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This dreaded fault popped up again!

Went to a newly installed job yesteday, which consisted of a ring circuit on a 32Amp 30Ma RCBO, where the sockets were of a module type, ie 2 sockets in a double gang box, but are actually wired individually within the 2 gang box. One of the sockets had the neutral and earth crossed. With the circuit energised the RCBO stayed on. When you plugged an martindale socket tester in everything was ok (load is <18Ma),. Fault was picked up only when the test machine was plugged in and loop reading was tried to be obtained, the RCBO then tripped.

Spoke to the manager about this, and his reply was 'why was it not picked up during the dead test?' I replied R1 Rn is not commonplace (defending the guy that did the dead test), and indeed you would still have to go to every individual socket to pick up the cross, which would make the test longer to do. He walked away shaking his head. Which left me questioning my own thought process.

So am I missing something here?

Any comments most appreciated!
 
A dead test between cores was never carried out unfortunately because the meter would have picked up a short between neutral and earth when doing continuity tests.
 
yeah but if you test between cores at the db and an earth and neutral connected in a socket then the tester would pick it up, I always test continuity at the db before connecting anything up, just incase an apprentice or someone with an hangover got 2 cores mixed up somewhere, it does happen.
 
yeah but if you test between cores at the db and an earth and neutral connected in a socket then the tester would pick it up, I always test continuity at the db before connecting anything up, just incase an apprentice or someone with an hangover got 2 cores mixed up somewhere, it does happen.

How? Neutral cores not on bar, and earth not on bar, and MAIN Neutral disconneted
 
he said a neutral and earth were crossed in a socket, if you test all core from the board before connecting into the board you would get a short between nuetral and earth if they were joined together, Unless the op means the earths were in the neutral terminal and the neutrals in the earth, I read the post as one neutral and earth joined together which would show up as a short circuit between cores when testing the loops
 
he said a neutral and earth were crossed in a socket, if you test all core from the board before connecting into the board you would get a short between nuetral and earth if they were joined together, Unless the op means the earths were in the neutral terminal and the neutrals in the earth, I read the post as one neutral and earth joined together which would show up as a short circuit between cores when testing the loops

As stated in the OP, they were 'module' sockets, so the earths were in effect 'clean', even when crossed you WILL not pick it up!

It means that at the said socket the earth pin, becomes the neutral, and the neutral the earth. Untill something with a load of >30Ma is plugged in you WILL not pick it up
 
yeah but if a neutral wire and an earth wire were actually connected together under a terminal then it would show, unless as stated the op meant the wrong cables in the wrong terminal then I read it wrong and agree.
 
yeah but if a neutral wire and an earth wire were actually connected together under a terminal then it would show, unless as stated the op meant the wrong cables in the wrong terminal then I read it wrong and agree.

Glad you understand, little difficult to explain, so lets hope we are all clear now
 
okay after reading the post again several times I have read it wrong, so your right
 
On a new install there should be an R1,R2 test AND R1,Rn carried out at every socket. Cross connect at the CU, then test with a plug adaptor at every socket. Only takes a few minutes and you know that everything is connected properly.
 
On a new install there should be an R1,R2 test AND R1,Rn carried out at every socket. Cross connect at the CU, then test with a plug adaptor at every socket. Only takes a few minutes and you know that everything is connected properly.

Agreed apart from the few minutes remark.

That said I would rather test every socket upon energising
 
well then in answer to your question I would say your thoughts are fine and the guy shaking his head won't be able to have his mind changed in anycase as it is only 3 wires isn't it according to non sparks haha
 
Agreed apart from the few minutes remark.

That said I would rather test every socket upon energising

Ok, a few minutes is optimistic. I have just finished a complete rewire on a property, and to cross-connect as I said in my earlier post and test at every point, noting every reading, took less than 20 minutes.
What I'm getting at is that there is no excuse to miss out parts of essential testing on a new install.
 
It is the mangers that do not appreciate how long it takes to test correctly. Especially when you have a long run of these tests to do. For example a 3 bed flat has over 60 socket (individual modules) on current project. That in itself will take longer than the whole of the remaining test. So that is 120 tests just for the sockets!

You will still need to test live at every socket, so IMO, doing it live will in effect will get a lot more results, and is a considerable time saver.
 
Energising and then live testing would be O.k , but not good practice, if there is no-one else likely to be put at risk of using an incorrectly wired socket or appliance and there is no risk of fire etc.

So the flat / house would have to be empty and secure.
 
Energising and then live testing would be O.k if there is no-one else likely to be put at risk of using an incorrectly wired socket or appliance and there is no risk of fire etc.

If the 'said' socket was used after energising then the RCBO would trip (given that the load was >30Ma).
That said when I live test, there is a permit to work in place!
 

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