IR Tests

[T&Earth]

Hi Everyone,

Could anyone please tell me what is meant by the term: 'The incoming neutral has to be disconnected so there's no connection with earth before carrying insulation resistance tests'.

Reference NICEIC Inspection, Testing and Certification 5th Edition (Practical Advice and Guidance)

Thanks a lot,

T&Earth

 

[Guest123]

Hi

Well as we know both neutral and earth are derived from the same point of the supply transformer i.e the star point so you could theoretically get false readings through this connection.

Having said that you should not be carrying out I/R tests with your double pole main switch closed anyway.

 

[T&Earth]

Hi Lenny

Thanks for the advice, I would always carry out this test with main switch open, that why it has confused me!

 

[cbw]

Sorry guys, do you mean main switch off?

One of you says open, the other says closed.... Confused

 

[Guest123]

Yes.

I said you shouldn't test with the switch closed i.e ON, and he said he always tests with it open i.e OFF.

 

[cbw]

See....easily confused!!!

Time for some cider

 

[Des 56]

Hi Everyone,

Could anyone please tell me what is meant by the term: 'The incoming neutral has to be disconnected so there's no connection with earth before carrying insulation resistance tests'.

Reference NICEIC Inspection, Testing and Certification 5th Edition (Practical Advice and Guidance)

Thanks a lot,

T&Earth

With a 3-phase board and a tripple pole isolator,the neutral is connected via a fixed link

 

[T&Earth]

hi Des 56

Thanks for your posting, its strarting to make sense.

Cheers!

 

[andrewhubbard]

hi i need a little help with my college coursework im a first year apprentice and need some help right the question is when tesing between phase and neutal tails at the consumer unit a reading of 0.6 M ohms was observed - describe the procedure you would adopt following this reading

thanks
drew

 

[Des 56]

Well first of all,testing between the tails would require isolation prior to the distribution board that you are testing
Do you mean the distribution board, load side of the isolator ?

If so
Are you testing with all mcbs/switches closed, electronic equipment isolated,dimmers neons etc etc removed/disconnected and then getting that reading ?

You may need to describe your procedure before doing this test?