2391 exam question

[Baal]

IR testing can be done on individual circuits once the installation is re-energised-they're trying to get you to list JUST the tests that require the installation to be isolated.

 

[brucelee]

cheers baal
thats how i read it but will check my notes and the paper again as i may have included Ir test
my tutor also said the question on volt drop is not a inspection and testing question or even a design question and so shouldnt have even been included i also asked him the correct way for future reference he said it wont ever come up and i will never need it he said I answered correctly but still would like to know right or wrong
I have only ever been shown to use mv/a/m x Ib x L divide by 1000
I had a feeling it was something to do with V=IXR and thats how I answered but it would be good I was in two minds but as it said use the info from figures provided so i did it that way there wording confuses to say the least

 

[Baal]

I think because it now forms part of the schedule of inspections, an inspector should at least have the basics on volt-drop and should certainly be able to quote the 3% and 5% maximums.
The question was probably ripped straight from a 2391-20 paper!

 

[brucelee]

cheers baal
I answered it that way and do know about the max volt drop for lighting and power circuits
so this is the type of question you would get for the 2391-20 as this is one of the courses i am thinking of doing
when i looked through the test again i understand more now as well as speakig to others from the forum there wording is set to confuse to say the least
at my college 10 of us took the exam and only 4 or 5 of us passed I was only 1 of two of us not working in the industry so was nervous to say the least
it would be more useful if they showed you the areas you did correctly or wrongly then you can revise these areas more especially if you have to do a resit which gladly I dont
the whole process from first starting revising and doing the course ,exam and then waiting almost 12 weeks for results took about 6 months or so wouldnt have liked to do it again and go through the whole waiting process
I am still waiting for the cert I have finaly got written confirmation last week

 

[WayneL]

IR testing can be done on individual circuits once the installation is re-energised-they're trying to get you to list JUST the tests that require the installation to be isolated.

Like I said earlier, I don't think I'd like to be poking around inside an energised CU doing a dead test.

I'm pretty sure it also contravenes the EAWR.

Howcome everyone get's in a flap about 'measuring' Zs, and the 'calculation' brigade come out in force - yet you think it's okay to IR test individual circuits in a 'Live' CU?

Also, what about the neutral/earth 'link' - that's gonna throw your results on individual circuits.....or are you talking about disconnecting circuits from the board now to perform the test.
Hope you disconnect the correct neutral, then.

In my opinion, you do a 'full installation' IR test whilst it's isolated

 

[Baal]

I agree with the EAWR comment but then you wouldn't be able to carry out a loop test or a phase sequence test etc as shown in guidance note 3.

The examiners report criticised candidates for merely listing the dead tests as an answer to this question, implying that IR would be the only dead test not carried out during the isolation.

 

[Plonker 3]

Like I said earlier, I don't think I'd like to be poking around inside an energised CU doing a dead test.

I'm pretty sure it also contravenes the EAWR.

No the EAWR states

Work on or near live conductors

14. No person shall be engaged in any work activity on or so near any live conductor (other than one suitably covered with insulating material so as to prevent danger) that danger may arise unless–
(a)it is unreasonable in all the circumstances for it to be dead; and
(b)it is reasonable in all the circumstances for him to be at work on or near it while it is live; and
(c)suitable precautions (including where necessary the provision of suitable protective equipment) are taken to prevent injury.

So you can work live if absolutely necessary

 

[brucelee]

I agree with the EAWR comment but then you wouldn't be able to carry out a loop test or a phase sequence test etc as shown in guidance note 3.

The examiners report criticised candidates for merely listing the dead tests as an answer to this question, implying that IR would be the only dead test not carried out during the isolation.

hi baal
the question
june exam q22 b) says
the owner has agred that the whole installation may be isolated in order for testing to be carried out. There has been a period of 1 hour allocated for this work . List the tests that must be carried out during this period ( Individual circuits may be isolated after this period )
and is worth 6 marks
so I answered
i) continuity of protective main and supplementary bonding conductors
ii) insulation resistance
iii) polarity
iv) external earth fault loop inpedence (Ze)
v) prospective fault current
vi) functional testing
as its worth 6 marks then you would have to give 6 listed tests I think this was one of three i struggled with and dont know if i got right mate what would you put

 

[Baal]

Hi Bruce
You have 60 minutes to carry out all of the above tests, they are giving you a clue so the answer is i) iv) and v)

The examiners report criticised students for merely listing all of the dead testing as this would not be possible given the time constraints.

 

[Jurasic Spark]

Yes, there are 3 tests here that require the isolation of the installation:

Continuity of protective bonding conductors
External earth fault loop impedance
Prospective fault current Why do you need it isolated for this test?

Don't write 'Ze' and 'PFC' etc-this exam is marked on correct terminology and the examiner will want to see the correct names for the tests.

. .

 

[WayneL]

Also, what about the neutral/earth 'link' - that's gonna throw your results on individual circuits.....or are you talking about disconnecting circuits from the board now to perform the test.
Hope you disconnect the correct neutral, then.

In my opinion, you do a 'full installation' IR test whilst it's isolated

Not giving us the way around this one then, Baal

 

[brucelee]

Hi Bruce
You have 60 minutes to carry out all of the above tests, they are giving you a clue so the answer is i) iv) and v)

The examiners report criticised students for merely listing all of the dead testing as this would not be possible given the time constraints.

wheres the clue i was told of chief tutor at bury college that as it states list and gives 6 marks then they are looking for
i)
ii)
iii)
iv)
v)
vi)
this is how he showed and how exam success shows and the many sample papers i have. I understand what your saying about time constraints but most of the tests i have stated take minutes do they not provide you with a assessment of each candidates test or do they just tell ya he failed he passed
or is it a state secret lol you have to be in the club so to speak
all the tests i have stated except insulation resistance takes a few minutes each
they would have had fun reading my paper as my writing went worse as the exam went on lol but they must have been able to as i passed to much relief
its easy for them to criticise us after the exam but who gets to criticise there way of interpreting the english language
cheers any way baal thanks for the replies

 

[Baal]

Well, I stand by my original answer, although I can see why for safety reasons IR might be included

I still have to go back to the 60 minute time constraint, this is an industrial unit with chemical etching and washing down areas, is it really feasible to carry out the 3 tests that I've listed plus have the installation prepared for a global IR test?

Even GN3 advocates that a global IR test be carried out on 'simple installations'

 

[Baal]

Hi Bruce,

We get an examiners report which tells us which questions are consistently poorly answered (ring continuity) but no individual student reports.

You have to remember that you're in an industrial situation here and carrying out tests such as 'polarity' or 'functional' could take 3 or 4 hours easily with access considerations and maybe 50 circuits.

 

[brucelee]

yeah mate
all questions relate to the scenario as far as polarity i was referring to live poarity at the supply and functional tests i put functional test of rcd
where can i have a look at the cheif examiners report i have seen them for previous tests but not this