Insulation Resistance, can anyone explain?

[SimonH2]

In this case the guy has been working as an electrician for at least 2½ years.

He still doesn't understand what insulation resistance is all about.

He is not "cut out" to be an electrician, and that's all there is to it.

That's a bit strong.
We don't know what his training was like, and it's quite possible that the people training him just did a really crap job. It could have been one of those "you do this, if you get that answer then it's OK" situations where the trainer teaches how to clip some leads on, press buttons, and note a number - but without actually giving any clue what it is that's actually being tested or why. I've witnessed courses like that (been on some I think) and think it's a c**p way to teach, because it turns out people who can pass the test but don't understand the subject.
On the other hand, if he's had proper teaching, but failed to grasp the theory and failed to ask about it at the time, then I would agree that it's quite something of a shortcoming and may indicate suitability or otherwise for the trade.

And as bernardgreen suggests, he may be a s**t-hot electrician doing installation work, just not cut out for testing.

 

[mattylad]

And he has shown that when he does not understand something he will ask for help understanding it.

 

[westie101]

Thinking back to college and a lecturer that didn't actually know how a particular HV protection system worked. Put something up that was years out of date and was amazed when he was told that ir was, was shown a modern design and how it worked!

So before the "pupil" is criticized, make sure you know if he/she has been taught correctly!

 

[ban-all-sheds]

He may well be cut out to be an "electrician" installing cable and components

That's not what I call an electrician.

 

[ban-all-sheds]

That's a bit strong.
We don't know what his training was like, and it's quite possible that the people training him just did a really crap job. It could have been one of those "you do this, if you get that answer then it's OK" situations where the trainer teaches how to clip some leads on, press buttons, and note a number - but without actually giving any clue what it is that's actually being tested or why. I've witnessed courses like that (been on some I think) and think it's a c**p way to teach, because it turns out people who can pass the test but don't understand the subject.
On the other hand, if he's had proper teaching, but failed to grasp the theory and failed to ask about it at the time, then I would agree that it's quite something of a shortcoming and may indicate suitability or otherwise for the trade.

And as bernardgreen suggests, he may be a s**t-hot electrician doing installation work, just not cut out for testing.

Sorry - no.

Insulation resistance is not a particularly hard thing to understand. Anybody who is cut out to be an electrician should grasp it as soon as it's explained, and should understand what an IR tester does, and why.

 

[RF Lighting]

I don't think I was ever properly taught about IR at college or any sort of testing really. I'll admit I didn't fully understand a lot of the theory side after I had passed my exams and bcome a 'fully qualified electrician'

I guess that there was no hope for me and I wasn't cut out to be an electrician, and I certainly couldn't learn it afterwards by asking people at work, and if the internet had been invented, I'm sure I might have asked on an internet forum too.

 

[ban-all-sheds]

It's not theory, and IR is not intrinsically bound up with testing.

This is a cable.

It has insulation.

The insulation has resistance.

How hard is that?

2nd lesson.

The value of the resistance should be over a certain amount otherwise you can get problems and/or it indicates that something might be wrong.

We poke 500V down it, and measure it's value.

How hard is that?

 

[bernardgreen]

Very simple to explain but that doesn't give any idea of why there has to be insulation on the copper wires. After all it will work if the wires are bare but kept apart.

That might seem frivolous but it is often the case that trainers take for granted that the students have a basic knowledge of electricity.

Unfortunately some students do not and dangerously some of those make it through to being "qualified" electricians without ever having been taught or having otherwise aquired the fundamental knowledge of what electricity is and how it does what it does.

I would go further and wonder if some of the trainers are also lacking in basic knowledge.

 

[SimonH2]

Unfortunately some students do not and dangerously some of those make it through to being "qualified" electricians without ever having been taught or having otherwise aquired the fundamental knowledge of what electricity is and how it does what it does.

Unless the exams/tests/assessments are rigged to require separate passes in each area, then it's usually possible to have a complete gap in one area and still pass. Eg, if there are 10 blocks of knowledge, and the pass rate is 90%, then you could in theory leave out one block altogether.

I would go further and wonder if some of the trainers are also lacking in basic knowledge.

I wouldn't wonder, I know some have gaps - I've had discussions with some in the past

Contrary to what some people think, teaching is not easy - and some of the best practitioners make lousy teachers.

 

[JohnW2]

Contrary to what some people think, teaching is not easy - and some of the best practitioners make lousy teachers.

Very very true. Furthermore, once when gets into traditional high-level academia (i.e. universities etc.), and again contrary to what many people think, many/most 'academics' are not in that role because they want to teach, have an interest in teaching or are 'good at teaching'. Some of the very worst teachers come from those with the greatest academic minds. It happens at lower levels, too. I had an A-Level maths teacher who was brilliant, and would have made a fantastic academic, but he was utterly useless as a teacher. Everything was so 'obvious' to him that he had a serious difficulty in comprehending why others didn't understand, and therefore was often incapable of helping them!

On a related tack, perhaps more relevant to this thread, many highly intelligent and knowledgeable people are poor in relation to practical skills, and vice versa - e.g. the person who has an extensive understanding of electrical theory (including IR!) but would make a pig's mess of chasing a wall or wiring a CU, or the converse. Hence, in many walks of life there is a case for a division of responsibilities - yet the tendency has been to move in the opposite direction, with increasing requirements for academic/theoretical knowledge on the part of 'hands-on' practitioners.

Kind Regards, John.

 

[ricicle]

"Those that can do, those that can't teach"

 

[JohnW2]

"Those that can do, those that can't teach"

Indeed. However, that expression is usually used in a negative sense, which, as I've implied, I think may often be wrong. There are plenty of people who cannot 'do', but are excellent at teaching the principles underlying what should be done.

... so I suppose a corollary of that one could be "Those who can teach do (teach), those who can't (teach) 'do' (real work) "!

Kind Regards, John.