anyone recommend an earth leakage clamp meter ?

[redwire]

Uni-T designs to the penny. Their OEM products are decent, but the Uni-T brand itself can be too cheap- where they just shoot themselves in the foot saving a nickel. They cheap out on purpose, it's not a mistake.

There are also "Current Clamp Adapter" that connect to your multimeter, for those who can't afford a full blown Fluke clamp meter. Not sure how much the i310S probe is.
These are more in demand for solar, "low amp clamps".

There was a DIY Current Clamp Adapter for multimeters project in Silicon Chip magazine Sept. 2003. They took a ring ferrite, cut it in two and glued into big croc clips like you use on car battery terminals. Pretty basic - your usual analog Hall sensor in the gap and op-amp for gain+offset. Lots of drift with temperature, so a better way is two Hall sensors differential.

[petehall347]

ok just installed the correct rcd.s in the correct places . master one is 100ma time delay and the others 30ma . this should ensure whichever circuit is the problem one is isolated and can been looked at if it ever trips again . i could be a bad cable but we will see next time it rains heavy which doesn't look like any time soon .
as for the clamp meter i bought the ethos 3650 it seems to work fine but a couple of gripes . one is the reading changes a little depending on where the wires go through the clamp .i can live with that . the other issue is annoying .its when opening the clamp if its done over the top with my thumb the clamp wont fully close .if i open it from underneath it closes fine but is awkward for my hand . i might send it back and try another new one .

[stj]

the fluctuation in readings is common with hall-effect sensors
it's partly caused by the earths magnetic field and partly caused by - to quote johny mnemonic:
"this shit, and and that shit, and all the other shit we surroiund ourselves with"

that was a great film btw - verry fortelling!

[petehall347]

now looking at rcd testers .. might go for a used robin one as they are not much to buy used . the plug in ones only see if the rcd works at a set test and nothing to say how quick .

[redwire]

What's wrong with using a resistor for an RCD test load? That's what I do.
Inside, RCD's do get old with the capacitors or mechanical failing (old lube). Or mains transients hit them. They don't last forever.
In North America, had to laugh the RCD's can jam due to old age, they try to trip but can't, get stuck BUZZZZZZZZZZZZZZ. So the SCR driving the coil shorts, the coil burns up, melts open circuit - it's a cooked mess, some failure mode nobody considered. The assumption is the solenoid is only ever briefly activated.

[petehall347]

What's wrong with using a resistor for an RCD test load? That's what I do.
Inside, RCD's do get old with the capacitors or mechanical failing (old lube). Or mains transients hit them. They don't last forever.
In North America, had to laugh the RCD's can jam due to old age, they try to trip but can't, get stuck BUZZZZZZZZZZZZZZ. So the SCR driving the coil shorts, the coil burns up, melts open circuit - it's a cooked mess, some failure mode nobody considered. The assumption is the solenoid is only ever briefly activated.

resistor wont tell me how quick it works or do various tests . has to be under 40ms for a 30ma rcd . .

[stj]

you could make one with a microcontroller and an opto-triac

[petehall347]

you could make one with a microcontroller and an opto-triac

yes i know that but its easier to buy a tester ready made , i would need one anyway to check the home made one was working properly .

[redwire]

Eaton RCD Application Guide
Look past 4.1.1. pg 23 Protection in TN networks has longggg trip times. Also some good info there.

I can't see the trip time being important, changing with age. It's the mechanical parts plus the electronic delay. RCD testers look expensive, I guess if you have the money for that.
A scope on line trigger can show the trip times.

[petehall347]

i would rather have a nice box made for the job then i can be satisfied my work is good . like i said they can be had for around £20 . https://docs.rs-online.com/01e2/0900766b800828c1.pdf

[petehall347]

the rcd tester i bought off that ebay for £12.50 arrived and the rcd,s tested good . the one i got is the ROBIN RCD KMP 5406DL . rain is coming soon so will maybe find out what was tripping it . or at least which circuit .

[redwire]

A friend owns a very old duplex house (~1912) with non-grounded wiring. So he installed all RCD breakers on each branch circuit to meet Code, a while ago. Each side of the duplex on separate energy meters.
Well, recently it rained and all 6 RCD breakers tripped (and won't reset) for one side of the duplex.

Best guess so far is the front entrance outdoor light fixture(s) are soaked. There are two light fixtures, one for each unit's front door in a common roof overhang.
But why trip all 6 breakers? My guess is there might be a cross-connected neutral to the light fixtures or worse. He says the light fixture junction boxes are way full of wiring when they should not be. On/off switch has a single wire leading to the fixture.
Or maybe a Line is energized all the time (neutral is switched) and water leakage current is somewhere weird.

[stj]

or the circuits are linked by some grounding in the walls.
old pipe maybe.

[petehall347]

so today i splashed out and bought a megger LT6 loop tester for £7.50 .

[redwire]

OK big spender, that LT6 looks interesting - it measures impedance between two nodes i.e. GND and Neutral but having mains power present is not a problem?

I have very carefully used my multimeter on Ohms for that lol. It sorta works - some sites have say 1.0VAC from PE GND to Neutral, usually with plenty of RF so a multimeter can get confused about it, read a silly Ohms value. It's just a quick sanity test to see if Neutral or ground is open (to a water pipe).

[petehall347]

OK big spender, that LT6 looks interesting - it measures impedance between two nodes i.e. GND and Neutral but having mains power present is not a problem?

I have very carefully used my multimeter on Ohms for that lol. It sorta works - some sites have say 1.0VAC from PE GND to Neutral, usually with plenty of RF so a multimeter can get confused about it, read a silly Ohms value. It's just a quick sanity test to see if Neutral or ground is open (to a water pipe).

it needs power to operate so i guess its just fine .

[petehall347]

finally got the loop tester and it trips the rcd . only way to use this one is bypass the rcd . or modify to use less testing current like 15ma .

[redwire]

I thought that RCD tester injects a little 1/2 wave-rectified current pulses into already existing wiring between say N and PE? It's different than the usuals that use a resistor Line to to N or PE to cause a current imbalance.

[petehall347]

I thought that RCD tester injects a little 1/2 wave-rectified current pulses into already existing wiring between say N and PE? It's different than the usuals that use a resistor Line to to N or PE to cause a current imbalance.

rcd tester might do . i now have a loop tester to check earthing . but cant just plug into wall and test as rcd trips . quite normal for this model .

[stj]

rcd test is just a resistor - i suppose a good tester could use a variable resistance somehow to ramp it till it trips in order to calculate the trip current.