hello and welcome to this third in a series of videos talking about twin and cpc conductors in
this video we're going to particularly focus in on one or two special variants of twin and cpc
conductors that we use in different applications in domestic settings so the first of the variants
that we're going to be looking at in this video is what we've got here which we refer to as twin
brown cable so the reason that we call it twin brown is immediately obvious when you look at
it when you look at the conductors there you can see that we no longer have a blue neutral
conductor but what we do have are two brown conductors we've got two line conductors now we
may need this because in a lighting circuit which is what we typically use one mil cable for we may
have a situation where we brought a permanent liner neutral to a light fitting we would then
run this cable from that light fitting down to a switch we pick up the permanent line connection
on one of these conductors at the light fitting it carries the permanent line down to the switch
and then the switch will uh connect and disconnect the switched line conductor so the
line the switch line conductor will come back up to the light fitting and connect into the actual
lamp itself and therefore we'll have control over when the light fitting is turned on and off this
has been really nicely explained in another video by gary so i suggest you check that video out
to understand the application of this more fully so this is twin brown and cpc cable
so the second variant that we're looking at in this video is what we've got here and this is
what we refer to as three core and cpc now again you might be looking at this and you might be
thinking but surely we've got four cores remember we only count the insulated cores so we've got one
two three insulated cores and a cpc so that's what we're looking at there now you may also be looking
at this and thinking where are these colours come from because we've still got a brown conductor
we've got no blue conductor and now we've got these additional colours which are black
and grey those of you with a little bit of prior knowledge may recognize that these are the colours
for what we refer to as a three line system very often referred to as a three-phase system
really it's a three-phase supply consisting of three lines but what we've got the important
point here is that we've got these colors it's very rare that you would use this type of cable
for a three line supply very very unlikely indeed because most domestic installations unless they're
extremely large mansion type buildings won't have three phases coming into them
so what we've got here then are the three colors brown black and gray the regulations state that
because we're going to be connecting this cable up to a single phase supply
that means that all of the colours need to be all of the line conductors need to be identified
as being line conductors on a single phase system which means that they need to be coloured brown so
what we do is we take our piece of brown sleeving and we pop that over our black conductor and we
pop another one over our gray conductor it doesn't necessarily have to cover the whole length of the
conductor it's just to indicate that this is a single phase line conductor now again the area
that you would use this for again is for lighting and in a lighting circuit you might have two-way
or intermediate switching and for those types of installation three-core comes in very very handy
it's far too complicated to explain on this video how it connects up but again Gary's demonstrated
an excellent video of how two-way and intermediate switching works and how we can use a three core
and cpc cable to allow for that so this would be used typically for the cable between switches on
a two-way or intermediate switching circuit and this is what we call three core and cpc
so the third option that we're going to be looking at in this video is what we've got here now this
is a low smoke cable now when you look at this cable you may look at that and think well i can't
see any physical difference between this and the other cables that we looked at and that's
right there's no real visible difference one small difference is we've got a white outer sheath there
but that's the only visible physical difference between these con these cables the reason that
we might want to install a low smoke cable is that if you've got a pvc cable installed in say
a domestic installation if a fire breaks out that fire could potentially be quite life-threatening
but actually more deaths are caused by the fumes given off during the fire than by people actually
being burnt by the fire so when the pvc insulation and sheath on a conductor get burnt when they
get hot they start to give off really dense black choking clouds of smoke and that is a real danger
both in terms of evacuating the building safely and also in terms if you breathe that in
it's very very dangerous and can kill you so a low smoke option is an excellent option
for reducing that risk when this burns it will give off some smoke it will give off some fumes
but it won't be the dense acrid black smoke that's given off by pvc and it's also
much less hazardous to people when they're trying to flee a building so this is an option personally
i think this is something that will become more and more common in domestic dwellings it's already
being specified by some councils and some building designers who insist on this being installed
so we'll see how that pans out over the next few years so that's some information covering
the variants of twin and cpc we saw the different types of cable there uh how is this going to fit
in with our learner experience here Gary how are they going to apply these different types of cable
here at the college it's going to be in that first eight weeks in the workshop period after health
and safety has been cleared that we're on those lighting circuits we'll be using twin brown drops
to switches and we're interconnecting two-way and two-way intermediate switches using the three core
and cpc that you discussed in your video as well don't touch on the white pvc stuff in some ways
is really good because it's very difficult to work with and make it look really neat and when
you've got no skills working with pvc cables to go to low smoke zero halogen when straight off is
a little bit difficult yeah so that'll be much further down the line maybe that'll get looked
and uncovered yeah once those basic skills have been developed and mastered yeah we always like
to put one circuit in with that yeah excellent that's great and of course Gary's already made
an excellent video featuring this type of cable on two-way intermediate light switching so we suggest
you check that out as well for some further information and see this actually being used
so i think that's all all that's left to be said is we hope this video has been some help