in this video presentation we're going to look at the maximum number of conductors that we can
install in a short straight piece of conduit we're going to take a scenario that talks about
PVC singles stranded conductors and asked you to work out what is the maximum number that you can
install in say 20 mm conduit just because in this case I can get the conductors within the conduit
it doesn't mean it's acceptable we'll need to use Appendix E in the on-site guide which will give
a factor for the cable that we use and a factor for the conduit and we can use those two numbers
in order to work out the maximum number of that conductor that can go within the conduit this
often comes up at level 2 exams and we would develop it further in the classroom to do more
complicated calculations where the conduit system is a lot longer and incorporates bends but for
this part of the presentation we're going to work out the maximum number of conductors of a certain
size that can be installed in a certain size of conduit so trying to keep myself out the way the
tripod let's work out what we've got here which is a piece of 20 mm conduit and 1.5 millimetre
squared conductors let's work out what the maximum number of these cuz that can be installed in this
if it's a short straight run we need Appendix E of the on-site guide cable capacities of conduit and
trunking and we're concentrating on the one for conduit and if we turn over single core thermo
plastic PVC insulated cables which we've got here in straight runs of conduit not exceeding 3 meters
so that's the question we've got how many 1.5 millimetre squared cables can we install in a
piece of conduit that's less than 3 meters and these straight we've now got table E1 and table
E2 to look at next table E1 the cable factor use for conduit in short straight runs the first two
lines or three lines for apologize are for solid conductors we've got stranded so it's got solid
one one five and two five and this is where people often go wrong in exams if they're asked to look
at one five look at the first one one five factor for solid is 27 however the conduit conduct as we
know the we use are stranded so the one five factor for the actual conductors is actually
31 so each one of these conductors that are 1.5 millimetre squares have a factor of 31 so that's
the first thing we need to find often the exams it sometimes ask you just to look up the factor
for the cable so you would be in a short straight run if you're looking at one five cable the factor
would be 31 if it was ten millimetre squared in a short straight run under three meters ten
millimetre squared stranded would be a hundred and forty six so next we need to look at table
E2 the conduit factor for short straight runs short straight under three meters we have the
factor for the conduits being the common sizes have been 16 20 25 and 32 mm we've talked about
that in previous presentations and I want to know what the maximum number of conductors of one five
that I can install within a 20 mm conduit so I have a factor here of 460 so the two factors were
working with are 31 the factor for 1.5 millimetres squared and the factor of 464 20 mm conduit in a
straight run under 3 meters we're going to take those calculations next and work out what the
maximum number of these are that can be installed within our 20 mm conduit okay so let's take our 20
millimetre conduit factor and the factor was 460 we take our 1.5 millimetre squared conductor and
we have a factor for that of 31 okay so we got our two factors 460 for the 20 mm conduit and 31
for our 1.5 millimetre squared stranded PVC cable all we're going to do now is divide the 31 into
460 so I've laid it out like this so if i put the divided there we will actually get a number
down here so let's do that on the calculator so let's do let's put it there 460 divided by thirty
one answer is it's fourteen point eight three let's go seven so we can get into the conduit
fourteen point eight three seven conductors now we obviously can't get that part of it so we've got a
number issue here often you round up don't you so we're beyond the five here after the decimal point
so we would round up however every single one of these calculations needed to be rounded down the
maximum number of conductors you can install in there is 14 so 14 being the maximum number that
we can install of 1.5 millimetres squared within a 20 mm conduit we never round up you couldn't
get slightly more than 14 conductors in because it exceeds the capacity of the conduit so for
this answer here what is the maximum number of 1.5 millimetre squared cables that can be installed in
a short straight run of PVC or metallic conduit doesn't matter which one it is it's about the
diameter so it doesn't matter which one it is it's being plastic it could be steel but it's
20 millimetres the maximum number of conductors is 14 okay so let's move this out the way let's take
the paper up the way and let's turn that over and let's go about doing another calculation so again
we're going to keep it in short straight runs not exceeding three meters this time I'm going
to choose 4 millimetres squared cable remember it's stranded and that has a factor of 58 and
let's choose 25 millimetre conduit and that has a factor of 800 so we will put those in
and we're gonna work out how many four mm squared cables we can install in 25 mm conduit let's do
that again so my conduit size is 25 millimetres and that has a factor of 800 my cable size was
4 millimetres squared and that has a factor of 58 so we're going to work out how many 4
millimetre squared cables can be installed within a 25 millimetre conduit exactly the same as before
we're just going to divide those through in the calculator across again and let's do 800 divided
by 50 eight equals thirteen point seven nine three okay so I said oh look at that so we've gone again
we've got thirteen point seven nine three exactly the same as before we can never round up and have
more conductors in than the number so we can't even know this again he's gone beyond the five
and normal math say we round up to fourteen we don't the maximum number of four millimetre
squared cables that can be installed within the conduit is thirteen conductors these questions
are often asked at EAL and City and Guilds level two exams we go on and develop this further in
the classroom whether I make any more videos on this time permitting we'll see but certainly we
need to master this at level two how to find the right section within the on site guide within the
appendix within appendix E making sure that we use the correct tables in this case for short
straight runs using the correct factor the factor in this case was for stranded cable and the factor
for the conduit and do the simple calculations which would perform there remembering that we
always round down the number two in order to find a number of conductors as a maximum that we can
install in this case within twenty five mil condo so once again I hope this video has been some help
you