flat down neutral to earth reading

[davesparks]

Do a periodic and make sure it gets a satisfactory

Do you mean do the inspection then carry out the remedial sand issue an EIC to go with it?

 

[Octopus]

Do you mean do the inspection then carry out the remedial sand issue an EIC to go with it?

I think he means fix issues as you come across them and just do an EICR!

 

[davesparks]

Then he still needs to list all of the issues on the EICR and issue EIC for the repairs.

 

[Risteard]

Well you need one as you have to prove the RCD is operating at the correct fault current.

Surely that's what the half-current test proves.

 

[Risteard]

I see I was beaten to it by a few minutes!

 

[davesparks]

Surely that's what the half-current test proves.

No, the half current test proves that it doesn't trip at too low a current.

The rated tripping current test proves that it trips within the correct time at it's rated current .

 

[Risteard]

No, the half current test proves that it doesn't trip at too low a current.

Obviously. I wasn't suggesting that it didn't need confirmed that it did indeed operate when the rated residual operating current was applied.

I was simply pointing out that if it does not operate at half of that current but does operate at the current then it is completely irrelevant at what precise current it is operating as that is not what the Standard requires.

 

[davesparks]

I wouldn't say that the actual tripping current is irrelevant!

But in the context of this thread where the RCD has been called in to question then the tripping time tests will be enough.

 

[aidley]

Dont worry about the certification a periodic is done logging faults which I have to rectify! Which then depending on faults found I will issue an electrical installation certificate or a minor works for the work done!

 

[Lucien Nunes]

A bit late to the party here but I can't believe no-one has asked what the Ze / Zdb is. If it's high, then you might well get away with an N-E fault without the RCD tripping. Of course, you must do that test with the faulty circuit disconnected!

 

[aidley]

It turned out to be an extreme case of damp! The house was rewired in 2008 my Robin meter was reading flat down but a colleagues new fangled meter read a bit higher than zero we isolated the damp legs and kept 500v ir test on it and got it upto 30meg ohms! The job has now been.passed on to the building team.who are going to try to sort the damp before we reevaluate the wiring!

 

[Lucien Nunes]

the neutral to earth reading was 0 ohms

So this vital piece of information was probably a long way out! Zero, to one significant figure as you wrote it, means less than half an ohm. That's a valid resistance for a short-circuit but not the result of damp, unless you've submerged the entire installation in seawater.

If you meant 0 megohms, that (as an engineer would interpret it) is less than half a megohm, which could be as high as 500,000 ohms - a far cry from 'zero' and of course it won't trip the RCD. Better still, as nothing is ever truly zero, give the nearest readable count (and of course the correct unit). E.g. stating <0.1 megohm would have been a clear indication of what kind of range and accuracy were involved.

We had an example of this in another thread recently - it's important to understand what the display on your instrument is telling you. No-one would think that 70 on the car speedo meant 70,000,000 mph but there seems to be less certainty about the reading on an MFT.