Insulation Resistance Testing Problems

[Djlelectrical]

Been to a Job this morning problems with RCD tripping, Global IR came back 0.016, Split circuits down and lighting tested (Including outside tested 0.018) however tested again 0.567 and then 1.03 each time the figure increases until it sits about 1.14. Testing done L&N - cpc and then N-Cpc (Highest reading given)

The offending circuit has outside lights which are Energy saving.. I am concerned about the testing tho. From first its a fail and then after a few hits its a pass (Just I know) but which reading would you take and is the an explanation to why the figures are increasing.. Its only a case for this one circuit..

Havant had time to split the circuit down to narrow it down due to the results fluctuating

 

[Deleted member 9648]

Usual culprit of an increasing IR is damp.....as the small current can actually 'dry' out the damp for a short period...try it at 1000v as long as you are not going to fry anything,sometimes it stays low at 1000v which helps with the tracing it process.

 

[Jay Sparks]

Check for water ingress in the outside lights. I had a similar problem, but there was no rcd, it was the mcb that kept tripping intermitantly. Opened the back of the outside light and water peeeed out. Just a thought. Could also be the cable that feeds the outside lights are damp. Could be a few things but with a reading below 2 Mohm, I would be investigateing furhter


Jay

 

[Jay Sparks]

Damn it wirepuller, you is too quick on the draw. I dont post much usefull stuff but when I do, I get out posted..lol

Jay

 

[Djlelectrical]

Thats great guys cheers.

So would you suggest that the first result was more accurate ?

 

[Deleted member 9648]

Thats great guys cheers.

So would you suggest that the first result was more accurate ?

Well summats gotta be tripping that RCD!

 

[Jay Sparks]

You didnt mention testing between L & CPC.... if you did, what was the result?

Jay

 

[Djlelectrical]

Well summats gotta be tripping that RCD!

Your right there is.. However 0.018 then yes this would be the cause however 1.03 although low this inst sufficant to cause RCD to trip

 

[Deleted member 9648]

Your right...but the first reading you got (0.018) would be the one the RCD was 'seeing' when the circuit was energised.

 

[Deleted member 9648]

Damn it wirepuller, you is too quick on the draw. I dont post much usefull stuff but when I do, I get out posted..lol

Jay

Now who else always moans I'm far too quick?......Oh yes,the missus.

 

[Djlelectrical]

You didnt mention testing between L & CPC.... if you did, what was the result?

Jay

I didn't test between L & CPC, tested L&N - CPC and N-CPC .. L&N - Cpc would show up a fault in L-CPC..

Never had a test result fluctuate so much, The damp suggestion seems feasible and would explain everything.. Especially why its tripping..

- - - Updated - - -

Now who else always moans I'm far too quick?......Oh yes,the missus.

Dont they all.. Well not when im haveing a quick beer with my mates..

 

[Djlelectrical]

Your right...but the first reading you got (0.018) would be the one the RCD was 'seeing' when the circuit was energised.

Cheers

 

[Jay Sparks]

Now who else always moans I'm far too quick?......Oh yes,the missus.

What, she says that to me as well....lol

 

[Jay Sparks]

I didn't test between L & CPC, tested L&N - CPC and N-CPC .. L&N - Cpc would show up a fault in L-CPC..

Never had a test result fluctuate so much, The damp suggestion seems feasible and would explain everything.. Especially why its tripping..



If you have installed cables in a wall and the muck chucker has been in and done his bit, if you done an IR test on them cables and hold the test button, you will find it will keep increasing. Ive sat there sometimes holding the button for a few minutes just to get the reading to >299.

Costs loads in new batteries though..lol


Jay