Does anyone know what RCD fault he is talking about

[Vortigern]

I think @littlespark answered the question. Or at least that's the best stab in the dark so far as there is little to go on. But it sounds no different to turning on the circuits one by one and as stated, you now might know which circuit it is, However that does not identify the precise fault just narrows it down. OP would have to give a more precise description for a more precise answer methinks @nicebutdim, good name by the way.

 

[Vortigern]

Tbh I always get anxious when attending an RCD tripping as it can be such odd things like strapping cables need reversing, or someone just steamed off the wall paper with no evidence of it, and there is water in a socket and other weird events. Real bit of detective work sometimes.

 

[King84]

Thanks everyone for your replies really appreciate it and Here is the video at 5:19 he is talking about this specific test

 

[King84]

post the link on here and it might give people a better idea of what you’re talking about?

 

[King84]

Is no one going to answer the question and explain the unknown method of testing, shown on an unknown video, from an unknown youtuber?

Maybe the OP might provide a link to the video, if they get a chance.

Thanks Sorry about late message and I did provide a link above now

 

[James]

I watched from 5min mark to the end.
didn’t really like the guy and thought he gave very little if any usefull information

fault finding is a mix of knowing common faults that you can check if the symptoms support it and a good understanding of how things work and basic principles.

in my opinion, it is difficult to learn more than the occasional tip that may speed up the process under certain conditions by watching YouTube vids.

 

[Julie.]

I watched from 5min mark to the end.
didn’t really like the guy and thought he gave very little if any usefull information

fault finding is a mix of knowing common faults that you can check if the symptoms support it and a good understanding of how things work and basic principles.

in my opinion, it is difficult to learn more than the occasional tip that may speed up the process under certain conditions by watching YouTube vids.

Agree, I found his "presentation" awful, and struggled to keep watching.

Passing information to his audience is most certainly not his forte!

To the OP - as James stated, although there may be some tips that come out of these videos, there is so much more dross and potentially dangerous practices shown or mentioned in many of these videos. Unfortunately, unless you are already familiar with good practices, you can't tell the good from the bad.

There are some good ones on YouTube, John ward, sparkyninja, David savery electrical - they all give proper information (although their each "unique" styles may or may not suit you, but when learning they are good sources, so do persist with them)

I couldn't really understand what he was saying either, I think it's just disconnecting the rcd neutral and noting the results.

In itself it doesn't tell you anything, if it's a intermittent tripping fault, these are notoriously difficult to find, not one technique will do it as it could be due to....... pretty much anything, and a combination of things as well - linked neutrals (which can be found with testing) only tripping when a large load starts... through to an internal fault in an appliance (which the customer never associates with the tripping, so doesn't even tell you that it was plugged in at the time).

Finding faults is a matter of truly understanding the fundamentals of electrics and how the protection operates, combined with working your way through the issue in a logical process.

 

[Risteard]

He talks about "disconnecting the Rns". This doesn't actually make sense, as Rn is the resistance of a neutral conductor and as such can only be measured and not disconnected. Rn is not a name for a neutral conductor. Sorry to be pedantic but it irritated me.

 

[Lucien Nunes]

I agree, you can't disconnect a measurement. He was trying to be cryptic and avoid saying the word 'neutral', perhaps so that he couldn't be accused of explicitly suggesting a dodgy method. I think he knows his job but what a lot of waffle! I could have said that with 75% less words.

As a few people have stated above, there are multiple techniques needed to cater for all possibilities with faults that cause intermittent or apparently random tripping. What I think is important to recognise is that 'RCD tripping' isn't a kind of fault by itself. The trips are just one symptom that shows up with many unrelated kinds of fault.

The faults most likely to cause intermittent trips can however be narrowed down into some clear categories:

1. Functional / normal leakage
a) No electrical fault but excess aggregate functional leakage for one RCD. E.g. large ring with low load but many appliances / computers etc with RFI filters. Identify by leakage measurements, identifying loads and usage patterns.
b) No fault on tripping circuit, aggregate leakage generally within limits but exaggerated at times, e.g. by voltage transients / spikes caused elsewhere e.g intermittent connection upstream or appliance with functional switching in neutral. Rare, difficult to find, might require logger.

2. Insulation fault
a) Intermittent hard fault from L or N to E, e.g. moving floorboards occasionally pinch cable against pipe. Identify by timing, usage patterns, insulation tests. Can include appliances with timed functions e.g defrost heater in fridge freezer.
b) Marginal continuous insulation fault L to E, e.g. water in external light. Identify by insulation tests, usually easy to find.
c) Hard continuous insulation fault N to E, e.g. neutral pierced by socket fixing screw. Identify by insulation tests. Can be misleading as trips can be triggered by load on other circuits, but faulted circuit will always be on RCD that trips.

3. RCD fault (rare, never seen it myself)
a) Internally faulty RCD. Identify by RCD tests, substitution.
b) RCD being affected by interference e.g. adjacent transmitter. Identify by inspection, testing, substitution, relocation.

4. External influences, e.g. cats, people maliciously interfering with RCD. Identify by psychoanalysis

From the diversity of fault types in that list, I think it's fairly clear that multiple tests and strategies might be needed to pin down the cause of tripping, not just lifting the final circuit neutrals from the bar one by one.

 

[ferg]

Intermittent tripping RCD is one of those really annoying faults that can take 20 minutes or multiple visits.
As others have said there is no magic bullet for finding the issue.
Basic testing and inspection gets most of them. Detective work and luck find the rest.
One thing I have found is that rushing and trying short cuts rarely works for me. Keeping it simple and methodical has served me well.
I recently found an issue that wasn't showing up via testing because it was a dry day. A bit of experience and luck later I found a crappy connection outside under a leaky gutter. On a different day I might have missed it and had to return when the fault showed itself again.