so I'll just have a look at some of the cables gonna use predominately in the workshop and
predominantly initially on our course using this style of cable which industry like twin earth
so start with the cable used widely in industry for installation such as domestic dwellings and
is known as twin and earth out there on-site at college we're not going to call it to an
earth unfortunately we're gonna call it PVC it's been here the gray outside sheath of the cable
being the first layer of PVC offering mechanical protection and then the second one so PVC PVC is
here is the insulation around the live conductors so PVC PVC twin for the to live conductors and CPC
on-site twin a nerve two conductors and what they call an earth so we've got PVC PVC twin
four to live conductors and CPC CPC standing for circuit protective conductor on our PVC PVC twin
CPC cables we have a brown conductor known as line a blue conductor known as neutral together when we
described them so when we're talking about the two conductors together we call them live conductors
so if 10 amps was flowing down the line conductor down the brown one 10 amps would return through
the neutral conductor so therefore they are both live conductors and a CPC difference with the CPC
is it is uninsulated it is uninsulated because it will not carry current under normal conditions the
CPC will only carry current when there's a fault to earth the maximum time it will carry current
for is 5 seconds however there are other maximum disconnection times the other most common one that
we'll look at is a maximum of naught point four of a second so default position that start your
course is that the CPC will carry count for a maximum of 5 seconds however we will look
at other maximums as we go through the course as a CPC is unsheathed throughout the the cable we need
to achieve it to identify a terminating point so therefore we need to cover it in a sleeve in a PVC
sleeve in in this case it's green and yellow to identify it as the circuit protective conductor
ok they're gonna call it earth on side we're gonna call it CPC here at College this cable is
also described by conductor size as well as being PVC PVC twin CTC cable we describe it by the size
of the live conductors so in this case is one millimeter squared so the area of the conductor
is one millimeter squared and we always describe it on the live conductor sizes and not the CPC
however in a 1 millimeter squared twin and CPC cable the CPC is also sized 1 millimeter squared
okay as we move through the cable sizes the CPC is smaller in cross-sectional area than the live
conductors for the same reason it's not sheathed throughout its run because it will only carry
current for a maximum 5 seconds ok when there's a fault to earth therefore it can be a reduced
size conductor compared to the live conductors let's look a little further at the construction
of PVC PVC twin and CPC cables this one is 2.5 millimeters squared conductor sizes up to an
including 2.5 millimeter squared always come as a solid copper conductor so both the neutral and
line in this case a solid copper 2.5 millimeters squared the CPC is a reduced size of 1.5
millimeter squared and again is solid copper we must also identify this insulating material here
for the on-site guide and regulations according to the IET this one is thermo plastic PVC insulating
around the conductor's and has a maximum operating temperature of 70 degrees C so in other words when
a conductor carries current it gets warm the temperature around the cable obviously also gets
it warm that's called the ambient temperature and it can work up to 70 degrees C so I will be asking
you in the classroom and in the workshop what is the maximum operating temperature of this type
of insulating material which is thermoplastic PVC and 70 degrees C when we move from 2.5 next cable
sizes four mil six mil 10 No so if we look at a piece of six millimeter squared PVC PVC twin and
CPC cable we can see now the copper conductors have gone beyond 2.5 so the construction this
time for the live conductors is six millimeters squared so and it's now stranded solid copper
okay the CPC must be 2.5 or less because it's one solid copper conductor and in this case
the CPC in a six millimeter squared PVC PVC twin and CPC cable is sized 2.5 millimeter squared so
we can see the difference in construction as we move through the cable sizes so six millimeter
squared cable a six millimeter squared stranded copper line and neutral conductors but the CPC
is only size two point five and therefore is of a solid construction so we looked at the
basic construction of PVC PVC twin CPC cables the outside gray PVC offering mechanical protection
can also be white in color the ones that are white in color no modern cables are low smoke
zero halogen cables so when standard gray PVC sheath cables are burnt it gives off a black
dense smoke some installations require that to be reduced in order to reduce the smoke given
off by PVC they insist on low smoke zero halogen cables which are white sheath PVCs there can be a
