Online assistance for electrical trade people in New Zealand and Australia Login  |  Register  |   Forgot Password
Assistance for electrical trade people




Click here to send Ron a pdf document for publication on this Topic

Documents must be less than 200k in pdf format

Posted By Topic: The Point of Earth Continuity Testing.

Jan 15 2019 21:18

Just a thought I had while testing a new house the other day , when testing - why do we need to know the resistance value of a PEC in a sub circuit if you're getting acceptable Loop impedance test results? Does the loop test not prove an acceptable earth conductor resistance value?

Jan 15 2019 21:42

If its RCD protected, no need for earth fault loop. I do a non trip earth fault loop just to confirm everything but your find the RCD will trip otherwise as the CB protection limits to 400ms where RCD limits to 300ms (usually 30ms in real life testing)
I have found a earth fault loop had showed me the main earth conductor was non existant (should have completed a earth continuity test before the EFLI, existing home)

Jan 15 2019 22:51

The quick and dirty answer is that you must test that the items that are required to be earthed, are actually earthed. And that your earth conductors are actually connected to the end of the circuit.

On the other hand, you don't actually have to test EFLI for most circuits, and not ones that have RCD protection.

Additionally, I use the earth continuity test as part of my polarity/correct circuit connections testing - as the neutral is disconnected from the circuit with the RCD off, testing the earth continuity confirms that it's the earth conductor connected to the earth terminal, and not the neutral. Better off to find any transpositions at this early stage, rather than at a live polarity testing stage.

I have also had one occasion where the continuity test has also found non-connected fittings (sheeted over), at the early dead testing stage, rather than later in the testing process.

Jan 16 2019 13:13

An EFLI test will confirm EFLI is low enough to operate protective devices that provide fault protection by automatic disconnection.
But the live test can't confirm that the fault current will flow in the PEC of the circuit. And neither form of EFLI test confirms that ALL points required to be earthed are actually earthed; because the EFLI test is only done at the furthest end of each branch of a circuit. For example, a circuit of lights is not required to have an EFLI test, but could have 20 or 30 points that ALL have to be checked that they are connected to the earthing system.

So the EC testing confirms ALL points correctly connected AND of suitably low impedance for the PEC part of the EFL; and we rely on the fact that if the rest of the loop has a high enough impedance to matter it will show up in operation eg as volt drop or similar.
Then for those circuits that matter a bit more, eg where we are likely to use hand-held equipment etc, the EFLI test confirms that even the worst case - the end of the circuit - is absolutely OK. Even then, with the 'dead' test we are making an assumption about the part of the lop upstream of the commencement of the final subcircuit (distribution, mains, submains).

The mandated tests can't be treated as each being standalone; rather they act together to confirm compliance. If you haven't confirmed earth continuity, you simply can't trust any of your IR tests.