Insulation Test Results

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Pepparz

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i'm having problems finding the correct answer to this question which has been taken from a 2394 exam question;

Whilst carrying out an insulation resistance test on a new lighting circuit the result is unsatisfactory. list THREE steps which need to be taken.
 

so, i would say report result on schedule of test results and inform client, but this isn't correct but, I don't believe that making good and retesting is correct either?

 
thanks but i don't think thats the answer they're after

 
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Whilst carrying out an insulation resistance test on a new lighting circuit the result is unsatisfactory. list THREE steps which need to be taken.

so, i would say report result on schedule of test results and inform client, but this isn't correct but, I don't believe that making good and retesting is correct either?

Hmm...

This is NEW install....

if someone does a job wrong they do not just write unsatisfactory tell the customer and then expect to get paid for some work that has been done wrong..

It must be corrected retested and then you can ask the customer for your money for doing the job... 

So three steps that need to be taken...

I would suggest..

1/  Verify your test meter is working correctly... (e.g. batteries good & test it on a check box)

2/ Open up all accessories to verify no cables have been trapped whilst closing up switches or light fittings...

3/ Whist accessories are opened if still unsatisfactory readings re-test individual lenghts of cable to identify which section has poor insulation resistance. This could indicate a damaged cable somewhere, snagged insulation, nail/screw in cable, crushed or damaged during installation. 

p.s.

well done for having a go and giving your thoughts on what the answer should be!

(some people expect help without trying first themselves!)

Guinness

 
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thanks for the replies but without sounding rude, i know how to fault find. this is from the perspective of a inspector and which may not be the installer.

the question is one which C&G have highlighted as people getting wrong whilst doing 2394.

i know how i'd proceed but wondered what answer the C&G want to hear.

i haven't yet done the 2394 so was just looking through past papers, this is one i struggled with answering correctly

 
i'm guessing its already been safely isolated

Well,,

I would...

Make sure my test gear works correctly
Make sure all loads etc are disconnected/bypassed
Retest, breaking down the circuit as necessary to identity the fault
also meters would have been checked before the first test and loads already disconnected.

think the question is slightly ambiguous anyway IMHO

 
thanks for the replies but without sounding rude, i know how to fault find. this is from the perspective of a inspector and which may not be the installer.

the question is one which C&G have highlighted as people getting wrong whilst doing 2394.

i know how i'd proceed but wondered what answer the C&G want to hear.

i haven't yet done the 2394 so was just looking through past papers, this is one i struggled with answering correctly

i'm guessing its already been safely isolated

also meters would have been checked before the first test and loads already disconnected.

think the question is slightly ambiguous anyway IMHO

I think you are making the classic mistakes that this sort of question is specifically designed to highlight...

2394 is Initial and Fundamental Inspection and Testing (2394)

http://www.cityandguilds.com/qualifications-and-apprenticeships/building-services-industry/electrical-installation/2394-initial-and-fundamental-inspection-and-testing#tab=information

And the biggest mistake anyone makes during any inspection / test / fault find or similar is to assume something you have not proved.

Every meter that goes faulty was working perfectly correct the time before when it was used..

To assume that a meter can never fail just because it was checked the previous day or earlier that same day is a dangerous attitude within electrical test and inspection..

(consider the safe isolation procedure..  verify tester still working after proving dead)

Any task where ambiguous or unexpected results occur the first check has to be

Verify the test equipment is still working correclty..

it can be a very costly or dangerous assumption that the test equipment never fails!

Inspection and testing is about only trust what you have proved yourself..

Do not assume anything..

Only make judgment on what you have tested and proved..

I think you are trying to read far too much into the question..

Consider some other past exams and the examiners reports.. 

http://www.cityandguilds.com/qualifications-and-apprenticeships/building-services-industry/electrical-installation/2394-initial-and-fundamental-inspection-and-testing#tab=documents

Look at additional documents..

for example...

