just took my 2391 test

[leonard]

some of the questions was from past papers.

 

[Banjo]

That's what I did Leonard I got 11.4 volts?

 

[exnavysparks]

Hi fellow 2391ers, seems c&g continue to love their ambiguity!! some questions in part 1 had me guessing and double guessing myself lol:sad3: what did you peeps work out the v drop to be?

 

[exnavysparks]

i like the sound of 11.4 v

 

[jstephens251]

I sat the exam last night too absolutely knackered now.
Volt drop question found a bit of a bugger i too came to 11.4v.
What did everyone put when inspecting the db with sight and touch? few marks i may have lost there!

 

[Former Sponsor TM]

For sight I put that the correct circuits were connected in the correct sequence in the main earthing terminal and the neutral terminal and that the MCB's and RCBO's were the correct size for the conductors leaving them. For touch I put that the earthing conductor was secure in its terminal and that the main switch operated properly. Can't remember the rest!

 

[cjp1]

I sat the exam last night too absolutely knackered now.
Volt drop question found a bit of a bugger i too came to 11.4v.
What did everyone put when inspecting the db with sight and touch? few marks i may have lost there!

This is the bit that I struggled on, from memory I put:
Touch:Check all terminations into circuit breakers RCBOs earth and neutral bars are secure
Check buzz bar covers and barriers are secure and all in place
Check that switches and circuit breakers and RCBOs swith on and off cleanly
Sight: Check that the circuit breakers and RCBOs are suitable for the perspective fault current that could flow
Check the type and rating of circuit breakers and RCBOs are suitable for the size(csa) of the circuit conductors (cables) that are installed.
I think I ballsed this question up but the others seemed to go ok.

 

[firemanowl]

Don't you have to add a x1.2 correction factor to the volt drop formula to allow for the rise in temp when the circuit is under load?
I think the answer to Q4 was something along the lines of:-
1, Confirm installation/circuit complies with designer's intentions
2, Designed, Installed and Inspected & Tested to comply with BS7671
3, Not damaged so as to impair safety
Just seen it in some notes, not sure where it came from though as nothing in GN3.
Good luck to everyboby, only a couple of months to wait.

 

[Banjo]

For touch i put

Connection of conductors - To check for any loose connections
Overheating of cables - Feel any cables that are overheating
Operation of protective devices - To check that all the protective devices were functioning correctly.

For sight

I put overheating and correct identification of condcutors.

Q4. If i remember correctly thats the on on inital verification fron GN3 i put.

1. All installed eletrical equipment and materials are of the correct type and comply to british standards.
2. All parts of the fixed installtion are correctly selected and erected.
3. No part of the fixed installation shall be visibly damaged or defective to impair safety.

Does anyone have the question papaer that they could post up?
good luck to everyone!!

 

[jstephens251]

Bugger I think the 1.2 factor is right for the voltage drop - got that completely wrong then!
Be interested to see the paper again

 

[cjp1]

Bugger I think the 1.2 factor is right for the voltage drop - got that completely wrong then!
Be interested to see the paper again

Not sure about 1.2 factor for volt drop, are you sure your not thinking of the X 0.8 tempreture correction factor for tabulated Zs to measured Zs .

 

[jstephens251]

i calculated total resistance by the 30A of motor and it got me 11.4v, felt like more was needed though...

 

[brucelee]

Hi did the volt drop question give you a resistance at 20C or a table with the m/ohm/m values at 20c if so then needed correcting by 1.2 for the increase in temp due to load current ie say a 1.83 m/ohm/m =10mm conductor with another added in parallel ie line and neutral at 20c will need increasing by 1.2 as its a conductor bunched or a core in a multicore cable for thermoplastic (pvc) 70C max operating temp
table A.3 in GN3

m/ohm/m x 2 x MF x Ib X L/1000 = Vd
1.83 x 2 x 1.2 x Ib x L/1000
which will give same value as the mv/A/M tabulated value from the regs when using
mv/A/M x Ib X L/1000
or
R1+RN x 2 x Mf x Ib x L/1000

be good if someone could remember the question or somehow found the paper in there bag lol


this sounds like a question i had for the 2391 june 2010 and the only thing i forgot to include was the MF of 1.2 which i realised later when discussing it with forum members
good luck to you all

 

[cjp1]

Hi did the volt drop question give you a resistance at 20C or a table with the m/ohm/m values at 20c if so then needed correcting by 1.2 for the increase in temp due to load current ie say a 1.83 m/ohm/m =10mm conductor with another added in parallel ie line and neutral at 20c will need increasing by 1.2 as its a conductor bunched or a core in a multicore cable for thermoplastic (pvc) 70C max operating temp
table A.3 in GN3

m/ohm/m x 2 x MF x Ib X L/1000 = Vd
1.83 x 2 x 1.2 x Ib x L/1000
which will give same value as the mv/A/M tabulated value from the regs when using
mv/A/M x Ib X L/1000
or
R1+RN x 2 x Mf x Ib x L/1000

be good if someone could remember the question or somehow found the paper in there bag lol


this sounds like a question i had for the 2391 june 2010 and the only thing i forgot to include was the MF of 1.2 which i realised later when discussing it with forum members
good luck to you all

Hi Brucelee, From memory the question said something like: the combined resistance of the line and neutral is ?? ohms can you calculate the volt drop on these conductors,
as Jstephens said he got 11.4v I think I did too
But I am sure that I forgot to put a 1.2 correction factor into the equation,
Cheers Chris.

 

[stiggy84]

you definetly have to use the x 1.2 to allow for max operating temp of 70 degrees, i did the same exam
just passed my practical today!!!