Insulation Resistance, can anyone explain?

[JohnW2]

All the op is asking is for an explanation of the IET logic, that 1MΩ is the pass point but on a new installation any experienced spark would expect circuit readings of >200MΩ. And anything less than this is a clear indication of a problem that needs to be investigated. So come on BAS, JohnW2, ricicle give him an explanation.

No, the OP was essentially asking what the IET's 'rules' were, and I could have quoted them to him.

As for any logic which may exist in the IET's view, you'd really have to ask them. I personally would be having kittens if I knew that the IR of the installation in my house was less than 50 times greater than the what the IET appears to regard as 'OK'!

Kind Regards, John.

 

[JohnW2]

Bear in mind that 1meg is the minimum across a DB, not per circuit. So if you had an installation with 12 circuits each measuring 10 meg then technically that would be a fail

True, but I think that's another example of 'twisted logic' on the part of the IET.

It's obviously final circuits which matter, since that's where any faults are going to exist. In what sense is it logical that a DB/CU with 2 final circuits, each with an IR of 2MΩ 'passes' (just), yet one with 10 circuits each of 9.9MΩ, or 20 circuits each with 19.9M² would 'fail'?

They surely ought to have expressed the overall DB/CU 'pass mark' as XMΩ/N (where N is the number of final circuits) ... not to mention that, at least to my mind, all their 'pass marks' are frighteningly low.

Kind Regards, John

 

[holmslaw]

..

 

[JohnW2]

He was'nt asking what the 'rules' are he was questioning the logic behind the rules.

I don't think we can have been reading the same OP ...

Can someone please explain to me in lamans terns insulation resistance. So the meter reads >200 on 500v which means everything is ok but at what point is it a fail is it at 100 or 50 etc? And how does 1M ohm realtes to all this. Ive always had a bit of a hard time taking this in

He clearly hasn't got a clue about the rules, certainly not enough of a clue to be asking about the logic behind them.

Kind Regards, John

 

[ricicle]

The op has been unfairly criticised by BAS, JohnW2, ricicle for asking a simple and justified question.

Justifiied in the fact that a practising electrician doesn't understand the simplicity of insulation resistance. Holmy you are wrong - again.

 

[ban-all-sheds]

The op has been unfairly criticised by BAS, JohnW2, ricicle for asking a simple and justified question.

It might be a simple and justified question from someone just starting his first ever electrical course.

It is absolutely not a justified or acceptable question from someone who has been working as an electrician for at least 2½ years.

My advice to CaptainKidd:

Give up trying to be an electrician, and find something you can actually cope with, before you injure or defraud someone.

 

[SimonH2]

The op has been unfairly criticised by BAS, JohnW2, ricicle for asking a simple and justified question.

Justifiied in the fact that a practising electrician doesn't understand the simplicity of insulation resistance. Holmy you are wrong - again.

In my experience it is quite common for people who are supposedly fully trained/skilled to not understand something - even what look like simple things. At least this person has been brave enough to stick his head up and ask rather than carry on in ignorance.

 

[JohnW2]

In my experience it is quite common for people who are supposedly fully trained/skilled to not understand something - even what look like simple things. At least this person has been brave enough to stick his head up and ask rather than carry on in ignorance.

Yes, the bravery is to be commended. However, there is surely a limit to how basic can be the deficiency in knowledge/understanding before one has to question whether an individual should actually be practising in a trade or profession - rather than bravely acknowledging that his/her basic lacks of knowledge and/or understanding warrant some further education/training before they start in practice.

In other words, what I would really applaud is someone saying something like this ... "I'm a recently qualified electrician but I've never been able to get my head around the subject of IR testing (or whatever). I would therefore be grateful if you folks could help me understand that topic before I start practising and selling myself as an electrician". I would then both applaud and do anything I could to help him/her to get up to speed.

Kind Regards, John.

 

[ban-all-sheds]

In other words, what I would really applaud is someone saying something like this ... "I'm a recently qualified electrician but I've never been able to get my head around the subject of IR testing (or whatever). I would therefore be grateful if you folks could help me understand that topic before I start practising and selling myself as an electrician". I would then both applaud and do anything I could to help him/her to get up to speed.

Would you?

You wouldn't criticise the person concerned for knowing that there was something fundamental which he didn't understand and yet simultaneously still considering himself to be a qualified electrician?

You wouldn't suggest that if he'd got to the end of his academic training and was still unable to grasp something that simple and fundamental that maybe he wasn't cut out to be an electrician?

 

[ban-all-sheds]

In my experience it is quite common for people who are supposedly fully trained/skilled to not understand something - even what look like simple things.

The key word there is "supposedly".

Without it your statement would be a complete oxymoron - if someone doesn't understand something fundamental to their job then they are not fully trained/skilled.

 

[ricicle]

I am a practising accountant but I don't fully understand tax returns. Would you like to employ my services ?

 

[ban-all-sheds]

Yes please.

Regds.,

Ken Dodd.

 

[JohnW2]

Would you? You wouldn't criticise the person concerned for knowing that there was something fundamental which he didn't understand and yet simultaneously still considering himself to be a qualified electrician?

That's just semantics. Yes, I would applaud and try to help him... and no, I wouldn't criticise him if he recognised that, despite having officially become 'qualified' (clearly a fault of 'the system', not him), he was not adequately prepared to start practising until his education had been enhanced, and had asked for help to achieve that.

You wouldn't suggest that if he'd got to the end of his academic training and was still unable to grasp something that simple and fundamental that maybe he wasn't cut out to be an electrician?

I would not pre-judge - there are any number of reasons why a person might have a deficiency in relation to one subject area. If, having used my best endeavours to try to help, I formed the opinion that the person concerned was never going to be competent enough ('cut out') to be an electrician, then yes, I would then suggest that to him.

Kind Regards, John

 

[ban-all-sheds]

That's just semantics.

No it isn't.

Yes, I would applaud and try to help him... and no, I wouldn't criticise him if he recognised that, despite having officially become 'qualified' (clearly a fault of 'the system', not him),

No - it's his fault, or rather his limitation. He's reached the end of his training. Yes, the "system" may have failed by declaring him qualified when he clearly is not, but the root of the problem is not the system, it is his inability to understand the things he needs to understand, and his lack of self-awareness and lack of decency which leads him to carry on regardless.

he was not adequately prepared to start practising until his education had been enhanced, and had asked for help to achieve that.

He's been through the entire academic training he's going to get.

He still doesn't understand it.

There's no hope for him - he is not capable of being an electrician, and that's all there is to it.

I would not pre-judge - there are any number of reasons why a person might have a deficiency in relation to one subject area. If, having used my best endeavours to try to help, I formed the opinion that the person concerned was never going to be competent enough ('cut out') to be an electrician, then yes, I would then suggest that to him.

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.

 

[bernardgreen]

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.

He may well be cut out to be an "electrician" installing cable and components and by following the rules he may well be very good and safe at such work.

But without a knowledge of matters like insulation resistance and what effect these matters have on the operation of components he will be unable to diagnose faults and thus un-likely to progress beyond installing cable and components.

In my experience it is quite common for people who are supposedly fully trained/skilled to not understand something - even what look like simple things.

That is my experience too. A local electrician admitted he had learnt more about electrics from his son's school homework than he had learnt on the approved training courses.