2391 practical exam - NEXT WEEK!!!

[thesoundmandan]

Hi everyone!

This is my first post so please be gentle!!

First of all, a general thank you to those of you who have posted replies in similar threads, it has been most helpful.

I now ask that the forces of greater minds and experience to unite and help little me in my quest to pass my 2391 practical exam next week!!

I managed to pass the written exam first time but unfortunately failed the first time round on the practical, something I hope not to repeat!

I have some experience, but not as much as many on this forum, so please have mercy on me. So here goes - I would appreciate some help with the general run down of the assement on the PIR (the first three tests on the assesment - faults/IR etc I am not worried about).

I have read some people saying as it is a PIR then the order of tests becomes somewhat irrelevant - is that true? What order is acceptable and the quickest in your opinions?

How would you space out the Schedule of test results with a three phase board feeding a single phase sub main? Leave a space, write SUB MAIN or similar and then fill out as normal?

Can I do IR test on the whole installation between phases (with dimmer switch on the sub main removed), between live conductors connected and earth, or do I test the Main and Sub main seperatley? (If yes for lives conected and earth, do I note this down on the schedule of test results, as there are boxes for live/live and live/earth for IR on the form.) I assume I would have to somehow have the contactor down on the motor starter and also flick any two way switches as I do the IR test.

What tests and how are they done on a FCU fed by MICC? (I haven't really worked with MICC so forgive me if that is a stupid question i.e - the tests are the same as for any radial circuit)

Should I be doing anything else with the starter motor circuit other than after safe isolation, link L1 and CPC of motor circuit at DB, measure between L1 and CPC at 3 phase socket outlet connected to load end of DOL starter, push in contactor of the DOL with insulated screwdriver to make the contact within the starter.

Repeat this using L2 and CPC and L3 and CPC, the highest reading becomes R1+R2 for the circuit.

The lighting circuit is wired in single core in metal conduit. I assume I check earth continuity by the r2 long lead method?

I am including a picture of a board which will be similar to the one I will be tested on, if there is anything else you think I should know, or general tips/advice please be my guest. I attended a 2391 practical training day which was very unhelpful, so hopefully I can get some real help here



Many thanks in advance, (if anyone could show me/send me an example of the schedule of test results written out for a setup like this I would be most grateful, as I have been told some conflicting methods!)

:Salute

 

[Doc Hudson]

Welcome to the forum, do you have a copy of guidance note 3? Chapter 3 has comprehensive guidance about the PIR and table 3.3 lists the possible tests to be made. It also clearly says that the tests considered appropriate by the inspector should be carried out. Periodic Inspection & testing is not a black and while set of rules do A then B then C. A certain level of experience and knowledge is required as to what can and cannot be tested safely and how much is needed to establish how safe or unsafe and installation is.

Doc H.

 

[thesoundmandan]

Thanks Doc for the quick reply!

I do have a copy of GN3, which I have read with much fervour, I think the trouble is I have got myself a bit flustered by reading to many varying responses (and the fact that I failed my practical the first time!).

So I was just wanting some clarification of what I am unsure of ,or reinforcing of what I already know to help calm so pre-exam jitters

Thanks again, any help greatly appreciated!

 

[meerkat]

Hi Dan,

I have got my 2391 assessment tomorrow, all colleges are different and its probably beneficial to be able to conduct a Periodic inspection and test in a variety of different ways, as long as all the tests are carried out safely.

Our college want us to do all the dead testing on both boards first, than move on to the live testing on both boards there after, I think you need to be flexible, as long as you know how to do the testing correctly and safely you will be fine.

Paperwork for our college is one Electrical installation condition report and Condition report inspection schedule for the whole installation, and a seperate Generic schedule of test results per board.

Insulation resistance test at our college is done globally per board if that makes sense, remember when IR testing the motor circuit, only test up to the isolator(isolator switched off)from the board, then test from the plug socket outlet end back towards the DOL starter, to test the second half of the circuit.

I hope this helps, good luck (MEERKAT)

 

[thesoundmandan]

Hi MEERKAT

Thanks for the reply, that does clear up a few things for me.

Its been a while since my first attempt so feeling a little rusty (I don't have a three phase board lying around to practice on

)

All the best with your assessment tomorrow, I'd be interested in knowing how you get on, and any post assessment tips you may have, I hope to be able to share mine in a weeks time!!

Fingers crossed, and remember the back of your hand isn't considered an approved way of proving circuits dead!! ROTFWL

 

[meerkat]

Hi Dan,

3 phase boards have 3 incoming line conductors, these need to be incorporated in our testing, remember that IR testing is a ten part procedure, L1-E, L2-E L3-E, L1-N, L2-N L3-N, N-E, L1-L2, L1-L3, L2-L3, PFC is made up of the highest reading of PEFC and PSCC and this figure is then multiplied by 2, everything else is fairly straight forward.

