Does anyone know what RCD fault he is talking about

[King84]

Hi
Basically I have visited a youtube link of another electrician and he is talking about how many electricians find RCD fault very hard to resolve and he mentioned it takes less than 3 minutes using the method he mentioned but not completely hence its really puzzling me so if anyone could explain this.

(If you got Dual RCD board, You can disconnect some of the rn which is obviously neutral and you have to disconnect them from one of the circuits and you gotto be careful as if its got load on it then it could still be 230V on it so just energise the circuit and put in connectors and make sure you try and draw out the load so you get that out and with in 3 minutes you can find an RCD problem)

This was very hard to grasp even upon question he didnt reply but still bothers me as we go standard by IR on circuits to find RCD fault but like how this could find out in 3 minutes with very weirdly explained method if anyone more experienced knows what this means, I really appreciate
cheers

 

[IAmSparkytus!]

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

 

[littlespark]

Without seeing the vid, it sounds like the “test” is disconnecting neutrals, turning the power on, then touching the (now live) neutrals against the bar until the rcd trips.

Effective, but dangerous.

 

[ipf]

I thought RCD's were supposed to be safety devices.
Messing about with live returns ain't the way to sort out problems with them.
Could be 3 minutes sorting problem but a hell of a lot longer in the grave.

 

[pc1966]

A common "confusing" fault is a N-E short in a board with single or dual RCD. Here the N normally has little voltage w.r.t. E (kind of the definition of neutral) and that is especially true with TN-C-S as they are common at the cut-out point.

The confusing thing is you can get the RCD tripping due to a high current on a circuit that is not faulted, simply because it generates enough N-E voltage due to the N impedance and current flowing. So another circuit that has the N-E short allows a diversion of current and the RCD sees it and trips.

Sparky comes along, home owners says "when I hoover this thing trips", sparky assumes the fault is on the sockets but finds the IR test OK. Actually it was the lights that were faults, but it was the hoover motor's inrush current that was enough to cause a fraction of a volt N-E and so divert 30+mA on the light's N fault and trip the RCD.

 

[Vortigern]

Of course you could always switch off all the MCB and switch on one by one and you can narrow down which circuit is (apparently See post above) causing the trip. A lot less dangerous.

 

[ipf]

Of course you could always switch off all the MCB and switch on one by one and you can narrow down which circuit is (apparently See post above) causing the trip. A lot less dangerous.

Yes, it seems to me he'll only find the cable (circuit) in question....not what is actually causing the RCD to trip.
Unless I'm missing something.

 

[nicebutdim]

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.

 

[Lucien Nunes]

I can't make any sense of that either and I don't think there's a single guaranteed way to find any kind of fault that would cause an RCD trip. But I do agree that a lot of people make heavy going of finding some types of faults because they don't think carefully enough about cause and effect or use the necessary calculations to analyse the problem. If you understand some basic electrical theory and have enough practical experience to recognise common types of fault and damage, most tripping situations yield to a bit of logic.

Maybe I should do a masterclass.

 

[ipf]

Maybe I should do a masterclass.

Maybe give it a mention on BBC Breakfast

 

[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