testing neutral conductors

[Superspark23]

Had another dispute with who i was working with today, with testing an new installation. Here goes

I always thought that the proper testing sequence is R1+R2, continuity of bonding, insulation resistance. Then ze, then zs. rcd

But the person i was working with today told me i should always test for insulation resistance before anything else. then do my r1 and r2 and then do an r1 + r2 to check the continuity of neutral, i've never heard of having to do this before but it doesn't seem a bad thing to do. but isn't the whole testing sequence designed to check that polarity is correct and you have an earth at the end of line. Therefore you don't have to check the neutral conductor, but on the ring you have to check the end to end of the neutral. but not on radials.

to me theres no point in doing the insulation resistance untill you know that everything has the correct polarity and there's no breaks in the circuit

 

[micknew]

You must do the insulation test first as if there is a leak due to poor insulation it will not give you a true R1+R2.

 

[spark 68]

I have on occasion done it the other way,IR first, but not on domestic.

The reason I have conducted the IR first on a new install (3 PH + N, done in 4 IR tests) is to ensure there was nothing 'naughty' across the lines, Lines-E and Neutral -E, and then did the 3 * (R1 + R2) tests and N + R2 to check for correct polarity, specifically on a long run, or when testing switch boards, as it can offer significant time savings.

The IR test has to be done first in this instance or it means you have to make more tests.

 

[JamesBrownLive]

Stick to the regs...

612.1
The tests of Regulations 612.2 to 612.6, where relevant, shall be carried out in that order before the installation is energised.

So you were correct in thinking that continuity testing comes before IR testing.

 

[GLENNSPARK]

Had another dispute with who i was working with today, with testing an new installation. Here goes

I always thought that the proper testing sequence is R1+R2, continuity of bonding, insulation resistance. Then ze, then zs. rcd

But the person i was working with today told me i should always test for insulation resistance before anything else. then do my r1 and r2 and then do an r1 + r2 to check the continuity of neutral, i've never heard of having to do this before but it doesn't seem a bad thing to do. but isn't the whole testing sequence designed to check that polarity is correct and you have an earth at the end of line. Therefore you don't have to check the neutral conductor, but on the ring you have to check the end to end of the neutral. but not on radials.

to me theres no point in doing the insulation resistance untill you know that everything has the correct polarity and there's no breaks in the circuit

and you wont be doing an r1+r2 for a neutral mate.....

 

[One_of_them]

^^ as above

stick with the test sequence in the regs. If you done an IR first then it might show up as all OK but you might have an un-connected cable somewhere that will still show on IR as been OK but if you done R1+R2 first then this would show as none continuity

 

[Inteificio]

I must admit this one confuses me.

I have been repeatedly quoted on do it first or it messes up your r1r2,

However if you fail on the IR (or any test), it would lead to me fault finding, repair and a FULL retest of the circuit.

So never really saw the point of the specific order of tests, apart from dead->live->RCD functional test (as been told the functional test can repair a fault that would otherwise be picked up by other tests).

As ever there is a chance I have overlooked something, so anyone throw a bit of light on it?

I only do the tests in order of the book as it says so, any order is good, so why not stick to the book?

edit: I always do R2/N as well, not mentioned in regs but a HUGE timesaver.

 

[One_of_them]

if you done your 2391 and done an IR test 1st I doubt they'd bother letting you finish

 

[spark 68]

GN3 does not preclude doing the tests in a different order, but it does make sense to follow the suggested sequence, as it means that the tests are self checking to a certain extent.

I agree with most posters on here, that in general you should check your continuity first (R1+R2), because as others have said if you have a broken conductor, then this will mean a re-test of at least two tests instead of one.

There are circumstances (such as the one I made above) where it is desirable to alter the sequence.

But in general you should follow GN3.

 

[GLENNSPARK]

as the title of this thread is on how to test neutrals.....how did we get to
R1+R2?.....it would be R1+Rn wouldn`t it....

 

[One_of_them]

i'll be honest, i ignored the title and just read the post and followed suit

 

[spark 68]

One case for doing the IR test first, is if you have a long distribution cable (too long/incovenient for a wander lead).

For instance 3ph+N, you can cut the IR tests down to four by temporary linking at one end, all conductors to earth except the one you are testing.

test between as follows:

E + N + L1 + L2 to L3

E + N + L1 + L3 to L2

E + N + L2 + L3 to L1

E + L1 + L2 + L3 to N

All being well here,this verifies that you have no connections between any line conductor, between any line conductor and N, and between any line or N conductor to Earth.

Then you can do your 3* (R1 + R2) tests, and a (Rn + R2) test.

A total of 8 tests, which is a significant time saving.
As you can see here, the IR test needs to be done first, as you are testing to the R2 each time, this saves checking for shorts between each line conductor line to E, and N to E, and Line to N,
In this case we have cut the amount testing down to the minimum required.

 

[sinaloan]

You should do r1 + r2 first, this ensures you have a complete continuity of the entire circuit before you pump a voltage down it. If you had a loose connection somewhere touching an extraneous conductive part and you did your IR test first then this could potentially become live when testing, therfore you should always do r1+r2 first and r1 +rn if you want to. all of the tests are in order for a reason :smile5:

 

[WDMDL]

Always continuity first.
Think about it...
1) by doing continuity first, you know your insulation test is going to be valid.
2) Poor insulation resistance (other than a short) is not going to affect your (R1+R2). Try calculating the effect of 0.01 Megohms (10,000 Ohms) in parallel with 1.0 Ohms.
3) I always wondered why there was no specific test of neutral continuity on a radial either. But having a few loose neutral faults on minor works it's something I just do as a matter of course after the (R1+R2) now.

Spark68, I agree with the tests you're doing, the method is what we used for testing multicore cables in my previous job...but still you should do the continuity first, as if you find a break in continuity, you'll have to do the IR tests all over again.

Simon.