UK What sequence to do when doing fault finding (AM2)

[Mustard85]

Did you ask for the reading and what it was tested between?
You should be able to work out which one of those four categories of faults this falls in to?

You have to test yourself. I think I had a reading of 22 Kohms between neutral and earth. I put down high resistance. I'm doubting myself now that it short circuit. I will phone the Assessor tomorrow to find out what faults I had wrong.

 

[radiohead]

You have to test yourself. I think I had a reading of 22 Kohms between neutral and earth. I put down high resistance. I'm doubting myself now that it short circuit. I will phone the Assessor tomorrow to find out what faults I had wrong.

You state in your OP that you were 'continuity and resistance' testing, and that an ohmmeter was used. An ohmmeter is not used for insulation resistance testing because it does not output a high enough voltage to break down and show up high resistance faults. A 500v insulation resistance tester is used which would read 0.02 Megohms on a fault of 22 Kohms. That would be an unacceptably LOW reading between N-E, not a high resistance. It would normally be termed a low insulation resistance to earth. A short circuit is normally a fault between live conductors, ie line to neutral.
I may have misunderstood your posts but it seems to me you were using the wrong meter to test insulation resistance.

 

[Mustard85]

You state in your OP that you were 'continuity and resistance' testing, and that an ohmmeter was used. An ohmmeter is not used for insulation resistance testing because it does not output a high enough voltage to break down and show up high resistance faults. A 500v insulation resistance tester is used which would read 0.02 Megohms on a fault of 22 Kohms. That would be an unacceptably LOW reading between N-E, not a high resistance. It would normally be termed a low insulation resistance to earth. A short circuit is normally a fault between live conductors, ie line to neutral.
I may have misunderstood your posts but it seems to me you were using the wrong meter to test insulation resistance.

This where I'm confused... If there a fault and the discription they give "there's an Insulation resistance issue when testing" my 1st reaction when read this was I can't do the IR on a Ohmmeter! Hopefully I'll get some answers tomorrow

 

[radiohead]

Ok, well hopefully you'll be able to come back with a bit more info tomorrow.

 

[Lucien Nunes]

If the insulation resistance is seriously low, such as the mentioned 22kΩ, you can find the problem using either an insulation tester or multimeter, as both will respond to that resistance. What you cannot do with the multimeter alone, for the reason that Radiohead clearly explains, is to subject good insulation to a stress test to prove that it is really good.

As an analogy, if water is gushing out of a faulty pipe joint, it doesn't take any special pressure test equipment to discover where the leak is. But, if the pipe appears watertight when there's some water standing in it, to say with certainty it won't spring a leak in use, you've got to put on as much pressure (or more) as it will have to withstand in use, and that is the specific function of an insulation tester.

 

[Mustard85]

Hi sorry for late reply. Work been crazy this week. I've had my results unfortunately they won't say what faults I failed on and I only need to 1 more faults to pass that section.

I've been speaking to sparks in work with me and they are saying they put the resistor in to simulate a fault like a nail through a cable and saying that the fault is short circuit.

Got my resit on the 2nd week of march. I'm fairly confident I understand what to do next time. There are clues in the discription I just need to take my time and understand how the circuit worked.

Thank you all for your comments and advice. Will let you know how the resit went

 

[DPG]

Good luck. .

 

[Mustard85]

Just to let you know that I've pass(100%) my resit for fault finding!!! Over the moon

 

[littlespark]

Well done, mate.
After all that discussion

 

[Mustard85]

Well done, mate.
After all that discussion

Lol Yea 1 of the fault was Insulation resistance failed, I was laughing during the exam when I saw that. It was a short circuit fault lol