ZE testing

[goasis]

Just watched one of 'Delroy the sparks ' videos on YouTube, now the guy has many yrs more experience than me but I do question some of his techniques, however in this recent he does a proper Ze( ie removing main earth,) but leaves the installation live, is this a done thing?! I guess the risk in reality is pretty small for the 2 mins, but surely if your doing a EICR and you can't turn everything off its a LIM or by enquiry?

 

[telectrix]

strictly speaking, the installation should be totally de-energised when doing this test as the whole installation is not earthed. however, the chances of a L-E fault occuring are slim.

 

[baldelectrician]

I noticed that as well

He also left a consumer unit with blanks missing at the end of one episode.

 

[Dustydazzler]

Ze 'should' be done with all loads switched off

 

[buzzlightyear]

Ze 'should' be done with all loads switched

Being a yooboo star he can do what he wants.

 

[Fender]

I wouldn't take too much notice of Delroy.

I stupidly watched one of his 'documentaries' recently.

The fault was an RCD kept tripping. The first thing he did was put his tong tester around both live and neutral tails at the same time, and recorded the milliamp readings.

Well, why not...

I fast forwarded to see what the fault was. It turns out that he couldn't find it.

And there we have it.

 

[Dustydazzler]

Delroy is my favourite celebrity electrician

He does all the grotty little jobs that we all love to hate like tripping rcds and extra sockets by sticking up some mini trunk

Unlike Artisan whos Vids are getting rather boring with 30 grand rewires and posh car chargers

 

[timhoward]

The fault was an RCD kept tripping. The first thing he did was put his tong tester around both live and neutral tails at the same time, and recorded the milliamp readings.

That's actually a valid way to measure earth leakage, the idea being that current going down live and NOT coming back through neutral will be leaking, so the reading is indicating the in-balance the RCD is seeing, i.e. the leakage.

I wouldn't take too much notice of Delroy.

He's a nice enough chap, and he has his ways of doing things, but this thread highlights that just because it's on youtube doesn't mean it's right.
The thing about him - what you see is what you get, no airs and graces, and seems as honest as the day is long! I quite enjoy watching him.

Some of his videos certainly have a few questionable moments in, like the one where he correctly deduces there's no main earth, but doesn't actually follow an earth conductor to see if there's an electrode, and then creates his own TNS on the supply cable without involving the DNO!

 

[Pretty Mouth]

The first thing he did was put his tong tester around both live and neutral tails at the same time, and recorded the milliamp readings.

Perhaps I'm missing something here, but... I know of no other way to reliably measure earth leakage.

 

[UNG]

I wouldn't take too much notice of Delroy.

I stupidly watched one of his 'documentaries' recently.

The fault was an RCD kept tripping. The first thing he did was put his tong tester around both live and neutral tails at the same time, and recorded the milliamp readings.

Well, why not...

So how would you reliably identify the magnitude of a leakage current

I fast forwarded to see what the fault was. It turns out that he couldn't find it.

And there we have it.

As we all know leakage currents can be one of the most difficult problems to find and also may only show intermittently causing random RCD trips

 

[David Prosser]

 

[7029 dave]

Ze is best measured at the cutout with everything disconnected towards the installation.(not so in the real world).

Isolate lock off DB's because it is a live test, disconnect main earth away from installation dont wont any parallel paths.

 

[timhoward]

Perhaps I'm missing something here, but... I know of no other way to reliably measure earth leakage.

The only other way I know of (which I wouldn't call reliable) is a PITA - ramp test RCD with no load, ramp test RCD with everything on and subtract one from the other....
Until I got a sensitive clamp meter I used to delight people by tripping everything loads of times to try and deduce what might be going on!

 

[pc1966]

To me there are two ways to measure Ze, and both should be done with the supply off.

• Disconnect the supply earth and test L-E to the now-floating supply earth.
• Disconnect all extraneous bonding and then test 'Zs'

In some ways the 2nd option looks safer, but is actually a higher risk.

Why? Well you might then have some 0.5mm flex to a boiler or gas cooker ignition system binding the supply to true Earth and if anything nasty happens on a PME supply it will roast.

for a domestic system I can't really see any issue with turning everything odd. They will need all circuits tested for an EICR and so at least at one point the supply would go off. Some commercial/industrial EICR might have an agreed limitation not to power off something critical like server room supply, etc, and in that case a proper Ze test is just not practical/safe.

I guess you probably could use on of the current-clamp style of earth rod / lightning protection system testers to check Ze (or at least parallel earth impedance) without powering off but not experience of them as not got one to play with. Sadly.

 

[Pretty Mouth]

To me there are two ways to measure Ze, and both should be done with the supply off.

• Disconnect the supply earth and test L-E to the now-floating supply earth.
• Disconnect all extraneous bonding and then test 'Zs'

In some ways the 2nd option looks safer, but is actually a higher risk.

Why? Well you might then have some 0.5mm flex to a boiler or gas cooker ignition system binding the supply to true Earth and if anything nasty happens on a PME supply it will roast.

Wouldn't any flex connection to the boiler etc, or similar path to true earth, also skew the result of the Ze test though?

 

[pc1966]

Wouldn't any flex connection to the boiler etc, or similar path to true earth, also skew the result of the Ze test though?

Good point, yes it would. And might be hard to check if it is present or not short of disconnecting the supply earth (at which point it is kind of academic as you might as well measure that way).

However, if your supply Ze is around the 0.3-0.5 ohm sort of region then return is probably in the 0.15-0.25 ohm region and such a thin cable might not make a lot of difference to the accuracy.

I guess the biggest risk is the supply Ze/earth is actually crap and you are only getting tolerable results via such a path

 

[MoserV8]

My view is absolutely Not! For Numerous risks. The Entire Load should all be switched off before disconnecting the the Main Incoming Earth. If you left these circuits "on" in an exam environment, you would be told to step back, your exam is over & pack up & quietly leave.

 

[Lister1987]

So, this 'video premiere' and partnership with Schneider; what are people's thoughts as I'm interested in why Schneider are teaming up with him, forgive me but there's nowt special about him, they could've teamed up with a better 'YT Celebrity'

 

[Dustydazzler]

So, this 'video premiere' and partnership with Schneider; what are people's thoughts as I'm interested in why Schneider are teaming up with him, forgive me but there's nowt special about him, they could've teamed up with a better 'YT Celebrity'

It will all swing on how many tuber subscribers they have...

 

[Lister1987]

It will all swing on how many tuber subscribers they have...

If that were the case surely they'd be humping @ArtElectrics leg off by now?