June 2011 2391 exam

[Richard]

Did any of you sit it? I didn't think it was TOO bad, couple of questions I was a little unsure of but overall ok. How did you guys find it? I can never think of the bloddy questions afterwards!

 

[Channie12345]

Yes, just sat it, not many calculations, it seem to be a bit easier that past papers I have seen.

 

[dean7828]

think i got the voltage drop calcs for the motor circuit up put 5% but think its 8% how long dose it take for the results to come through

 

[dean7828]

am i right is saying that a 100ma rcd is tested at 50ma and 100ma at 200ms?

 

[Richard]

am i right is saying that a 100ma rcd is tested at 50ma and 100ma at 200ms?

I wasn't sure as i'v read somewhere that you don't perfrom the 5x test, but i could well be wrong!

 

[dean7828]

thats what i thought, 5x would be 500ma test current so way too high

 

[Richard]

Also as it's a BS EN rcd, I think that makes it 300ms

 

[Richard]

What two test do you have to have all circuits Isolated to perform?

I went for continuity of protective conductors, External earth fault loop impeadance

 

[thorneellis]

This was my second attempt since last year, did think it was a lot easier than previous past papers, but then again i thought that last year. No mention of drawing earthing systems. just describe the continuity of gas bond and insulation resistance of lighting circuit if i remember correctly

 

[joe_berks]

am i right is saying that a 100ma rcd is tested at 50ma and 100ma at 200ms?

i remember that question was "what two test currents should be applied to the 100mA RCD?" or something like that. i put 1x and 5x . at 1x it is less than 300ms and at 5x it should be within 40ms

 

[thorneellis]

**** didnt realise we had to calculate the voltage drop i thought it was just after the percentage volt drop acceptable. i wrote 5% for the 240 socket and i thought the 3 phase was 8%............few points gone for me there then

 

[Richard]

What made me think was the half times test though

 

[joe_berks]

damn i put 'continuity' and 'insulation resistance' but i now realise i didnt read the question properly... ALL CIRCUITS isolated. Thought i done well but starting to doubt it now !

 

[Richard]

Where do you get the 8% voltage drop for three phase figure from? I'm stuggling to find that one

 

[Sparky Ninja]

i remember that question was "what two test currents should be applied to the 100mA RCD?" or something like that. i put 1x and 5x . at 1x it is less than 300ms and at 5x it should be within 40ms

Wouldn't that be x0.5 and x1, so 50mA and 100mA?

 

[joe_berks]

appendix 12 of 7671 for the 8% figure.

 

[joe_berks]

oh no it was 5% ! starting to really doubt myself now thought i had it in the bag .

 

[luke]

Just sat the exam myself, found it ok really, first time so fingers crossed. The question on the rcd is 1/2 x test 50mA and 1 x test 100mA 300ms. The only rcd you test at 5x test current is a 30mA rcd otherwise you put to much current into the installation. Is the pass rate 60 % ?

 

[dean7828]

im sure 5x test applies to a 30ma rcd for additional protection and must operate within 40ms

 

[dean7828]

i well got some right got some wrong just hope its enough! not the end of the world if not good luck chaps

 

[joe_berks]

can anyone else remember more questions from the exam ? i left with quite a bit of time to spare feeling confident but have already found out i got a couple wrong !

 

[Jurasic Spark]

Just sat the exam myself, found it ok really, first time so fingers crossed. The question on the rcd is 1/2 x test 50mA and 1 x test 100mA 300ms. The only rcd you test at 5x test current is a 30mA rcd otherwise you put to much current into the installation.

Correct... but not the right reason.

415.1 x5 only where RCD is used for Additional protection. By definition this is an RCD not exceeding 30mA but could be one lower such as a 10mA RCD.

 

[honda127]

Where do you get the 8% voltage drop for three phase figure from? I'm stuggling to find that one

im sure its 5% FOR POWER AND 3% FOR LIGHTING

 

[honda127]

Dnt be worrying too much lads it will do your head in , i was so sure i failed i paid to sit this exam but got my results from march one and i passed.Really i felt i made a total bullocks of it

 

[sharpy1983]

The tests for a 100mA RCD are still 1x and 5x. and the maximum disconnection for this type of RCD is 300ms, Glad this come up as we were discussing it only yesterday!!!

