so in this video presentation we're going to go back and look at the three plate loop in method
and the connections in the ceiling rose in the consumer units and one way switches Joe yeah
however the 18th edition has made some alterations to our thinking on domestic line circuits what's
that thinking change to so previously in the 17th edition RCD protection was highly recommended
and required in certain circumstances however it was possible to kind of work around
that RCD requirement there were other ways that we could install our cables to prevent it having to
use an RCD however in the 18th edition lighting circuits and a domestic installation have to be
RCD protected doesn't matter how we install the cable you've got to have an RCD on there
and that RCD is offering additional protection and must be rated at 30 milliamps and below
we've also touched on and we'll continue to touch on in future presentations
about the A type and the AC type our RCDs yeah so we've got here a mocked up board
and this contains an RCCB uh and i'm sure that through the magic of editing Gary will be able
to bring up the symbol for that you can see on here so this is the symbol for an AC RCD
it is yeah and the AC RCD while it does offer RCD protection protection against earth fault leakage
it's not always necessarily going to trip cars why might this not be a suitable RCD for all circuits
now what's what's changing so as we're evolving our wiring systems and we're introducing more
and more circuitry that's actually working on DC LED lighting games consoles TVs etc
that we're finding that the AC RCD is becoming very limited and sometimes wouldn't even function
under earth fault conditions so therefore the mocked of installation we've got here just to keep
it going i've swapped it over from an RCCB and i've swapped it over to use a miniature RCBO so
we've got two different ones here so we've got the standard RCBO and the miniature RCBO and we can
see joe yeah as you can see on there again through the magic of editing we'll see that there's a very
different symbol that appears on here now which indicates this is what kind of RCBO Gaz this is an
A type RCBO and under the 18th edition wiring regulations you've got to match and at least look
at and install the correct RCD protection based on the circuitry that's been installed based on the
load that it's supplying yeah so that's a really important point so if we bring the camera in now
we're going to look at the connections within the consumer unit the switches and the lighting points
to reiterate the three plate loop in method so joe we've brought the camera in and we're looking at
the consumer unit first the circuit we've wired or mimicked is three baton lamp holders one way
controlled by three switches we're starting with the connections in the consumer unit
can you just go through the connections for me please i see we're using a miniature RCBO
6 amps type B and rated at 30 milliamps yeah so you'll notice uh different to the common
circuit breaker that we had before with the RCD protection here you'll see the RCD protection
no longer exists here this is just an ordinary 100 amp main switch what we've then got here is the
RCBO now you'll notice in the top of the RCBO there's two connections one for the line and
one for the neutral remember an RCD operates by monitoring the current flowing through the line
and back down the neutral again if that current is the same then the RCD is happy if it starts
to see that there is less current in the neutral than there is in the line conductor for example
it knows that current is leaking somewhere either through an earth conductor or through a person
and it knows that it's time to trip so you can see coming at the top there there's our line
connection there's our neutral connection and then right tucked at the back here there's a
neutral connection coming out and that goes from the RCBO and onto the neutral bar we can also see
as previously stated there is an A type RCD and we've identified the circuits with number one
on the line neutral and circuit protective conductor for ease of installation and ease
of identification during say fault finding or removal of circuits as previously stated we now
know under the 18th edition wiring regulations all domestic lighting circuits regardless of how the
wiring system has been installed needs additional protection by an RCD rated at 30 milliamps or less
so Joe can just explain what we're trying to mimic here as a circuit yeah so what we're looking at
here is this might be a typical domestic lighting circuit let's say it's the upstairs lighting on a
domestic property so what we've got although the cable runs are a lot shorter than they would be
in the real world all of the connections and all of the principles remain exactly the same so first
of all what we're doing is we're taking a one millimeter squared conductor and that is coming
from our consumer unit to our first lighting point so let's call this bedroom one okay within this uh
conductor we've got a line conductor and a neutral and that comes up to here those are permanently
live cables so there's no switching taken place yet from this point we then continue with a
permanent line in neutral to the light in bedroom two and then to the light in say bedroom three
from each lighting point we then drop down to the switch and we drop down with a twin brown in this
case now it is possible to do this with a brown and blue conductor however that blue conductor
must have some brown sleeving on it to indicate that it is a line conductor and not a neutral
so this picks up the permanent line from inside the light fitting it goes down to the switch the
switch then makes or breaks the line conductor onto the switching line which then comes back up
and into the switch line terminal inside the light fitting therefore this switch will then operate
the lighting circuit so if we look inside the back of the ceiling rose where the battery lamp holder
is connected we can see this is our incoming cable Joe from a consumer unit say on the ground floor
coming up to the first floor into light one say in bedroom number one so we're bringing in a neutral
conductor and a permanent line conductor the trick now is that the permanent line conductor
in this case from the consumer unit it goes in a terminal marked loop our neutral conductor goes
in the terminals marked N and then we've got to look at bringing a second cable down here
which is going to come down to our switch this is the twin brown you discussed earlier so the twin
brown will take a permanent line out of loop and a returning switching line which goes in
L okay it's a bit confusing L is really a switching line conductor in order to turn
on the light fitting itself we can now see the lamp pads connected to one side of it a neutral
and the other side of it a controlled switching line allowing us from the one way switch below
to turn on and off the lighting point in order to make the circuit safe we have a circuit protective