(MEERKAT)

 

[Doc Hudson]

Our college want us to do all the dead testing on both boards first, than move on to the live testing on both boards there after, I think you need to be flexible, as long as you know how to do the testing correctly and safely you will be fine.(MEERKAT)

As a simple common sense point to note, unlike installation work, where you would have dead circuits you have installed that needs testing prior to enrgising. A periodic inspection is normally on a live installation. If it were a real work situation, one of the first things to establish is are there any parts of the installation that must have power kept or that require notice before they can be safely de-enrgised. Also are there any items of equipment vulnerable to any tests you may chose to do. As the installation should start off live, safe isolation and locking off would be very important during any testing. Do the colleges have your boards live at the start of your test?

Doc H.

 

[meerkat]

Hi Doc,

Boards are live so you can faliliarise yourself with the circuits and there operation, then you perform a safe isolation, and the dead testing can begin.

Familiarisation also helps you to find the items that may need to be linked out (Dimmer switch), and experience and knowledge assist in knowing what may be vulnerable to test.

I am not really sure why they use this method, maybe they feel its safer, but it certainly takes a lot longer, than the methods suggested by previous successful 2391 candidates, on this web site.

(MEERKAT)

 

[thesoundmandan]

Any advice/tips on MICC and r2 for lighting circuit in metal conduit?

Thanks!

 

[thesoundmandan]

Ok, being doing lots more revision and practice and feeling a bit better about things......but, still a few queries if I may.

If the lighting circuit is wired in single core in earthed metal conduit, (I think the earth was taken from the conduit), I will have to use the wander lead to prove earth continuity at each point, fine so I get R2.

Will I be expected on a PIR to do Zs for the lighting circuits? GN3 says on PIR's EFLI to be done at Origin of installation, distribution boards, accessible socket outlets and extremity of radial circuits.

Also Zs on the MICC, do I measure at the back of the face plate? What do I put for the cpc size on the SofTR?

Thanks everyone - really appreciate you help

p.s MEERKAT - hope you got on ok?

On the SofTR for the sub main - Ze at origin I assume is the same as the three phase Ze.

 

[meerkat]

Hi Dan,

I managed to pass ok, so chuffed about that, just got to wait for the written results in about 6 weeks time.

Lighting circuit is wired in singles in metal trunking, there is a seperate CPC within the trunking, so link out Line and CPC at the DB and measure at the light fitting between SW Line and CPC for R1+R2 using switch for polarity.

EFLI is both, Ze(external)and Zs, Zs is the complete EFLI of the circuit, which is the furthest point in the circuit for radial circuit(Lighting)

Measure in the same place as you did the earlier R1+R2 reading with circuit live, or calculate Zs using Measured Ze and Measured R1+R2 as in the formula Zs = Ze + (R1+R2)

Cable sizes can be found on circuit information found on the inside cover of the DB, motor circuit was wired in SWA and I put Armour down for the size of CPC as shown on the circuit details.

Circuit details will be listed for the MICC cable including the size of CPC if (3 core MICC) or sheath if (2 core Micc).

Ze at origin is for SOTR1 for DB1(3 PHASE)

SOTR2 for DB2(Single phase)should be ZDB as this is measured with Earthing conductor of DB1 connected, which is the same reading as the Zs reading for the Sub main circuit, I hope that makes sense.

HTH, good luck (MEERKAT)

 

[thesoundmandan]

Hi MEERKAT

Congratulations!! :Applaud

You must be very pleased I have just got back from a training day about the practical and am now feeling a lot more confident about doing it again (what a difference a day makes!)

Just a couple of things I want to make clear if could help me one more time! I am pretty confident with all the other tests.

For the SOTR1, where you have the feed to the sub-main in the circuit description, did you measure r1 and r2, and insulation resistance up to the main switch of the sub main and write these in the results box?

And where exactly do you measure 'Zs at DB' for both boards? could you 'walk' me though it. I get taking Zs from a lighting circuit radials, etc, but there was no 'Zs at DB' on the old PIR forms, just 'Ze at origin' on the SOTR, so I am a little unsure.

Thanks again, I do very much appreciate it.

Dan

 

[meerkat]

Hi Dan,

thanks for the congrats!!

SOTR1, Sub main circuit, link Line and CPC at board1, measure at incoming Line, top of main switch and CPC rail at board2, this will be the R1+R2 reading for the sub main (dead test).

Insulation resistance do a global on board1, all mcb's on, ensure DB2 Main switch is in the OFF position, that way you are testing all circuits on board1 and the sub main upto the main switch only.

Record the readings which should be >200MOhms, against both Live conductors and against Live conductors and earth, so 2 readings against every circuit on Board1 on SOTR1.