little bit more tricky to put 90-degree bends in and a little bit more tricky to pull in they're
a little bit more rigid and standard PVC cable has got little bit more flex in them so that's
another consideration so the PVC PVC twin and CPC cables the twin and earth cables that we will be
installing in industry and in our workshop have a brown line conductor and a blue neutral conductor
however this was changed in 2004 to these colors prior to 2004 we were using conductors that were
like so where we had a Red Line conductor and a black neutral conductor and as before a bear
CPC conductor that was sheath green and yellow ack terminating points so very mind that the
installation that you put in may have a brown and blue conductor for line and neutral but we
may well face regularly conductors that are law is red and our black is neutral as well
as installing PVC PVC twin and CPC cables we will also be installing PVC three core and CPC cables
these conductor colors are brown black and grey and as before a bare circuit protective conductor
identify determinations with green and yellow Slevin as the with the twin and CPC cables these
colors were changed to these in 2004 prior to 2004 our colors were red yellow and blue within
our three core cable so bear that in mind as well would you run through a few of the other cables
going to use very early on in our course this is a flexible cord anything up to an including four
millimeters squared in this design of cable is called a flexible cord over the four millimeters
squared first being six mill is a flexible cable and we would describe this one as nor point five
for the size of the conductors within the cable three core flexible cord now we're not going
to call it a twin and CPC or earth in this case we're always going to describe the flexible cord
and flexible cables as the number of conductors reason being in a flexible cord or a flexible
cable they're always all the same size so the neutral the line and in this case the earth in
this cable are all naught point five millimeters squared so therefore it's a three core flexible
cord so this type of cable will be used later on in the course and it's a steel wire armored cable
this part here being steel armor and around the cable offering mechanical protection and we've
got the conductors in this case it's a fork or one so we've got brown black gray and the introduced
of a blue conductor at this stage if it was a two core steel round the cable it would be just brown
and blue for the two cores if it was three core it would be brown black gray okay we've got the
four core steel or armored here there were change on this cable is the actual insulating material
around the conductors is no longer thermoplastic PVC but thermosetting PVC and that has a maximum
operating temperature of 90 degree C and not the seventy of thermoplastic so thermosetting
PVC insulated conductors and that means that for the equivalent same size so if it was a
2.5 millimeter square PVC PVC twin and CPC cable or a 2.5 millimeter squared steel Romick cable
the steel armored cable can carry more current for the same size of conductors because these
can be run hotter up to 90 degrees C with the thermosetting PVC sometimes called cross-linked
polyethylene and that's XLPE cable next type of cable is PVC singles this time there is no gray
or white outside mechanical protection they're just single insulated conductors being lying CPC
and neutral the actual mechanical protection offered by the grey outside PVC sheathing of
PVC PVC twin and CPC cables is now going to be offered by something such as plastic conduit
so the conduit becomes the mechanical protection the circuits are inserted inside the conduit which
offers the protection therefore the conductors themselves only required to be single insulated
PVC and this is thermoplastic PVC so therefore has a maximum operating temperature of 70 degrees C
the mechanical protection could also be offered by steel conduit plastic trunking steel trunking so
we're looking at single insulated cables further protected by the wiring enclosures and in this
case they're PVC Cingular insulated conductors the last time when you look at in this presentation
is the concentric cable for those of you have watched my video on earthling Arrangements TNCS
i talked about the type of cable that goes into the bottom of the cutout being a concentric cable
one that has a copper combined protective earth neutral and a center conductor unfortunate in
red insulation nowadays they're being brown that Center conductor being the line conductor as an
aluminium conductor itself so this conductor here offers both the neutral and protective conductor
and a center aluminium being the line conductor and that was for the TNCS earthing arrangement
this type of cable being the concentric cable so let's hope that helps with a basic introduction to
our cables construction operating temperatures and names of conductors as well so we'll be
down in the workshop we'll be expecting you to be relaying information about the name of conductors
maximum operating temperatures and their basic construction as we look to move through our course