Busy completing al the inspection report repairs on a site and found a strange event while doing the loop impedance testing.

At the time of the inspection report, we had a high loop impedance test result, we contacted the council and they sent someone out within 48 hours, the problem was sorted out, apparently there was a loose connection.

I went back to site to check the loop impedance reading, it was 0.69 ohms, happy with that result. I do a loop impedance test at every single socket outlet to make sure everything is ok, on Monday I noticed the reading displayed higher than 2000 ohms, thought it might just be a bad test lead connection.

Checked all the earthing around the building, 0.00 ohms you might say impossible, actually not. I did zero the leads on the fluke multi tester and the readings were zero. Considering I have just spent 3 days sorting out the earthing, I am not surprised.

I tested the voltage L-N, L-E and N-E and all seemed to be within spec.

Then today as I was finalising the tests I noticed the 2000 ohm reading on the display, so I opened the meter and tested again at the meter, the reading was 0.69 ohms. I disconnected the earth and did the test again, 0.69 ohms. Maybe the 2000 ohms was just a glitch.

Was busy checking the last socket and again, 2000 ohms again.

So I setup the multi meter at a socket outlet reading voltage N-E, this is where it got interesting. The neutral to earth voltage was 0.9 VAC, nothing wrong with that, then it happened the neutral to earth reading started climbing to over 10 VAC.

I checked the loop impedance when the N-E voltage was at 0.9 VAC , the loop impedance reading 0.69 ohms. We switched on all the elements on the stove, and then it happened again, as the N-E voltage increased from 0.9 VAC to over 10 volts, so the loop impedance test went from 0.69 ohms to 2000 ohms.


This people is why it is so important to do a full load voltage test L-N, L-E and N-E.