August 2391-10 taken today

[Richard Burns]

Hi
I have just sat the 2391-10 exam today and I am running it through far too much in my mind.

So thought I would post.

Did any one else do this and what did they think?
I got stuck on some grammatical errors in the questions but overall felt it was fairly typical, hopeful on a pass but just have to wait and see (for ages).
Messed up an 8 point question not seeing the wood for the trees and putting in too many instrument tests (is an approved voltage tester an "instrument?") but overall I think it went well.
Good luck to all who took the exam.

 

[Richard Burns]

That question caught me out as I did not remember that the exact wording in GN3 says "socket outlets and similar accessories, correctly connected"; this was pasted in to the question (probably to help) and I read it as excluding all accessories and correct connections which does not leave you with much!
answer should have been any of fuses, single pole control and protection devices, multipole switches, screw fit centre contact lampholders (excluding some E14 & E27).
I think I dropped marks for that one!

On the checks required on conduit and trunking before cabling is installed I again misread the question but did cover all the above except the inspection boxes. However as an idiot I missed reading part b) and did not answer the "describe in detail how to do the above checks and state the sense used in each case" (10 marks down the drain)

 

[Richard Burns]

The question state the effect on the operation of a circuit breaker when it is connected in the neutral conductor only in the event of: line -earth fault, live-live short, overload on circuit,

This annoyed me as the correct interpretation of the question says what happens to the "operation of the circuit breaker" and in all cases the answer is nothing because the circuit breaker will retain its operational function.
this should have been worded either state the effect on a circuit if a circuit breaker is connected in the neutral conductor only... or state how the circuit breaker operates when it is connected in the neutral condcutor only...

 

[Richard Burns]

an electrical installation 230V public supply with maximum permitted voltage drop (in volts) for a lighting circuit, 8kw electric shower, 12kw cooker, had me worried as i think it is 6.9v, 11.5v, 11.5v but can't see the purpose of the three answers except to catch you out. have I got this wrong somewhere?

 

[parker56]

you have it right

 

[parker56]

my ans was
line-earth no disconnection
live-live disconnect
overload disconnect

 

[malcolmsanford]

Just sat it myself last night I also put voltage indicator yes! And rt was 2.11ohms which requires circuits to be tested separately well that's what I put!

Why would you want to test the circuit separately??

 

[tony mc]

I think he has entered the wrong value and forgot that its Mohms not ohms!!!

 

[malcolmsanford]

Lol Tony if it was ohms then it would need checking, I never noticed it was just ohms written.

No I took it as 2.11Mohms and wondered why he would put that each circuit needed investigation.

 

[tony mc]

Exam pressure getting mixed up with what GN 3 actually states.

So 2.11 Mohms would comply!

 

[malcolmsanford]

Exam pressure getting mixed up with what GN 3 actually states.

So 2.11 Mohms would comply!

Yes the twitching sphincter Syndrome, gets you every time

 

[parker56]

im sure the Q 1/200+1/18+1/2.5+1/180+1/145=1/RT
I also got 2.11MOHMS
it also ask for any commets to be recorded in observations & recommendations.
so I put futher investergation of low readings of cicuits reading 18 & 2.5Mohms code 3, but circuits do comply

 

[Richard Burns]

Right, exam over analysed to death now not sure if I have passed, I must stop now:
Other answers:

Three conditions before MEWIC to be issued:
Do not impair safety of existing; designed constructed and tested to BS7671, complies with BS7671
(signature line on MEWIC)(only got one of these)

Prepare for IR testing:
Loads removed, sensitive devices disconnected or linked out, no shorts between conductors
(last one not precise enough, perhaps; should be L or N to E)

Insulation resistance other question resistance: as length, CSA, temperature rise:
IR Down ohm Up
IR None ohm Down
IR None ohm up

Insulation resistance calculation was just nasty getting so close to the limit
Observations: circuit with 2.5Mohm near the limit requiring investigation, may indicate circuit deterioration.

Section B
Certificates required for new installation and periodic test:
EIC with SofTR and SofI and PIR with SofTR and SofI

TNS diagram description was OK I think may have forgotten to say it was the secondary winding of the supply transformer.

RCBO test
Idn 30mA 300ms on positive and negative cycles, 5Idn 150mA 40ms on positive and negative cycles, 0.5Idn 15mA no trip on positive and negative cycles
(added +ve and –ve at the last minute)
Do Ze to ensure presence of effective earth
(I think)

Tests of lighting circuit:
Continuity, Insulation resistance, polarity, Ze,
Low resistance ohmmeter, insulation resistance tester(ohmmeter in chapter 4), low resistance ohmmeter, Earth fault loop impedance tester
(messed up the number of marks and tried to add stuff to make it up to 8 marks for each not 8 marks overall probably only got 4)
Reasons for order:
Ensure all CPC/ earth in place, ensure no short circuits/leakage, ensure no wrong connections
(really not sure about that one, can’t remember what I answered)
No instrument: Functional test at end

Sorry for the rambling on.
Hope everyone did well.
Roll on 10th October, please!

 

[mini-si]

Tests of lighting circuit:
Continuity, Insulation resistance, polarity, Ze,
Low resistance ohmmeter, insulation resistance tester(ohmmeter in chapter 4), low resistance ohmmeter, Earth fault loop impedance tester
(messed up the number of marks and tried to add stuff to make it up to 8 marks for each not 8 marks overall probably only got 4)
Reasons for order:
Ensure all CPC/ earth in place, ensure no short circuits/leakage, ensure no wrong connections
(really not sure about that one, can’t remember what I answered)
No instrument: Functional test at end

Sorry for the rambling on.
Hope everyone did well.
Roll on 10th October, please!

Hi richard on the testing of the lighting circuit hope you ment Zs and not Ze.lol as all the other existing circuits that were not under test would be live with no earth. Opppps

 

[pirhead]

I thought it was a very easy paper with comparison to others. Learned a good tip for remembering things to look for during periodic inspection SADCOW=SAFETY, AGE, DETERIORATION, CORROSION, OVERLOAD, WEAR AND TEAR. It might be useful in the future

 

[russty]

Anybody at all had there results yet from this exam?
Using the results calculator gives a date of monday just gone they should of annouced it, but havent heard anything myself yet?

Results receipt calculator