More Odd Faults: Stumped and not ashamed to admit it!!

[securespark]

As you of all people know, anything's possible!

I strongly suspect that there is something still in circuit I don't know about yet, because that NE fault (if indeed it is a fault) is not enough to cause the mcb to pop off.

And if there is still something in circuit, it could be the culprit of both low readings. Wouldn't that be nice?

 

[toasty]

Secure,

You say you don't want to megger LN as you aren't sure sure everything is out of circuit. I take your point, it would be no fun frying an expensive electronic item that had been forgotten about.

Instead of meggering, why not just connect L and N up to the mains (via a suitable breaker/fuse) and use an accurate ammeter to measure current.
That'll give you the LN resistance indirectly with V/I=R. You stand more chance of finding items with relays and the like this way too (garden lights, programmers, timers etc..) as they get the opportunity to energise.

Hope this is of some use.
-Dan

 

[sjwkmje]

As you of all people know, anything's possible!

I strongly suspect that there is something still in circuit I don't know about yet, because that NE fault (if indeed it is a fault) is not enough to cause the mcb to pop off.

And if there is still something in circuit, it could be the culprit of both low readings. Wouldn't that be nice?

Had a very simular fault in a house about 6 months ago on a ring final. Did not want to megger L-N incase we forgot anything. So we started to trace each cable from the CU to each socket and found nothing. Was there for a good half a day, then we decided the floors had to come up so out came the circular saws as it was sheet and before we was just using the ceeling for access. Found inside the CAVITY wall a JB, from the ring final to a peace of 4mm feeding a ring final in the new kitchen extension. The kitchen had a breaker in the CU for what looked like a ring final. Found out that just protected two sockets. But the other sockets in the kitchen then fed the outhouse, and there was a couple of outside lights on an un-switched spur. Took us a while to find that and a nice bill for the customer after we had to rewire the ring final in the kitchen, and re test both circuits.

So we had ring final > JB > 4mm > ring final with 3 sockets > 4mm > outhouse ring final > FCU > lights. I cannot remember the intial test results.

That could not have been done by a compitent spark! Talk about spurs. Amazing what you can find. Took me and another spark about two days to find it.

Adam

 

[securespark]

Found it today...

A SON floodlight outside displaying an LE & NE fault. However, instead of rupturing the 1362 13A (!) fuse, it tripped the 30A Type 1 breaker.

You live & learn...