Earth leakage meter.. Do I really need one?

[Mikegh]

Good read all the same. One to file away

Ya they make good docs , only had a flick through and can't say I follow it all, it but when it comes to the A and the B type how will you know whats going on with a basic AC clamp. Leakage current and RCDs is getting so complex

At least with a IR tester you can test all the fixed wiring and basic checks on connected equipment

 

[DPG]

It's nice to know what leakage levels you have on each circuit. See if you are close to nuisance tripping.

 

[UNG]

I think if you need to ask other people to justify a purchase you are considering then you will get a mixed response as we all have our own way of getting to the end result of finding the fault. An earth leakage or low current clamp meter is just another tool in the box to aid that hunt for the problem you are presented with and may speed up the fault finding / identification process or it may not
I do have one of the cheaper earth leakage clamp meters it is not something I use everyday / week or month but it was at the right price at the time. With so many potential parallel earth paths in an installation it is worth making sure that the clamp can accommodate the live and neutral tails of an installation as measuring the imbalance of the current will give a more accurate reading than just clamping the earth conductor

In the last few years I have spent more money on logging equipment than anything else as when the fault is an intermittent fault you can guarantee it will never show when you are on site trying to hunt it down and may only show every few days or weeks. My decision has been and was based on many years of fault finding experience and looking at ways of improving how I went about it, it earns it's keep and me money so that is my justification for it's purchase

 

[LastManOnline]

An earth leakage or low current clamp meter is just another tool in the box to aid that hunt for the problem you are presented with and may speed up the fault finding / identification process or it may not

That's what I have been wrestling with. I will likely continue to faultfind successfully without it but any tool that speeds up the process and makes it more convenient is certainly a well worth while investment. I do however feel it would be a little pointless at this stage to buy one that does AC only as I want to future proof

 

[pc1966]

That's what I have been wrestling with. I will likely continue to faultfind successfully without it but any tool that speeds up the process and makes it more convenient is certainly a well worth while investment. I do however feel it would be a little pointless at this stage to buy one that does AC only as I want to future proof

I suspect for many years you will fine AC leakage from a lot of electronics is the case to worry about for single/dual RCD bards. At least by measuring it you can explain to the customer why the thing is trip-happy.

I am a little sceptical of DC leaks being a big thing outside of PV and EV, even then many EV charges already have that sort of protection built in.

In the UK / ROI with predominantly TN supplies I expect any fault that exposes AC-derived DC to the metalwork will blow the fuse/MCB anyway, though I can understand in the TT would of much of EU the issue of DC appliance leaks might well be of a deeper growing concern.

 

[Mikegh]

From my cursory glance through that linked article
What it was saying was the B type let's through 60ma of harmless DC current , whatever that means
Its not blinded by the DC I suppose is the important thing

Now how you go about checking and quantifying all these various leakages and testing is for the "higher ups" than me

Think I'll stick with the Megger and trial and error and multiple RCBOs for problem solving

 

[Mikegh]

From the article:

"Figure 23 illustrates that Schneider Electric 300mA type A RCDs can be used upstream a 30mA Type B RCD without risk of blinding: Type A protection of the device is guaranteed even in case of a 60mA smooth DC residual current. If the smooth DC residual current reaches the value of 60mA, the 30mA type B RCD will trip"

Seems to be an important point

 

[pc1966]

"Figure 23 illustrates that Schneider Electric 300mA type A RCDs can be used upstream a 30mA Type B RCD without risk of blinding: Type A protection of the device is guaranteed even in case of a 60mA smooth DC residual current. If the smooth DC residual current reaches the value of 60mA, the 30mA type B RCD will trip"

See also:

RCD "blinding" by DC

A recent thread was discussing having a delay RCD (type A or AC) for TT before a garage CU with a type B RCD for an EV charger. The question was would this be OK or not? Standard advice is the type B should be direct off supply (possible problem for TT) or fed from another delay type B (at...

www.electriciansforums.net

 

[Marvo]

20 years ago you could calculate the leakage on a circuit or an installation by running a 250v IR test and doing the math to work out the leakage current. Nowadays with all the standing functional leakage from switchmode power supplies and LED drivers the leakage current rarely bears any resemblence to the IR value measured as a dead test.

I'd say a leakage current clamp meter is an essential item and nowadays and leakage current must be measured as a live test using that device rather than trying to calculate it from an IR dead-test result.

I'm not sure a a clamp meter that measures AC and DC is essential unless you're working with a lot of type-B RCD's.

 

[newfutile]

You may want to look at note 2 here in the regs:
531 .3.2 Unwanted tripping
Residual current protective devices shall be selected and erected such as to limit the risk of unwanted tripping. The
following shall be considered:
(i) subdivision ofcircuits with individual associated RCDs. RCDs shall be selected and the circuits subdivided in such a way that any earth leakage current likely to occur during normal operation of the connected load will not cause unwanted tripping of the device. See also Section 314
(ii) in order to avoid unwanted tripping by protective conductor currents and/or earth leakage currents, the accumulation ofsuch currents downstream ofthe RCD shall be not more than 30 % ofthe rated residual operating current
NOTE1: ThiswillalsoallowabetterselectionofthetypeofRCDsaccordingtothenatureofthecircuitortheload.
NOTE 2: RCDs may operate at any value of residual current in excess of50 %of the rated residual current. (iii) use ofshort time-delayed RCDs, provided the applicable requirements ofChapter 41 are met