in this video presentation we're going to continue the discussion on about additional protection
we know an RCD rated at 30 milliamps or below will offer additional protection to a circuit we also
know from discussions in both the classroom and the workshop that socket outlets rated at 32 amps
or below will require additional protection remember it's the rated value of the socket
and remember the socket outlets at home are all rated at 13 amps we also went on to suggest that
all lighting circuits and dwellings under the 18th edition require additional protection so domestic
lighting circuits now have to have RCD protection a 30 milliamps and below in order to offer that
circuit additional protection we've discussed bathrooms in the classrooms and how additional
protection will be required in those areas and locations we're going to look at one more in
this presentation we're using section three of the on-site guide in order to find out another
one of the requirements for additional protection it says here under 3.6.1 protection by RCDs we've
got h says the following additional protection for cables without earth metallic covering installed
within walls or petitions with metallic parts not including the screws or nails not protected by an
earth steel conduit or likewise so let's draw that through so if we're going to install cables in
metallic stud work very common now in domestic and commercial installations to have a metallic frame
in which the plasterboard is on one side or both in order to create a stud or false wall
we must make sure that the circuits within those so run within those are protected we can do that
by installing an earth metallic sheath cable steel were armored we could install a steel conduit
mineral insulated fp200 or fire tuff that's not very common the likelihood the circuits
being wired in that commercial or domestic installation will be your PVC PVC twin CPC cables
therefore there is a big risk that the cable could be damaged nicked or pulled in and rubbed against
the actual frame itself ideally the electrician will install protection in this case there is a
rubber grommet here in order to prevent rubbing against the actual metal frame itself but it's
not a requirement it's good practice i recommend that we do it often the hole is drilled and when
we're pulling cables in that we could have the following we could end up damaging the insulation
around the actual conductors themselves so this being the actual mechanical protection is damaged
and then inside maybe we've rubbed against the insulation around the copper conductors
obviously there's a massive risk now the risk being that we could end up nicking into our cable
and this frame itself could become live if this frame becomes live you may not notice it you might
be touching the insulated plasterboard and never find out the fact that the frame inside is live
however the frame could be attached to maybe a door the door frame itself has a metal hinge the
metal hinge comes through and that's screwed into here and therefore the metal hinge of
the door could become live and you can imagine the consequences when you're trying to paint in
around that hinge you might put some paint on the metal hinge you might wipe it off and only at that
time you discover that the hinges become live and there's a massive risk of electric shock to the
person so in order to overcome that all circuits run within metal framed stud walls require either
to be in earth metallic cable systems steel wire armour etcetera that we suggested earlier or
those circuits need additional protection by an RCD rated at 30 milliamps or less and you can see
how important it is that we make sure that they are installed with RCD protection in the event of
poor installation or damage over time you can imagine these cables could move
or vibrate you know people knocking into walls just general movement of cables
that it could wear against the outside breaking through the mechanical protection breaking through
the insulation conductions and potentially livening up the steel frame so for that reason
under section three which we've been looking at in the on-site guide we see that circuits installed
in metal frame stud walls that aren't earth metallic sheath cables
require additional protection by an RCD rated at 30 milliamps or below so for this quick
presentation that links to my lessons in the classroom i hope this video has been some help
you