Here we go again! The snake oil salesmen are back again, attempting to sell a solution to a problem which doesn't really exist to any great extent.

Volt drop test?

I apply the usual tempered but proven method of go-no go, If it works ok, then VD is fine.

How repeatable are loop test results?

In my (limited) experience high current L-N tests are reasonably reliable and repeatable (unlike some low current "RCD-compatible" L-PE tests) - so it shouldn't be difficult to obtain reasonably plausible R1+Rn values even from an existing installation with unknown precise cable routes/lengths - from that it's just a reasonably straight-forward (if tedious) case of plugging those values and the expected load current into Ohm's law. Especially tedious if distribution circuits are involved and you have to work out the expected load from all the other circuits too (including diversity), but still each step isn't that difficult.


Thinking about it, what's probably more useful than a different meter is a change to the software sometimes used to record/verify EICR results - plug in L-N loop impedance values for the origin, each DB and furthest point on each circuit (alongside the Zs/Z_DB values) and then let the computer do the workings out. We might spot a few more bad N connections before they melt that way too.


   - Andy.

My Megger LTW320 three wire loop tester has a buried function which enables it to display the voltages between conductors when it realises there is a problem with the neutral conductor. All three polarity indicating LEDs light up and the display indicates the voltages between the conductors in sequentially.


So although it doesn’t display it on regular testing it is monitoring the neutral and will flag an issue.


Andy