so my learners have been with me for six weeks and we've installed our first lighting circuit
which is a one-way lighting circuit the effort to connect the consumer unit the batten lamp holder
and the one way switch are identical to that in industry however we know the the effort to get
the cable from the distribution board to the light and from the light down the switch would be vastly
different in industry so the connections are the same the effort about the cables in isn't the test
we're going to carry out is also identical to the one that we would carry out into industry however
our readings will be phenomenally small because of the short cable therefore the limited amount
of resistance would have in circuit the first test we're going to carry out is the continuity
of the CPC I want to prove that the CPC gets from the consumer unit to the lighting point
and also down to the switch we should perform this test at every single lighting point and
switch on a circuit we only have one light on one switch on ours however if an industry you had 10
lighting points with 10 switches the test would be carried out at every light and every switch
and as we progress from the consumer unit to the first room second room etc we expect to see the
reading increase as we get to the furthest point of our radial circuit the further we are away from
the consumer unit the more resistance offered by the cable we will also include at the same
time the polarity test proving that the switch will operate the light so we're going to perform
that test next I'm gonna set my instrument up and see how we get on with that we're using the
Megger MFT tester and in order to do a continuity test you must use the red and green located holes
in the top it wouldn't matter if I use the blue lead but I've still got to use L1 and L2 which
are represented by red and green so I am going to use my red and green leads so then we go and
because the leads themselves are also made of copper as is our link we're going to need to
remove the resistance of these during this test I need to set it on to ohms in this case it's in
the oranges square here and it's got the Omega symbol so I'm gonna need to rotate it around to
ohms and see the interesting will come on and now what I'm going to do is link together both
the link itself to prove it isn't broken and remove its resistance on to my crocodile clip
like so and we can see they have a reading of 0.01 you press the test button only once and
I've now got a reading in this case of 0.11 which isn't zero so I need to press it just once again
and now I have zero be very careful with this instrument that it isn't zero flashing if the
zero is flashing it is below zero and would leave the test button pressing at least once more we
have zero we've removed the resistance of both the leads and the link therefore we're ready to start
the continuity of CPC and polarity test first of all I'm going to remove the line conductor
at the top of the circuit breaker for the circuit these under test I've only got one circuit here
so for my B6 from the lighting circuit I'm just going to disconnect my line conductor and then
I'm going to use my crocodile clips to link the disconnected line conductor to the earth bar it
doesn't matter where the crocodile clip goes this is a solid brass bar so we can clip anywhere on it
we don't have to clip directly on top of the screw to the CPC that we've got this disconnect my line
conductor and I'm going to connect it to the earth bar oh I've disconnected my line conduct under
test I've connected to my earth bar so I'm going to perform the continuity of CPC test now at my
lighting point and then my switch remembering if I had more than one light or more than once
switch I would do at every point on the circuit the link is connected in are consumer unit and we
have walked out into the installation in this case we only have one lighting point so we're going to
go to that lighting point and connect between the switching line and the earth terminal and where
the CPC's are connected remembering we're only on week six with more learners and is a bayonet
cap lamp holder we know as we move forward that this was an Edison screw we'd need to prove the
priority from within inside the lamp holder itself making sure the center pin is line and the screwed
part is neutral we're at stage one we're just introducing testing so I'm going to clip onto
the earth terminal and onto the switching line try and keep any other way so you can see what
we're doing and I've got a reading of 0.13 of a ohm 0.12 of an ohm so 0.12 of an ohm we have a low
resistance reading therefore the circuit is in the on position if I turn it now off we see we have a
reading which has gone off the scale so in other words an open circuit the circuit is off turn it
back on we have a low reading ohm off and it's settled down now at 0.14 of an ohm but operating
a switch we prove polarity we must leave in the on position for insulation resistance test which
is coming later in the sequence but that isn't it finished we've only proved the CPC has made
its way to the in this case batten lamp holder we've also proved it turns on and off we must make
sure there is also a CPC of the switch because both accessories could be changed for exposed
conductive part so in other words a metallic light fitting or a metallic switch so let's test it next
to the switch itself so we left the switch in the on position when we tested the batten lamp holder
above I've connected onto the earth terminal in the back of the lighting box and I'm going to
probe on to the line conductor this time we get a reading of 0.1 of an ohm that is less than the
reading we got at the light fitting which is the furthest point on the radial circuit we'd
record the highest reading so we were recording a reading of 0.13 of an ohm for our continuity
reading there is no need to operate the switch at this stage we only operate the switch when
we approving priority of the light we don't need to operate the switch when we're actually at the
switch itself so to recap them we linked line and CPC in the distribution board itself there
the line conductor under test in this case the one for the lighting circuit was linked to the
earth bar we only had one lighting point and one switch went to the furthest point in this case of
the radial circuit and we tested between switching line and CPC and we got a reading of approximately
zero point one three of an ohm we operate the switch at the same time we were there and we
saw a full scale deflection the instruments who went from the reading to infinity and back again
we left in the on position before we go down to the switch the switch we tested between the line
conductor and the CPC secured in the back of the box we got a reading of 0.1 of an ohm we record
the highest reading in circuit so we were going to record under our continuity box heading 0.13
of a ohm for this circuit that I've tested we're going to record it into the box heading R1+R2 R1
represents the line conductor and R2 represents a CPC so we've linked together R1 the line conductor
to R2 the CPC and we've measured the continuity of that path we've also proved polarity at the
same time by operating the switch and we left the switch in the on position ready for the next
test for us which will be insulation resistance remember if you have more than one lighting point
and more than one lighting switch in a circuit you must test every lighting point and every switch on
the circuit in order to prove the CPC gets to each point in turn and prove polarity recording
the highest reading logically at the end of the circuit on a radial circuit however it would be
the highest reading wherever you achieved it that you would record I hope this has been some help