In this presentation I am going to go through the 3 stages to test a the ring final circuit
is one similar to one that we would find in the domestic dwelling even though it's
on then a smaller test rig board therefore the circuits wired 2.5 millimeter squared twin and
CPC cables you might be happier with 2.5 twin and earth as this type of cables it's wired in we go
through all three stages to prove it's the ring will also prove polarity at the same time during
this test mine is a test rig therefore I haven't done the safe isolation procedure out there in
industry you will need to make sure first of all that you confirm the circuit has been isolated
in this case the whole installation has been turned off before entering the enclosure and
then disconnecting conductors I have two neutral conductors to cpc's and to line conductors that I
need to remove now in order to start stage one of the ring final circuit test so I've disconnected
the line neutral and CPC conductors and what I've also done is added a set of tape to one of the PVC
PVC twin and CPC cables so this one this side i've added brown green and yellow and blue to identify
that as one set or one of the outgoing legs the other alternative leg is left un-taped this will
make testing and showing in the testing process a little easier as we move through after setting my
test instrument up onto the ohm scale to measure continuity which I've shown in the previous
video presentation stage one requires me to do an end-to-end test on line neutral and CPC and they
are recorded there's a lowercase r1 the lowercase rn and a lowercase r2 in your testing paperwork
we're then going to take those readings and we're going to do a calculation with them but let's do
stage one first which is the end-to-end test so stage one requires us to measure end-to-end
line end to end neutral and end to end on the CPC if we start with the line conductors measuring
their continuity in ohms we get a value of zero point four three for this circuit your circuit
will be different but more so is zero point four three of an ohm we expect a neutral conductor
because it's exactly the same cross-sectional area in other words two point five millimeters squared
and they're about the same length we expect to get a very similar value for the neutral conductor and
in this case I've got 0.43 as well then we're going to do the CPC the CPC is smaller in a 2.5
millimeter squared PVC PVC twin and CPC cable it's only 1.5 the mathematical relationship between the
to is one point six seven so we would expect this reading to be one point six seven times greater
than four point three let's see what we do get expect the reading to be higher smaller conductors
greater resistance and for this circuit we've got nought point seven seven so that is higher
those what we expected I've also recorded on a scrap piece of paper the values of readings for
lowercase r1 rn and r2 because I'm going to need to do a calculation to prepare myself for stages
two and three of the ring final circuit test so we're going to use a calculation in a minute for
stages two and three that requires us divided by four I've briefly explained this divided by
four which will go over further in the classroom when we measured end to end our resistance of our
conductors we obviously went out and back whether cable is disconnected but in the circuit that
actually joined together in the same termination whether it be neutral CPC or in the top of the
circuit breaker in this case therefore two point five here but when in circuit they're actually
twice as big you make a cable twice as big you half its resistance also at this stage we're going
out and back but when we put the two together we actually half its length if we half the length of
a conductor we half its resistance so therefore double the size half the resistance half the
length half the resistance 1/2 of 1/2 is 1/4 how do you mathematically find 1/4 we divided by four
so that's how we come up with a divided by four which will further go over in the classroom so
before carrying out any more tests I have to work out what I expect to get as my R1 + Rn value this
is done by adding lowercase r1 and lowercase rn together and dividing it by 4 I've got a reading
of zero point two one five for my reading of R1 + Rn the regulation state I can be plus or minus
0.05 of this reading when I carry out my stage two test in order to carry out stage two of the
Ring final circuit test I am required within the distribution board to link opposite the line so
I've got one with a tape against opposite neutral one without a tape likewise line
and neutral of opposites and my first reading is taken at the connector block itself we know the
reading should be zero point two one five for my circuit plus or minus 0.05 of an ohm so let's see
what reading we get so if I measure across my connector block and press nice and firmly I've
got a reading of naught point two one and within the distribution on board itself which matches the
reading I expected by my calculation so the first part of stage two is completed and it's the one
people generally miss they forget to carry another test with them to consumer unit first before going
around and checking each socket outlet on the ring final circuit itself so I'm now going to
go around to every socket outlet on this circuit on the ring final circuit hopefully achieve in a
