trusting your meter

[securespark]

I have put screws through T&E and tested a dead short then remove the screw and all is well.

You mean you have found historic evidence of someone having drilled through a cable, you have reintroduced the fault, meggered, the short is apparent and on removal of the screw, the fault disappears?

 

[EFLImpudence]

EFLI did you go same college as studentpark

No, too far to go home to lunch.

as you both seem to think you can test a ring at an accesory while still connected at the dist board,

Errr - Yes

what insulation readings would you expect to find between neutral and earth

Anyway, I don't think studentspark actually stated where the first tests were conducted.
It was you who said -

if the two legs were still in the fuse,

He may well have disconnected the cables at the board.

 

[AdrianUK]

Seen exactly this before. The original purpose of the high level supply was for a fused spur to feed an infrared heater or a wall mounted fan heater.

T'was removed by a kitchen fitter ... need I say more.....

Adrian

 

[studentspark]

To answer a couple of the questions

IR tests were done with L-N-E disconnected from the board

Continuity can be tested at any point though.

The screw through the cable was something I did in the shed, just finding out what happened to cables as they get damaged. It often seems be the case that a cable can be penetrated by a screw, and once removed it test OK.

This was the main point of my question. Do you trust your meter or what you visually see.
Of course the answer is a bit of both, but I like thoughts and advice from those more experienced.

I do understand that my testing technique will be questioned, and I welcome that as I want to improve, but its a shame that some posters seem more interested in hunting down, rather than offering experience, thoughts and a bit of advice.

 

[EFLImpudence]

IR tests were done with L-N-E disconnected from the board

Ok.

Continuity can be tested at any point though.

It can indeed, as can other tests.

The screw through the cable was something I did in the shed, just finding out what happened to cables as they get damaged. It often seems be the case that a cable can be penetrated by a screw, and once removed it test OK.

This was the main point of my question. Do you trust your meter or what you visually see.
Of course the answer is a bit of both, but I like thoughts and advice from those more experienced.

It is a bit of both - and previous experience in interpreting what the meter tells you.

I.R. tests may be perfect but they do not detect any damage unless there is contact.
There could be nails and screws only touching one conductor, could be the line, or the insulation could have been chewed away - things like that.
We can't do everything.

I do understand that my testing technique will be questioned, and I welcome that as I want to improve,

I can't see how you could have done any better.

 

[JohnW2]

The screw through the cable was something I did in the shed, just finding out what happened to cables as they get damaged. It often seems be the case that a cable can be penetrated by a screw, and once removed it test OK. ... This was the main point of my question. Do you trust your meter or what you visually see. ... Of course the answer is a bit of both, but I like thoughts and advice from those more experienced.

I think the short answer has to be that if one knows or suspects that there has been physical cable damage, one should totally ignore a satisfactory IR measurement and take steps (however disruptive) to expose and examine the damage. Time to again wheel out ....

Untitled

• JohnW2
• 24 Nov 2012
• 7

For fairly obvious reasons, this rodent damage IR tested fine (>500M&#937, but it would clearly only take a little disturbance (possibly by more rodents) to result in a catastrophe.

Kind Regards, John

 

[333rocky333]

If thats aimed at me, no ones hunted you down,
A suspect ring you should treat no different to a newly installed ring

As i said You dont test a ring from an assecory before energising and im sure your college aint taught you to do that.


testing at the board would be pointless if the rings incomplete still, by the missing accesory you found as your first test should be end to end continuity

when your qualified and delve into faultfinding you will find lots of unexplained things, which you will learn to not ponder on as your unlikely to find the answer and can quess and assume till the cows come home.


As for an insulation test from an assecory with the main switch off as EFLI suggests ask your lecturers opinion, it would only take 1 leaky neutral on the neutral bar or a dodgy appliance on another circuit to throw a wobbly with your readings

 

[studentspark]

 

[EFLImpudence]

If thats aimed at me, no ones hunted you down,

wear cap it fits the if
Just in a bad mood, then?

A suspect ring you should treat no different to a newly installed ring

Read the OP again.
What are you complaining about?

As i said You dont test a ring from an assecory before energising and im sure your college aint taught you to do that.

After energising???
It was disconnected at the board after de-energising.

testing at the board would be pointless if the rings incomplete still, by the missing accesory you found as your first test should be end to end continuity

He discovered it was incomplete by testing at the board.

when your qualified and delve into faultfinding you will find lots of unexplained things, which you will learn to not ponder on as your unlikely to find the answer and can quess and assume till the cows come home.

Not got an inquisitive mind, yourself, then. HE DID FIND THE ANSWER.

As for an insulation test from an assecory with the main switch off as EFLI suggests ask your lecturers opinion, it would only take 1 leaky neutral on the neutral bar or a dodgy appliance on another circuit to throw a wobbly with your readings

Then the test would be deemed unsatisfactory and investigated but if >999MΩ perhaps OK?
Global IR ?

 

[333rocky333]

Give it arest
You his mum mollycodling him.

He asked whether he should reconnect it,
I said reconnect it and then test like you should do a new circuit as he had doubts about its integrity.
No one asked you to poke in and Quote my moves, youve done that a lot with bas lately ive noticed

He says he wants advice then dont encourage sloppy ways

 

[333rocky333]

. HE DID FIND THE ANSWER.

Really, what was it then