Insulation Resistance query

[JummyD]

When doing domestic testing, I spend quite a bit of time removing loads & vulnerable equipment prior to carrying out IR tests- allowing me to test between L - N without risk to vulnerable equipment or getting inaccurate readings. I’ve spoken to a number of sparks who go straight to testing L&N together to Earth.

I’m interested to know how far you would go to remove vulnerable equipment before opting for the easier test??

 

[westward10]

I very rarely bother on an EICR.

 

[pc1966]

Given most domestic stuff is wired in T&E with the E between L&N you are likely to see most potential problems with the safe L+N to E testing.

You would still need to deal with any SPD as they are often connected to E but if you see a big difference going 250V to 500V you can be fairly sure they are the reason so look for power blocks with surge protection built in, etc.

 

[bill01803]

Always do L&N to E as it is accepted practice and much quicker, and do global IR if possible, if result is low then do each circuit seperately.

 

[JummyD]

Thanks for the comments. This would save me a lot of time & I know bs7671 allows the test but wondered if the majority of sparks opted for L&N to E straight off.

Thanks

 

[pc1966]

As @bill01803 says, doing a global L+N -> E test is a good starting point for any checks or before work, as it can be down without disconnecting anything by switching off the main isolator, and if low it warns you that a can of worms is about to be opened.

 

[radiohead]

On existing circuits, particularly lighting with downlights, outside lights etc it is simply not practical to test L-N, and I am of the opinion that those who claim to always test L-N are simply lying. I would love to see them go round and disconnect 30 integrated downlights and half a dozen outside lights prior to their 2 minute test. Half a day to disconnect everything, 2 minutes to test and another half a day to reinstate.....Yeah right.
However where new circuits are being tested for initial verification, in most cases it will be practical and correct to test L-N as the layout of the circuit will be known and testing can take place before any loads are connected.
And as has already been stated, with T/E wiring with a bare copper conductor between live conductors it is highly unlikely that a L-N fault would happen without tracking to the bare conductor as well.