2391 question paper help!

[ringer]

I did the long night course. Far better chance of taking in what you need to know. More opportunities for questions and discussions. It's one thing knowing how to answer the questions, quite another understanding why I & T is done a certain way. Knowing how to interpret the regs, GN3 and the certs is most of the battle. I wish you luck but don't see how you can reasonably cover all the ground in four days.

 

[liddley]

thats my reason for asking, just wondered what is covered in the four day course.Must admit the night course does sound a better way of doing it.
But the four day course is the one my employer has put me on so beggers cant be choosers I suppose.

 

[Sparky Ninja]

Doing the course in four days allows for better learning if it is delivered properly.
Doing it in the evening wastes a lot of time revising prior learning.

With four straight days you can dedicate the time more effectively.
When I deliver it over 4 days it's simply
Mon & Tues = syllabus
Wed = Practical assessments
Thur = Revision and mental preparation for the exam conditions with the exam that night.

When I deliver over nights too much time is taken assuring everybody is at the same level of understanding.

 

[liddley]

just out of interest with the practical assessment,
lots of people have told me they were criticized for taking to long at filling the test sheets in. Are we expected to use for e.g. NICEIC test sheets or just the basic model forms from Bs7671 ??

 

[Sparky Ninja]

just out of interest with the practical assessment,
lots of people have told me they were criticized for taking to long at filling the test sheets in. Are we expected to use for e.g. NICEIC test sheets or just the basic model forms from Bs7671 ??

I use the templates in BS 7671. Your training provider my use their own.
The time for the practical assessment is 2 hours and some colleges will tell you this and put a clock in front of you.

I had a City & Guilds external verifier come to assess me delivering the 2391 assessment and I had a guy spend just under three hours on the assessment. I was asked why it was still running after two hours and my response was..

He's been safe, and consistent throughout and has not delayed through the testing stages, why should I stop him and fail him?

I was told that I had an excellent understanding and how the assessment should be moderated.

The 2 hour time frame is there for us to manage the learners through a schedule, it is not mandatory. If a guy has taking 2 hours and not got through to the live tests for example, then I would consider stopping them and letting them revise/practice a little more.

I tell my guys to have a crack, write everything on notes, then when they finish, make a cup of tea and sit down comfortably filling in the certificate.

 

[liddley]

question:
A twin cable has a phase an neutral resistance value of 100M ohm and an individual conducter resistance of 0.8 ohm determine the values if the cable:

A) was doubled in length

B) length was same but cross sectional area was halved.

Cant get my head round this one, am I right in thinking that double the length, then double the amount of insulation and double the value for question A

If the cross sectional area was halfed obviosly the resistance of the individual conductor would be greater?question B

This 2391 is going to finish me off with worry!!

 

[telectrix]

A. halve the IR and double the conductor resistance.

B. halve the csa and the resistance will double.

 

[liddley]

So for this question are they looking for just a written explenation
Or
A) 50Mohm
1.6 ohm

B) 100Mohm
1.6ohm

 

[telectrix]

it says it in the question. " determine the values......", so you have to put the figures in the answer.

 

[liddley]

Question:
Following repairs to a motor and before its reconnection , an insulation resistance test is to be carried out on the securely isolated three phase motor circuit State:

A) the two test carried out to complete the schedule of test results.

B) how the cable between the motor starter and the motor maybe included in the tests.

my answers
A) line/line insulation test and line/earth insulation test.

B) make safe exposed cable ends that would connect into the motor with suitable cover/joint box make sure starter is in on possition and take car not to damage any electronics in the starter unit with high voltage used in insulation tests.
either by omiting them or limited test betweem line/earth not line/line???

Am i anywhere close with this question

 

[SJD]

Is the motor starter something you can just switch on when isolated, or does it require power for the connection to the motor to remain closed? If the latter, you are going to have to do something else than just have it in the 'on' position?

 

[liddley]

Thinking about it, I think omitting it from the circuit altogether would probally be the best option. like you say power is requiired to keep the starter on. and as seen as its a dead test thats being preformed thats not going to happen?

 

[SJD]

Or you might want to test it separately? [I don't think missing it out is an option here ...]

 

[spark 68]

For the 2391 you need to test the motor circuit in two parts, ie. cable from DB to isolator/starter and from isolator/starter to motor.

As SJD has said ^^^^ the starter requires to be powered to operate.

You would also have to IR test all Lines-Earth, as the starter may have electronics incorporated, and the motor will have windings across the lines.

This applies also for Zs readings, as it is forbidden for safety reasons to do live tests at the motor terminals.

Iam not giving you all the answers here, as this will not help you, but this information is not given in GN3, so Iam including this to help you out.

This will, or should be explained more in depth on your course, if in doubt ask the training provider!

 

[liddley]

you mention it is forbidden to prform Zs tests from a motor terminal? Is this a regulation in Bs7671?
Not familiar with motors and such as most of my work is domestic and light commercial premises.