've got this brown conductor here that would be in the fuse as part of our polarity
test now requires put all the covers back on leave the switch in the on position in order that we
can carry out our insulation resistance test next so let's change our instrument from ohms because
we're measuring the resistance of the conductors for continuity and let's move it around into the
megohm scale the megohm scale here and we're going to be testing it 500 volts DC in order to perform
our insulation resistance test on our 230 volt light and circuit so the instrument's all set
up ready for installation resistance test we've put the covers back on our load's been removed
so we've got no lamps in circuit our switch has been left in the on position we need to remember
to remove our loin conductor from our earth bar and put it back in the top of the circuit breaker
like so remembering to get the torque screwdriver off your lecturer and tighten that back up ours
is currently out on location so we go back in with our connection return it to the required
torque setting the RCCB needs to be off because there are electronic components in there and will
be damaged potentially by the 500 volts DC pass through the circuit we always leave our circuit
breaker off however our circuit breaker doesn't have any electronic components in it the reason
being the test when we test it tests outwards but it also tests down if we left our breaker
on the 500 volts would pass through it and across the bottom of the RCCB which does have electronic
components in so we'll leave that one in the off position I know you're a bit further away for this
test but we've done it many times on the channel so hopefully as you're watching this as one of my
learners you'll you'll hear me where I'm putting it and you'll go oh yeah Gaz I'll remember what
we're doing so switch is on covers on RCCB off breaker off set to the appropriate scale on an
instrument and we're ready to go first of all we're going to connect onto the earth bar it
doesn't matter where we're going to the earth bar so I'm onto the earth bar and on the top
of the breaker and we press and hold our button and our reading is greater than 999 Megohms take
a finger off the button we go on to the neutral bar doesn't matter where we go on the neutral bar
and I read is greater than 999 Megohms we move our crocodile clip across and we go into the
neutral bar the one that normally falls off on camera and just keep it on today onto the top
of the Breakaway the line conductor so do line and neutral next and we press and hold and we go again
and that's our insulation resistance test completed so at level one when we completed
our conduit exercise our one way lighting circuit we carry out the continuity of CPC test recording
the highest reading of the box heading R1 plus R2 when we operate the switch at the lighting
point we prove that we switch and fuse in the line conductor we can tick the polarity box we put our
covers back on we leave our switch on we turn our RCCB off and also our circuit breaker we change
our scalar and instrument into the mega ohm scale and we carry insulation resistance as discussed
even if I'm not currently teaching you and you're working out at Tresham College
I hope this video has been some help