Help Questions on IR of new consumer unit

[mnmwill]

So if you IR a circuit and you don't get the expected result in my case I expected to get >299 from my Megger instead got 160Mohm why would that be ?



Ty

Why would you expect to get >299Mohm? How old is the actual installation? Over time the IR readings decrease, as long as you have >2Mohm then that is fine. Personally I would look into more if it was down to, say, 5Mohm, but 160Mohm is a good reading.

 

[easysushi]

Why would you expect to get >299Mohm? How old is the actual installation? Over time the IR readings decrease, as long as you have >2Mohm then that is fine. Personally I would look into more if it was down to, say, 5Mohm, but 160Mohm is a good reading.

Its 7 years old, on some circuits by doing L-N, N-E, L-E I was getting >299 but on others it would start at 120Mohm then creap up to I 160 and above. Also what about downlighters do you have to remove all transfomers in order to do a proper test or will LN-E suffice


Ty

 

[SEC-Tom]

Another question on a new installation were fitting around 60 downlights in one flat and I think they are all going to be transformers..

This would be a pain for our tester to remove all of these but I believe a LN-E test isn't allowed of a EIC??

 

[Sintra]

Another question on a new installation were fitting around 60 downlights in one flat and I think they are all going to be transformers..

This would be a pain for our tester to remove all of these but I believe a LN-E test isn't allowed of a EIC??

Correct limitations not permitted on an EIC only on a PIR.

To save disconnecting trannys and removing lamps etc. the best way is to test the circuits before these are fitted and then finish testing when job complete.

We always do testing in at least 2 stages for an EIC.

 

[peterb2428]

So if you IR a circuit and you don't get the expected result in my case I expected to get >299 from my Megger instead got 160Mohm why would that be ?



Ty

Probably thinking about >299 because when you do these tests on courses you always get >299 but in reality you will often get a reading below and 160 is well above 2ohms so wont need investigating

 

[Sparky Ninja]

We always do testing in at least 2 stages for an EIC.

Exactly right.

It's called initial verification, then testing and inspection. The requirement for L&N - E when carrying out IR should never occur when doing an initial verification as this testing is done prior to application of loads to the circuits.


Whe carrying out IR on periodics, readings will vary with age due to the degrading of the installation. Although you can justify that 1Mohm is the minimum, you will then assess the other readings and they will affect your decision to the date of the next inspection.

 

[Eggster71]

You'll also get lower IR readings due to conductors in parallel. If you split and test each circuit individually they'll almost certainly be >299

 

[easysushi]

Well I thnak you all for your input it has cleared a few things up for me.

I also passed my NICEIC asseesment today, so am over the moon. But I have to say this forum is great if your not sure or need to clarify something.


Cheers to you all



Ty