so in this presentation we look at the insulation resistance test the third dead test according
to BS 7671 so we have done continuity of protective conductors including main and
supplementary bonding within continuity of ring final circuits and we're ready now to carry out
the insulation resistance test as you can see the installation has been locked off I've also
proved the installation is dead which I've shown in a previous presentation and now we're ready
to continue with the insulation resistance test so let's just recap of what's happened up until
this point hopefully during the continuity test we've left all circuits in the on position so
the cooker a switch has been left on all switch socket outlets have been left on so the insulation
resistance test will get to the front of the plate my switching sequence for the lighting
circuit has been left in the on position and these two switches are 2 way and they have been left on
this is a one-way switch we've just got to now confirm that all loads have been removed so in
this case the three lamps need to be removed and also the electronic devices which is the RCCB's
need to be left in the off position we do not want to pass the test voltage of five hundred
volts DC through those electronic components we have no other sensitive items in circuit
such as digital time clocks smoke detectors etc PlayStation TVs that could be damaged during this
test so we're possibly now ready to look at doing the insulation resistance test so I moved towards
doing my insulation resistance test I just want to recap what I've done with the terminations
within the consumer unit during the first two tests continuity of protective conductors and
continuity ring final circuits I've returned the tightness of these connections within the
consumer unit back to manufacturers rated Newton meters of torque so at this stage at test three
I don't particularly want to start removing conductors from the consumer unit for the
insulation resistance test however BS 7671 when it shows you the model forms recording your test
results suggest the insulation resistance test must be done between live conductors so in other
words between the line and neutral and between live conductors to earth so in other words we
should have a combined line and neutral together tests to earth often missed what we generally
do is line neutral line earth and neutral earth three tests but there's only two boxes in which
to record and it requires a combined test of the live conductors together to earth so I'm
going to show you how I come up with a way of getting round doing this test without removing
the conductors and without doing all three tests and then just saying well I'll record the worse
reading of between line and earth or neutral and whichever one's worse I'll put that in the Box BS
7671 requires us to do a combined live conductors to earth and that's what we would do in this test
also I suggested that I'd left all switches in the on position which I have however upstream
is another consumer unit and I've actually left the isolator in there in the off position I only
want to do the insulation resistance test for the circuits within this part of the domestic
dwelling and record among my schedule of test results the second consumer unit will have its
own set of test results for that consumer unit so I think we're now in a position where we're
possibly ready to do the insulation resistance test so see how we're going to do that so shown
on previous video presentations I'm going to set my Megger MFT up in order to carry
out insulation resistance for us in the red scale and we're going to need to put it onto 500 volts
DC and I'm gonna short together my conductors to prove the leads have not become broken I'm
also going to use a link again this time that I've used before on continuity testing so I'll
link these together to improve I've got a short and I've got a slightly older test probe that
I can get and more more of a connection with my crocodile clip and still have some tip exposure
okay so that's going to be really handy when I'm trying to do this combined live conductors to
earth insulation resistance test so press my test button and I have a dead short so we're happy the
instrument is ready to carry out the insulation resistance test I've got a small tweak on how I'm
gonna do it here to combine my live conductors to earth test so let's see how that looks inside the
consumer unit under test so I'm ready to carry out this combined live conductor so line a neutral to
our earth connection so I've got my probe already connected on to my earth bar I've got a Megger MFT
lead this time one of the older style ones with more tip exposed is a dead test that's not an
issue I'm gonna put one end of my crocodile clip onto there and the other crocodile clip on to the
neutral bar for the first circuit under test so when I now probe into the top of my circuit
breaker I've got a linked live conductors to earth for the test for the insulation resistance
press and hold the test button and I've got a reading greater than the Machine can read
her in this case greater than nine nine nine mega ohms I pull off and I'm doing to move my
crocodile clip now onto the next one which has two circuits served from the RCCB and repeat the
test again so I'll go to the top of the first circuit breaker so live conductors to Earth a
reading greater than the Machine I move across the next one again greater than nine nine nine
mega ohms I move the crocodile clip again so I've now linked the final circuits over
here so the neutral and line conductors are linked together on top of the circuit breaker
greater than nine nine nine for live conductors to Earth and move again for the next one and
again greater than nine nine nine mega ohms so I've now did a combined live conductors line
neutral together to the earthing conductor I'm now required to do a test between live
conductors so I'll need to test now between the line and neutral of each of the circuits
so we go back now to our test probes so I've moved back to my conventional probes
I've linked onto the first neutral bar on the test between that and the top of the
first breaker so we go in press and hold my test button between live conductors have got
a reading greater than nine nine nine mega ohms and we move across pick up the next two
and we repeat the process again and then finally move it to our third
in our case neutral bar and the final two circuits
and then the last one and all of those readers were greater than machine can read so greater than
nine nine nine mega ohms however no need to get excited just yet we've still got to go back into
the installation and throw our two-way switches back into the opposite on position and repeat
the insulation resistance test for that light in circuit again so let's go into the installation
and do that so the consumer is isolated and completely dead I've locked it off in the double
pole to link main switch in the tails itself I'm now going to walk off into the installation and
throw all those two ways switches back into the other on position I only have one set here so this
set of two way switches need first of all with one switch turning off one switch turning back on
and then I go back to the consumer unit and do the insulation resistance test again for that circuit
so in the two ways which is now thrown into the opposite on position in order to the insulation
resistance test of the other strapper I can repeat the test for that lighting circuit only so I'm
still on to the between live conductors between line and neutral further reading greater than nine
nine nine mega ohms I'm now going to replace one more leads gonna link together the live conductors
connect onto my earth bar and do the final test now between live conductors together to earth
and a greater than nine nine nine mega ohms I've now completed the insulation resistance test
with the live conductors together to earth and between live conductors in other words
setting between line and neutral I've repeated the test for the lighting circuit that had the
two-way switches in we're not throwing them into the opposite on position in order to test
the other strapper I now believe that these results can be added to my test paperwork
and the insulation resistance test is now complete hope this video has been some help