ELCB and Voltmeter

[John]

A I liable to cause a trip by using a volmeter between live and earth - to trace a circuit?

[Martin Brown]

Not unless it is a very old one drawing serious current. Why can't you trace using live to neutral?

I prefer a neon screwdriver myself even though they are deprecated.

All bets are off if you short live to earth though.

[spuorgelgoog]

Shouldn't do.

Assuming a typical digital meter impedance of 20 Mohm, you'll be loading the circuit by 0.02 mA, which shouldn't trip an RCD or ELCB.

If my calcs are right of course.

Owain

[tabbypurr]

no chance. Unless you short it out by accident.

NT

[Alan]

Yes. Depending on what make/model of voltmeter. A multimeter generally doesnt trip the RCD,as thye have avery high impedance. Some of the cheaper ones, even made by a 'decent' brand can cause the RCD to trip, if the correct sequence is not followed. The Fluke T100 would trip the RCD unless a L-N voltage reading is taken first. No idea how it worked like that, but check your voltmeter manual first.

[tabbypurr]

even rock bottom $2 analogue multimeters are 1k/volt, on a 250v scale that's 1mA, less on a higher v scale. There's no way that's tripping an RCD unless it's right on the edge already, in which case you have a problem that needs sorting. And that tripping a voltage ELCB? No chance at all.

NT

[ARW]

It was meant to work like that. A bit of a bastard if there is no local neutral.

[Brian Gaff (Sofa)]

Anything is possible but I'd hope not, but what are you actually trying to find? Brian

[Brian Gaff (Sofa)]

So what does it mean if there is 10v on earth to neutral? Brian

[ARW]

It has not been made clear if it is a voltage or current operated ELCB.

The OP may be using older terminology and meant RCD.

[charles]

there's an unbalanced load between the 3 phases.

[Steve Walker]

Or a parallel run of cable close enough to induce a voltage on the one you're measuring if the neutral is disconnected. I have one cable that when isolated at the double pole isolator, floats at 90V to earth if there is no load across it!

SteveW

[John Rumm]

If you have TN-S earthing, then you could see a fair potential difference to earth since the N carries high current but does not have zero impedance - so there will be some voltage rise between your property and the substation (and the live will typically see a comparable voltage drop). The earth however will be a close approximation of the Neutral potential at the substation.

With TT you can see a similar magnitude. With TN-C-S you can still see some, but its only the result of current flow in your property, and so will vary more depending on where you measure it.

[John Rumm]

The short answer is "no" for most "normal" multimeters. However could you clarify what you mean by ELCB?

Do you mean a current operated ELCB - i.e. what we call a RCD these days, or do you actually mean a Voltage Operated ELCB (obsolete, but still installed in some properties).

See: