- This video carries on from the continuous CPC
and polarity test that we carried
on our radial socket circuit here at Lineside Studios.
Once again, we're gonna use our Metrel MI 3125 BT
multifunction tester
in order to carry out this insulation resistance test.
We can see in the distribution board
we've still left it with the line,
the neutral and protective conductor disconnected,
and we've ensured that the circuit has all loads removed,
and all our socket fronts are in the on position,
so the insulation resistance desk gets
to the furthest point of each outlet when we carry it out.
However, before I can start the work
I'm gonna need someone to carry out that work.
So I need to find out where Rick is.
Rick, it's often overlooked
that Circuit Protective conductor
we've currently got disconnected, needs returning
and connecting to the earth bar.
And he says here, "Is essential the incoming earth
is connected to the MET,"
as well as our earthing conductor is present,
"and any other protective bonding conductors
before carrying out the insulation resistance test."
- Yeah, before we get into anything too technical though,
let's have ourself a biscuit.
What have we got here?
An extremely chocolatey biscuit selection from Tesco's.
Would you like one?
- Oh, I'd love one.
Ah, thank you Rick.
- Cheers, they're delicious.
- So let's set up our Metrel MI 3125 BT tester
in order to carry out this insulation resistance test.
I've powered it up and it shows us as a test
so that we were last carrying out.
We were doing the R1 plus R2 continuity test
of this radial socket circuit.
I need to scroll through to insulation resistance
using this button here we can see the word "next".
Scroll through, next one's ring final circuit,
which we don't need.
And then we're onto the insulation resistance test
identified with ISO.
And you notice on the top row there
you've got the voltage being passed
through the circuit during the test being 250 volts DC.
And we want to change that to 500 volts DC.
We do that by pressing this button here.
We'll talk about when we can use 250 in future videos.
Now I'm gonna change that,
I can go down to a hundred or I can go up.
So if I dropped it down, I can go to a hundred,
or I can go up to 500 volts and 1,000 volts.
So I wanna stick with the 500 volts DC for this test.
What is fantastic is this end screen here,
which sets the minimum past value for this test.
So you can set this yourself.
And I've set this at one megohm,
So anything below megohm would show as a fail,
anything above would show as a pass.
Again, if I move to it,
I can set it considerably lower or considerably higher.
Well, we're gonna set it at its maximum.
It's maximum is maximum being 200.
So anything that we get 200 or greater will be a pass.
Anything below that would show as a fail.
But that's really good, isn't it?
Imagine you've gone into an installation,
you looked at previous reports and saw
that circuits were hovering around, say, 10 megohm,
you could set that at the point
of which you wanted to show whether it be a pass or fail,
and you could see deterioration over time.
So we've set the instrument up.
It might be now
that you want to look at the help screen, okay?
In order to work out what you need to do with your leads.
So if I press the help screen,
it's showing the adapter needs connecting to the instrument
which we'll do in a second.
And it shows the fact that we've gotta connect
our neutral and protective earth leads together
for this test, and then have our line lead separately.
So let's do that next.
So in the top of the machine, we're gonna slide across,
in order that we can put in our adapter.
We pop that into place as we drop back down,
we've just seen there that these leads need piggybacking.
So we've got the neutral one
and the protective earth one joined together,
and our line lead, and I'm gonna use my crocodile clips
in order to carry out this test.
So pop those into position.
And now we need to come back out of this screen.
We do that by pressing the help button once again,
and now we're back to where we started.
And now we could perhaps test the leads
are in good condition.
So in other words, I wanna prove that these haven't broken,
there's no snap, say, where it connects
into the actual connection
for the crocodile clip, or they're damaged.
So by simply joining the two leads together, okay,
we should find that we now have a dead short.
Okay? So that would give us obviously zero,
and it will show a fail,
but it'll actually show that we have continuity
or a completed lead before carrying out this test.
So press the test button.
We should expect it to fail.
We've got zero, is what we expected.
We see we've got an X to say we've failed.
And what I really like is we've got this LED light here
to tell me that I have a result that I wasn't happy with.
Remember, my result had to be 200 megohms
or greater in order to get a pass.
So that proves to me then that the leads are
in good work in order, and now we're ready to carry out
the test on the installation.
It's time to set Rick to work,
and we absolutely love this Metrel tester
with the magnet on the back who attaches it to the trunk in.
And now we've gotta put that circuit protective conductor
into the earth bar.
Remember, and we've gotta confirm that there is
a source of earth into the installation,
The earthing conductor is present
and any protective bonding.
And because it's gonna stay in situ,
we're gonna return it to required torque set,
and using our Wiha torque screwdriver.
Well first of all gonna test between our live conductors,
it doesn't matter which order we do these in.
So we're gonna go
between our line connection and our neutral.
And when we press our test button
we can see we get a reading
greater than the machine can read.
So our reading there is greater than 999 mega ohms.
Next we're gonna test between our line conductor
and the earth bar where our CPC is connected.
And once again, when we press our test button,
we can see it's greater than machine can read,
greater than 999 megohm.
Next we're gonna test
between our protective conductor and our neutral connection.
And once again, when we press our button,
we can see we get that reading once again.
But what I really like here is the fact
that we get that tick to say
that we've got a reading that was acceptable,
as well as that visual indicator through that green LED.
Remember, we set it at 200 megohms as our fail point.
Rick shuffled off to squirrel away
a few more of those biscuits,
but I've got a question for you.
Are you always returning
that protective conductor to the earth bar
before carrying out your insulation resistance test?
Or like me, maybe in the past you've been guilty
of doing it with all three conductors disconnected?
I'd love your feedback on that below.
You might be looking at this bag here
and wondering what the MI 3125 BT tester from Metrel
comes with in order to see that.
Check out the video on screen just there.