conductor connected in the terminal marked with a earth symbol where they're all housed
together so all the CPCs are in one terminal this doesn't require a CPC as it's made of plastic
but could be laid to turn for an exposed conductive part such as a metallic light fitting
the other neutral the other line in the loop and the other CPC is the continuation of a permanent
line from loop the neutral and circuit protective conductor on the outgoing cable in this case we're
mimicking it going to another bedroom so that would take a permanent line and neutral and CPC
and we repeat the process of what we've done inside here as we've previously discussed in
the classroom these type of bayonet cap lamp holders have no polarity so as we look at the
two pins in there it doesn't matter which one's connected to the line and which one's connected
to neutral and we've discussed in the classroom about Edison and screw and the polarity on those
so the cable is now dropped down from the ceiling rose above and this is the twin brown
and CPC cable that we discussed so one of these conductors here of the twin brown will be in the
common and bringing down the permanent line connection and one of them will be the
returning switching line conductor which we're connected in the L section of the batten lamp
holder and ceiling rose remember that l is for really switching line we've secured a CPC into
the back of the box again because it's fully insulated the CPC is not required but is there
in case we change it for an exposed conductive part the cable size is one millimeter squared
for all conductors including the CPC in this cable the switch itself is a one gain one way so as we
look at it here on the other switch we can see one gang for one switch on the front and as we turn
it over we can see we've got a connection between common and L1 making it a one gang one way switch
so i've moved across now you might be able to tell but i have i've moved across to lighting point two
we discussed just a moment ago this cable here bringing in our permanent line connection which is
connected in loop our neutral connection connected into the neutral and our CPC connected to here
with the other circuit protective conductors again the conductors are all one millimeter squared
and we repeat the process again so one of these brown conductors will be coming down to the switch
one of them will be coming back from the switch and connected in what's called
L which is a switching line and we repeat the process again going out
with a neutral and permanent line remember all those cables also have a circuit protective
conductor and the process repeats itself again okay then joe so we're at the last point on
our lighting circuit but i can see some subtle differences here can you tell me what's going on
yep so here you can see we've brought our cable from the previous light fitting into this light
fitting but inside here you'll notice that we seem to be missing some conductors now the reason for
this is we've technically reached the end of the circuit so what's happened here we've brought
our permanent live in and that's going into the loop terminal we've brought our neutral in and
that goes into the neutral terminal but we're not wiring another light fitting off this one
and therefore there's no need to take another permanent line neutral and CPC out of the circuit
the other key point that you may notice in here is this conductor here so here we've got a blue
conductor so our brain would normally go that's a neutral but you'll notice that it's got some brown
sleeving on it now that brown sleeving indicates that this what would be classed as a neutral
conductor is actually acting as a line conductor now so this is designed to act as a line conductor
now the reason for that this is just to illustrate a point that it is both possible
and permissible to use a brown and blue conductor as our switch drop running down to our switch here
however if a brown and blue conductor is used then it's very important that this blue conductor has
brown sleeving over it to show anybody who comes back to this installation that this conductor is
actually acting as a line conductor and not a neutral so that brown sleeving is very very
important other than that this cable is just acting purely like a twin brown it's picking
up the permanent line it's taking it down to the switch where the switch will then make or break
the conductor onto the switching line conductor which in this case is the blue over-sleeved with
brown which goes into our line term our live terminal and we'll operate the lamp so we're
down at that final light switch and we can clearly see now the blue conductor has been over sleeved
with brown in order to identify as a switching line conductor and we can see the brown conductor
coming into the common as well so we can see how twin and CPC cable can be used at switch drops
and commonly is in industry at college we tend to use twin brown but be aware that in industry
the likelihood is that you'll be using twin and CPC at switches and identifying it both ends
with brown sleeving please note as well the top of the electric enclosure has had its IP rating
confirmed back to IP4X so object exceeding one mill cannot enter in other words dust and debris
can't fall in and that's the same for all of them as we go along often at college we can't do that
because obviously these boxes are temporarily installed marked and the installation removed
so that's another look at the connections in the three plate ceiling rose method joke commonly
used in domestic dwellings and we said the light fittings however i've been battling lampholders
when we get to the real world what we like to be fitting it's becoming more and more common
now that we're fitting some kind of LED type fit in here we've got an example of a lovely recessed
LED down light provided for us very kindly by Collingwood Collingwood lighting uh so it's more
likely that we'll be coming across some kind of LED fitting uh whether that's a permanently
connected led like this one or perhaps a LED lamp that has the traditional bayonet cap lamp holder
on there so it brings up a couple of points that are under the 18th edition that we need to look
at the equipment we're installing and select the correct type of RCD so whether it be the original
AC type which we're probably moving away from and looking at probably a minimum of now an A type
RCD and we also know under the 18th edition warren regulations that we must install additional
protection by an RCD rate of 30 milliamps or less on all lighting circuits yeah just to reiterate
that that point is essential that you match the RCD type whether it be a ac or one of the others
to the load that you're connecting up that's a really really important point we can't make a
blanket statement about what type of RCD to use on what circuit you've got to make your own judgment
call on that but knowledge is power so keep stay tuned and we'll have a video on the different
types of RCD coming up soon it's time to end it so we do yep we hope this video has been somehow