I thought it was ok. some questions I guessed but most I was pretty confident on. plus questions 21-26 didnt seem as bad as some others Ive seen on past test papers.

 

[sharpy1983]

I thought the voltage drop question was 3% for lighting and 5 for power too

 

[sparks_114]

I too just sat the exam, question no 19 (the one after the 100mA RCD question) is the one that threw me with the short circuit capacity of an circuit breaker. I had no idea of the difference between Icn at 6KA and Ics at 10KA and the question being what would happen if a fault current (PSCC I believe) of 8 KA were to exist? I asked a good few others after and likewise no one seen to know. Overall I did think it easy (ish) for a 2391er but only the hard results will tell. All the best to you fellas.

 

[brucelee]

good luck to all now the wait begins

dont worry if there are only 1 or 2 questions that your not sure off then you have probably done enough

 

[luke12345]

I too just sat the exam, question no 19 (the one after the 100mA RCD question) is the one that threw me with the short circuit capacity of an circuit breaker. I had no idea of the difference between Icn at 6KA and Ics at 10KA and the question being what would happen if a fault current (PSCC I believe) of 8 KA were to exist? I asked a good few others after and likewise no one seen to know. Overall I did think it easy (ish) for a 2391er but only the hard results will tell. All the best to you fellas.

Icn is the max PFC that the be interrupted safely but the breaker will no longer work
Ics is the max PFC that can interrupt safely without loss of performance

think you've mixed them up in the question, so basically 8KA would knacker the circuit breaker

 

[NEV]

Sat the exam had a complete brain meltdown, the paper was a lot easier than other ones i read however i just couldn't think. Hopefully i did enough? 9 weeks to wait

 

[AlanWirral]

I did the exam today too. As said compared to past papers I've done it seemed a lot easier! Shame there was no fault path diagram as that would have been 15 marks in the bag for the VD questions I did 6.9 for lights and 11.5 for both power questions. 100mA RCD is only did 1/2 times and 1 times.

6 weeks to wait now fellas :-O

 

[72-van]

I sat it tonight as well ..

the vd question i got wrong and the kA breaker question

any one know the right ansa to the one on that was on about the three type of TT tester ..

i opted of earth fault loop imp tester for all three might get one point ?


72-van

 

[james.cumming]

On my 2391 12 people attended the course. 9 people turned up for the written exam. At the end of the exam 3 people were left.
If you are not up for this you will never pass. Do it at night school it gives you more time to revise.

 

[LGT88]

I sat the exam and thought the paper was ok. Despite this i think I might have mucked up. In the insulation procedure question 25, despite given correct procedure and values. I wrote record highest live to earth insulation resistance (moment of stupidity). Does anyone know if I will lose all 15? Gutted!

 

[Richard]

I did the exam today too. As said compared to past papers I've done it seemed a lot easier! Shame there was no fault path diagram as that would have been 15 marks in the bag for the VD questions I did 6.9 for lights and 11.5 for both power questions. 100mA RCD is only did 1/2 times and 1 times.

6 weeks to wait now fellas :-O

Ahh I came up with 20V for the 3 phase circuit? 5% of 400V

 

[sharpy1983]

For the test and inspection on the scenario question, was the type of test to be carried out a Periodic test and inspection, and the docs to be completed Scedule of inspection, Scedule of test results and a Periodic test report?

 

[luke]

Yes it was a periodic test. The docs would be schedule of test results, schedule of inspections and a periodic inspection report for an electrical installation, i believe they are quite fussy about the correct wording for the report.

 

[sparks_114]

As many are talking about the volt drop question the correct answers were: 3% for lighting from a public distribution system (so 6.9V of 230V), 8% for the 3 phase motor supplied from a (private) factory generator (so 32V of 400V, I think it was 400V), 5% for the immersion heater in a domestic home (supplied from a public distribution system so 11.5V of 230V). I think I remember these in order. Percentages for volt drop can be found in appendix 12 of BS76 71 Table 12A

 

[72-van]

Can any one remember any of the other questions ?

 

[IQ Electrical]

Just to clarify:

There is no requirement for a 5 X IΔn test on a 100mA RCD/RCBO and if the decice was manufactured to BS61008/61009 then the maximum tripping time is 300mS.

On the short circuit current question (Ics and Icn) remember the meanings by thinking of n for knackered!