reading closer to the one we calculated of 0.2 and we're going to operate the switch at each
socket outlet and this will partly prove polarity and partly proved as ring final circuit this can
only be completed during the third stage of the test and so we'll complete stage two first 0.22
socket outlet goes so you may have change rooms or move locations circuit goes off
oh just try that again that readings considerably higher it could be there's some contact resistance
here okay entering the the outlet a few times will cause the reading to drop it might be that
the switch hasn't been made or opened or closed in a long time and therefore opening and closing
it will help reduce the reading but we are considerably above the 0.22 we calculated
and it doesn't fall within tolerance so there's a couple of things we can do we can obviously
take the front off and probe into the back to get a better electrical connection but also
when we do that we might find that this isn't on the ring finial circuit maybe in addition to
the ring final circuit it may be a spurred socket outlet and therefore we would expect that reading
to be higher it's only socket outlets there potentially on the ring final circuit which
we believe those are at the moment this could be that is a spurred socket outlet so we'd obviously
have if it was spurred so from this socket we'd have this socket at 0.22 ohms and then
the resistance of the cable that gets us to this point would be added to that value maybe to get
us in this case to 0.34 so the only way we can do that is by taking the front off and having a
look and see if it is a spurred socket outlet having removed the socket outlet front screws
we can now see it makes perfect sense it is a spurred from the ring final circuit only has
one line one neutral and one CPC hence the reading is higher at that point that's worth making a note
now for our stage 3 testing because we will find that every socket outlet the ring final
circuit will conform to a measurement that we've actually calculated prior to doing stage 3 but we
expect the higher reading to be at the spur socket outlet and it may be that that's the reading that
we record during stage 3 of the testing process so let's see how that's going to go as we did
before starting stage 2 before starting stage 3 we need to calculate the expected reading for
R1 + R2 by adding together the end to end values little r1 and little r2 and dividing by four
and this time we got a reading off at zero point three ohms which can rise or fall 0.05 from that
value so this time for stage three I've swapped my conductors around I've got opposite line to
opposite circuit protective conductor opposite line to opposite CPC and as before I'm going to
take my first reading across the connector block and we expect that reading to be 0.3 ohms plus
or 0.05 of an ohm so let's see what reading we get so firmly against are connected conductors
and we get 0.3 ohms so now we can go to each sock our on the ring final circuit for the next stage
so stage 3 will complete our testing process it will prove as wired as a ring final circuit and
will reprove priority of the socket outlets in other words the position of all three pins and
it will prove that the switch will operate or turn the socket outlet on and off so we have to
go round as we did before when we did stage to go to each socket outlet in turn we should get
a reading of 0.3 ohms plus or minus 0.05 ohms so we go as high as not 0.35 we can go as low
as 0.25 so let's go around and see what we get so the first one spot on at 0.3 ohms and second
one is 0.31 with in tolerance this time it's not 0.33 ohms again within tolerance fractionally the
over at this one so we'll do what we did before where we operate the switch a couple of times
and we will take it in and out it's ring final circuit let's turn it on again and this time
we've got 0.33 ohms it goes in the other side because it has a switch 0.33 we know this one's
on the ring final circuit from previous testing 0.3 we expect this one to be higher because we
know it's a spurred socket outlet from the ring final circuit and it's likely to be the
one that we recorded on a test paper workers R1 plus R2 so let's see what we're gonna get this
outlet at this outlet we get 0.52 ohms and that would be recorded as our R1 plus R2 value on our
test paperwork we've done all three stages of the ring final circuit so we've proved its wired as
a ring we've proved the polarity of the socket three positions of the pens and we've proved the
actual switch on the front also opens and close so we can tick the priority box at this stage
as well on completion of the testing process I've returned my conductors into the consumer unit I've
tightened them up using my torque screwdriver was set to the required manufacturers torque rating in
Newton meters set up by Crabtree so we've got to return those conductors back and correctly tighten
them into the consumer unit as I suggested in one of my previous video presentations so that's the
ring final circuit test number two in the order of dead tests according to the regulations that
we've just completed there is three stages to the ring final circuit test all three stages need to
be completed in order to prove why there's a ring final circuit and to prove polarity