Candidates were asked to inspect newly installed socket-outlets to ensure compliance with BS 7671. The answers provided by candidates were usually correct but lacked detail. "Connections" need to be checked but the answer needs to include what in particular is being checked. This could be that they are "tight", the conductor is in the correct terminal or maybe that no excessive amount of copper conductor is exposed. The lack of detail means that full marks were not awarded. Checking for overheating may be valid for periodic inspection but it is not valid for initial verification as the circuit has not yet been energised.
Things that you imply are obvious and you would do anyway must be written and detailed clearly to avoid ambiguity of the answers..

or..

There were three questions where candidates appeared not to read the question carefully. When asked to state three practical steps that an inspector can take during the inspection and testing process to ensure the safety of persons in the building, some candidates incorrectly listed the checks to be carried out on the installed electrical equipment.

Another question asked for an explanation as to why a continuity of protective conductor test should be carried out before an insulation resistance test. Many answers explained what was being tested during the continuity test but gave no indication as to why this test must precede the insulation resistance test.

When asked to state the three steps to be taken when a correctly carried out insulation resistance test produced an unsatisfactory reading, a number of candidates incorrectly referred to the removal of loads and electronic devices. As the test was carried out correctly, the loads and electronic devices would have been removed.

SO..

The IR test has been carried out correctly but the results are wrong..  (Low resistance of and unknown magnitude)

The circuit is disconnected from the board as it is dead test..

there are three key components involved..

1/ an IR tester

2/ some cable

3/ some accessories, switches / j-boxes

It has got to be one of the three introducing the low reading...

So re-test the three items!!!!

What if a load had been missed...?

what if a fixing screw has cut into the neutral wire causing a continuity path from Neutral to Earth..

Once you have done all of those three and carried out any remedial work identified then you will have a satisfactory test result!

 
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thanks for the response. i think i was probably reading too much into it.

obviously if you were testing our own install and found poor IR results you'd investigate further making sure the meter is sound.

i just was looking at it from an inspectors point of view and not the installer, as if this was the case the inspector wouldn't look for the fault, just report the readings after checking correct meter operation.

IMO i think its poorly worded, or the answers that obvious that i missed it!!

 
City & guilds english; a multifaceted language which leads the reader down many avenues which make it hard for the reader to grasp the true meaning of what they are trying to answer.

What do you think they want hear rather than what may be more logical and familiar to the reader.

Well....

That's how I see it.

Edit: good post spec loc :)

 
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thanks for the response. i think i was probably reading too much into it.

obviously if you were testing our own install and found poor IR results you'd investigate further making sure the meter is sound.

i just was looking at it from an inspectors point of view and not the installer, as if this was the case the inspector wouldn't look for the fault, just report the readings after checking correct meter operation.

IMO i think its poorly worded, or the answers that obvious that i missed it!!

Personally I doubt many business would succeed very long working like that...

e.g.

electrician 'A' installs a new circuit...

electrician 'B' inspects it but has an erroneous reading... 

The fault has got to be rectified by someone locating the area which the problem exists if 'B' is not doing this investigation then either...

you pass it back to electrician 'A'..  who probably hasn't got the test equipment needed, as if he had, the fault would have been identified before electrician 'B' came along !

Or you pass it to another man electrician 'C' who has then got to redo some of 'B' & 'A's work to back track and identify and fix the problem.

Whereas electrician 'A' would already by part way to locating the problem due to the investigations already carried out ..

If he can narrow it down to a smaller area and either fix it himself..

Or then call back electrician 'A' (who knows the cable runs etc..)  to do final remedial work.

At the end of the day if you can reduce the number of repeat visits this should save money in the long run....

Businesses that don't waste money generally succeed better.

:popcorn

 
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i just was looking at it from an inspectors point of view and not the installer, as if this was the case the inspector wouldn't look for the fault, just report the readings after checking correct meter operation.
I forgot to add your scenario could be valid for a company if they so wished..

