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Discuss 2391 - would like to double check advice from tutor in the Electrical Courses & Electrical NVQ's area at ElectrciansForums.co.uk.

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  1. chronyx
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    chronyx Regular EF Member

    Location:
    Surrey, UK
    Would appreicate any clarification of what I have been told at college.

    The tutor has told us to use 240V for calculations as this the output of a sub-station. Do you agree, or should I use standard 230V?

    We were also told to remove the bonding conductor from the pipe clamp to test the continuity without parallel paths, but surely the logical thing is to disconnect at the board so that you also test the connection from the clamp to the pipe?

    For those who remember the test board, am I right in assuming the MIMS cable sheathing earth is verified by the standard R1/R2?

    How did you test the motor starter R1+R2 and insulation resistance values? Press in the contactor, or split the supply and load and test individually?

    Cheers chaps :cheesy:
     
  2. rich.250
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    rich.250 Electrician's Arms

    Location:
    Cornwall
    Business Name:
    Rich Williams Electrical
    I would use 230, and did on my 2391

    Disconnect bonding at the db

    Yes r1+r2 is verified in the same way on mi

    And I would be tempted to link out the contactor to be able to test r1+r2 at the motor

    Hope this helps
     
  3. chronyx
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    chronyx Regular EF Member

    Location:
    Surrey, UK
    Certainly does Rich, thank you very much and enjoy what's left of the weekend. :D
     
  4. rich.250
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    rich.250 Electrician's Arms

    Location:
    Cornwall
    Business Name:
    Rich Williams Electrical
    No worries mate.
     
  5. brman
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    brman Guest

    it has been suggested to me that for the motor we measure method 1 to the contactor and use method 2 to measure R1 and R2 for the contactor to motor then add them all together.

    I guess it all comes down to which is going to be quicker as they are all valid approaches. I suspect his checklist expects him to see method 1 on at least one circuit but after that I reckon it is your choice as long as it gets the right results.

    And yes, 230V has been drummed into us, as has removing the bonding at the MET and measuring to the pipe, not the clamp.
     
  6. chronyx
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    chronyx Regular EF Member

    Location:
    Surrey, UK
    Thank you, this is a great help to my classmates too! The tutor is a nice bloke but not a natural teacher.
     
  7. i=p/u
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    i=p/u Electrician's Arms

    how you going to check you 3phase stuff, is it L1 to earth nd check at points on circuit then the same for L2 asnd L3
     
  8. brman
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    brman Guest

    I believe so. Basically treat it as 3 different circuits. Until you come to the IR test where you need to test all combinations of course.
     
  9. rich.250
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    rich.250 Electrician's Arms

    Location:
    Cornwall
    Business Name:
    Rich Williams Electrical
    Yes as brman says.
    If you think of the schedule of tests for 3phase. It will be three lines, so 3 r1r2s.
     
  10. SirKit Breaker
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    SirKit Breaker Guest

    If you get any questions that need voltage, other than one where you need to work it out, you will be given the voltage value.

    i.e. You wont get a question starting like:- On a single phase supply. It will be worded, On a single phase supply with a nominal voltage of 230v, or words to that effect.

    You may need to do volt drop calcs, but even then you will be told the voltage. The 2391 exam does not leave things open to interpretation.

    Cheers.............Howard
     
  11. SirKit Breaker
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    SirKit Breaker Guest


    You are worrying too much. You will be walked through the tests as part of the course, before you do the practical assessment. It doesnt matter how you do the tests, as long as you do them all, do them properly, and work safely.

    Cheers............Howard
     
  12. chronyx
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    chronyx Regular EF Member

    Location:
    Surrey, UK

    I've done the course, and it was of limited use. Like I said, we were told how to do the bonding test incorrectly.
     
  13. chronyx
    Offline

    chronyx Regular EF Member

    Location:
    Surrey, UK
    My exam is today, so having a revision session!

    Would anyone be able to confirm what details can be obtained only by enquiry (From the DNO) rather than measurement?

    I am thinking earthing arrangement and in some cases the supplier protective device.

    Number of phases?

    Ze, frequency, phase sequence, Ipf and voltage can all be measured.
     
  14. timbobelfast
    Offline

    timbobelfast Electrician's Arms

    Location:
    Belfast
    DNO enquiry will be Ze and Type and size of main over current protective device.

    Got my exam tonight aswell so best of luck to everybody else taking it.
     
  15. brucelee
    Offline

    brucelee Electrician's Arms

    Location:
    leigh,lancashire
    good luck to you both
     
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