Where to put IR results for L/N to earth????

[Jay Sparks]

Hi Guys & Gals,

Gonna be doing a cu change soon and I was just wondering, when I do my IR test I will be connecting Line & neutral together and testing to earth. I will also be doing line to earth and neutral to earth. My question is, were do I put my L/N to earth results on the shedule of test results? I was thinking of putting it in the Line/Neutral part, is this what you lot would do or is there a different way.

By the way I will be using this for my Elesca assesment.

Cheers

Jay

 

[Risteard]

Depending on the certificate it would either be Live/Earth or both Line/Earth and Neutral/Earth. You aren't testing between Line and Neutral so Live/Live or Line/Neutral could not have a result recorded.

 

[stansmith]

hi might be a silly question but what is the reasin for testing L+N to earth at the same time?

 

[topquark]

hi might be a silly question but what is the reasin for testing L+N to earth at the same time?

It is normally done when there is equipment at risk in the installation, it avoids having a PD across L/N so avoiding any damage to SELV etc.

 

[Jay Sparks]

Hi,

Thanks for that. So on the shedule of inspections, most of the items would be n/a, like selv, felv, routing of cables etc as you would not know these. Or would you just inspect every thing as if it was a full rewire?

Cheers

Jay

 

[ezzzekiel]

Varied view on this obviously selv ticked if its installed but cable routing and the like could be n/a or ticked as the description of works box states what you are responsible for so everything is in relation to that

 

[Silly Sausage]

hi might be a silly question but what is the reasin for testing L+N to earth at the same time?

It is normally done when there is equipment at risk in the installation, it avoids having a PD across L/N so avoiding any damage to SELV etc.

Especially in a non domestic situation where there is virtually no way you can guarantee everything is disconnected from circuit under test. It's the IR test to do as stated in GN3. Do it at 250V first if you've got any doubt.

 

[stansmith]

ah right cheers guys my company seems to encourage limiting out L-N IR tests especially if unsure of whats on the circuit so never had to use that method good to know though, Thanks

 

[topquark]

ah right cheers guys my company seems to encourage limiting out L-N IR tests especially if unsure of whats on the circuit so never had to use that method good to know though, Thanks

Useful to do when contemplating a CU change as well, you can do a "soft test" of the whole installation to see if there are any insulation problems that need to be fixed before changing the CU.

 

[ezzzekiel]

still throws up some poor results via connected equipment though so best to disconect what you can

 

[SW1970]

Hi topquark, sometimes on a periodic I'll do the soft test on an individual circuit and get an acceptable IR of, say 70Mohm. Clearly it's a pass and there's probably something resistive in the circuit. I would normally attempt to find the resistive item and link across it or remove it to do a full test. Is that overkill? If you can't easily find it would you stop there and say it's a pass or would you still attempt to find that resistive factor. Thanks SW

 

[Silly Sausage]

On PIRs, I think just the LN to E test is fine, it'll expose any possible danger to persons, if your L to N were breaking down, what's the worst going to happen, short circuit, breaker trips. I'm quite happy to be pursuaded otherwise on that though.

Depends on how much you want to charge for your testing I suppose.

 

[topquark]

Hi topquark, sometimes on a periodic I'll do the soft test on an individual circuit and get an acceptable IR of, say 70Mohm. Clearly it's a pass and there's probably something resistive in the circuit. I would normally attempt to find the resistive item and link across it or remove it to do a full test. Is that overkill? If you can't easily find it would you stop there and say it's a pass or would you still attempt to find that resistive factor. Thanks SW

No, not overkill, it's being thorough IMHO

As you say, it's easily a pass anyway. For me I'd still be trying to identify a cause, if just one circuit showed that and all others were much higher readings. At the end of the day, it's a judgement call. I hate things I can't readily explain (it drives me nuts, well more nuts ). I'd probably spend up to 20 mins or so on something like that (assuming it's a fixed price PIR, otherwise ask for permission to spend the time).

 

[Jay Sparks]

Varied view on this obviously selv ticked if its installed but cable routing and the like could be n/a or ticked as the description of works box states what you are responsible for so everything is in relation to that

Im only changing the cu, so in the box I will write cu change. That is all I will be responsable for. But I suppose it dosent hurt to inspect everything anyway. I have read a few interesting threads on this subject and I have found that everyone has there own view on this subject and each of them have a valid point, so without starting another long debate about this subject, I think it best just to inspect all and tick the box's as approriate.

Cheers

Jay