But you mustn't confuse company procedures with BS7671 guidance or good practice:-

Consider three hypothetical small businesses each with 5 employees..

all concentrating on domestic wiring

Company A do site work with a build contractor, they always work on larger site where 40+ houses are being built at a time..

Each man has a key task

employee 1: First fix just carries cable & back boxes etc..

employee 2: Second fix just carries socket, switches fittings etc..

employee 3: Dead tester just does Continuity & IR tests

employee 4: Live tester just does Earth loop, PFC, RCD etc..

employee 5: team leader: bit of everything manage and help out others if slip behind schedule signs off certificates..

Company B do social housing with a council in a 40 mile radius of the city, they work in teams of two.

employee 1: Installer First & second fix..  (team 1)

employee 2: Tester dead & Live tests.. (team 1)

employee 3 & 4: team 2 same roles as team 1..

employee 5: team leader: programs job into diary by geography & manages materials to ensure at site when teams arrive to do their work etc..

Company C provide alteration and maintenance for private customers on a one-off callout basis

employee 1: All aspects of work Install / test / Certify / Fault find etc.. has large fully stocked van full of kit to cover most common call outs & alterations.

employee 2, 3, & 4 same roles as 1..

employee 5: team leader: answers customer phone calls, books employees to jobs, organises emergency materials or assists if double handed work needed and no other employees local.

They will all have different company procedure about how they progress or delegate fault investigation work..

BUT..

whoever does it will need to follow basic ground rules for investigating the problem in a safe way  

whilst verifying which components of the installation are working and which components are faulty.

Excluding essential health and safety guidance and procedures

C&Gs are not interested in  various company procedures that are just down to the structure of a company.

Guinness

 
Hi All,

Well, it says that the "results were unsatisfactory" I would suspect that this means [in city and guilds world] that the insulation test had been carried out correctly, with a meter that can be assumed for their purposes, to be working correctly.

Sooooo, i would say;

1, Carry out further inspection to find fault.

2, Rectify fault.

3, Retest.

Did I pass, did I pass!!!!!!

john...

 
Hi All,

Well, it says that the "results were unsatisfactory" I would suspect that this means [in city and guilds world] that the insulation test had been carried out correctly, with a meter that can be assumed for their purposes, to be working correctly.

Sooooo, i would say;

1, Carry out further inspection to find fault.

2, Rectify fault.

3, Retest.

Did I pass, did I pass!!!!!!

john...
As this is 2394 it is a new installation and is not in service yet.

Therefore you should assume that the testing should not continue until the unsatisfactory result has been rectified. Now, with C&G you have to remember that the person carrying out the inspection is not always the same person as the installer and so may not be responsible for finding and correcting the fault.

so I would go with 

1. notify the installer of the final circuit that there is a fault with it.

2. rectify the fault

3. retest 

Is this a stand alone question or one part of a multi-part question???  if its part of a multi-part question then the proceeding question can also give clues as to the answer that is required.

Knew I'd find it.  Bottom of page 31 of GN3

any defect or omissions revealed by the inspector shall be made good, and as necessary inspected and tested again, before the EIC is issued; it is not the responsibilty of the person or the organisation carrying out the inspection and testing to make good defects and omissions.

 
All current using equipment removed (lamps, chokes tec.)

All circuit breakers open

All switches closed - not forgetting any 2-way or intermediate switching

All test gear working

Fault on circuit (not clear where the fault is though at this point are we)

As above - regarding about everything including the GN3 page 31 :)

Connect N/L together  test to earth.  This would rule out faults to earth.  

If then 'fault' between L/N on IR reset instrument to' Low resistance Ohm meter settings' and test.  Not the resistance and work out the 'Load' in amps.  This may indicate that there is something left in circuit.  Please note:  No such thing as a 'dead short'

This sounds like a question from section B ?.  Not a lot to go on here.

I'd ask your lecture to explain this to be honest.

One clue would be the number of points for the answer - 1 point each would indicate a VERY short answer for each point ; -)

 
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