tonights 2391 exam....(10th march 2011)

lynj · Mar 10, 2011

one thing to say and that is did c&g forget how to be staightforward?

felt like some of the questions were half thought......

anyone else take it?

Paul.M · Mar 13, 2011

BEDFORD ELECTIC said:
it dose not matter about the wording for the questions ???
you know if they want you to list the FREEKING R.C.D times !
im just trying to jog peoples memorys, and work out if iv passed.

Bedford I wasn't being condescending in any way, shape or form and I think what you have done above is great. Thank you for taking the time and effort putting it together. The wording of this paper was particular difficult to say the least and by the looks of things a lot of good sparks that know what their doing in the field got caught out in the class room.

chrissimm · Mar 13, 2011

Jurasic Spark said:
That would depend on whether it was a BS number (200ms) or BSEN (300ms). I haven't seen the paper so don't know.

If my memory serves me well it was a BSEN 61008 but don't quote me on that. Possibly somebody else who done the exam can remember.

Cheers Chris

BEDFORD ELECTIC · Mar 13, 2011

Pm me for past pappers, and stuff ?
IF YOU CAN REMEMBER A 2391 MARCH 2011 MARINER QUESTION POST IT !

when conducting a insulation resistance test on the lamp post curcit, test between live conductors together and c.p.c.
its not practical to remove the contole gear
the photocell on top of the lamp-post must be coverd up to enable the onward wiring of the curcit to be included in the test.
( THE PHOTO CELL---- ACTS AS A LIGHT SWITCH----- all ways include the strapper wires ect ect )
500v dc

Q) discribe how you would conduct a insulation resistance test on a curcit that has SURGE PROTECTION ?

A) test at 500v dc as normal
(BS7671 443.2) surge protection is basicly a bolt of lightning hitting part of the installation.

Q) name 3 locations witch have zones

A) location containig a bath or shower / sauna / swimming pool / water fountain

Q) how do you test the rcd (8 marks)

A) 50% --- 15ma---no trip
100%---30ma--- within 200ms
500%---150ma within 40ms

Q) when the new circit is connected, what will happen to the insulation resistance value, for the whole installation ?

A) the value will decreass

Q) why can you not do Zs-Ze to get the value for R1+R2

A) Ze may containe parralel paths

Q) why dose BS7671 state the mariner cannot be a T.N.C.S system

A) the dangers of water and electric / lower body resestiverty / contact of the body with earth potential.

Q) visual inspection in the shower block c.c.u, list 4 thing to look for (4 marks)

A) external influances
basic protection
correctly selected and erected
any visibal damage
Q) what in the above are you looking for (4 marks)

A) is there warter / dust ???
can some one touch live parts ???
in acordance with BS7671 ???
damage / ware and tear

Q) name 2 bits of infomation, that can only be obtaind via the supply authority.

A) ????? ????????? ????????? ???????? ????????????? ?????????????? ??????????

Q)name the 2 people who can decide the time for a periodic Inspection Report.

A) the designer / the tester

Q) work out the values for R1+R2 (3 marks)

A)0.96+127
-------- = 188
4
Q) name 3 things that may afect the next PIR date (3marks)

A) external influances
type of installation
maintenace shedual
Q) what is the maximum voltage drop for...
lighting ?
power ?
motor ?
A)3 %
3 %
3 % ( see page 358 in Bs7671)
............................Pm me for past pappers, and stuff ?...............................................

IQ Electrical · Mar 13, 2011

You disconnect a surge protective device or you conduct the IR test at 250V DC but with 1 MOhm still used as a minimum value BS7671:2008 page 158.

The disconnection time on a BS EN 61008/9 RCD at 1X I delta n is 300ms. I would bet large sums that C & G would not use a 'BS' residual current device in this exam.

I can't comment on the rest without the paper as there are too many variations on the important parts of the questions.

BEDFORD ELECTIC · Mar 13, 2011

Pm me for past pappers, and stuff ?
IF YOU CAN REMEMBER A 2391 MARCH 2011 MARINER QUESTION POST IT !

when conducting a insulation resistance test on the lamp post curcit, test between live conductors together and c.p.c.
its not practical to remove the contole gear
the photocell on top of the lamp-post must be coverd up to enable the onward wiring of the curcit to be included in the test.
( THE PHOTO CELL---- ACTS AS A LIGHT SWITCH----- all ways include the strapper wires ect ect )
500v dc

Q) discribe how you would conduct a insulation resistance test on a curcit that has SURGE PROTECTION ?

A) test at 500v dc as normal
(BS7671 443.2) surge protection is basicly a bolt of lightning hitting part of the installation.

Q) name 3 locations witch have zones

A) location containig a bath or shower / sauna / swimming pool / water fountain

Q) how do you test the rcd (8 marks)

A) 50% --- 15ma---no trip
100%---30ma--- within 200ms
500%---150ma within 40ms

Q) when the new circit is connected, what will happen to the insulation resistance value, for the whole installation ?

