Testing Questions - help.

[spark 68]

OSG (red) page 84 figure 10.6 - Are the MCB's off?? It looks like they are off - are they??

But description on page 83 states circuit breakers closed (on)?

Yes they are off lol, but it does not match the text in the red OSG, that drawing should be in the new GN3 for testing indvidual circuits, or at least the labelling.

 

[spark 68]

Linking L-N and test to earth - Is this perfectly acceptable if and when assessed by an assessor for competent person schemes? (long way off yet).

Yes perfectly acceptable on an existing installation, on a new build or rewire and the like you should do the L-N test on the cables before the accessories are fitted.

As I said some items don't like 500V up 'em, and it is possible to damage vunerable equipment, and on a job if you break it you have to fix it/replace it, and some central heating controller panels and the like are bloody expensive.

 

[chrisgc]

Yes perfectly acceptable on an existing installation, on a new build or rewire and the like you should do the L-N test on the cables before the accessories are fitted.

As I said some items don't like 500V up 'em, and it is possible to damage vunerable equipment, and on a job if you break it you have to fix it/replace it, and some central heating controller panels and the like are bloody expensive.

Totally understand about doing the 250v IR test first.

Is it not wise for electricians to have a brief disclaimer form for when assessing or testing installations (for IR test), in case something is blown due to voltage being put through?

Just a thought really as we sign forms for many things in life like operations, dental treatment etc for experts in their field to operate yet if anything goes wrong they have you sign disclaimer beforehand to cover themselves.

Would it not be an idea for electricians too and prudent in the likely hood that something was damaged by mistake?

 

[spark 68]

Totally understand about doing the 250v IR test first.

Is it not wise for electricians to have a brief disclaimer form for when assessing or testing installations (for IR test), in case something is blown due to voltage being put through?

Just a thought really as we sign forms for many things in life like operations, dental treatment etc for experts in their field to operate yet if anything goes wrong they have you sign disclaimer beforehand to cover themselves.

Would it not be an idea for electricians too and prudent in the likely hood that something was damaged by mistake?

By linking the L to N you remove the risk all together, the other option is to double check that everything is disconnected by testing at 250V first, and only if that is clear then do the test at 500V, you can also link/bypass any vunerable equipment.
Again it is better to test @ 250V first in case you have missed something.

I would only bother with the L-N test if it was a newly installed circuit/s that I know exactly what is what, but on a CU change and an EICR etc. I just do the L+N to E test, as I said this is an acceptable method..

Sometimes Neon indicators on shower switches and the like give false readings on the L-N test.

 

[spark 68]

I have just re-read your earlier posts and you say you have a N-E fault at the remote CU, as the MCB's are single pole devices turning these on or off in the remote CU won't isolate or narrow your fault down.

I would start by opening the main switch at the remote CU then test between N and E bars, if your fault is now clear then it may be a supply cable fault, if it it is still reading faulty then you will have to do as some of the other posters have said much further back in the thread, and start disconnecting the Neutrals from the N bar in the remote CU, and test each one to earth, this will at least narrow it down to one circuit, unless you are really unlucky and have more than one fault lol.

Edit: do you have any RCD's or RCBO's in the remote CU ?

 

[ackbarthestar]

Five pages of distance learning and there's still confusion.

The answer was in the first couple of replies.....

 

[chrisgc]

I have just re-read your earlier posts and you say you have a N-E fault at the remote CU, as the MCB's are single pole devices turning these on or off in the remote CU won't isolate or narrow your fault down.

I would start by opening the main switch at the remote CU then test between N and E bars, if your fault is now clear then it may be a supply cable fault, if it it is still reading faulty then you will have to do as some of the other posters have said much further back in the thread, and start disconnecting the Neutrals from the N bar in the remote CU, and test each one to earth, this will at least narrow it down to one circuit, unless you are really unlucky and have more than one fault lol.

Edit: do you have any RCD's or RCBO's in the remote CU ?

There are no RCD's or RCBO's on the remote CU.

 

[Guitarist]

Just wondering Chris, have you been taught fault-finding techniques at all, or are you learning "as you go" ? It's very important to really understand the mechanics of your system before "probing away".

 

[chrisgc]

Just wondering Chris, have you been taught fault-finding techniques at all, or are you learning "as you go" ? It's very important to really understand the mechanics of your system before "probing away".

Am probing only on one CU (of which I know the person and he is not in the property as of yet. So getting used to the tester I have. Was used to a megger tester a few years ago (not for long though).

I have a metrel tester at the moment. So getting used to it.

 

[Guitarist]

Am probing only on one CU (of which I know the person and he is not in the property as of yet. So getting used to the tester I have. Was used to a megger tester a few years ago (not for long though).

I have a metrel tester at the moment. So getting used to it.

I can appreciate the fact that some testers take a bit of getting used to. That is a bit different to understanding how to test, and what results to expect. Just wondered what your training entailed.

 

[chrisgc]

I completed the part P and 17th edition but I know that this is no replacement to someone who has done electrical work for many years.

I just find that some of the test explanations in different books tend to be different so thats where a lot of confusion lies.

Ideally I would love to work as an electricians mate but I have had no joy there.

I would happily help out for just petrol money or just to shadow someone regularly to get proper hands on experience.

 

[spark 68]

Hi Chris,

You seem to be on the right track, you may be better trying the 2392 course, this is the initial verification course and covers testing. This is not as difficult as the old 2391 or the new 2394/5 courses and would be a good stepping stone for you if you are interested in testing.

Fault finding is an acquired skill, and not suited to everyone, some people pick it up like a duck to water and others seem to struggle no matter how much training, it is just one of them things, this is no disgrace either.

 

[chrisgc]

Hi Chris,

You seem to be on the right track, you may be better trying the 2392 course, this is the initial verification course and covers testing. This is not as difficult as the old 2391 or the new 2394/5 courses and would be a good stepping stone for you if you are interested in testing.

Fault finding is an acquired skill, and not suited to everyone, some people pick it up like a duck to water and others seem to struggle no matter how much training, it is just one of them things, this is no disgrace either.

Any recommendations of where to gain the 2392 course as sounds like a good step forward?

 

[spark 68]

Any recommendations of where to gain the 2392 course as sounds like a good step forward?

The local college might be a good start, as the courses tend to run over a period of weeks rather than days, the training provider courses are typically 4 days and try to cram everything in to short period of time.
As far as I know the 2392 just covers single phase testing, and is more basic than the much more difficult 2391/4/5 courses, but is a start.

The secret of testing is to break everything down into smaller and simpler parts, and try to understand what it is you are testing for. Draw the circuits out if it helps, take your time and don't try to take everything in at once.
Once it clicks into place you will understand.

Then when you have some understanding and more confidence you can test in larger chunks and get faster, you will then be able to test and 'see' where the possible faults may be, and how to proceed.

It is important not to be intimidated or overwhelmed by the larger installs, as these are just more of the same or similar basic units.

Get a copy of GN3 if you haven't already got it.

Good luck.

 

[Guitarist]

With the greatest respect Chris, the part P and 17th edition course are really just for electricians who are already trained, and will not give you a basis for carrying out electrical work. There is a reason most of us did a 4 year apprenticeship