here's a question for you is a torque screwdriver a substitute for competence
no sir possibly the shortest video we've ever made but this is part of a series we've been
making called talk the torque where we've been exploring the use of torque screwdrivers and
electrical terminals and the feedback we've had so far and there's been lots of it in the comments
is obviously there's lots of issues where a torque screwdriver won't detect problems with
terminations yeah so think about competency maybe we've put the connections into the main switch
our towels have gone in there we know we've got that stranded conductor going in there
we've tightened them up to maybe 2.5 newton meters of torque what we often do then is let them settle
in don't we we maybe give them a little bit of a move and then we re-torque tighten them
so we know when we've left that consumer unit they're in a good shape and yeah that's i mean
that on new installs yeah you're in charge of that electrical installation you know where all your
terminations are but think about the scenario we've got today Gary where a lot of people are
revisiting an existing installation right possibly for an EV charger or a heat pump
and they're all coming down down the road and they choose not to fit a new consumer unit to
put a small consumer unit in which means they're going to be start should we say moving the tails
ah right okay so we've got those tails we're moving them maybe there's some henley blocks
in service maybe the meter tails get moved around a little bit as we're adding to the system are you
suggesting then that maybe we're not going back to those terminals or we can't in the meter case
yeah and they're working themselves loose is there any evidence to suggest that's happening
there was actually so in the mists of time when people used to fit plastic consumer units and
possibly tails didn't have glands or support additional support with them. Electrical
Safety First did a lot of tests looking at various types of meter tail various types of main switch
and as a result of that i think a lot of the changes that we have in the later editions of
wiring regulations were incorporated and that was to do with the smart meter rollout so people were
going in changing a meter right and then suddenly there was loose terminals in the consumer units
in some cases fire now i will leave a link to that report below because it's quite
good reading when you get into the topic of how do you prepare your meter tails you know do you twist
multi-strand ones together do you flatten them out um yeah there's some good reading in there but
let's just say for now in those scenarios a torque screwdriver won't get you out of trouble so in
conclusion once we start wiggling and moving it it could actually pull out wasn't it the results were
the tails would pull out so that's one of the issues that we could have what about the the one
that i found in my college setting that i'd often go up to a job and they'd say it doesn't work or
i couldn't get it to test or when we went live nothing worked yet we tested perfectly the old
insulation's not a very good conductor PVC doesn't conduct electricity very well does it Gordon i
think what you're getting up there people have actually trapped the PVC in the terminal and this
happens a lot particularly with cage terminals so you've got to be really bad to do with a screw
terminal because you've got to push it quite a way in there to do it but yeah you've you've tensioned
down onto the actual plastic of the conductor you've got to the required torque setting
you've created a joint that at some point is going to fail probably going to get hot and
that's when you obviously see that melted plastic and and obviously that spirals from there so that
cage terminal set to the required torque setting torqued up by the person won't solve the problem
of trapping the PVC in there okay so the tool doesn't get you out of that case does it yeah
now an extra one is obviously the right size conductor in the right size hall and these
okay so you see this obviously a lot in consumer units obviously what do we do to increase the size
of the conductor yeah we look to double them over and obviously those holes are going to accommodate
probably up to 16 millimetre squared cable you think your earthing conductor's going into the
earth bar your neutral bars are the same size etc and you might be putting in a one mil and then it
finds its way it works its way maybe to the side of the screw i think it's also quite um quite
a chance of doing that when we think of stranded cable yeah so if all of a sudden you're using 1.5
ml stranded no strands separate because people haven't twisted them up or doubled them over
yeah we create a problem then don't we there's not as much conductor clamped into the terminal
yeah and again the same thing some of those uh our MCB's come with what we call classics under
those incredibly fine stranded wires and you'll see this is even written into the regulation that
those types of conductors should have some sort of special treatment now we don't mean give them a
biscuit obviously adding a suitable crimp terminal or in some cases a ferrule to the end of them as
well yeah so we've got not as much copper as we should expect in the terminal can cause us an
issue and that brings us to the one where i think a lot of electricians have been going around
buying uh mirrors that look like they should be used by dentists to inspect the underside
maybe where the bus bar is going isn't it so that bus bar misses maybe in one of the positions but
the rest of them are clamped into position aren't they yeah so you've missed the cage
clamp so again cage clamps are incredibly popular now i think most mcb's and switchgear have them
yeah so you've positioned all your all your items in line but as you've put one in you have missed
the uh yeah you've missed the cage clamp uh interesting some manufacturers have actually
designed that problem out and because they bring a shield up behind it to make that impossible
but others don't but there's an even that's one you wouldn't believe it gary
is that the one where you say you turn it in the opposite direction and actually it tightens down
maybe onto a tail etc on the cage clamp yeah yeah so you can it is possible and i wouldn't
suggest ever trying this but yeah you sometimes pretend it's tightening up with the conductor
when i'm turning it anti-clockwise right because actually you're winding the cage clamp on top of
the conductor that you've missed with the uh with the cage clamp in the first place okay well i
think you probably would find that with a torque screwdriver because i think you'd be going the
opposite way with the torque screwdriver however it was brought up in the comments again the torque
screwdriver won't overcome poor practice will it that's it what's our fifth tip from not going to
get you out of jail with a top screwdriver if you damage the conductor okay so you know there's lots
of ways in order to strip our cables if you go in there maybe a bit aggressively with the side
cutters or pliers and you dent the copper okay it obviously becomes a weakened area and then
it doesn't take much does it of movement on that conductor and obviously that can break even though
again you may have done the termination up to the required torque setting yeah but you
know a similar scenario can happen there is with people we've got the torch screwdrivers
but some people over tighten conductors anywhere and put the screw into the conductor
and that flattens it and then also creates a weak point as well doesn't it it does yeah it does and
there's the other one isn't that whereas maybe if we go back to stranded cable you've got some of
the strands in the cage clamps on top of the mcb and then some of them are missing sitting down
the back so all of a sudden the point of the most amount of current that's being drawn is only got
three or four strands in and the rest of them are floating in the back so i think we can conclude
gary from that catalog of cable disasters there that uh a torque screwdriver is certainly not uh
going to get you out of jail and replace uh common sense and competence no i think it's in your tool
kit along with your mft tester in order that you can have an installation that when you've left it
you're very happy that it's tested correctly and to the required manufacturers of talk
at terminating points however if we've missed anything please leave it in the comments below
and it all remains is for me to say is there's no such thing as a calibrated arm