A) the value will decreass

Q) why can you not do Zs-Ze to get the value for R1+R2

A) Ze may containe parralel paths

Q) why dose BS7671 state the mariner cannot be a T.N.C.S system

A) the dangers of water and electric / lower body resestiverty / contact of the body with earth potential.

Q) visual inspection in the shower block c.c.u, list 4 thing to look for (4 marks)

A) external influances
basic protection
correctly selected and erected
any visibal damage
Q) what in the above are you looking for (4 marks)

A) is there warter / dust ???
can some one touch live parts ???
in acordance with BS7671 ???
damage / ware and tear

Q) name 2 bits of infomation, that can only be obtaind via the supply authority.

A) ????? ????????? ????????? ???????? ????????????? ?????????????? ??????????

Q)name the 2 people who can decide the time for a periodic Inspection Report.

A) the designer / the tester

Q) work out the values for R1+R2 (3 marks)

A)0.96+127
-------- = 188
4
Q) name 3 things that may afect the next PIR date (3marks)

A) external influances
type of installation
maintenace shedual
Q) what is the maximum voltage drop for...
lighting ?
power ?
motor ?
A)3 %
3 %
3 % ( see page 358 in Bs7671)
............................Pm me for past pappers, and stuff ?...............................................

IQ Electrical · Mar 13, 2011

'Bedford Electic' why are you multi posting the same stuff over and over?

Jurasic Spark · Mar 13, 2011

IQ Electrical said:
'Bedford Electic' why are you multi posting the same stuff over and over?

Yes I was thinking the same.
And his still getting the same ones wrong!!!

paulanderson22 · Mar 13, 2011

Q) discribe how you would conduct a insulation resistance test on a curcit that has SURGE PROTECTION ?

A) test at 500v dc as normal
(BS7671 443.2) surge protection is basicly a bolt of lightning hitting part of the installation.

????
I answered 250v d.c. surge protection, lower the test voltage but minimum value should still be 1 meg ohm.

selv and pelv 250v 0.5
upto 600v ac (i think!) 500v dc 1 meg ohm
over 600v ac 1000v dc 2 meg ohm

if i remember correctly!!

Zorro · Mar 13, 2011

R<50 V/Ia

Steve_Wilson · Mar 13, 2011

I don't remember that question coming up but if it did, I would have put down that link the live conductors and test between them and cpc at 500 v DC. No danger of damaging the unit that way. Everybody recently has said about the 30mA rcd, are we now fairly confident that the answer to Q26 was 30mA or are we still stabbing in the dark? I still maintain Shakespeare would have had trouble understanding the comprehension and grammer used in this exam. Please note, I never understood him either

paulanderson22 said:
Q) discribe how you would conduct a insulation resistance test on a curcit that has SURGE PROTECTION ?

A) test at 500v dc as normal
(BS7671 443.2) surge protection is basicly a bolt of lightning hitting part of the installation.

????
I answered 250v d.c. surge protection, lower the test voltage but minimum value should still be 1 meg ohm.

selv and pelv 250v 0.5
upto 600v ac (i think!) 500v dc 1 meg ohm
over 600v ac 1000v dc 2 meg ohm

if i remember correctly!!

paulanderson22 · Mar 13, 2011

im sure that was one of section a questions.
for the lighting install the scenario stated there was a service cut out in the base of the fitting.
i answered that i would operate all service cut outs and perform ln le ne and all conductors to steel armour.
tricky because i would assume either test method should pick up marks, both testing methods ensure no damage to equipment

Liamsparks · Mar 13, 2011

I think its one for the examiners to discuss between them selfs when they go for their "markers meeting" this week.

jimmy_one_ball · Mar 13, 2011

For the two bits of info only obtainable by enquiry to the DNO (or whatever it was) I answered Frequency and nominal voltage reasoning that everything else you can either see or measure yourself. Alright you can measure the voltage but the nominal is dictated by them at 230.

I read Q26 as additional protection, did they use the word additional? I thought they did, can't really remember now, anyway I said 30mA and the test procedure was for 8 marks suggesting to me they wanted the 5 X IAn as well.

Also can anyone remember the very last part of Q26 , the TT installation has a max dissconection time of 0.2s, how is this affected by the RCD tripping time (of 300ms)!!! I said replace the RCD with a BS type with time of 200ms (0.2s) I realise this is now pants as 0.2 TT time is for overcurrent not additional protection so the answer would be no effect i think.

I also went for the L+N to cpc IR test at 250V dc

Still think I've flunked it. The electrode test, I went for the ELFI tester and did one test for each of the 3 phases and said to use the highest reading, not the mean average of the three like you would with the Electrode potential test. I've never heart of a polyphase TT so I just guessed that's what you might do!

Anyway GL all, see you back here after the re-sit lolZ ATB