Ze for board1, after safe isolation of installation, disconnect main earthing conductor from the earth rail, set tester to earth fault loop, Ohmic setting on 2 lead test, connect black probe to disconnected earthing conductor, and red probe to the incoming Line conductor, power will need to be on as this is a live test, but the installation itself must NOT be energised. Record the reading as Ze at the origin.

Ze is only ever measured once, which is at the origin (Board1).

Every board there after, the same reading is taken, with the CPC of the sub main left connected to the earth rail, and the reading becomes Zdb for each respective board.

Zdb is measured between the incoming Line conductor at the main switch and the earth rail of every board, basically a(Zs reading of the sub main of each board).

So if you have 3 boards on an installation, you should have 1 Ze reading and a Zdb reading for boards 2 and 3,(put a line through Ze and over write it with Zdb for SOTR2 and SOTR3 and record the readings)

SOTR1 will have the Ze reading on it, SOTR2 will have the Zdb of board2 on it and SOTR3 will have the Zdb of board3 on it, so as you get further away from the origin the PFC is getting smaller at each board.

I hope this makes sense, good luck, (MEERKAT)

 

[thesoundmandan]

Hi MEERKAT,

That makes perfect sense, thanks so much. Once I have a clear picture in my head I'm fine, just get flustered if I think I've not fully understood.

I know I said one last time for help in my previous post, but I honestly forgot one ( hopefully ray ) other question.

Did you have many LIM's or N/V's on your inspection schedule? For instance, going on the test rig photo of my first post, you cannot obviously check the

1.1 Service cable condition (n/v?)

1.2 Condition of service head (n/v?)

1.3 Condition of tails - Distributor (n/v?)

1.5 Condition of metering equipment (n/v?)

as this is a test rig, so you're not actually at the supply intake, or do you tick as this is a simulation of a no-faults setup?

Also, what did you (if your rig was similar) or would put for

5.10 Concealed cables installed in prescribed zones (see Section D. Extent and limitations)

(522.6.101)

5.11 Concealed cables incorporating earthed armour or sheath, or run within earthed wiring system,

or otherwise protected against mechanical damage from nails, screws and the like (see Section

D. Extent and limitations) (522.6.101; 522.6.103)

Normally this would be a LIM, but all the cables are either clipped direct, or in conduit/trunking, not concealed, so would this be N/A? Sorry if I'm over thinking this, just really don't want to fail on something silly with the paperwork.

With the test rig in the photo, this is how I would imagine the Inspection Schedule to look like, I would be so grateful if you could have a quick run through and see if there is anything obvious I've missed, or might need changing (I appreciate you only have the photo to compare to).

Thank you so, so much again, your help really has been invaluable, :worship

Dan

Page

 

[meerkat]

HiDan,

I think you will find that there will be no observations to comment on, in other words the installation has no faults or deviations, and is in a satisfactory condition.

We actually completed the old style periodic inspection and testing paperwork, PIR SOI and SOTR.

Paperwork is fairly straight forward, mostly involving N/A against the like of SELV, PELV, Double insulation, Reinforced insulation, Obstacles, Placing out of reach, Presence of supplementary bonding conductors, Adequate arrangement for alternative supply, FELV, Non conducting location, Earth free local equipotential bonding, electrical seperation, Presence of supplementary bonding, Segregation of Band 1 and Band 2, Segregation of safety circuits, Presence of fire barriers, Particular protective measures, Selection of equipment for External influences, every thing else pretty much gets a tick.

You may find they provide a template(the Original SOI)to use to assist in paperwork completion.

I dont think they will fail you on your paperwork, you may well just loose a few marks from your overall score, I used a scrap of paper to record most of my readings as it is easy to become distracted and miss something, be prepared to be asked questions during your testing, as to why we do the testing the reasons for the sequence and what significance the results may have (Disconnection times)(Overcurrent protective devices ratings etc).

Remeber stay calm, compose yourself, I used the sequence of C R I P E R, for each board so that I didnt miss anything, however not all the tests will be applicable as you will probably only have an RCD on on the single phase board, good luck, (MEERKAT)

 

[thesoundmandan]

Hi MEERKAT,

Just wanted to say a big 'THANK YOU' again!! I am pleased to say that I passed :^O

Testing went fine (was very tight for time!), and my paperwork was all ok!

Now to catch up on some sleep!! :z

Thanks again, you have been a great help,

Dan.

 

[meerkat]

Hi Dan,

Well done and congratulations!!!!

I still have 6 weeks or so to wait till I get my written results, so with a bit of luck maybe I will pass too, C U L8R, (MEERKAT)

 

[thesoundmandan]

Hope it all comes back ok,

Then we'll both be qualified for about three minutes before they change the regs again

:coat

 

[Manator]

Well done on your recent success

 

[thesoundmandan]

Thank you!! Feels good