Query regarding insulation resistance testing

[JamesBrownLive]

Everything I have read so far about 'Insulation Resistance' testing only ever mentions 3 procedures:

Line - Neutral
Line - CPC
CPC - Neutral

But on the 'Minor Works' cert the first test it specifies, in the part pertaining to insulation resistance testing, is:

Line - Line

I've got the Chris Kitcher book on testing, but there is no mention of a line-line test.

So now I am a little confused

Can someone please tell me how this test is performed, and if it is common?

Cheers

 

[J@mes]

line line for 3 phase installations where appropriate?

 

[JamesBrownLive]

line line for 3 phase installations where appropriate?

That sort of makes sense, but would there not need to be 3 boxes for results...

L1-L2
L1-L3
L2-L3

Or am I just being 'Blonde' again?

Cheers

 

[camerabloke]

line = live
line = neutral

 

[J@mes]

The certs have a separate box for live-neutral (well the ones I have do anyway!)

 

[Mr Mark Sparks]

That sort of makes sense, but would there not need to be 3 boxes for results...

L1-L2
L1-L3
L2-L3

Or am I just being 'Blonde' again?

Cheers

my cirts say line to line record lowest reading (1 box)

 

[nickblake]

Live to earth, neutral to earth,neutral to live , and live to live in three phase , but when testing ensure all items are unplugged and that their are no PIR's connected in the circuit and that all RCD's are also disconnected to.

 

[IQ Electrical]

line = live
line = neutral

Not quite, the neutral is classed as a 'live' conductor but not a 'line'

 

[JamesBrownLive]

my cirts say line to line record lowest reading (1 box)

Ok, so when testing 3 phase, when doing the line-line test I test all 3 as I mentioned, L1-L2, L1-L3, L3-L2 but use the box on the cert to record the lowest value I have measured??

When doing the other tests, involving a line (L-N and L-CPC) do I have to repeat the test with each phase and again record the lowest value measured?

In other words I end up doing...

L1-L2
L2-L3
L3-L1
L1-N
L1-CPC
L2-N
L2-CPC
L3-N
L3-CPC
N-CPC

And record the lowest values from the tests in the 4 boxes provided?

Is that correct?

Cheers

 

[J@mes]

Yes on a 3 phase system you have to test each phase to one another and then each phase to neutral and each phase to earth.

I'm sure you can link the 3 phases together at the board and then test them to cpc and neutral in order to speed things up, but obviously if you get a low reading you'd need to test them separately to see which one is faulty.